Track Day Temps

[Victorydodge]

I recently had the first opportunity to get the Gen V out on the track at Michigans Grattan Raceway. Overall I was impressed my the car and felt much more confident than I ever did in the Gen IV. However I had one concern, it was fairly warm that day (temps averaging around 85) and the after 6-7 laps the car would be reading temps of 236-240, once ever as high as 242. What are most of you seeing for temps when really pushing the car hard at the track?

For further info-

the car had 1900 miles on it at the time
the oil had been freshly changed and was at the top full mark
the coolant level was perfect
on the street the car never gets even remotely warm

[VENOM V]

That is higher than I have seen at that ambient temp, I am surprised. I've tracked my Viper many times at many different tracks (probably 15+ track days, lost count), often in the 90s and hotter. The first really hot track event was 107 F ambient. Car never touched 240 F, maybe I hit 235 F. The next really hot event I ran slicks in 106 F ambient, and was driving harder than before, and I briefly touched 240 F. I backed off a lap, then hit it hard again and never touched 240 F.

This car is the coolest running track car I have ever run.

According to Erich Heushle, keep it under 245 F and you're ok. However, I don't want to run any higher than 240 F.

Perhaps double check that your coolant and oil are at their max level. Vipers consume oil at the track.

[BLUETA#1]

If you drive hard, the car easily hits 240 on a warm day. I have managed to lower the temp about 5 degrees so far. I am making another modification for an event in 3 weeks…then a third modification for the week after. IF these work, I will post all the details.

[FLATOUT]

If you drive hard, the car easily hits 240 on a warm day. I have managed to lower the temp about 5 degrees so far. I am making another modification for an event in 3 weeks…then a third modification for the week after. IF these work, I will post all the details.

I have also tracked my gen V's many time and NEVER saw elevated temps like you guys are seeing. This is the exception not the norm. I would check the coolant system for air pockets.

[BLUETA#1]

I have also tracked my gen V's many time and NEVER saw elevated temps like you guys are seeing. This is the exception not the norm. I would check the coolant system for air pockets.

You are not talking to enough people. I have a little private network of 6 owners who track and we go back and forth on ideas. If you are driving hard, its the norm.

[greygt3]

Just for comparison purposes only, don't read anything into this.

I'm here looking into a ACR but I'm coming from the Porsche GT3, GT2 world. I tracked my Porsches often and I live in Texas so it's hot. Water temps would never rise above standard road driving temps as would the oil temp. It was never a concern ever.

Just thinking out loud here but am wondering how these temps will effect the motor longevity? This is a wet sump motor after all as opposed to a dry sump setup.

I've been reading all the ACR reviews and think it's going to be something special.

[VENOM V]

You are not talking to enough people. I have a little private network of 6 owners who track and we go back and forth on ideas. If you are driving hard, its the norm.

Hmmm, like Flatout I am tracking with a lot of Viper track rats and I have never heard if this being an issue. I drive hard and heating issues are not the norm here in CA, which has tracks that regularly see summer ambient temps in the 90s and 100s. Maybe you have a track that for some reason is particularly harsh on temps, but it is the exception not the norm.

My built Camaro track car had heating issues until I added two oil coolers with custom shrouding. A few weeks ago I tracked at Laguna Seca with a bunch of Vipers that ran flawlessly. A C7 ZO6 came in puking all of its coolant during a session with ambient temp only in the high 60s. I asked the owner about temps, he hit 267 F coolant and 309 F oil. Yikes.

But Vipers running hot? I'm with Andy, probably low water or oil, or an air pocket.

I'd be curious if others are also having heating problems.

[VENOM V]

Just for comparison purposes only, don't read anything into this.

I'm here looking into a ACR but I'm coming from the Porsche GT3, GT2 world. I tracked my Porsches often and I live in Texas so it's hot. Water temps would never rise above standard road driving temps as would the oil temp. It was never a concern ever.

Just thinking out loud here but am wondering how these temps will effect the motor longevity? This is a wet sump motor after all as opposed to a dry sump setup.

I've been reading all the ACR reviews and think it's going to be something special.

I think you would be pleasantly surprised at the longevity of the Viper V10. The whole car is pretty bullet proof on the track. I've been tracking mine quite a bit, have almost 15,000 miles on it. The only issue I've had was an O2 sensor failure that was replaced under warranty. The ACR is even more durable, with spherical rod ends and I believe it has a differential cooler as well.

[BLUETA#1]

But Vipers running hot? I'm with Andy, probably low water or oil, or an air pocket.

No, no and no. I have professional factory racing and extensive testing experience. Those were all fine. The temps are correlated to speed…lap times. I see it at the track….last event the fast Vipers, Camero and McLarens all overheating. The cars that were a few seconds slower were fine.

[BLUETA#1]

Just for comparison purposes only, don't read anything into this.

I'm here looking into a ACR but I'm coming from the Porsche GT3, GT2 world. I tracked my Porsches often and I live in Texas so it's hot. Water temps would never rise above standard road driving temps as would the oil temp. It was never a concern ever.

Just thinking out loud here but am wondering how these temps will effect the motor longevity? This is a wet sump motor after all as opposed to a dry sump setup.


I've been reading all the ACR reviews and think it's going to be something special.

I have had a GT3, RS, etc. The Viper is my first American car. It’s a ball to drive and a beast. I love it. However, the P-cars never ran above 195 degrees when pounding on them. I can cover all the new GT3s at COTA….for about 6 laps.

[VENOM V]

But Vipers running hot? I'm with Andy, probably low water or oil, or an air pocket.

No, no and no. I have professional factory racing and extensive testing experience. Those were all fine. The temps are correlated to speed…lap times. I see it at the track….last event the fast Vipers, Camero and McLarens all overheating. The cars that were a few seconds slower were fine.

Well my lap times are pretty quick at some tracks too, and I also race. Haven't had issues with the Viper's temps. At Buttonwillow, Thunderhill, Laguna Seca and others, no overheating problems. Not surprised Camaros have had issues, they are notorious for it.

I don't doubt you've had overtemp issues in mild weather, just surprised that's all. First time I've heard of it being an issue.

[BLUETA#1]

Well my lap times are pretty quick at some tracks too, and I also race. Haven't had issues with the Viper's temps. At Buttonwillow, Thunderhill, Laguna Seca and others, no overheating problems. Not surprised Camaros have had issues, they are notorious for it.

I don't doubt you've had overtemp issues in mild weather, just surprised that's all. First time I've heard of it being an issue.

I probably as not clear…I never said mild weather. Ambient temp over 90 is when its an issue. I am confident that the issue will be fixed by September. If we get it, I will publish it.

[VENOM V]

I probably as not clear…I never said mild weather. Ambient temp over 90 is when its an issue. I am confident that the issue will be fixed by September. If we get it, I will publish it.

Ok that makes sense at those hotter ambient temps, looking forward to hearing about the solution.

[Nemesis]

I see 240 regularly in my TA and GTS on the track, ambients from 75-94.

[BLUETA#1]

I see 240 regularly in my TA and GTS on the track, ambients from 75-94.

Thank you!

