[cmitchell17]

I posted this here, and not in the issues section, because I know a lot of people like to put in aftermarket colder thermostats.

I notice that if not on the gas and just cruising around and not stationary, my coolant temps will go below 165F sometimes and usually stay around 165F unless I get on it of course. I know all GEN III/IV engines I've had would run always at around 200F even when its 30F outside and you are going 50mph down the road. I think they have revised a lot of stuff as far as the cooling system on these GEN Vs but I know its not supposed to be that cool?

I can't really remember how it was in the summer, but it seems like my thermostat maybe stuck open a little or maybe leaking coolant by?

Not sure if its worth it to try to pull the housing and test the thermostat in some boiling water. I've heard you have to order a whole new housing you can't just buy a thermostat, unless I guess you could maybe by an aftermarket one.

I tend to think way to thermodynamically, and want the hottest coolant temp that still is safe for the materials, gaskets, fluids, etc. which is basically how its run from the factory. Yes I know people run aftermarket cooler ones in an attempt to reduce knock and try to get back to best timing. I think more along the lines of coolant robs torque the colder you let it get the more heat transfer and the more energy wasted out the radiator. It would be an interesting calculation to do the math to see if the cooler thermostat temps rob more energy than what is gained by restoring optimal timing, I run E85 all the time so I'm not concerned.

[lt4camaro]

Originally Posted by cmitchell17

I posted this here, and not in the issues section, because I know a lot of people like to put in aftermarket colder thermostats.

I notice that if not on the gas and just cruising around and not stationary, my coolant temps will go below 165F sometimes and usually stay around 165F unless I get on it of course. I know all GEN III/IV engines I've had would run always at around 200F even when its 30F outside and you are going 50mph down the road. I think they have revised a lot of stuff as far as the cooling system on these GEN Vs but I know its not supposed to be that cool?

I can't really remember how it was in the summer, but it seems like my thermostat maybe stuck open a little or maybe leaking coolant by?

Not sure if its worth it to try to pull the housing and test the thermostat in some boiling water. I've heard you have to order a whole new housing you can't just buy a thermostat, unless I guess you could maybe by an aftermarket one.

I tend to think way to thermodynamically, and want the hottest coolant temp that still is safe for the materials, gaskets, fluids, etc. which is basically how its run from the factory. Yes I know people run aftermarket cooler ones in an attempt to reduce knock and try to get back to best timing. I think more along the lines of coolant robs torque the colder you let it get the more heat transfer and the more energy wasted out the radiator. It would be an interesting calculation to do the math to see if the cooler thermostat temps rob more energy than what is gained by restoring optimal timing, I run E85 all the time so I'm not concerned.

speaking of horsepower only, its been said every 10 degrees is about 1% of power loss or gain. Hypathetically a engine running 180 degrees versus 200 there could be a 2% gain. At 200 degrees, timing is already being pulled , plus there is the fact of cooler denser air being injested.

[95 imp]

So, if I run my engine 100* cooler, I pick up 10% hp?

[6spdhyperblue]

The thermostat is stuck open. Happened on my Silverado

I like the katech 174* with moderate fan settings runs 188ish. The temp is stable in the summer too especially on E

[lt4camaro]

Originally Posted by 95 imp

So, if I run my engine 100* cooler, I pick up 10% hp?

What I said was, for every 10 degrees you can gain or lose 1%. Example, there can be a 9 horsepower difference between a 450 horse engine running at 180 degrees versus 200 degrees and maybe more if running at 170 degrees. Two things coming into play regarding todays tuning tables and a engine pulling in cool dense air. The intake manifold, throttle body, cylinder heads will be cooler and not warming the air, a look at a typical LT1 timing table shows timing already being pulled at 194 degrees of water temp, you will also see timing being pulled when intake air temp gets hotter and hotter. Trick is to get the engine to pull in as much ambient air as possible ( not heated engine compartment air) and run lower water temps with in reason on a street car. Also run the highest octane pump gas to negate spark retard. High temps promote spark knock, knock sensors retard spark. Keep the timing tables maxed out and ingest as much cool air as possible not only creates horsepower but also stops horsepower loss

[cmitchell17]

Originally Posted by 95 imp

So, if I run my engine 100* cooler, I pick up 10% hp?

You would find in the real world the difference is negligible. If you are talking about intake air temperature and not coolant temperature, then you theoretically get something like 1 hp for every 10 degrees cooler intake air temperature. This is just because the engine is actually taking in more oxygen and has nothing to do with thermodynamic efficiency.

You always want to run your engine (coolant temperature) as hot as you possibly can while still being safe from engine damage. You'll see a lot of people don't under stand thermodynamics. The reason why there is aftermarket (and even I guess Katech has one, which is a well respected company that knows what they are doing) thermostats that are cooler, is to try to let you cheap and compensate for running inadequate lower octane fuels on a engine that was designed to run on higher octane fuel.

If you understand things like conservation of energy, the way heat flows, and a little bit of thermodynamics (you don't even have to understand entropy) you will see by having cooler coolant temperatures more heat >= energy >= horsepower is sucked out of your combustion chamber, goes into the coolant, and gets wasted out through the radiator into the air.

