Track Day Temps

[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...A5R2ZV6BECZP4H

[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???

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[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.