[Nine Ball]

Some vid screen shots of my last two track days, near the end of 20 min sessions. Car still has factory coolant, and Mobil1 0-40 oil.

84F ambient, 210 coolant, 233 oil

http://i466.photobucket.com/albums/rr29/ynotdv8/2014%20Viper%20TA/TrackTemps-Oil233-Cool210.jpg (http://s466.photobucket.com/user/ynotdv8/media/2014%20Viper%20TA/TrackTemps-Oil233-Cool210.jpg.html)

91F ambient, 213 coolant, 237 oil (this track was short, stayed in 3rd gear entire time at high rpm) Arrow pcm installed.

http://i466.photobucket.com/albums/rr29/ynotdv8/2014%20Viper%20TA/temps-trackday.jpg (http://s466.photobucket.com/user/ynotdv8/media/2014%20Viper%20TA/temps-trackday.jpg.html)

This is the good thing about helmet cameras, you can go back and review all the gauges later :)

[FLATOUT]

You are not talking to enough people. I have a little private network of 6 owners who track and we go back and forth on ideas. If you are driving hard, its the norm.

I talk to customers everyday that track a lot, and track my gen V's as often as I can, it's not the norm. I'm not saying your car isn't having a problem just that these cars have had very predictable track temps since we started running them in 2013.

Ben Keating, Ralph, and a bunch of others in our community drive the cars very HARD on track and have not run into problems with elevated temps.

[BLUETA#1]

I talk to customers everyday that track a lot, and track my gen V's as often as I can, it's not the norm. I'm not saying your car isn't having a problem just that these cars have had very predictable track temps since we started running them in 2013.

Ben Keating, Ralph, and a bunch of others in our community drive the cars very HARD on track and have not run into problems with elevated temps.

We will agree to disagree…its not me…its several other cars as well. It’s a fine line. Run a 2:33 at COTA and its 220. Run a 2:29 lap and its 240 within 2 laps. I was at the Viper event at COTA last year…every car that I happened to time, except the race cars of course, were in the 2:30s. (That's still quick.)

[Stealth]

I just returned from a 85F HPDE at CA Speedway in Fontana, CA yesterday. I made a separate thread and address temps in that thread as well.

[TrackAire]

We will agree to disagree…its not me…its several other cars as well. It’s a fine line. Run a 2:33 at COTA and its 220. Run a 2:29 lap and its 240 within 2 laps. I was at the Viper event at COTA last year…every car that I happened to time, except the race cars of course, were in the 2:30s. (That's still quick.)

At the lap times you've listed, 4 seconds a lap is a lot of speed difference so I can definitely see an increase in temps. It may also be an aero issue where the air is just not flowing into and out of the heat exchangers as efficiently as should.

I just test drove a fairly stock C5 Z06 yesterday and was pretty shocked to see the oil temps hit 240 degrees when driving slightly aggressively on the road during the test drive. Water temps stayed in check, but I didn't expect the oil to jump that fast. There are a lot of cooling upgrades available for the Vette because of this. I think it is only common sense that a few small mods may be needed on the Viper to help drop the water temps 15 to 20 degrees during all out driving with a high caliber driver behind the wheel.

What role does humidity play on the cooling of a car?.......what helps dissipate heat better through the radiators, high humidity or low humidity?

[FLATOUT]

We will agree to disagree…its not me…its several other cars as well. It’s a fine line. Run a 2:33 at COTA and its 220. Run a 2:29 lap and its 240 within 2 laps. I was at the Viper event at COTA last year…every car that I happened to time, except the race cars of course, were in the 2:30s. (That's still quick.)

I NEVER said that YOUR car didn't have an issue, and I will repeat that again. But what you are saying to me is that you have 9 cars that have this issue and you are saying that all of them are being driven harder and faster than what Ben Keating was capable of doing at COTA that day. I just don't believe that, there has to be another issue going on.

Again it may be happening but it is not the norm. The ACR's that were testing at VIR recently didn't have this problem either. Maybe Lally wasn't driving it fast enough, who knows.

[BLUETA#1]

I NEVER said that YOUR car didn't have an issue, and I will repeat that again. But what you are saying to me is that you have 9 cars that have this issue and you are saying that all of them are being driven harder and faster than what Ben Keating was capable of doing at COTA that day. I just don't believe that, there has to be another issue going on.

Again it may be happening but it is not the norm. The ACR's that were testing at VIR recently didn't have this problem either. Maybe Lally wasn't driving it fast enough, who knows.

You are rearranging my words to make an argument. Here is the deal. My car freaking overheats when I am on it. (I know cars as a factory race driver and tester.) I have quietly…off the boards...researched it and I have some across several more people who hit 240 when then go hard. I am not suggesting that anyone is faster than anyone else. Can we end this unless you have any new suggestions two help the problem?

[ViperGeorge]

Unfortunately I must agree with BLUETA#1. My car also gets freakin' hot on the track. Last track day ambient was 77, coolant hit 243 in about 10-15 minutes, oil hit 267. Remember too that the PCM pulls timing at those temps. I have an Arrow PCM and headers. I checked the cooling system, no air that I could find. Bled it from the bleeder, jacked right side up high too but still no air. I've added Water Wetter and changed the oil to Mobil 1 15w50. I will also probably do an IPSCO under-drive pulley. I will see what else I can seal up around the radiator but the Gen 5s already have a top close out panel. After I get my pedal assembly fixed I got to get back to the track.

There is something not right with at least some of these cars. Mine is a 2015 TA 2.0. My 2009 ACR NEVER saw temps this high. I gotta admit I am regretting getting rid of the 2009 ACR. I sure hope someone figures this out because it sucks not to be able to go hard for more than 10-15 minutes.

[Stealth]

It basically depends on how hot the ambient temperature is, how hard you push the car and your driving style. As I noted in the other thread, I plan to use more brakes and less heel-toe in the future to keep temps cooler (driving style issue). There are also places where I can run in 5th instead of 4th at this track. (CA Speedway). Who knows, Ben K. and others may use these and other techinques to manage temps in the race cars. Of course, those are race cars.

My Gen V GTS with Aero and Arrow PCM and Corsa tires ran great at CA Speedway HPDE yesterday. The car did not generate any error codes, did not go into any type of limp mode, and cooled quickly when I dropped the rpms a bit. Nevertheless, the Gen Vs can get a bit warm when pushed (235--261F Oil). Several other cars at the HPDE that were going a bit fast had actual heat issues--brake pedal to floor, reduced power, error codes, etc. It was about 85F at the track.

[ViperGeorge]

It basically depends on how hot the ambient temperature is, how hard you push the car and your driving style. As I noted in the other thread, I plan to use more brakes and less heel-toe in the future to keep temps cooler (driving style issue). There are also places where I can run in 5th instead of 4th at this track. (CA Speedway). Who knows, Ben K. and others may use these and other techinques to manage temps in the race cars. Of course, those are race cars.

