Cylinder Head Temps

[Angrey]

The hardcore track rats will see 235-250 intermittently but I wouldn't personally want to see anything higher than 235. You start to get into the risk zone of warping the heads.

IAT's and CHT's are connected, but not how being discussed. The IAT2 measurement is just prior to entering the heads and has more to do with how heat soaked the intercooler/exchanger system is and the temp of the air being drawn in and how much boost/pressure is being applied. A high IAT'2 will contribute to higher CHT, but the vast majority of what's driving the CHT is the combustion and cooling that you're receiving from the oiling/radiator system (meaning even if you have great IAT2's, it's only going to marginally help reduce high CHT's if the oil is hot and the engine coolant is hot and struggling to keep the heads cool).

Most of the tuning nanny protections are in the IAT2 temps because that's the more immediate threat to creating knock. The protections for the heads aren't as much for knock as they are for simply protecting permanent damage to warping the heads.

If you're getting high CHT's you should absolutely start with a bigger/better radiator and fan settings. Then take a look at the shrouding and trying to increase velocity across the radiator (there's an entire novel thread about this over in the GT350 section I think).

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[Unas2k5]

Highest I’ve seen on my car is 220s and my IATs are usually within 5 degrees of the outside temperature IIRC

 

[SpeedLu]

I have a Stage 2 Procharger with the PP1 radiator, and my cylinder heads regularly hover around 220° when I drive hard, but I am in Louisiana where it's extremely hot and humid. It only takes a few hard pulls to hit 230°. I've always wanted to run cooler but I'm not sure what else I can do without spending a bunch more money.

 

[Redfuzzbutt]

Potential stupid question. IAT2 is important to us to understand the effectiveness of the intercooler/heat exchanger for the PD guys, which has an obvious effect on HP.

However, IAT2's are only read by adding the additional sensor (in my case, the VMP). So, units without the ability to read the IAT2 can't factor in that data, correct?

So the majority of the logic being used for timing is based off of the CHT, correct? Which cylinder is that temp being read at?

 

[S5501960]

Mine will run 50+ ambient in those conditions on hot and humid Texas days but only when cruising at a higher load, like 85-90 MPH. When cruising at lower speeds (maybe 70 MPH or so), it is probably +40F.

I am phase 2 all stock A10 w/ 3.55 gears and taller rear tires (275/40/R20) to offset gears a bit, it is still around 2400 RPM at 90 MPH. I am also a non-performance pack so smaller radiator which I am betting also contributes to a bit higher temperatures. I will often see major fluctuations in temperatures without much logic other than turning higher RPMs even under lower load will just build a ton more heat, like 220+ CHT cruising at 90MPH sometimes, other times it is at 205 CHT under similar conditions.

OP is yours smaller non-pp radiator or do you have the larger radiator?

Mine is a Shelby GT with a Shelby radiator that's larger than even what's on a PP1 car. So I'm guessing that's probably not the issue.

 

[engineermike]

So the majority of the logic being used for timing is based off of the CHT, correct? Which cylinder is that temp being read at?

The timing is heavily a function of charge temp but also coolant temp, which is measured directly, to a lesser extent. That is, unless your trusted tuner zerod out these corrections which is more common than you would think.

 

[Redfuzzbutt]

The timing is heavily a function of charge temp but also coolant temp, which is measured directly, to a lesser extent. That is, unless your trusted tuner zerod out these corrections which is more common than you would think.

I thought coolant temp was inferred, based off of CHT, amongst other things.

 

[engineermike]

I thought coolant temp was inferred, based off of CHT, amongst other things.

You are correct. I was thrown off because basically all calculations use ECT not CHT. So borderline spark timing is a function of ECT which is inferred as a function of CHT, load, rpm, etc.

 

[Redfuzzbutt]

You are correct. I was thrown off because basically all calculations use ECT not CHT. So borderline spark timing is a function of ECT which is inferred as a function of CHT, load, rpm, etc.

Backtracking just a quick moment, is IAT2 utilized as part of the logic for tuning a vehicle?
Obviously it affects many things but without the ability to read that temp (which many of us are concerned about, rightfully so), the primary focus should be CHT. Where is that read? Which cylinder?

