Track Day Temps

[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]

Attachment 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.

030.jpg
031.jpg

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

GTSR cooling.jpg
GTSR cooling 2.jpg

[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.

030.jpg
031.jpg

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

GTSR cooling.jpg
GTSR cooling 2.jpg

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.