Track Time Limited due to High CHT

[NeverSatisfied]

Hi Never - to your point, I ran a calculation to determine the impact of shifting at 6500 rpm vs. 7200.

I have a little analysis I put together when I was trying to decide which tranny to get (A10 or M6). I took the Coyote torque and HP curves and basically simulated a run down a straight away (apex speed to max speed). I would average the torque and HP over that speed range as you would shift through the gears and compare doing that with a M6 vs. A10. All stock including tires. As you know, I picked the A10 as my horse.

For this shift point evaluation, I used 63-140 mph. So that's 3rd gear at the apex and shifting into 7th and topping out at 140 mph. Here are the results w/ no transmission or driveline losses included in either case. The magnitude is off since no losses are included but the relative difference between the shift points are valid. See below for the results. Better to shift higher if cooling allows. Cheers.

7200 rpm shift Point:
Ave Torque = 2044 ft-lbs
Ave Power = 454.6 hp

6500 rpm shift Point:
Ave Torque = 1948 ft-lbs (-4.7%)
Ave Power = 435.7 hp (-4.2%)

Credit to you for doing the work--it'd be interesting to look at the analysis over an entire lap.

In desperation as I was fighting through my issues a couple years ago, I spoke with Vorshlag about the 2018 they developed. They had the same heat generation challenges at 6500+. They found short shifting at times to stay closer to torque peak resulted in faster laps for them and significantly less heat problems in their 6MT.

I still ripped mine to 7250 for every shift once I had it loaded up with coolers and vents.

 

[Egparson202]

Question is how much of this difference and we are talking 20 hp here is going to be lost because of overheating. Also last time I checked Coyotes are not making linear power all the way to red line anyway or at least mine Gen 2 don't make much power after 6500 rpm anyway.

Good counter-point.

The surest way to solve this riddle is to break out the stop watch. That’s right, folks. Calculations are a great place to start. But as my uncle was fond of saying, the stop watch doesn’t lie. Who’s up for a little experimentation?

 

[MandoGt350R]

No, different design but similar and serve the same purpose.
Race Louvers does wind tunnel test their vents so the numbers they claim are factual.

Thank you. Guess I'll look to get these.

 

[67Fast_V]

Credit to you for doing the work--it'd be interesting to look at the analysis over an entire lap.

In desperation as I was fighting through my issues a couple years ago, I spoke with Vorshlag about the 2018 they developed. They had the same heat generation challenges at 6500+. They found short shifting at times to stay closer to torque peak resulted in faster laps for them and significantly less heat problems in their 6MT.

I still ripped mine to 7250 for every shift once I had it loaded up with coolers and vents.

Thanks . I would be some work to do this for an entire lap, as every straight away is different. But I did estimate the dtime for this run, since its very close to the back straight on my local track. The calc shows 0.5 secs reduction in time shifting at 7200 rpm vs. 6500, when factoring in the difference in drag (higher speeds shifting at 7200 rpm). Glad to hear yours see some high rpm too .

This Sunday will be a good data point for me on cooling. However, Tamb is not cooperating. I want FL hot. But its going to be a chilly day in South FL. High of 77F, so that means I will have to scale/adjust the data.

 

[67Fast_V]

Good counter-point.

The surest way to solve this riddle is to break out the stop watch. That’s right, folks. Calculations are are great place to start. But as my uncle was fond of saying, the stop watch doesn’t lie. Who’s up for a little experimentation?

Hi EG - I agree that calculations go only so far, real data is better. But the calcs were good enough to help me make a decision on which tranny to go with. However, I do have some stop watch data to share, more by coincidence than anything else. See below.

Last month I ran Sebring and there was a 2020 GT PP2 car on the track in the same session as me. He was in front of me and I gained some ground on him leading up to the back straight. He was maybe 4-5 cars in front of me at the apex leading on to the back straight.

About 2/3 the way down, I had to lift to avoid getting too close to him. I closed the gap pretty quickly and then backed-off. My car was most certainly quicker than his. And believe me, it has nothing to do with my driving or any skill I might have which is not much. Plainly, it was all car. My A10 vs his M6. I just push the gas down and pull a lever. Not hard. Now his driving or shifting could of been off, but it wasn't obvious. But there is a kicker to this real life "stop watch" comparison.