My Gen V GTS with Aero and Arrow PCM and Corsa tires ran great at CA Speedway HPDE yesterday. The car did not generate any error codes, did not go into any type of limp mode, and cooled quickly when I dropped the rpms a bit. Nevertheless, the Gen Vs can get a bit warm when pushed (235--261F Oil). Several other cars at the HPDE that were going a bit fast had actual heat issues--brake pedal to floor, reduced power, error codes, etc. It was about 85F at the track.

Remember though, at 240 degrees the PCM is already pulling timing. This will reduce power and slow you down.

[Steve M]

Remember though, at 240 degrees the PCM is already pulling timing. This will reduce power and slow you down.

To make matters worse in the power department, whenever it pulls timing it also adds fuel.

[Stealth]

If temperatures rise next time I will adjust driving style a bit to keep temps in the 230sF. :t89186:

[ViperGeorge]

If temperatures rise next time I will adjust driving style a bit to keep temps in the 230sF. :t89186:

I believe it is already pulling timing at that temp.

[Stealth]

OK, I will just leave it in the garage... .

[ViperGeorge]

OK, I will just leave it in the garage... .

I'm beginning to feel the same way. I need to figure this out for sure.

[Stealth]

Just to clarify: my car ran great at a HPDE in 85F+ and threw no error codes whatsoever; other cars were side-lined. Most of the time it was running 225-240F Oil Temp. When it hit hotter temps it was cooler a couple of turns later on the same lap. When I ran an earlier HPDE session in May 2015 with temps around 70F at the same track I hit 224F or so (I do not watch the gauges every second so it could have been slightly higher then). The first HPDE (1 day, 4 20 min sessions) was with OEM PCM. The second HPDE in the hotter ambient temps was the same duration but with the Arrow PCM. I am running 91 Pump Octane. I really attribute the higher temps to higher ambient temps and driving style.

Sitting in traffic in SoCal the car can hit 205+F. Normal cruising Oil Temp is 192F or so.

My feeling is that the car is great and running well. Very smooth idle no codes. My fluids are cycled regularly. At 4,200mi. I changed differential, tranny, brake, clutch and oil (about my 3rd oil and filter change).

That said, if there are simple changes I can make to make the car run even better and more safely, then I will certainly consider such matters.

[ViperGeorge]

Just to clarify: my car ran great at a HPDE in 85F+ and threw no error codes whatsoever; other cars were side-lined. Most of the time it was running 225-240F Oil Temp. When it hit hotter temps it was cooler a couple of turns later on the same lap. When I ran an earlier HPDE session in May 2015 with temps around 70F at the same track I hit 224F or so (I do not watch the gauges every second so it could have been slightly higher then). The first HPDE (1 day, 4 20 min sessions) was with OEM PCM. The second HPDE in the hotter ambient temps was the same duration but with the Arrow PCM. I am running 91 Pump Octane. I really attribute the higher temps to higher ambient temps and driving style.

Sitting in traffic in SoCal the car can hit 205+F. Normal cruising Oil Temp is 192F or so.

My feeling is that the car is great and running well. Very smooth idle no codes. My fluids are cycled regularly. At 4,200mi. I changed differential, tranny, brake, clutch and oil (about my 3rd oil and filter change).

That said, if there are simple changes I can make to make the car run even better and more safely, then I will certainly consider such matters.

Are you running headers? See http://driveviper.com/forums/threads/10017-Warning-to-those-with-Headers?p=156903#post156903

I believe the heating issue could be a result of the headers being too close to the oil cooler lines. Hot oil equals hot engine. Stock exhaust no problem.

[BLUETA#1]

Stock exhaust.

[ViperGeorge]

Stock exhaust.

Well that is not what I was hoping. I really thought the heated oil lines could explain the engine heat. Probably still contributes though.

[FLATOUT]

Stock exhaust.

Can you post a video of a lap or two that caused the excessive heat? As fast as you are running at COTA I would like to see and hear what looks like on the car when these temps are jumping up on the car.

Andy

[mjorgensen]

Well that is not what I was hoping. I really thought the heated oil lines could explain the engine heat. Probably still contributes though.

Oil temps are controlled by coolant so if the car is over heating then the oil temps are going to rise, doubt it is the other way around.

[Stealth]

Are you running headers? See http://driveviper.com/forums/threads/10017-Warning-to-those-with-Headers?p=156903#post156903

I believe the heating issue could be a result of the headers being too close to the oil cooler lines. Hot oil equals hot engine. Stock exhaust no problem.

No headers. Stock CATS and Corsa Cat-back exhaust. Again, I had no error codes, and most of the sessions was running 223F--241F. There were a couple of times where temps were elevated--just after heavy braking using heel-toe from 130mph to 25mph or something. The car cooled down quickly and ran fine.

[TrackAire]

I'm too lazy to do a search, but does the Gen 5 suffer the same issue some Gen 4's had with the radiator hose sucking shut at high rpms?

[Rapidrezults]

Can you post a video of a lap or two that caused the excessive heat? As fast as you are running at COTA I would like to see and hear what looks like on the car when these temps are jumping up on the car.

Andy

I would love to see this as well, just to get an idea of where the RPMs are during the session.

[BLUETA#1]

Can you post a video of a lap or two that caused the excessive heat? As fast as you are running at COTA I would like to see and hear what looks like on the car when these temps are jumping up on the car.

Andy

I back off at 240 before the idiot light goes on at 245. (Trust me it hit 245 once and I have never let it get that high.) There are no sound or power differences. My brother just got his GT4. He took it right to the track. On the streets its runs at 210 degrees. As soon as you are on it, the car in engineered to run at 190 when pushing it hard. Amazing.

[ViperGeorge]

I'm too lazy to do a search, but does the Gen 5 suffer the same issue some Gen 4's had with the radiator hose sucking shut at high rpms?

This is a good question although even with the collapsing hose on my Gen 4 ACR it never got hot on the track.

[TrackAire]

This is a good question although even with the collapsing hose on my Gen 4 ACR it never got hot on the track.

The answer could be as simple as the differences in hoods and engine compartment design and the way the air evacuates out of a Gen 4 vs a Gen 5. Even a 20% reduction in air flow can have measurable effects on the cooling.

[BLUETA#1]

The answer could be as simple as the differences in hoods and engine compartment design and the way the air evacuates out of a Gen 4 vs a Gen 5. Even a 20% reduction in air flow can have measurable effects on the cooling.

You got it!

[SSGNRDZ_28]

Has anyone removed their hood vents to aid in cooling?

[mjorgensen]

Food for thought G4 to modified G5 and what do you see on the nose of the GTSR?

12516
12517
12519

[ViperGeorge]

Food for thought G4 to modified G5 and what do you see on the nose of the GTSR?

12516
12517
12519

Someone should make a grille that has thinner cross bars. I also see the tow hooks on the blue Gen 5, they seem to block air. How many folks with cooling issues are running them? I am for sure but I may need to rethink that. Would getting more air through the radiator help keep header heat down as well? I seem to remember that the fan shroud looked pretty restrictive on a Gen 5 as well. This is needed for low speed but would seem to hinder high speed cooling.

