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Track Time Limited due to High CHT

TeeLew

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Thought I had it concurred! Either the abnormal load at Nelson’s or ambients over 80F seem to be my problem area.
As opposed to insufficient cooling capacity? 80*F is no big deal. Nelson Ledges is not a particularly taxing track to the cooling system.

When you make a lot of power, you must reject a lot of heat. Keeping a powerful car cool on a racetrack is no trivial task.
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When you make a lot of power, you must reject a lot of heat. Keeping a powerful car cool on a racetrack is no trivial task.
One of the biggest differences between street and track.
 

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As opposed to insufficient cooling capacity? 80*F is no big deal. Nelson Ledges is not a particularly taxing track to the cooling system.

When you make a lot of power, you must reject a lot of heat. Keeping a powerful car cool on a racetrack is no trivial task.
I figured a 90%+ boxed in Mishimoto radiator, separated oil cooling, & full RaceLouvers was sufficient--and it is if you want to lap at 9-9.5/10.

At 9.5/10+ when you're trying to feed your fragile ego by hanging with the turbo s2k on slicks and the caged Z06 is where the problem crops up for me.

I do think Nelsons is a little harder on the cooling system that you give it credit--that track is an ass pile of time with the skinny pedal near or on floor and very little time on the binders.
 

TeeLew

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I figured a 90%+ boxed in Mishimoto radiator, separated oil cooling, & full RaceLouvers was sufficient--and it is if you want to lap at 9-9.5/10.

At 9.5/10+ when you're trying to feed your fragile ego by hanging with the turbo s2k on slicks and the caged Z06 is where the problem crops up for me.

I do think Nelsons is a little harder on the cooling system that you give it credit--that track is an ass pile of time with the skinny pedal near or on floor and very little time on the binders.
"Sufficient" based on what metric? Hitting limp-mode is not a good gauge. When running Coyote engines competitively, the optimum operating temp for water is 185 deg. You're running 65-75 degrees OVER optimum.

Running hard makes it worse, but you weren't in hot conditions. In July or August, you're running 3-4 laps before pulling in.

Mid-O is worse for cooling than Nelson, specifically because you only get 1 of those high-speed runs. At Mid-O, you're constantly running slow and turning through the whole back section. Limiting the airflow is a bigger deal than running full throttle with plenty of cooling air. Long straights are where your boxing efforts really help.
 

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"Sufficient" based on what metric? Hitting limp-mode is not a good gauge. When running Coyote engines competitively, the optimum operating temp for water is 185 deg. You're running 65-75 degrees OVER optimum.

Running hard makes it worse, but you weren't in hot conditions. In July or August, you're running 3-4 laps before pulling in.

Mid-O is worse for cooling than Nelson, specifically because you only get 1 of those high-speed runs. At Mid-O, you're constantly running slow and turning through the whole back section. Limiting the airflow is a bigger deal than running full throttle with plenty of cooling air. Long straights are where your boxing efforts really help.
I think youre mistaking CHT for ECT when referencing acceptable temps. If you can keep CHT down to 180-190 on a street car with a condenser, I want to know how you get it done.

I am going to install an aftermarket ECT gauge.

Your theory sounds good on track comparisons, but I'm seeing higher temps at Nelsons than Mid O and I've got the rad pretty well boxed.
 

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TeeLew

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Nevermind, run WTF you want. It's not my problem.
 
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67Fast_V

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I thought I would share my recent experiences with the group.

My cooling mods so far:
1. 3-row radiator (SVE or Mishi- I can't remember now)
2. Opened up the grill as much as possible
3. Tracspec louvers (sides)
4. Boxed in the radiator approximately 90%
5. Harrop style air to oil cooler

#4 & 5 I did recently since my last track day where I was still hitting CHT limp mode by lap 3. My setup is further complicated due to the stage 2 Whipple with an oversized heat exchanger.