I was running 240-250 CHT at that time in my lap and the engine computer would not let me shift at 7000 rpm. I would have to go into my data recorder to find the time and get the exact temp and rpm. But it wasn't pretty (likely shifted at 6200-6500). The guy was holding me up after that and would not let me pass him. I was quicker, even with temp issues. I gave up on the session and even let Miata's pass me. Was frustrating but it's just for fun. I was going to talk to him afterwards but didn't bother. It really wasn't important.

Well he found me at the end of the event and apologized and we chatted a bit. He knew I was quicker and that he held me up. Nice guy though and we had a laugh about the incident. No big deal. And then he gave me some interesting tid bits.

He told me what his car is ('20 PP2), as I didn't know at the time when I was on the track w/ him. He also told me that he installed a cold air box and modified the exhaust system. So his PP2 is not stock where I'm 100% stock except for SRF and wrapped exhaust pipes for the rear diff. And yes, I even have the stock crappy brake pads which have to go soon. What's also interesting is that he didn't overheat the coolant or oil. Not sure about the diff. Didn't ask.

Summary:
Stock '20 A10 PP1 with ~245 CHT had to lift on a '20 M6 PP2 w/ mods. Nothing to do w/ driver or any skill difference.

Conclusion: The A10 is impressive, both in performance ... and in overheating

 

[bnightstar]

Good counter-point.

The surest way to solve this riddle is to break out the stop watch. That’s right, folks. Calculations are a great place to start. But as my uncle was fond of saying, the stop watch doesn’t lie. Who’s up for a little experimentation?

to be fair I did test it and after first lap on my local 2 km long track the pulled timing from high CHT (230f) is causing a drop in lap times by 0.3 seconds it's not that big of a deal if you are just out to have fun much bigger deal if you are out to win Time Attack Events.

 

[bnightstar]

Summary:
Stock '20 A10 PP1 with ~245 CHT had to lift on a '20 M6 PP2 w/ mods. Nothing to do w/ driver or any skill difference.

Conclusion: The A10 is impressive, both in performance ... and in overheating

You have like what 2 up changes in an MT car in a straight you can loose up to 0.5 secs doing 1 change if you don't do it fast enough or good enough. So this anecdote proves nothing because you can't be sure how the other driver change gears and we know A10 is faster in a straight line like 1 second on a 1/4 mile or so. and 0.5 seconds 0-60 so this is not a surprise. Biggest question is who can do more laps faster so if you and a PP2 car get out on track and race for let's say 10 laps what will be the real difference in times and not math wise because math can't calculate which will overheat faster and what the drop in times will be. Overall A10 is great trans for sure much faster in straight line but we know that Auto's are faster shifting then MT's now it's not new info.

 

[Egparson202]

Good conversation here. And more than one point to consider it seems. There’s the A10 vs M6 topic and comparisons for sure. The specific comparison I was suggesting is to capture lap times using different shift points. Ideally in the same session, but certainly throughout an event. With traffic and changing conditions it isn’t always possible to get clean data, but it’s an important tool if we want to cut our lap times. We may find a particular approach is faster or slower than we thought. The key is that we are better positioned to make objective comparisons against the stopwatch. If you have the benefit of some modest data acquisition that captures segments it becomes pretty easy.

So, for example, we could objectively answer questions like: what are the optimal real world shift points for lap time? Staying within mechanical safety margins? Accounting for weather?

 

[67Fast_V]

Good conversation here. And more than one point to consider it seems. There’s the A10 vs M6 topic and comparisons for sure. The specific comparison I was suggesting is to capture lap times using different shift points. Ideally in the same session, but certainly throughout an event. With traffic and changing conditions it isn’t always possible to get clean data, but it’s an important tool if we want to cut our lap times. We may find a particular approach is faster or slower than we thought. The key is that we are better positioned to make objective comparisons against the stopwatch. If you have the benefit of some modest data acquisition that captures segments it becomes pretty easy.

So, for example, we could objectively answer questions like: what are the optimal real world shift points for lap time? Staying within mechanical safety margins? Accounting for weather?

I understand. Let me do this. I have an event this Sunday and I will do a test specific to your point. The track has a long straight section where I can get up to 140 mph.

