98 K1500 Thermostat

[big_mike]

Its all based on what is in the PCM programming. Almost every engine I have ever messed with pulls timing when coolant and intake air temps are elevated. When you drop the coolant temp the air entering the engine also cools down which is practically free HP. Finally running cooler also helps keep the clutch fan from engaging. The clutch fan can have a huge effect on ETs as well even if it is not fully engaged. The cooler the engine runs the more it free wheels.

Clutch drag is real paracitic loss, we can agree there. But coolant temp does NOT effect air temps in the manifold. Long discussions about this on LS1TECH years back concerning guys running the Weiand aluminum intake over the composite FAST. Only hp differences were in design, air temps we're not effected. The air does not stay in the intake long enough when the throttle is open and air is flowing. Yes there is a few degrees heat soak if sitting at complete idle but even then it's minimal in a NA engine.

Intake air temps are effected by weather conditions and potentially engine bay temperatures. If your running a open element in the engine bay you'll see higher temps from sucking the hot air trapped under the hood than from the stock box drawing air from the fender. And we can agree again hotter air temps effect fueling and decrease power. Cooler air charges burn better in the chamber making more power.

 

[L31MaxExpress]

Clutch drag is real paracitic loss, we can agree there. But coolant temp does NOT effect air temps in the manifold. Long discussions about this on LS1TECH years back concerning guys running the Weiand aluminum intake over the composite FAST. Only hp differences were in design, air temps we're not effected. The air does not stay in the intake long enough when the throttle is open and air is flowing. Yes there is a few degrees heat soak if sitting at complete idle but even then it's minimal in a NA engine.

Intake air temps are effected by weather conditions and potentially engine bay temperatures. If your running a open element in the engine bay you'll see higher temps from sucking the hot air trapped under the hood than from the stock box drawing air from the fender. And we can agree again hotter air temps effect fueling and decrease power. Cooler air charges burn better in the chamber making more power.

The intake system is absolutely effected by heat soak and when you are stuck in traffic (or staging lanes) the hotter coolant temps can heat soak the intake more. Combined high IATs and Coolant temp can cause the PCM to pull 6-10° of timing in hot weather especially until the IAT sensor has had tine to cool off. Runni g coolrr has made a drastic difference in everything I have tried it on. When I swapped the thermostat on the Express vans 350 when it was stock what I noticed is that it no longer fell on its face above 90°F ambient temps and it was much more responsive when traffic went from a dead stop back to 80+ mph. I could pin the throttle open and it would actually go rather than ******* down and sounding like an airplane with the clutch fan screaming. Datalogging the difference timing advance stayed much more advanced running cooler.

 

[L31MaxExpress]

I will also add that I also changed my engine tune to where it would not pull timing until the IATs were in the 120°F range and the coolant temp was over 195°F. I noticed as the PCM would pull timing my 350 would run even hotter.

This was a stock engine tune run in about 95°F weather.

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This was a run with the PCM reflashed to my liking in the same 95°F weather. In the tune I also enabled my pusher condenser fan to come on at a much cooler temp which helps keep the engine cool.

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The difference is night and day. Only difference between the run was PCM tune, cooler coolant temps, cooler IATs and no clutch fan drag on the 2nd run.

 

[L31MaxExpress]

I jus looked at a stock 0411 5.7 Van tune. At 210°F the PCM is pullin 6° of timing for elevated coolant temps. By 140°F IAT the PCM is also pulling 5° of timing for elevated IATs. They are added together as well. When you stomp the throttle WOT from a stop that can put your timing well after TDC at lower RPM.

 

[big_mike]

What your seeing in difference is in your tune changes far more so than coolant or iat temps.

 

[L31MaxExpress]

What your seeing in difference is in your tune changes far more so than coolant or iat temps.

I think you missed that I said I noticed the same difference with the stock tune with a Cooler vs Hotter running engine. Stock tune exaggerates the difference drastically. There is roughly 11° of timing retarded out of the factory tune above 90°F ambients with the factory thermostat.

 

[Missouri Mule K30]

The cooler the air and fuel entering the combustion chamber the more horsepower attained. A Givin. Higher coolant temps, thinner oils, are better for fuel mileage but are actually cooking everything under the hood.

Now there is truth in the at speed the air entering is cooler than at idle, but not as cool as it could be. Exhaust manifolds are heat sinks also keeping temps even higher, that is one reason that manufacturers have gone to tubular exhaust manifolds. I also remove the rubber seal on the hood to get airflow through the engine bay again to reduce temps.

But I am not a computer type mechanic, but am looking at helpful information, no government intervention needed. Their are many valid arguments. What I am looking for is exactly that information.

You men are far more advanced than I. But I have RUN A RACE OR THREE. Race tracks are lots of FUN. Been their done that got the t shirts.

But far more different. I guess that I want to still apply the same principals that I used in the past. Maybe hard to break old habits, that is why I asked for information but did not want confrontation, just real world intel by men that have worked with 90's tech.

Thanks Gentlemen as each other helps the other. United We Stand
Divided We Fall