[mjorgensen]

Someone should make a grille that has thinner cross bars. I also see the tow hooks on the blue Gen 5, they seem to block air. How many folks with cooling issues are running them? I am for sure but I may need to rethink that. Would getting more air through the radiator help keep header heat down as well? I seem to remember that the fan shroud looked pretty restrictive on a Gen 5 as well. This is needed for low speed but would seem to hinder high speed cooling.


12520

The upper cross fin in the grill has nothing behind it so if it were neatly cut out then you would get more and smoother airflow to the radiator also. The replacement part if you mess it up is only like $150 so not terrible as an experiment.

You were also supposed to notice that on the GTSR they SPLIT the brake ducts to get more air deflected through the radiator... hmm.

[TrackAire]

Food for thought G4 to modified G5 and what do you see on the nose of the GTSR?

12516
12517
12519

Ok, I'll play mentally undernourished, I'm not sure what you're referring to. Other than the shape difference (Gen 4 looks like it has a little more intake surface area), the Gen 5 appears to have an A/C condenser compared to the race car.

[mjorgensen]

Ok, I'll play mentally undernourished, I'm not sure what you're referring to. Other than the shape difference (Gen 4 looks like it has a little more intake surface area), the Gen 5 appears to have an A/C condenser compared to the race car.

Air flow through the smooth surfaces of the G4 and lack of brake ducts would likely be much more efficient as far as cool air to the radiator. and the racecar brake ducts are split to give more air to the radiator...

[SRT_BluByU]

No headers. Stock CATS and Corsa Cat-back exhaust. Again, I had no error codes, and most of the sessions was running 223F--241F. There were a couple of times where temps were elevated--just after heavy braking using heel-toe from 130mph to 25mph or something. The car cooled down quickly and ran fine.

Just to be clear your talking about your coolant temp and not your oil temps - correct?

[BLUETA#1]

Has anyone removed their hood vents to aid in cooling?

Testing that next. I ran one test…I found a long road where I could run high RPMS and read the temps. I stayed in 2nd gear. Next, I propped the hood open with some foam blocks, bungeed the hood down and ran the same RPMs. Cooler. My bother who builds airplanes wants me to do one thing to move air, I want to try another. (I can’t track with bungee cords!) When I am done testing and tweaking by mid-September, I will post results. When you A/B test, the tests need to be done back to back and I can only change 1 thing at a time…this all takes time.

[ViperGeorge]

12520

The upper cross fin in the grill has nothing behind it so if it were neatly cut out then you would get more and smoother airflow to the radiator also. The replacement part if you mess it up is only like $150 so not terrible as an experiment.

You were also supposed to notice that on the GTSR they SPLIT the brake ducts to get more air deflected through the radiator... hmm.

I see the split brake duct now. Hard to notice it in the picture. So one half of the brake duct is actually supplying air to the radiator and the other half to the brakes?

[mjorgensen]

I see the split brake duct now. Hard to notice it in the picture. So one half of the brake duct is actually supplying air to the radiator and the other half to the brakes?

Yes, here are some more pictures, I'm also wondering how the individual splitters affect the airflow that is supposed to be getting kicked up into the engine under the manifolds, you can see how the air was intended to go without the splitters and with them how it is likely broken up. I'm not an engineer so I just have theory's but if someone is and have a comment please LMK.

12523
12524

GTSR does not appear to have a fan shroud (different uses because racecar I know) but still looking at all the added cooling area.

12525
12526

[FLATOUT]

Really good pictures for reference. Hmmmmmmm...........

[ViperGeorge]

Yes, here are some more pictures, I'm also wondering how the individual splitters affect the airflow that is supposed to be getting kicked up into the engine under the manifolds, you can see how the air was intended to go without the splitters and with them how it is likely broken up. I'm not an engineer so I just have theory's but if someone is and have a comment please LMK.

12523
12524

GTSR does not appear to have a fan shroud (different uses because racecar I know) but still looking at all the added cooling area.

12525
12526

Mark, are those extra undercarriage pieces directing air into those round holes where the O2 wires are? That's what it looks like.

[Voice of Reason]

The GTSR also has ducting that funnels all air from the radiator out through the hood vents vs ours that relies on hopes and dreams to funnel the air, leaving some hot air to wash over the engine. That "hot" air may be keeping our headers from melting everything in sight though so maybe it's good we don't have the ducting.

[Simms]

May have already been discussed, but any possible improvements with an aftermarket radiator like the old G2's?

[mjorgensen]

The GTSR also has ducting that funnels all air from the radiator out through the hood vents vs ours that relies on hopes and dreams to funnel the air, leaving some hot air to wash over the engine. That "hot" air may be keeping our headers from melting everything in sight though so maybe it's good we don't have the ducting.

That is where my last round of pictures comes in, the ends of the under panel rake up to make the air flow up towards the sides of the engine and when the splitters are introduced that normal airflow has to be disrupted if you look at the potential turbulence they can create in that area.

[ViperGeorge]

Mark of IPSCO installed one of his under-drive pulleys on my TA yesterday. Beautiful product and highly recommended. Our thinking is to slow the water pump down some at high rpms to allow the water to stay in the radiator a little longer. We believe at high rpms the water is moving too quickly through the radiator to shed enough heat or the pump is cavitating at high speed. Either way the under-drive pulley should help. I believe they installed a smaller pulley on the Gen 4 ACR from the factory. Does anyone know if that is true? I also insulated all lines running near the headers with DEI Cool Tube Extreme. By the way, the under-drive pulley appeared to have no impact on charging voltage or anything else during normal driving.

Car went in for service today to replace the pedal assembly. Once it is fixed I have to get back to the track for some testing.

[mjorgensen]

Mark of IPSCO installed one of his under-drive pulleys on my TA yesterday. Beautiful product and highly recommended. Our thinking is to slow the water pump down some at high rpms to allow the water to stay in the radiator a little longer. We believe at high rpms the water is moving too quickly through the radiator to shed enough heat or the pump is cavitating at high speed. Either way the under-drive pulley should help. I believe they installed a smaller pulley on the Gen 4 ACR from the factory. Does anyone know if that is true? I also insulated all lines running near the headers with DEI Cool Tube Extreme. By the way, the under-drive pulley appeared to have no impact on charging voltage or anything else during normal driving.

Car went in for service today to replace the pedal assembly. Once it is fixed I have to get back to the track for some testing.

Pulley part numbers are the same for the ACR and regular Vipers 08-10 5037204AB

I hope the pulley helps your issue George, it definitely cannot hurt.

[FLATOUT]

George I am running the IPSCO underdrive pulley on my 15 and also ran it on my 14 TA. I wonder if that did contribute to my lower track temps. As Mark J mentioned below keep us posted.

Andy



Mark of IPSCO installed one of his under-drive pulleys on my TA yesterday. Beautiful product and highly recommended. Our thinking is to slow the water pump down some at high rpms to allow the water to stay in the radiator a little longer. We believe at high rpms the water is moving too quickly through the radiator to shed enough heat or the pump is cavitating at high speed. Either way the under-drive pulley should help. I believe they installed a smaller pulley on the Gen 4 ACR from the factory. Does anyone know if that is true? I also insulated all lines running near the headers with DEI Cool Tube Extreme. By the way, the under-drive pulley appeared to have no impact on charging voltage or anything else during normal driving.

