Straight Talk on High Engine Temperatures

artichoke · 12-13-2006, 10:28 PM

Our friends the SRT engineers today told us straight out to get cooler thermostats in the first two posts here:

SRT Q&A Session: 12/13/06

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Quote:
Originally Posted by ResumeSpeed

A question about engine oil additives in the SRT's, some companies are pushing additives on the premise that there is a need to bring the oil temperature down. Can you comment on the quotes below and explain the SRT team's opinion on oil additives?

"Anytime you have oil temp over 220 F you should do what ever you can do to bring down the oil temp. We always target 200 F for a safe running temp. Example you add our additive and the oil temp drops from 240 down to 220."

"It's possible to make additives that improve on top-flight engine oils because of all the restrictions put on manufacturers of engine oil by the Government... that's why there is NO MOPAR sanctioned additive"

240 F is not too high for the SRT engines.

We ran 167 mph for 35 minutes (until we ran out of fuel) with no oil issues.

So our oil may be destroyed after a few hundred miles of 240F; all they did was 100 miles and thought to boast about it.

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Today, 04:55 PM #40 (permalink) SRTengineers vbmenu_register("postmenu_333874", true);
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Quote:
Originally Posted by Maxwedgie

What are the benifits of the high engine temp on the 6.1? Why were they designed this way, emissions?

Correct - it's catalyst temps.

So it's not that the engine runs better, or that it's to help the oil expel volatile waste materials.

**Rambit** · 12-13-2006, 10:49 PM

Sorry, I'm just not following your logic here. They weren't referring to thermostats and coolant temps at all, just higher oil temps, answering RS's question about additives. All they said is they didn't have any problems running oil at 240.

When they DID touch on thermostats, all they said was not to use lower ones.

Rambit

B D HEMI · 12-13-2006, 11:00 PM

It was clear that the SRT guys suggested strongly NOT to use lower ternperature thermastats ! The engine was designed to run at higher temperatures .
B D HEMI

**Rambit** · 12-13-2006, 11:03 PM

Quote:

Originally Posted by B D HEMI

It was clear that the SRT guys suggested strongly NOT to use lower ternperature thermastats ! The engine was designed to run at higher temperatures .
B D HEMI

Thank you!

Rambit

artichoke · 12-13-2006, 11:48 PM

Well I hadn't read your question and their answer:

SRT Q&A Session: 12/13/06

Quote:
Originally Posted by Rambit

Which brings to mind a question I've asked before, but never received a clear answer to. What are the DISADVANTAGES, if any to using a lower temp thermostat? I believe it has been mentioned fuel ecconomy would decrease. Do you see any other problems with this?

Rambit

This question continues to surprise me. Out in LA I was bombarded with owners convinced they had a system that was running to hot. I will reiterate - we've tested the SRT8s under the hottest conditions, harshest tracks and steepest grades to ensure it meets our customer requirements. The coolant system is rock steady for thermal. You don't want to change the thermstat. We've selected the current to meet both hot and COLD durability cycles.

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But I'm still not convinced. It's like their answer (in the previous chat) to why they selected 0W40 rather than say 20W50 oil. It's something that works even at the North Pole. They even wrote COLD in all caps. Another broad hint imho ...

I don't live at the North Pole. Rambit and B D Hemi, you live a bit closer.

But here near NYC, it really never gets to -40 degrees.

**Rambit** · 12-14-2006, 12:14 AM

Quote:

Originally Posted by artichoke

Well I hadn't read your question and their answer:

SRT Q&A Session: 12/13/06

Quote:
Originally Posted by Rambit

Which brings to mind a question I've asked before, but never received a clear answer to. What are the DISADVANTAGES, if any to using a lower temp thermostat? I believe it has been mentioned fuel ecconomy would decrease. Do you see any other problems with this?

Rambit

This question continues to surprise me. Out in LA I was bombarded with owners convinced they had a system that was running to hot. I will reiterate - we've tested the SRT8s under the hottest conditions, harshest tracks and steepest grades to ensure it meets our customer requirements. The coolant system is rock steady for thermal. You don't want to change the thermstat. We've selected the current to meet both hot and COLD durability cycles.

__________________________________________________ _________

But I'm still not convinced. It's like their answer (in the previous chat) to why they selected 0W40 rather than say 20W50 oil. It's something that works even at the North Pole. They even wrote COLD in all caps. Another broad hint imho ...