I will run some laps shifting at 6500 down that straight and then run some laps shifting at 7200 rpm. This is a good check for my calcs. I should get some clean laps with minimal traffic. Maybe 2-3 per session. I have a data recorder in the car with me to log all engine parameters available through the OBDII port. So I can look at the exact shift points and the time(duration) to travel down the straight or from say 60mph to 135. Easy comparison to do.

Lap time and even segment times (which I do have) are messy because of my driving inconsistencies, traffic, tires loosing grip, etc. But a delta down a straight should be easy to compare and of course that's where it comes into play in terms of improving lap time. The only pinch point is difference in engine temps, timing pull, ambient temp, etc. between the runs. I will have all the data recorded, so we can compare.

@bnight - I have the answer to your question. The stock to stock, the M6 wins everytime. I'm only good for 2 of your 10 laps and then I have to drive 3/4 throttle and shift at 5500rpm to make it through the other 8. However, this "limp" condition is only temporary. As others on the Forum have done, my plan is to "fix" the various systems so that I can run flat out for 25 mins. But it costs money, time, and not so easy to do. Goal of 238F max CHT which would be ~228F ECT ... something reasonable enough for WOT track conditions. Also oil at < 280F, trans at <230F, diff at < 270F. Can I achieve this.... 70% confidence. Others may say 0%.

 

[NeverSatisfied]

I understand. Let me do this. I have an event this Sunday and I will do a test specific to your point. The track has a long straight section where I can get up to 140 mph.

I will run some laps shifting at 6500 down that straight and then run some laps shifting at 7200 rpm. This is a good check for my calcs. I should get some clean laps with minimal traffic. Maybe 2-3 per session. I have a data recorder in the car with me to log all engine parameters available through the OBDII port. So I can look at the exact shift points and the time(duration) to travel down the straight or from say 60mph to 135. Easy comparison to do.

Lap time and even segment times (which I do have) are messy because of my driving inconsistencies, traffic, tires loosing grip, etc. But a delta down a straight should be easy to compare and of course that's where it comes into play in terms of improving lap time. The only pinch point is difference in engine temps, timing pull, ambient temp, etc. between the runs. I will have all the data recorded, so we can compare.

@bnight - I have the answer to your question. The stock to stock, the M6 wins everytime. I'm only good for 2 of your 10 laps and then I have to drive 3/4 throttle and shift at 5500rpm to make it through the other 8. However, this "limp" condition is only temporary. As others on the Forum have done, my plan is to "fix" the various systems so that I can run flat out for 25 mins. But it costs money, time, and not so easy to do. Goal of 238F max CHT which would be ~228F ECT ... something reasonable enough for WOT track conditions. Also oil at < 280F, trans at <230F, diff at < 270F. Can I achieve this.... 70% confidence. Others may say 0%.

I wonder if there's a happy medium of lower RPM shifts during the slower sections of the track where the gear spacing is closer to stay on the high end of the torque curve? Then winding it out on your longest straight where the gear spacing gets further apart in the higher gears?

Either way consistent lapping with some short shifting is way better than 2 hot laps followed by multiple laps of loafing. There's considerable speed to be had working on tightening the nut behind the wheel.

 

[bnightstar]

@bnight - I have the answer to your question. The stock to stock, the M6 wins everytime. I'm only good for 2 of your 10 laps and then I have to drive 3/4 throttle and shift at 5500rpm to make it through the other 8. However, this "limp" condition is only temporary. As others on the Forum have done, my plan is to "fix" the various systems so that I can run flat out for 25 mins. But it costs money, time, and not so easy to do. Goal of 238F max CHT which would be ~228F ECT ... something reasonable enough for WOT track conditions. Also oil at < 280F, trans at <230F, diff at < 270F. Can I achieve this.... 70% confidence. Others may say 0%.

To be fair my car is M6 and still has problems running long laps because of high CHT and pulled timing. And MT82 has it's own set of problems. My understanding regarding temepratures is 2 options if you want a daily get an Mach 1 it has all the cooling and aero build in so no need to worry to diff's there are still a problem. Or in GT do 3 pass radiator, race louvers, front grill delete and OIL Cooler as well as trans cooler and diff cooler and you should be good to go. I assume that eventually this coolers if not already available through FP will be available some time as most of the perf parts from GT350 and GT500 are can't see a reason why not for Mach 1. With that in mind some of the cooling options like cutting the hood for race louver vents is something that I don't want to do to my car. But this also is true for most other track modes. After all I want to use my car for daily driving as well.