Today I had a track day at MSR in Cresson. Ambient temps were low 90's most of the day.
In session 1, CHT never went past 235*, Session 2 I got up 250*, Sessions 3 & 4 spent most of the time around 250* but there was a moment on the front stretch where I got up to 259* but once I hit the twisty bits it cooled down to 248*. Session 5 I got up to 263*. I didn't have much of a cool down between session 4 and 5 so I think that contributed. The air to oil cooler and the boxing I did helped out so that I got some complete sessions. I never hit limp mode but I am still not comfortable with those temps and I am still short-shifting. I think that my last move is to go with a center vent.
Thanks for the update, ZPD. Those are some very sporty CHTs and I thought mine were unmanageable. I think you win that category, unfortunately. Just a few thoughts and questions for you to help, potentially.

I don't have any info on that radiator. If you want to provide the size of tubes (width, 0.75"? & height, 0.080"?, etc), tube length, number of tubes, and fin density (fins per linear inch), I can compare it to other radiators and provide feedback.

Is your grille an aftermarket variety or OEM modified? How much did you increase the grille opening area from stock? Any idea on the size (total area)? I know this is tedious to sort, but if you can provide some numbers I can compare it to what I have done and provide feedback.

You will definitely need the hood vent area with a big grill, so adding center makes sense. Unfortunately it will not solve the issue ... but will help and is worth doing.

How confident are you that you are sealed up 90%? I only ask because I missed massive front leaks the 2nd time going through it. Like 50in^2. It was the 3rd time that I finally saw them. There are all sorts of tricky leak areas in the front. The interface between the front facia bumper cover and the mating geometry is a mess when those bits come together. Wide open areas. Flow will go through the front frame bar and run out the ends as an example. Just something to think about.

I like that oil cooler location. If I was to install an aftermarket oil cooler, I would locate it there. What are your oil temps? Just curious how these compare to the normal 285-295F.

And finally, having an intercooler and boost and hp to go w/ it, makes it much more difficult to cool. If you are making say 650 hp at the crank, that's 40% more cooling you will need over a stock NA engine. Plus that extra big intercooler is going to make it more taxing (higher air temp that the radiator sees). Maybe you want to think about pull back some boost, run E85 if not already, and run some water spray misters like Flyhalf has done. Just some suggestion.
 
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67Fast_V

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Whelp I’m back to drawing board… ran Nelson’s over the weekend. 85f ambient and sunny. High speed high load course. Running 305 re71r hitting 235 cht which seems to be the magic number to begin derate. It’s also when calculated oil temp gets to “warm”. Up to 234 if it’s derating anything I can’t tell. There’s no warning on dash you can just tell it’s pulling back the reins.

It only does this when I’m really pushing it like 9.5+/10ths.

Gonna try going to distilled water water wetter and spend more time getting the radiator fully boxed close to 100%.

Seems like I’m right on the edge like I just back out a hair and it cools back down in seconds and removes derate.

Thought I had it concurred! Either the abnormal load at Nelson’s or ambients over 80F seem to be my problem area.
I know what you mean, running hard makes a big difference to the heat load that must be rejected. Spending time sealing makes good sense. The water wetter won't help you though, unfortunately.

The cooling issue that we have is not on the water side but on the air side of the radiator. Can't get rid of the heat. What we need is more airflow through the radiator or more radiator surface area. So your additional sealing will drive more air through the radiator and hence will help address the issue.

Can't remember if you have an aftermarket or modified grille. If not, that will give you a nice reduction in temps and likely enough for you to run full tilt at Nelson based on the current 235F as the starting point.

Did you ever get your oil temps measured? Curious what you are running. Cheers.
 

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I know what you mean, running hard makes a big difference to the heat load that must be rejected. Spending time sealing makes good sense. The water wetter won't help you though, unfortunately.

The cooling issue that we have is not on the water side but on the air side of the radiator. Can't get rid of the heat. What we need is more airflow through the radiator or more radiator surface area. So your additional sealing will drive more air through the radiator and hence will help address the issue.