Back in the 70s Cummins did some research into trying to eliminate the cooling system on engines for the military, the goal was more to make the engines more reliable by making them not require cooling, and not necessarily more efficient. They used some exotic ceramic materials and achieved the highest efficiency for any engine, I believe to this day but I haven't seen an official paper on it. Of course the engine they made was probably way more unreliable and probably had millions of other issues (ceramics are brittle and prone to cracking) and I'm sure was extremely expensive. But basically if you don't cool and engine you make it more efficient and more efficient also means more available horsepower.

If you don't believe me that the radiator and cooling system "sucks" power from your engine, go out and see how your engine drives when it hasn't warmed up versus when its fully warmed up. There are some factory limiters and rev limiters at extremely cold temps for a few seconds, but generally until the engine is fully warmed you can sense a loss in response and power. This is because the engine block and coolant is very cold and is "sucking" heat from the combustion chamber at a way higher rate than it does when its fully warmed up. This heat could be turned into power at the wheels, so its kind of like until your engine is fully warmed up, you are "short circuiting" it.

Also all these people claiming that lowering coolant temps for power increase because it "heats" the incoming air too much, should really go do some heat transfer calculations and report back. The amount of heat transfer is so negligible especially to a moving fluid.

[cmitchell17]

Originally Posted by 6spdhyperblue

The thermostat is stuck open. Happened on my Silverado

I like the katech 174* with moderate fan settings runs 188ish. The temp is stable in the summer too especially on E

Thanks, so I guess they are having issues with these from the factory, that's surprising.

So they are just leaking by the seal? Or was there something else going on with the spring or something? Or I guess you just swapped in a new one and didn't really know the cause?

[6spdhyperblue]

The seal was intact and unit was visibly fine, leads me to think it was stuck and just not opening and closing at the correct temps. On the truck I swapped in a stock replacement and it worked correctly.

I noticed it as I was doing some trans tuning and saw the coolant not going above 150 on a cold winter day. FYI the stat in our cars is 194 and the truck I believe was 210 or around there..was last winter. Temps Marked on the unit.

[lt4camaro]

Originally Posted by cmitchell17

You would find in the real world the difference is negligible. If you are talking about intake air temperature and not coolant temperature, then you theoretically get something like 1 hp for every 10 degrees cooler intake air temperature. This is just because the engine is actually taking in more oxygen and has nothing to do with thermodynamic efficiency.

You always want to run your engine (coolant temperature) as hot as you possibly can while still being safe from engine damage. You'll see a lot of people don't under stand thermodynamics. The reason why there is aftermarket (and even I guess Katech has one, which is a well respected company that knows what they are doing) thermostats that are cooler, is to try to let you cheap and compensate for running inadequate lower octane fuels on a engine that was designed to run on higher octane fuel.

If you understand things like conservation of energy, the way heat flows, and a little bit of thermodynamics (you don't even have to understand entropy) you will see by having cooler coolant temperatures more heat >= energy >= horsepower is sucked out of your combustion chamber, goes into the coolant, and gets wasted out through the radiator into the air.

Back in the 70s Cummins did some research into trying to eliminate the cooling system on engines for the military, the goal was more to make the engines more reliable by making them not require cooling, and not necessarily more efficient. They used some exotic ceramic materials and achieved the highest efficiency for any engine, I believe to this day but I haven't seen an official paper on it. Of course the engine they made was probably way more unreliable and probably had millions of other issues (ceramics are brittle and prone to cracking) and I'm sure was extremely expensive. But basically if you don't cool and engine you make it more efficient and more efficient also means more available horsepower.

If you don't believe me that the radiator and cooling system "sucks" power from your engine, go out and see how your engine drives when it hasn't warmed up versus when its fully warmed up. There are some factory limiters and rev limiters at extremely cold temps for a few seconds, but generally until the engine is fully warmed you can sense a loss in response and power. This is because the engine block and coolant is very cold and is "sucking" heat from the combustion chamber at a way higher rate than it does when its fully warmed up. This heat could be turned into power at the wheels, so its kind of like until your engine is fully warmed up, you are "short circuiting" it.

Also all these people claiming that lowering coolant temps for power increase because it "heats" the incoming air too much, should really go do some heat transfer calculations and report back. The amount of heat transfer is so negligible especially to a moving fluid.

You need to monitor some serious 1/4 mile drag guys. Watch what the same car does on a 90 degree day versus a 50 degree day. There is always a .3 to .5 ET difference and up to a 5 trap mph difference, which equates to serious horsepower difference. Watch these guys on warmer days, they never make back to back runs, they go to the pits and allow substantial cool down by circulating cool water thru the cooling system or a long natural open hood and fan cool down. Thermal efficiency, high temps and lean fuel mixtures are good for emissions . I also understand different metals and components need to be up to certain temps allowing for correct clearances and expansion etc. But overall cool water temps and cold air create the most horsepower not efficiency. Cooler combustion chambers, cooler heads, cooler pistons allow for more spark advance, more power.