 

[Egparson202]

I understand. Let me do this. I have an event this Sunday and I will do a test specific to your point. The track has a long straight section where I can get up to 140 mph.

I will run some laps shifting at 6500 down that straight and then run some laps shifting at 7200 rpm. This is a good check for my calcs. I should get some clean laps with minimal traffic. Maybe 2-3 per session. I have a data recorder in the car with me to log all engine parameters available through the OBDII port. So I can look at the exact shift points and the time(duration) to travel down the straight or from say 60mph to 135. Easy comparison to do.

Lap time and even segment times (which I do have) are messy because of my driving inconsistencies, traffic, tires loosing grip, etc. But a delta down a straight should be easy to compare and of course that's where it comes into play in terms of improving lap time. The only pinch point is difference in engine temps, timing pull, ambient temp, etc. between the runs. I will have all the data recorded, so we can compare.

I’ll also be on track this weekend with some long straights, so let’s both do it. My plan will be to start with a session made up of first half shifting 700-800 rpm short of redline and second half shifting at redline. Then maybe do a session the other way around. Together that may indicate which is quicker and how well the car recovers.

I plan to follow that up with full sessions dedicated to each of the techniques. At the end of Day 1, maybe the data will support a theory which can be validated on Day 2. If I get the weather I’m expecting, I may not learn a lot. It’s gonna be cool. But we’ll see what we can learn.

 

[ihasnostang]

i would love to see someone develop a horizontally mounted oil cooler underneath the car with a fan. You can only have so many heat exchangers on the front. Would be interesting to see with a thermister what kind of temps are after the rearmost heat exchanger.

concept: no clue how or where it would fit.

 

[67Fast_V]

I’ll also be on track this weekend with some long straights, so let’s both do it. My plan will be to start with a session made up of first half shifting 700-800 rpm short of redline and second half shifting at redline. Then maybe do a session the other way around. Together that may indicate which is quicker and how well the car recovers.

I plan to follow that up with full sessions dedicated to each of the techniques. At the end of Day 1, maybe the data will support a theory which can be validated on Day 2. If I get the weather I’m expecting, I may not learn a lot. It’s gonna be cool. But we’ll see what we can learn.

Sounds good, EG. I just have 1 day (4 sessions), so will do my best to keep the variables down. Will take some patience (and focus) to shift consistently at 6500, especially with 4 gear changes for each run. Sort of a side discussion but what I like best about the A10 is the ease of shifting under lateral load. I really struggled with that in my previous car (C7 Z06) and never did it well w/ 3 yrs on the track. Going straight is not an issue but shifting pulling 1.0g+ is tough in long high-speed sweepers. So hats off to those that can master that skill. Good luck this weekend. I assume you will be running the GT350. Cheers.

 

[67Fast_V]

To be fair my car is M6 and still has problems running long laps because of high CHT and pulled timing. And MT82 has it's own set of problems. My understanding regarding temepratures is 2 options if you want a daily get an Mach 1 it has all the cooling and aero build in so no need to worry to diff's there are still a problem. Or in GT do 3 pass radiator, race louvers, front grill delete and OIL Cooler as well as trans cooler and diff cooler and you should be good to go. I assume that eventually this coolers if not already available through FP will be available some time as most of the perf parts from GT350 and GT500 are can't see a reason why not for Mach 1. With that in mind some of the cooling options like cutting the hood for race louver vents is something that I don't want to do to my car. But this also is true for most other track modes. After all I want to use my car for daily driving as well.

Roger that. Cooling isn't easy, even on the M6. Thanks for sharing and the tips. Can't bite off the Mach 1 cost. Will give this PP1 a go for now. I don't like adding weight to an already too heavy car, so that is a very important consideration for me. So want to minimize adding coolers. For sure I will need a bigger trans cooler. I can do the heat transfer calcs and size everything up to get down to the target temps w/o adding to much No problem to install myself, except for the ten thousand details. I'm just getting started w/ the car and have a lot of data to gather. This will be an interesting project. I was just floored that the stock engine cooling was so bad. But hopefully the radiator sealing will address a big chunk of the problems I had last month.