Car went in for service today to replace the pedal assembly. Once it is fixed I have to get back to the track for some testing.

[BLUETA#1]

George I am running the IPSCO underdrive pulley on my 15 and also ran it on my 14 TA. I wonder if that did contribute to my lower track temps. As Mark J mentioned below keep us posted.

Andy

I was going to do that next….where can I get that part? You are correct…the water needs to slow down!

[FLATOUT]

I was going to do that next….where can I get that part? You are correct…the water needs to slow down!

http://www.ipsco.org

[TrackAire]

What thermostat temp settings do the ACRX cars use?

Since most peoples cars are not full on race cars staying at one specific rpm range, it would be difficult to design a flow restrictor that restricts flows enough water to keep in in the radiator long enough for a reduction in BTU's but flows enough to the motor for cooling at the wide range of street driven rpms a non full race Viper sees.

In other cars, I've always found that a 180 degree thermostat was ideal for track use and resultant lowered temps with just the right amount of flow, coolant time spent in the radiator and decent street performance by not running too cool.

I would guess that water pump cavitation might also be a culprit at higher rpms. Does the Viper thermostat have a spot where a small hole can be drilled to always allow for some flow to squeak by? This might help lessen cavitation.

Was the collapsing radiator hose question ever answered?....it does happen on a Gen 4 so I expect there is a chance it's happening on a Gen 5.

[ViperGeorge]

What thermostat temp settings do the ACRX cars use?

Since most peoples cars are not full on race cars staying at one specific rpm range, it would be difficult to design a flow restrictor that restricts flows enough water to keep in in the radiator long enough for a reduction in BTU's but flows enough to the motor for cooling at the wide range of street driven rpms a non full race Viper sees.

In other cars, I've always found that a 180 degree thermostat was ideal for track use and resultant lowered temps with just the right amount of flow, coolant time spent in the radiator and decent street performance by not running too cool.

I would guess that water pump cavitation might also be a culprit at higher rpms. Does the Viper thermostat have a spot where a small hole can be drilled to always allow for some flow to squeak by? This might help lessen cavitation.

Was the collapsing radiator hose question ever answered?....it does happen on a Gen 4 so I expect there is a chance it's happening on a Gen 5.

Dick Winkles does not recommend a cooler thermostat. He does recommend a higher pressure cap though. The collapsing hose issue though is a good point which has not been answered as far as I know.

[ViperGeorge]

Pulley part numbers are the same for the ACR and regular Vipers 08-10 5037204AB

I hope the pulley helps your issue George, it definitely cannot hurt.

I think it was actually the Comp Coupes that used a smaller pulley.

[Colo08]

Dick Winkles does not recommend a cooler thermostat. He does recommend a higher pressure cap though. The collapsing hose issue though is a good point which has not been answered as far as I know.

A spring in the hose will keep it from collapsing, and the under drive pulley was use by dodge on their Comp Coupes to help slow down the water pump.

[TrackAire]

Dick Winkles does not recommend a cooler thermostat. He does recommend a higher pressure cap though. The collapsing hose issue though is a good point which has not been answered as far as I know.

I remember seeing some talk of not using a lower thermostat for street cars since it will screw with the computer, but after the first hard lap, the temps will be above that threshold very quickly. The lower temp thermostat may not work on the street, but it is what it is. The key with using a slightly lower temp thermostat is getting better cooling by controlling the amount of coolant and how long it stays in the radiator for the heat exchange to occur. If the thermostat temp is too high, the water may be staying in the radiator too long and by the time it goes to the block/cylinders, they are damn hot and you get steam pockets, etc. It would seem to me that if data logging the temps and you see a continual rise in temps every lap, this could be the issue. If the load on the engine/vehicle stays the same lap after lap, then the temps should stabilize and not increase if the cooling system is functioning correctly. If they increase lap after lap, then there is not enough cooling or a defect in the cooling system.

The only way to find out if this works for a road course car is to try it......we may find that a 180 degree thermostat might make things worse, there is no way of knowing without actually running it. Every car I've ever tried it on for road course type events, it has helped keep the temps stable when replacing a 195 degree or higher thermostat.

[Bob Woodhouse]

Howdy 09, you probably already know this, but for those not aware, in your thread you mentioned an Arrow PCM and headers. More power, gotta love that, but one of the ways the modded pcm gets it is through reducing the WOT fuel and changing the ignition timing. The more conservative stock unit over fuels the engine slightly at WOT for cooling and of course the timing is a bit more conservative too. All this to insure the Viper masses don't melt a piston. Some of the heat you see might be related to that awesome PCM but lets not put a price on our fun, or for having the fastest lap for that matter. Thanks for sharing.

[mjorgensen]

I was going to do that next….where can I get that part? You are correct…the water needs to slow down!

I can also sell you the same pulley Karl.

[ViperGeorge]

I remember seeing some talk of not using a lower thermostat for street cars since it will screw with the computer, but after the first hard lap, the temps will be above that threshold very quickly. The lower temp thermostat may not work on the street, but it is what it is. The key with using a slightly lower temp thermostat is getting better cooling by controlling the amount of coolant and how long it stays in the radiator for the heat exchange to occur. If the thermostat temp is too high, the water may be staying in the radiator too long and by the time it goes to the block/cylinders, they are damn hot and you get steam pockets, etc. It would seem to me that if data logging the temps and you see a continual rise in temps every lap, this could be the issue. If the load on the engine/vehicle stays the same lap after lap, then the temps should stabilize and not increase if the cooling system is functioning correctly. If they increase lap after lap, then there is not enough cooling or a defect in the cooling system.

The only way to find out if this works for a road course car is to try it......we may find that a 180 degree thermostat might make things worse, there is no way of knowing without actually running it. Every car I've ever tried it on for road course type events, it has helped keep the temps stable when replacing a 195 degree or higher thermostat.

But once you are above the temp where the stock thermostat opens there should be no benefit since at 200+ both the stock thermostat and the 180 would be wide open. No?

[ViperGeorge]

Howdy 09, you probably already know this, but for those not aware, in your thread you mentioned an Arrow PCM and headers. More power, gotta love that, but one of the ways the modded pcm gets it is through reducing the WOT fuel and changing the ignition timing. The more conservative stock unit over fuels the engine slightly at WOT for cooling and of course the timing is a bit more conservative too. All this to insure the Viper masses don't melt a piston. Some of the heat you see might be related to that awesome PCM but lets not put a price on our fun, or for having the fastest lap for that matter. Thanks for sharing.

I wondered this as well but Dick Winkles says he does not think that is the problem. One of tests I have to perform is a back to back run with both PCMs to see what happens. Back to back with and without headers is too difficult to do.

[mjorgensen]

But once you are above the temp where the stock thermostat opens there should be no benefit since at 200+ both the stock thermostat and the 180 would be wide open. No?

Yep

[Bob Woodhouse]

What thermostat temp settings do the ACRX cars use?

