Mixed info about coyote hp limit

Bartly said:

I’ve been out of the sports car/engine thing for 20 years so I didn’t know enough to debate it with him or his guy. I figured the technology was different enough to allow all of the boosted coyotes to last. Seems like if it was an epidemic you’d here more about blown engines.

In a way it’s good to hear that it long WOT pulls is what might be causing any ring problems. Only good because I don’t do them ever really, mostly just getting up to 70-90mph as fast as I can is about all I do when pushing the car. I tend to watch my catalytic converter PIDs and usually let that tell me when to stop pushing the car.
Thank god I finally got a good tune that rarely shows any positive knock. The last 1 1/2 years I was sweating it because no matter who or where I was getting my tune revisions from all WOT logs had knock in the +4-6 range, just happy that’s behind me. Figuring I’m only at 580whp, but am only on 91 octane so hopefully the engine lasts a long time.

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+1 I also watch the "cattemp" PID on my nGauge. With or without cats, exhust gas temp is the best way to get an indirect measurment for the stress on the rings.

Do you know what sensor logs cat temp?

Rear 02's and we have them turned off because we have no.cats.

ahl395 said:

+1 I also watch the "cattemp" PID on my nGauge. With or without cats, exhust gas temp is the best way to get an indirect measurment for the stress on the rings.

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What's the correlation between cat temp/gas temp and cylinder temps? Obviously the hotter the exhaust the hotter the combustion chamber, but is there some sort of correlation between those temps and what the cylinder sees? Also what's a temp that we should start worrying?

ahl395 said:

+1 I also watch the "cattemp" PID on my nGauge. With or without cats, exhust gas temp is the best way to get an indirect measurment for the stress on the rings.

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Isn't that inferred though (probably from lambda sensor output)? My car doesn't have a legit exhaust gas temp sensor. I do agree that exhaust gas temps are a good metric, you can correlate it well to fueling (similar to using a wideband) since lean makes the exhaust hot and rich cold, there is a nice bell curve.

EFI said:

What's the correlation between cat temp/gas temp and cylinder temps? Obviously the hotter the exhaust the hotter the combustion chamber, but is there some sort of correlation between those temps and what the cylinder sees? Also what's a temp that we should start worrying?

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One important part of the correlation is fueling:

https://imgur.com/a/coEKo

You can see the exhaust gas is hottest around the stoich point (lambda 1). So if you're WOT and seeing hot temps that's not good, can indicate lean conditions. Fuel is a much better coolant than air is, so it takes a LOT more air (when lean) to cool the exhaust temps down. When rich the fuel works real well to cool down, so you can see that your power enrichment is correct under WOT with EGTs if you are unsure about your built in lambda sensors (wideband O2s).

But, again I don't think any of us have factory installed legit EGT sensors so may as well look at lambda instead.

EFI said:

What's the correlation between cat temp/gas temp and cylinder temps? Obviously the hotter the exhaust the hotter the combustion chamber, but is there some sort of correlation between those temps and what the cylinder sees? Also what's a temp that we should start worrying?

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I do have cats, so I’m always worried about melting them. The hottest my CATTEMP PIDs have shown was 1944 deg F, that was with the tune that came with the supercharger. With my new tune hottest they measure is 1600F or so. I usually ease off when I see them approaching 1500. I know it’s all inferred, but I’m sure it doesn’t hurt to watch them and use them.

The main factors contributing to high EGTs are AFR & timing if I recall correctly. I've tuned using EGTs & wideband in the past and it lends itself to a more stable tune IMO. However, I've never tuned an S550 so I can't speak to the impact EGT has on the platform. I'd suspect that it's still an easy way to get a direct measurement of how your timing and AFR are affecting combustion.

edit: I should add that I typically used it as a safegaurd during tuning for boost. For example, with boosted cars, You have the option of adding timing, fuel, or more boost. Often times, it's most efficient to add more boost than anything else. Of course, you get to a point where you're now reducing timing and adding fuel to manage knock because boost makes more power than timing in most cases. Unfortunately, if you do this you're going to raise EGT which isn't automatically bad. However, you need to know when you're pushing out 2k degree Fahrenheit EGT because you're probably already in the process of melting valves. There is a line there that shouldn't be crossed, but its different for every platform. For the cars I worked on, it seemed to be around 1600 before we ran into issues IIRC but its been a whiiillle. I just had to look over old logs to find that number but thats for a turbo 4 cylinder car.

EGT became crucial on my e85 cars. They wouldn't even knock before destroying stuff.