Can't remember if you have an aftermarket or modified grille. If not, that will give you a nice reduction in temps and likely enough for you to run full tilt at Nelson based on the current 235F as the starting point.

Did you ever get your oil temps measured? Curious what you are running. Cheers.
Never got to gauges. Gonna try again this weekend. Pitt race next weekend hopefully to test.

Will get artistic with the aluminum tape on the air inlet ducting while I have the bumper off as well. Didn’t think about capping crash bumper.

I’ve seen marginal improvement switching to higher distilled concentration in past so will drain and add % distilled

Hopefully have ect, oil temp, oil pressure, trans temp and diff temps at pittrace

In the past I’ve found a sweet spot on radiator opening. You want laminar flow through ducting and into radiator as much as possible. Wide ass opening into radiator just moves turbulence to radiator and reduces effectiveness unless you can get it all out.

Other thought I’ve pondered is eliminate the shoud and add two fans. My daily use is not bumper to bumper traffic at 105 ambient. That shroud looks highly restrictive at speed.
 

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67Fast_V

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Never got to gauges. Gonna try again this weekend. Pitt race next weekend hopefully to test.

Will get artistic with the aluminum tape on the air inlet ducting while I have the bumper off as well. Didn’t think about capping crash bumper.

I’ve seen marginal improvement switching to higher distilled concentration in past so will drain and add % distilled

Hopefully have ect, oil temp, oil pressure, trans temp and diff temps at pittrace

In the past I’ve found a sweet spot on radiator opening. You want laminar flow through ducting and into radiator as much as possible. Wide ass opening into radiator just moves turbulence to radiator and reduces effectiveness unless you can get it all out.

Other thought I’ve pondered is eliminate the shoud and add two fans. My daily use is not bumper to bumper traffic at 105 ambient. That shroud looks highly restrictive at speed.
Roger that. Can't go wrong w/ instrumentation.

When you get the tape out and bumper cover off, take a look at the rubber boots on the far left and right side. There are big gaps around the perimeter of the boot that seals around the grill inserts when the bumper cover goes on. Hard to explain but i'm sure you know what I'm talking about. The rubber boots have missing sections and doesn't seal well. Thumb size gaps around the perimeter. About 10 in^2 wide open gap. Ugly and painful to seal.

I made inserts to fill the gaps and then I reached in as far as I could underneath to seal it off w/ tape. Painful. And more pain to remove when it's time to remove the bumper cover again. But necessary for a good seal. Also there are passages inside the bumper cover that allow air to escape. Special covers/plates needed. If you start looking hard, you will find them.

Also the radiator top cover (8 push pin cover) doesn't seal well and there is a bunch of leaks around the hood latch panel (not to mention the previously discussed side leaks). Take a look. More pain to seal. Best time to seal some of this is w/ bumper cover off. Also I made a custom cover for the top of the radiator (~4" x ~26") which is under the OEM cover. So not relying on the OEM cover to do anything. It's all sealed under the cover.

On the fan shroud, yes this is 4th orifice and will be somewhat restrictive to flow. So good idea to open this up if you can. As mentioned, I gutted mine. Still have the OEM 2 fans. I put some aluminum brackets inside the shroud to isolate the fans. I need to work on posting some pics. My calculations show about a 5% increase in radiator flow w/ open fan shroud.

Well Good luck w/ the tape.
 

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Roger that. Can't go wrong w/ instrumentation.

When you get the tape out and bumper cover off, take a look at the rubber boots on the far left and right side. There are big gaps around the perimeter of the boot that seals around the grill inserts when the bumper cover goes on. Hard to explain but i'm sure you know what I'm talking about. The rubber boots have missing sections and doesn't seal well. Thumb size gaps around the perimeter. About 10 in^2 wide open gap. Ugly and painful to seal.