[95 imp]

I doubt the air in the intake manifold/intake port is there long enough to raise its temp. At 1000 rpm each valve is opening every 8 seconds. At 6k, 50/sec
Every time the valve opens you suck in 13.5 CFM (per cylinder @ 1K rpm @ 100% efficiency.) That jumps to 163 CFM @6K.

So, 163 CFM 50X per second @ 6K.

Under hood air... different story. Very inefficient because, as Cmitchell said, hot air is less dense. That means less oxygen per CF. It also leads into what you said, more prone to knock.

As far as drag racing, They do that to prevent heat soak and usually those engines have VERY small cooling capacity to save on weight. Half filled blocks (or solid blocks with no water jackets). You're running the engine for 20 seconds (burnout, stage and run) and the engine gets shut off at the top of the track until the next round.

[lt4camaro]

Originally Posted by 95 imp

I doubt the air in the intake manifold/intake port is there long enough to raise its temp. At 1000 rpm each valve is opening every 8 seconds. At 6k, 50/sec
Every time the valve opens you suck in 13.5 CFM (per cylinder @ 1K rpm @ 100% efficiency.) That jumps to 163 CFM @6K.

So, 163 CFM 50X per second @ 6K.

Under hood air... different story. Very inefficient because, as Cmitchell said, hot air is less dense. That means less oxygen per CF. It also leads into what you said, more prone to knock.

As far as drag racing, They do that to prevent heat soak and usually those engines have VERY small cooling capacity to save on weight. Half filled blocks (or solid blocks with no water jackets). You're running the engine for 20 seconds (burnout, stage and run) and the engine gets shut off at the top of the track until the next round.

Just about every carb performance intake has the heat crossover eliminated and the intakes are raised so there is air space between the intake and the valley to keep the plenum of the intake manifold as cool as possible. Heat can be a enemy in the wrong place at the wrong time. Hot cylinder heads, combustion chambers and blocks raise the need for higher octane to reduce detonation or one needs to back off timing which lowers horsepower.

[cmitchell17]

Originally Posted by lt4camaro

You need to monitor some serious 1/4 mile drag guys. Watch what the same car does on a 90 degree day versus a 50 degree day. There is always a .3 to .5 ET difference and up to a 5 trap mph difference, which equates to serious horsepower difference. Watch these guys on warmer days, they never make back to back runs, they go to the pits and allow substantial cool down by circulating cool water thru the cooling system or a long natural open hood and fan cool down. Thermal efficiency, high temps and lean fuel mixtures are good for emissions . I also understand different metals and components need to be up to certain temps allowing for correct clearances and expansion etc. But overall cool water temps and cold air create the most horsepower not efficiency. Cooler combustion chambers, cooler heads, cooler pistons allow for more spark advance, more power.

I think in a scenario if you tried to test it back to back with 2 different identical cars that had the same timing and no knock and they were both operating at MBT but one had the stock 194F thermostat and one had a 160F thermostat, I bet you could tell zero difference between the 2 unless you had very expensive equipment. If you did have that expensive equipment, I bet you would see the one with the 160F thermostat made less power.

Now if you had the same scenario but each car was running less than the recommended 93 octane and each one was pulling timing from knock retard, then you switched one to a 160F thermostat, I bet the 160F thermostat one would then be quicker, by a easily observable and measurable amount and would probably, maybe, stop pulling knock retard timing.

I really wish I could do a calculation to see just how much horsepower, and yes I mean horsepower literally, heat is a form of energy which heat transfer over time is power, which can be described in the same units as the power that goes to your tires. It would be a rough one however but you could make some pretty accurate assumptions.

Also increasing timing doesn't just mean more power, increasing timing when the conditions warrant it increases power. When the conditions don't, then increasing timing reduces power in a very very non linear exponential way. That extra waste energy/power goes into your coolant. If its retarded too much then it goes into the exhaust.

[95 imp]

Originally Posted by lt4camaro

Just about every carb performance intake has the heat crossover eliminated and the intakes are raised so there is air space between the intake and the valley to keep the plenum of the intake manifold as cool as possible. Heat can be a enemy in the wrong place at the wrong time. Hot cylinder heads, combustion chambers and blocks raise the need for higher octane to reduce detonation or one needs to back off timing which lowers horsepower.

Yes, you want an air gap (if possible) on your manifold or, a non conductive material (plastic), heat crossover plugged, and drawing ambient air, not under hood air.

Air is a very good insulator. That's how home insulation works as well as double pane windows (air gap).

You want as much heat retained in the chamber as possible to promote HP.

https://www.enginebuildermag.com/201...s-even-better/

We are able to run 11.5-1 on 91 and 93 because of the oil squirters cooling the back side of the pistons down. (losing efficency). Otherwise we'd need 100+
octane.

[cmitchell17]

Since I hate waiting on parts, I went to the dealer and got a whole new thermostat housing even though it was a lot more than ordering one but not that much after shipping. I tried to look at and compare the new PN thermostat to the old one I had and I couldn't see any differences, they looked identical.

It did fix the issue and now my coolant temp goes to 190-205 even when cruising down the road at 40-50 mph.