Since most peoples cars are not full on race cars staying at one specific rpm range, it would be difficult to design a flow restrictor that restricts flows enough water to keep in in the radiator long enough for a reduction in BTU's but flows enough to the motor for cooling at the wide range of street driven rpms a non full race Viper sees.

In other cars, I've always found that a 180 degree thermostat was ideal for track use and resultant lowered temps with just the right amount of flow, coolant time spent in the radiator and decent street performance by not running too cool.

I would guess that water pump cavitation might also be a culprit at higher rpms. Does the Viper thermostat have a spot where a small hole can be drilled to always allow for some flow to squeak by? This might help lessen cavitation.

Was the collapsing radiator hose question ever answered?....it does happen on a Gen 4 so I expect there is a chance it's happening on a Gen 5.

Lets clear this up, thermostats open at a specified temp, 180, 190 etc. That is what they open at, well below the operating temperature in every case. Above that opening temperature, they all flow the same amount. Lets not get confused by the number thinking it will run cooler. To that point, pro race Comp Coupes ran with modified stat, basically we braised them in the open position but kept the housing for the proper restriction. Reliability was the purpose since on occasion a stat can bind partially open. If you question yours, put it in a pan on the stove and watch.

[Steve M]

Howdy 09, you probably already know this, but for those not aware, in your thread you mentioned an Arrow PCM and headers. More power, gotta love that, but one of the ways the modded pcm gets it is through reducing the WOT fuel and changing the ignition timing. The more conservative stock unit over fuels the engine slightly at WOT for cooling and of course the timing is a bit more conservative too. All this to insure the Viper masses don't melt a piston. Some of the heat you see might be related to that awesome PCM but lets not put a price on our fun, or for having the fastest lap for that matter. Thanks for sharing.

I'll say yes and no to this...it could potentially add heat, but there are still safety measures in place. If the car starts running a high engine coolant temp, the PCM will pull timing and add fuel. To me, this sounds like a flow restriction to the radiator of some sort. I've been wrong before though...the only way to rule out the PCM is to do a back-to-back comparison.

[TrackAire]

Yep

I think where some issues may come into effect is the term open and fully open. Many thermostats "fully" open 15 to 20 degrees higher than their rated temperature. As Mr Woodhouse pointed out, a lower temperature thermostat in itself will not magically make the vehicle run cooler but it is part of the entire cooling process in a street driven car that is tracked. As he pointed out in the Comp Coupes, thermostats were locked in the open position so they could not fail, but were left in place to create some flow restriction. Most cars will actually overheat if the thermostat is completely removed because the water flows too quick through the radiator at higher rpms. IMO, it is easier to set up a full on race car since you know your operating rpm range, the ability to manipulate air flow through the radiator and the average MPH speeds you'll be competing at. Without a lot of testing, it really is a crap shoot to believe that in a street driven Viper that the thermostat is fully wide open in all track conditions when you have to account for coolant flow in gpm, rpms, air flow, mph and ambient temps. This is before we even rate the stock thermostat to know what it does at specific temperatures, how fast it opens fully and how fast it closes based on temps.

This quote explains what I'm trying to convey best:

"The key to low-temp thermostat success is that coolant is allowed to flow more freely during low load sections of the racetrack, ensuring that the radiator is able to keep the engine within the optimal temperature range in the high-load sections of the track. So if you’re maxing out your cooling system at the racetrack and experiencing some overheating issues, for example, a low-temp thermostat will often solve this problem by letting the radiator work more at part-throttle lower engine loads and in the process delay or completely eliminate any overheating during wide-open throttle high-engine loads."

The thermostat is only part of the equation since everything must work in unison. I don't look at the thermostat as temperature control but more flow control that lets the radiator and air flow regulate and dissipate the BTU's created by the car. The challenge is most of us have street driven Vipers and we have to work around the PCM, stop and go driving, emissions, wear, etc. Even if the lower temp thermostat gives you only a 5% cooling advantage on the track, we still talking 12 degrees lower temps if you're regularly hitting 240 degrees. If my Viper is at 228 degrees, I'm not real concerned but once the temps hit 240, I start looking at the temp gauge more than the track, lol.

For the price of lower temp thermostat, it really is worth the experiment to see if it helps.

[BLUETA#1]

I just completed an interesting test with the hood vents. The slope in front of the vents are designed to create a negative pressure over the vents, that in turn sucks out the hot air.

I attached some tassels on the leading edge of the vents and drove the car. I observed the height of the tassels as I drove. Some tassels even laid flat on the vents as I drove 90 mph!!

I removed the vents, (not easy!) and I drove the same road, same speed. ALL of the tassels were higher. In other words, the vents reduce the negative pressure coming out of the engine bay! Good bye vents.

Water Wetter and a higher pressure cap helped a bit I was not expecting a lot. The temp took longer to spike with the water wetter. I went with the competition cap to give me some margin of error.

Before the next event, the front grill comes off and I have aluminum racers tape to seal off the air leakage at the sides of the radiator. I am doing one thing at a time.

[darbgnik]

I've got a water wetter question. When I added water wetter to my old Gen 3 before a track event, the coolant expanded so much it came out of the overflow, and it was not overfilled to start. Anyone else ever notice this?

[LmeaViper]

Pulley part numbers are the same for the ACR and regular Vipers 08-10 5037204AB

I hope the pulley helps your issue George, it definitely cannot hurt.

I take it one would then need a different belt size? Or is this not the case?

[SSGNRDZ_28]

Could this be as simple as coolant / water ratio? Maybe try thinning out the coolant with distilled water to 70/30? Is the factory ratio 50/50?

http://www.challengers101.com/CoolantMix.html

[WDW MKR]

Mark of IPSCO installed one of his under-drive pulleys on my TA yesterday. Beautiful product and highly recommended. Our thinking is to slow the water pump down some at high rpms to allow the water to stay in the radiator a little longer. We believe at high rpms the water is moving too quickly through the radiator to shed enough heat or the pump is cavitating at high speed. Either way the under-drive pulley should help. I believe they installed a smaller pulley on the Gen 4 ACR from the factory. Does anyone know if that is true? I also insulated all lines running near the headers with DEI Cool Tube Extreme. By the way, the under-drive pulley appeared to have no impact on charging voltage or anything else during normal driving.

Car went in for service today to replace the pedal assembly. Once it is fixed I have to get back to the track for some testing.

You might be onto something with the cavitation... I don't have any first-hand experience with the GEN V to say either way. I can say that the "more time in the radiator" theory is inaccurate. Heat transfer in a closed loop system is proportional to flow rate: more flow is more cooling until you either create excessive pressure drop or capitate the pump. Attempting to "hold" the fluid in the radiator longer to cool more does the inverse to the upstream fluid that is still inside the engine... it's all the same volume of fluid making a repeat trip.

[TrackAire]

Could this be as simple as coolant / water ratio? Maybe try thinning out the coolant with distilled water to 70/30? Is the factory ratio 50/50?

http://www.challengers101.com/CoolantMix.html

Do you think that there is a chance that the coolant that came from the factory has the wrong ratio (not 50/50)? I wonder if whoever does the fill of the coolant measures it out water to antifreeze or does it come pre-diluted from the antifreeze manufacturer?