I don't live at the North Pole. Rambit and B D Hemi, you live a bit closer.

But here near NYC, it really never gets to -40 degrees.

Can't speak for B D Hemi, but my climate is very similar if not the same as yours. I'm only a 100+ miles from Detroit! I've highlighted their response for you. Seems pretty clear what that statement means. As to your comment re oil, they've previously stated they wanted a broad spectrum oil to cover ALL climatic conditions. The oil has nothing to do with this. Read NR's post in the GSM thread concerning coolant temps and heat soak.

Rambit

Tork Monster · 12-14-2006, 01:48 AM

I just read through the SRT Engineer's responses to our questions. The answers to the low-temp thermostat questions were inconclusive in my view.
Some of the responses:
What are the benifits of the high engine temp on the 6.1? Why were they designed this way, emissions?
Correct - it's catalyst temps.
This is known: the higher temperature allows the cats to fire up faster and burn more completely.

Regarding Rambit's question about whether ther are any DISADVANTAGES of running cooler:
This question continues to surprise me. Out in LA I was bombarded with owners convinced they had a system that was running too hot. I will reiterate - we've tested the SRT8s under the hottest conditions, harshest tracks and steepest grades to ensure it meets our customer requirements. The coolant system is rock steady for thermal. You don't want to change the thermstat. We've selected the current to meet both hot and COLD durability cycles.
...this does not answer the question. It just says the higher temp is O.K.

One comment they made about durability:
But many owners swear that by putting in a lower thermostat they are getting noticeably better ET times, and they have track slips to "prove it" - so once and for all, will installing a lower thermo result in BETTER ET times or not?
Ask these same people a year from now after city driving and the answer may differ. SRT does not recommend any changes to Thermostat. If it helped performance without offsetting durability then this would be easy. We've never done durability HOT/COLD start on the lower thermostat temp. Therefore we won't recommend.
They can not recommend because they have no data. They did mention city driving, indicating the concern was not getting the engine up to temperature. This will cause water to build up in the oil because it is not being "boiled off" with high-temp operation. They have to cover all cases when they design a car for all buyers.

I also feel that they have to choose their words carefully; they can't recommend installing a low-temp stat if it will increase emissions. And not if it could decrease durability.

Operating a car without getting it up to temp has always been a no-no because of sludge build-up in the engine.

The question in my mind is how hot for how long will burn off the moisture and eliminate this concern? Well... 220 would do it. But the low temp stat I insatalled is set at 180 (GSM). I watched the EVIC temp gauge closely while keeping the manual fan switch "OFF" and the temp rose pretty quickly to 215. If you keep the fan switch turned off and sit in traffic any length of time, the temp will reach the computer's set temp (230?) and switch on the fans automatically. By that time the moisture will be eliminated.

I am not going to change my low-temp stat, but I will be watching the temp gauge closely and the condition of the oil.

Meister · 12-14-2006, 03:11 AM

If anyone is still confused about the negative power impact of high coolant temps, simply re-read with understanding the comment given in response to a question about under-reporting the true power output of the SRT4.

To paraphrase: "No, we don't under-report the true horsepower of the SRT4 - we merely wait till it's in severe heat soak to dyno it."

That should be good for a minus 30 hp or so from what a properly cooled engine would produce.

**stevesrt8** · 12-14-2006, 05:18 AM

no one involved in racing will dispute that a cooler engine makes more power. But HP books in their engine rebuilding manuals published data from Ford showing the relationship between piston/cylinder wear and temperature. As temp goes down cylinder wear goes up. Period.

The only question is whether this can still occur in modern engines due to advanced materials, better/more precise machining, and better lubrication. And it's still a good question, as you can ask 3 different people and get 3 different answers.

DP03 · 12-14-2006, 08:45 PM

My guess is that the engineers would be crucified by DCX for recommending stat changes for one reason and one reason only...emissions. They pretty much admitted that emissions were a concern in one of their answers. Even those of us that have changed out stats, the car will still reach the hotter temps for part of the time when the car is moving slow. Unless you force the fans on all the time.

I have a fan switch but only use it when racing or in extreme traffic for longer periods. I am absolutely convinced that longevity will not be affected and that it is being used as a reason by SRT to ensure emissions compliance. Hell, the 6.1 has not been around long enough to measure durability. Some of GM's high performance push rods have, and they have not suffered in this department, and have gained performace to boot with lower running temps...

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