I made inserts to fill the gaps and then I reached in as far as I could underneath to seal it off w/ tape. Painful. And more pain to remove when it's time to remove the bumper cover again. But necessary for a good seal. Also there are passages inside the bumper cover that allow air to escape. Special covers/plates needed. If you start looking hard, you will find them.

Also the radiator top cover (8 push pin cover) doesn't seal well and there is a bunch of leaks around the hood latch panel (not to mention the previously discussed side leaks). Take a look. More pain to seal. Best time to seal some of this is w/ bumper cover off. Also I made a custom cover for the top of the radiator (~4" x ~26") which is under the OEM cover. So not relying on the OEM cover to do anything. It's all sealed under the cover.

On the fan shroud, yes this is 4th orifice and will be somewhat restrictive to flow. So good idea to open this up if you can. As mentioned, I gutted mine. Still have the OEM 2 fans. I put some aluminum brackets inside the shroud to isolate the fans. I need to work on posting some pics. My calculations show about a 5% increase in radiator flow w/ open fan shroud.

Well Good luck w/ the tape.
be great to see your artwork with the fan shroud. I started thinking along the same lines of just gut the crap out of the OEM shroud and keep the two fans.
 

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So how do you accomplish that 185F CHT?
The first thing that people have correctly pointed out is that cylinder head temp will be hotter than coolant temp. That's a legitimate point. I don't know what the difference is between head and coolant temp. I'm speaking about the cool side of the coolant when I'm talking about 185*. My guess is the head is no more than 20* hotter than the coolant, but take that number with a dash of salt. We need to find out for real.

I don't exactly know what it will take to accomplish proper engine temperatures, but this is what Porsche has to do to cool ~430 horsepower reliably on a racetrack in pretty much any condition.

PorscheCupCooling.jpg


and a picture (although slightly different model)...

csf-center-radiator.jpg


My guess is that this is what is going to be about what it takes to cool the car appropriately. Nobody wants to listen to me, because it's a complete pain in the ass to do this much work, but if you really want the car to run at it's best, this is probably the magnitude of job ahead. By all means, shoot the messenger.
 

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The first thing that people have correctly pointed out is that cylinder head temp will be hotter than coolant temp. That's a legitimate point. I don't know what the difference is between head and coolant temp. I'm speaking about the cool side of the coolant when I'm talking about 185*. My guess is the head is no more than 20* hotter than the coolant, but take that number with a dash of salt. We need to find out for real.

I don't exactly know what it will take to accomplish proper engine temperatures, but this is what Porsche has to do to cool ~430 horsepower reliably on a racetrack in pretty much any condition.

PorscheCupCooling.jpg


and a picture (although slightly different model)...

csf-center-radiator.jpg


My guess is that this is what is going to be about what it takes to cool the car appropriately. Nobody wants to listen to me, because it's a complete pain in the ass to do this much work, but if you really want the car to run at it's best, this is probably the magnitude of job ahead. By all means, shoot the messenger.
hey, thanks for the explanation, it really helps understand what exactly you are referring to. just my opinion - no need to get upset, we are all trying to figure out a collective solution, I don't feel that anyone is trying to ignore you, but that's just my view.

I'll wait for others comment on your numbers, as I only know that calculated coolant temp is usually 5-7 degrees Celcius below measured CHT, so it translates to around 24F delta at 200F CHT. However, I doubt that this calculation is for cool side of coolant and how much we could rely on it. I don't have an aftermarket coolant temp sensor.
 

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I’m gonna be lazy on this one. I have a hard time understanding the value in Ford’s strategy of using lots of calculated values. Speculating that it gives them a cost savings and some latitude in reporting values that help manage people’s reactions on both the high and low end of the scale.

Fine, I guess. But it feels like enthusiasts are left to chase their tales because the gauges are not dependable, literal values we can trust. The scene seems ripe for a vendor to produce a gauge and sensor package so we have a fair chance to understand the true operating parameters and the effect of any mods we make.
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