Isn't there a test you can do for antifreeze concentration using a hydrometer? Crazy if we find out some Gen 5's are coming from the factory with more antifreeze than water.

[XSnake]

I just found out this weekend that Motul makes a coolant additive as well. Friend used it this weekend at the track and it helped with his coolant temps on his Lambo. Motul Mo Cool

[ViperGeorge]

I take it one would then need a different belt size? Or is this not the case?

No, same belt size. The tensioner takes up the slack.

[ViperGeorge]

You might be onto something with the cavitation... I don't have any first-hand experience with the GEN V to say either way. I can say that the "more time in the radiator" theory is inaccurate. Heat transfer in a closed loop system is proportional to flow rate: more flow is more cooling until you either create excessive pressure drop or capitate the pump. Attempting to "hold" the fluid in the radiator longer to cool more does the inverse to the upstream fluid that is still inside the engine... it's all the same volume of fluid making a repeat trip.

We'll have to see if the under drive pulley helps. Car is being serviced and then I have to get back to the track. The "hold" the fluid in the radiator longer theory comes from some folks that have had this problem on other cars where slowing the trip helped. Maybe those cars were having cavitation problems which under drive pulleys helped. Either way a test is in order.

I also still wonder about the collapsing hose issue that someone mentioned. There were videos of Gen 4's doing this but I don't know if a Gen 5 does it and what the effect would be.

[Jack B]

50/50 does not give you max cooling


Do you think that there is a chance that the coolant that came from the factory has the wrong ratio (not 50/50)? I wonder if whoever does the fill of the coolant measures it out water to antifreeze or does it come pre-diluted from the antifreeze manufacturer?

Isn't there a test you can do for antifreeze concentration using a hydrometer? Crazy if we find out some Gen 5's are coming from the factory with more antifreeze than water.

[Rapidrezults]

I will be at Thunderhill on Friday in what's looking like 95-98 degree temperatures. I will keep a close eye on my temps and report back. I will even exaggerate my gear selection to see if I can get the temps to rise.

Again, Arrow PCM, Octane Boost. No headers.

[ViperGeorge]

I will be at Thunderhill on Friday in what's looking like 95-98 degree temperatures. I will keep a close eye on my temps and report back. I will even exaggerate my gear selection to see if I can get the temps to rise.

Again, Arrow PCM, Octane Boost. No headers.

Thanks. I was running a mix of 91 and 100 octane at the track last time. Probably averaged to about 94-95.

[TrackAire]

50/50 does not give you max cooling

No it does not, but I'm thinking that what generally comes in the cars from the factory. But what if the antifreeze is 70% and the water 30% and the owner tracking his Viper has no idea?

The 70% antifreeze to 30% water is commonly done by shops that are located in cold parts of the USA. It would be very interesting to see some Gen 5 owners pull samples with a hydrometer to see what the coolant concentrations are.

If somebody at Conner has the job of mixing antifreeze and water, are they getting in 50/50 or are the ratio's drastically off?? Only a quick basic test can answer that question.

[SSGNRDZ_28]

Do you think that there is a chance that the coolant that came from the factory has the wrong ratio (not 50/50)? I wonder if whoever does the fill of the coolant measures it out water to antifreeze or does it come pre-diluted from the antifreeze manufacturer?

Isn't there a test you can do for antifreeze concentration using a hydrometer? Crazy if we find out some Gen 5's are coming from the factory with more antifreeze than water.

Here's a simple tester (there are more expensive ones as well). Would be interesting to know percentages of the cars in question and if there is any variance car to car from the factory.

Increasing the water ratio (to ~70/30) would cool the car down (and raise the freezing point but who cares on a Viper)

http://www.amazon.com/Fahrenheit-Ade-Advanced-Optics-Refractometer/dp/B0089EEWYE/ref=pd_cp_469_2?ie=UTF8&refRID=0Z40VBA5R2ZV6BECZP4H

[mjorgensen]

I have been looking back through all the pictures I took of both of these 2.0's and they BOTH have the small deflector flaps in front of the front tires. It has been stated in the past that they are not supposed to be put on at the factory when the splitters are being used. I would take them off and see if it helps. If you look straight on the way the splitter intersects with the flap and then the up flow trough built into the front under tray you can see how the air is supposed to flow up into the area that would feed straight to the headers. This path is totally disrupted with the flap in place AND the splitters front inside edge that would cause turbulence right when that air should be flowing smoothly to that area. It can't hurt to take them off and see. The 2.0 splitter would trap even more air and channel it to the center of the fascia rather then allowing it up this "chute" then the 1.0 splitter would, maybe that is the difference and why we have not seen this earlier???

12666
12667
12668

[TrackAire]

I will be at Thunderhill on Friday in what's looking like 95-98 degree temperatures. I will keep a close eye on my temps and report back. I will even exaggerate my gear selection to see if I can get the temps to rise.

Again, Arrow PCM, Octane Boost. No headers.

I think you're going to find that rpm's is what ultimately makes the car get hotter. Run it closer to the red line for a couple of laps to see what effect it has on temps. I just don't think our street cars are efficient when kept at max rpm's for lap after lap. Shifting even 400 or 500 rpm sooner will make the biggest difference in lowering the coolant temps (just my guess)

The Mustang we went around the track in would get to 250 degrees at Thunderhill on a high 90 degree ambient day after 5 or 6 laps. The day we went out, the data logger never showed more than 211 degrees (I think the ambient temps were in the low 90's or high 80's that day) That's how much difference the cooling mods made on that car. Even on a 100 plus degree day, temps never get over 216 degrees. And I rev the heck out of it.

But when I drove the car to Sonoma for the Shelby Club event last week, coolant temps stayed at 168 to 170 degrees anytime I was over 40 mph. Way too cold for engine longevity, etc IMO. And that was with a 180 degree thermostat. Getting stuck in traffic on the way home, temps were approaching 200 degrees. The crazy thing is, the stock electric cooling fans don't come on until you hit 217 degrees, lol. Modern cars just run hotter by design.

[stradman]

Hi Guys, sorry to resurrect thread however I just wanted to see if there is any different opinions formed about oil temps since this thread was created 2 years ago. I must say, I did a couple of track days last weekend and with outside temps about 85 degrees, found that on some hard laps along with high revs due to some very tight corners requiring downshifting etc, the oil temp did creep up to 255 degrees. Coolant did go up to 220/225. It quickly came down again in the cool down lap. And really no problem with the car at all. I'm running Motul 300V oil. Just wanted to hear if there are any other thoughts from the regular track guys.Cheers

[ViperGeorge]

Hi Guys, sorry to resurrect thread however I just wanted to see if there is any different opinions formed about oil temps since this thread was created 2 years ago. I must say, I did a couple of track days last weekend and with outside temps about 85 degrees, found that on some hard laps along with high revs due to some very tight corners requiring downshifting etc, the oil temp did creep up to 255 degrees. Coolant did go up to 220/225. It quickly came down again in the cool down lap. And really no problem with the car at all. I'm running Motul 300V oil. Just wanted to hear if there are any other thoughts from the regular track guys.Cheers

My TA 2.0 would run hot with Mobil 1 15/50, water wetter, underdrive pulley, Arrow PCM, Bellanger headers, and high flow cats. 243 coolant, 265 oil. My new ACR does not seem to get nearly as hot. My guess is that the track extension on the ACR-E pushes more air through the radiator. Just a guess though.