 

[SBR70.3]

First track day and I had major issues with CHT's on the 3rd-5th sessions. I bought the CSF radiator. Bonus about swapping radiators is it opens up the engine bay to make upgrading your front sway bar easy AF! My Steeda sway bars allegedly will arrive today and getting everything installed is my evening project.

Next step for me is ducting the radiator and race louvers for the hood.

 

[engineermike]

Backtracking just a quick moment, is IAT2 utilized as part of the logic for tuning a vehicle?

I’ve seen people call iat2 the one in the maf and others call it the one after the intercooler. Personally I like to use iat and mct because there is less confusion and the mct acronym is what’s used in the tuning parameters. Mct is in the manifold just ahead of the cylinders, and has a profound effect on borderline spark timing. It’s used in many other places in the tune as well, way more than iat. If you have both, iat is only really used in a correction for the maf.

 

[Angrey]

As Mike pointed out and other asked:

1) Yes, unless you add the second harness jumper and sensor, your "IAT" is going to read at the intake. The reason most people use the term IAT2 is because it's the second IAT after charge, just before the cylinders. Most PD kits it's a sensor installed in the rear of the blower housing and a jumper that intercepts the IAT signal to the computer. If you have a menu of sensor values on the dash screen, it will still read as IAT, but it will be the 2nd IAT after the air is blown.

2) The Coyotes do not have a dedicated coolant sensor (not sure why Ford did this) but it has a cylinder head temperature sensor and it "infers" the coolant temp based off logic and time. Fun fact, it has two transducers, because the range of coolant temps is too wide to handle with one, so it has this really complex algorythm to try to determine which band (upper or lower) is applicable. You can actually throw the car for a loop and have weird ECT's if you turn the car on/off within a certain time frame because it's all based off what the CHT is and how long the car has been running.

3) Like I said in the previous post, the dominant factor in the CHT is combustion and engine coolant/oiling. Hotter IATs will help contribute, but the majority of CHT's are based on how much fuel/air you're combusting and how much your coolant and oil is bringing the temps down. So solving IATs is going to have a minimal impact on CHT's, if that's an issue, efforts to improve the radiator/fans/water pump/shrouding etc are going to be more productive in getting them under control.

 

[furdfan2018]

The hardcore track rats will see 235-250 intermittently but I wouldn't personally want to see anything higher than 235. You start to get into the risk zone of warping the heads.

235 CHT is not even kind of close to warping a head. That is only 220-225 coolant temp.

It is common in some of the higher end builds to ceramic coat combustion chambers and for that to be done, the coater will bake the head at 250-280* for a few hours.

At 600* aluminum loses roughly half its strength. Sustained temps of 570* to 770* depending on the alloy will anneal the aluminum removing any previous heat treatment properties.

Modern cylinder heads won't even begin to get "soft" until well after 300-400*.

 

[Angrey]

235 CHT is not even kind of close to warping a head. That is only 220-225 coolant temp.

It is common in some of the higher end builds to ceramic coat combustion chambers and for that to be done, the coater will bake the head at 250-280* for a few hours.

At 600* aluminum loses roughly half its strength. Sustained temps of 570* to 770* depending on the alloy will anneal the aluminum removing any previous heat treatment properties.

Modern cylinder heads won't even begin to get "soft" until well after 300-400*.

Your car, you're free to do as you will. "Soft" is a relative term in the first place when you're running 12mm studs at 100+ ft-lbs.

And the part you're missing is that at high boost, it doesn't matter what temp, the combustion is working the head and the gasket clearance and if you cool it rapidly...........it warps. You don't need to melt a kitchen pan or even heat the aluminum or the steel beyond yield to observe this.

 

[furdfan2018]

Your car, you're free to do as you will. "Soft" is a relative term in the first place when you're running 12mm studs at 100+ ft-lbs.

And the part you're missing is that at high boost, it doesn't matter what temp, the combustion is working the head and the gasket clearance and if you cool it rapidly...........it warps. You don't need to melt a kitchen pan or even heat the aluminum or the steel beyond yield to observe this.

Right, but 225 coolant temp? Come on bro. not gonna happen.

Now.. would I recommend you keep beating on the car at 225? of course not, but I can promise you there is 0 (ZERO) chance of warping a coyote head at 225.

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