SlaughterOfTheSoul said:

The main factors contributing to high EGTs are AFR & timing if I recall correctly. I've tuned using EGTs & wideband in the past and it lends itself to a more stable tune IMO. However, I've never tuned an S550 so I can't speak to the impact EGT has on the platform. I'd suspect that it's still an easy way to get a direct measurement of how your timing and AFR are affecting combustion.

edit: I should add that I typically used it as a safegaurd during tuning for boost. For example, with boosted cars, You have the option of adding timing, fuel, or more boost. Often times, it's most efficient to add more boost than anything else. Of course, you get to a point where you're now reducing timing and adding fuel to manage knock because boost makes more power than timing in most cases. Unfortunately, if you do this you're going to raise EGT which isn't automatically bad. However, you need to know when you're pushing out 2k degree celsius EGT because you're probably already in the process of melting valves. There is a line there that shouldn't be crossed, but its different for every platform. For the cars I worked on, it seemed to be around 1950 before we ran into issues.

EGT became crucial on my e85 cars. They wouldn't even knock before destroying stuff.

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You mentioned 2k degrees Celsius, you sure it wasn’t Fahrenheit? 2000 C = 3632 F, way past melting point.

JUST SEND IT!! These gen 2’s will take an ass beating.

Bartly said:

I do have cats, so I’m always worried about melting them. The hottest my CATTEMP PIDs have shown was 1944 deg F, that was with the tune that came with the supercharger. With my new tune hottest they measure is 1600F or so. I usually ease off when I see them approaching 1500. I know it’s all inferred, but I’m sure it doesn’t hurt to watch them and use them.

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Even though its "Inferred" the Ford modeling for stuff like that is WICKEDLY good.

Bartly said:

I do have cats, so I’m always worried about melting them. The hottest my CATTEMP PIDs have shown was 1944 deg F, that was with the tune that came with the supercharger. With my new tune hottest they measure is 1600F or so. I usually ease off when I see them approaching 1500. I know it’s all inferred, but I’m sure it doesn’t hurt to watch them and use them.

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For what it's worth, with cats I saw as high as 2300F. Removed cats dropped to 1800F, after methanol injection dropped to 1600F ( After a decent WOT pull )

Nothing changed in my tune for these changes, which is why I think it goes off the actual O2 sensor. Removing cats doesn't change fuelling, and the O2 is right in the middle of the cat so it makes sense it would see a ton of heat versus being in the open exhaust stream. Methanol is known to lower EGTs but since fuel trims adjust for the meth being injected, how would the computer know to read a lower "cattemp" if it's inferred.

I could be wrong, but to me it seems the O2 acts as a EGT sensor.

EFI said:

What's the correlation between cat temp/gas temp and cylinder temps? Obviously the hotter the exhaust the hotter the combustion chamber, but is there some sort of correlation between those temps and what the cylinder sees? Also what's a temp that we should start worrying?

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I'm not sure on those numbers. I can say that at part throttle exhust gas temps rise higher and quicker than at WOT. I assume because at part throttle the motor isnt able to breathe as much to expel the heat as when it's at WOT.

I typically just keep an eye on it if it goes higher than it typically does. And if I see the temp drop due to a new mod I consider it a good thing lol.

Tommy V said:

Rear 02's and we have them turned off because we have no.cats.

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Even with the rear O2s turned off for catless the cat temp monitor still works

kcc0521 said:

Do you know what sensor logs cat temp?

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It's labeled CATTEMP, there's Bank 1 and 2.

ProChargerTECH said:

Even though its "Inferred" the Ford modeling for stuff like that is WICKEDLY good.

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Can you confirm that it is inferred and does not go off the rear O2 sensor then?

ahl395 said:

Can you confirm that it is inferred and does not go off the rear O2 sensor then?

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Not PCTech, but I'm having a hard time coming up with a way to infer temps in an accurate-ish way that don't involve either the header or the rear lambda sensors. That is the most direct relationship to correlate and infer an EGT, since the fuel mixture has a very profound predictable effect on EGT. Maybe they thought of something more clever than that though.

oesman said:

Not PCTech, but I'm having a hard time coming up with a way to infer temps in an accurate-ish way that don't involve either the header or the rear lambda sensors. That is the most direct relationship to correlate and infer an EGT, since the fuel mixture has a very profound predictable effect on EGT. Maybe they thought of something more clever than that though.

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For me the amount of boost also affects the temp, which the ECU has no way of knowing. Isnt it possible there is a temp probe in the rear O2?

That PID doesn't show up in my logs using the "Generic 2011+" PIDs on my nGauge. Is there a way to change that? I forget.

Exhaust gas temperatures are estimated. Exhaust components temperatures flange/ Cats/ O2's are inferred from that estimate. O2 sensors have a duty cycle vs exhaust gas to maintain desired tip temp. They do not have a temperature sensor built into them, just an operating temperature range. Flange probably comes from cylinder head temp and exhaust gas. The Cats are probably some temperature between those two.

There's a lot of math going on behind the scenes. This is the main reason Ford is using a CHT sensor and not a ECT sensor. They can accurately infer a lot of temperatures based on CHT and other estimates, and not have to have 5 different sensors.