[Arizona Vipers]

Hi Guys, sorry to resurrect thread however I just wanted to see if there is any different opinions formed about oil temps since this thread was created 2 years ago. I must say, I did a couple of track days last weekend and with outside temps about 85 degrees, found that on some hard laps along with high revs due to some very tight corners requiring downshifting etc, the oil temp did creep up to 255 degrees. Coolant did go up to 220/225. It quickly came down again in the cool down lap. And really no problem with the car at all. I'm running Motul 300V oil. Just wanted to hear if there are any other thoughts from the regular track guys.Cheers

225 coolant and 255 oil is fine.

[docwviper]

Can you post a video of a lap or two that caused the excessive heat? As fast as you are running at COTA I would like to see and hear what looks like on the car when these temps are jumping up on the car.

Andy

I agree with some of the others. I have a racelogic Vbox setup in my car and I've put in the engine temp to appear on screen with all my other metrics such as air intake temp. It will be a little bit before I'm at the track but I'll post. Maybe its my driving style but I'm experiencing what others are as well.

[Nemesis]

I believe one of the large culprits here is driving style, I think there are some who are running the car to red line every shift, and that isn't optimal because you are beyond the peak of the torque curve and only generating additional unneeded heat in the engine.

[stradman]

I believe one of the large culprits here is driving style, I think there are some who are running the car to red line every shift, and that isn't optimal because you are beyond the peak of the torque curve and only generating additional unneeded heat in the engine.

Yes I agree to an extent. Caning the car to an inch of its life doesn't help with heat. Although its fun....; )

[Nemesis]

Yes it is fun, but it is not getting you down the track any faster.


Yes I agree to an extent. Caning the car to an inch of its life doesn't help with heat. Although its fun....; )

[ViperGeorge]

I believe one of the large culprits here is driving style, I think there are some who are running the car to red line every shift, and that isn't optimal because you are beyond the peak of the torque curve and only generating additional unneeded heat in the engine.

This is a good point. At what RPM does torque peak? I should reset my Raptor shift light to get me to shift earlier.

[PkB2014]

I believe one of the large culprits here is driving style, I think there are some who are running the car to red line every shift, and that isn't optimal because you are beyond the peak of the torque curve and only generating additional unneeded heat in the engine.

Peak HP comes right before redline @6200 RPM, but torque is at 5000RPM. So you are saying we should be shifting closer to 5000 instead of 6200? What would be optimal shift point as to not fall too low below peak RPM on shift? Based on the gear ratios, 5700 RPM or so looks like a good choice since it would only drop you down around 4500 RPM on upshift.

[ViperSRT]

If you are trying to accelerate at the maximum you need to maximize the area under the power curve. With Gen 5 peak power happening up high that means shifts just before fuel shut off. The torque argument only works if you multiply the torque by gear ratio to get thrust for each gear and then optimize for maximum thrust (which will be essentially the same as maximum power).

[stradman]

If you are trying to accelerate at the maximum you need to maximize the area under the power curve. With Gen 5 peak power happening up high that means shifts just before fuel shut off. The torque argument only works if you multiply the torque by gear ratio to get thrust for each gear and then optimize for maximum thrust (which will be essentially the same as maximum power).
So red lining it is then?!

[donk_316]

You guys should also list what front aero you have. TA1 TA2 ACR or nothing. There was a thought that the splitters could be helping with cooling

[Bruce H.]

While upshifting a little early definitely generates less heat, the ideal shift points to maximize acceleration will be determined by maximum torque at the wheels in the various gears. That factors both engine peak torque and gear ratios. Consider the torque multiplying effect of the transmission, and that wheel torque in 3rd gear at redline rpm is likely greater than it is in 4th gear at the engine's peak torque rpm. When you shift early you are throwing away the lower gear's gearing advantage.

[Arizona Vipers]

While upshifting a little early definitely generates less heat, the ideal shift points to maximize acceleration will be determined by maximum torque at the wheels in the various gears. That factors both engine peak torque and gear ratios. Consider the torque multiplying effect of the transmission, and that wheel torque in 3rd gear at redline rpm is likely greater than it is in 4th gear at the engine's peak torque rpm. When you shift early you are throwing away the lower gear's gearing advantage.

This. ↑↑↑↑↑ Not to mention you will lose 80-85 horsepower on a Gen 5 shifting at 5K RPM's versus 6K RPM.
Talk to any fast road racer or drag racing on here and none of them shift the car at 5400RPM. Nobody pushing a car to drive as fast as it can go will ever shift at torque peak vs redline.
The Gen 5 does NOT require you to short shift the car to keep it from overheating. I beat the shit out of my ACR and it never goes over 220*
This is why every modern car built with paddle shifters, shifts at redline, not at torque peak or it would lose at least 15% of it's peak horsepower, not even considering the rear wheel torque lost from gear ratios.
A Gen 5's torque peak is around 5400 RPM's., about 490 ft/lbs at the wheels, about 495 horsepower.
At 6300K RPM's, the same motor is making 460 ft/lbs, but 550 rwhp ( HP = Torque x RPM ÷ 5252 ) If you shift at 5400 RPM, you have a 570hp Viper, not a 645 hp Viper.
As soon as you shift from 2nd gear to 3rd gear for example, you lose lose 24.7% of your rear wheel torque at RPM vs RPM (2nd gear ratio is 1.58 vs 1.19 3rd gear)
You can go 90mph in 2nd gear, the fastest way to 90mph is in 2nd gear, not shifting to 3rd gear early. You can go 119 in 3rd gear. The fastest way to 119mph is redlining 3rd gear, not shifting early to 4th.
If anyone's car here is overheating because you drive the car to redline, you've got other problems going on.
Watch this video of me breaking the Nasa TT1 record at WHP Main track and you can see I'm in 2nd gear the entire track except the long straight and my car never goes over 200*
https://www.youtube.com/watch?v=c3aQoa2XmwA
My lap times were MUCH slower shifting into 3rd gear.

[ek1]

I am not an expert by any means, but just an observation - shifting at near the redline definitely affects temps. I just started shifting more aggressively and using lower gears to power out of turns and I am seeing oil temps in the 225-235 range on a regular basis in the end of the session, with ambient temps of about 70F.

[Arizona Vipers]

I am not an expert by any means, but just an observation - shifting at near the redline definitely affects temps. I just started shifting more aggressively and using lower gears to power out of turns and I am seeing oil temps in the 225-235 range on a regular basis in the end of the session, with ambient temps of about 70F.

Yep. The more horsepower you generate the more heat you generate. 235 oil temp is normal on a track, as you get faster you'll see it go a lot higher. Anything under 270 is fine. The C7's out at the track are all running near or over 300.