MGorman

Your observations are correct concerning intake air temperatures ....

I've done "technical" SCUBA diving using mixed gases, so I'm familiar with how to use the gas laws to figure out what kind of effect a change in temperature has on the pressure, for example, for a gas.

Using Charles Gas Law, we know that an "ideal gas" has the formula PV/T = k where k is a constant. So two states of the same gas can be denoted as

PoneVone PtwoVtwo
--------------- = --------------
Tone Ttwo

This is hard to do without subscripts .... LOL

Let's assume a Volume of 600 cu ft (about what an LSx engine inhales at redline in one minute, and see what a change in temperature does to the volume .... we will assume Pressure remains constant so we can leave that out of the equation (since Pone = Ptwo)

Vone Vtwo
-------- = -------
Tone Ttwo

or

600 Vtwo
----- = -------

560 660

We take the absolute temperature (I'm assuming an ambient temp of 100 degrees F and an underhood temp of 200 degrees .... so we add 460 degrees F to each to get absolute)

The answer is 707 cubic feet.

In other words I have a greater than 15 percent change in the weight (in this case I'm using volume .... but same calculation) of air the engine is inhaling between 100 degrees and 200 degrees ..... Let's just say that means I get 10 percent more HP from my engine at an intake temp of 100 degress .... for a stock Corvette engine that is 30+ HP ..... just for inhaling cooler air ...... think a 160 degree thermostat is gonna give you 30+ HP ????

Now by the time "cold" air actually reaches the cylinder it is warmer than when it first entered the engine (it is absorbing heat from the intake manifold, the intake valve ... etc.) ... so you won't see this large an increase ... but you get the point ... "cool" intake air is VERY important to your engine's ability to produce HP.

Ever had that feeling on a damp cool morning like ... wow ... this car is powerful ... that "dense" air is producing more power than you will get at 7000 feet on a hot day.

 

I see what you’re saying, but these neat tidy formulas rarely translate exactly to complex “real world” situations such as we’re discussing. There are just too many variables.

I really think we’re not too far apart in our thinking. Lets say for the sake of argument we pick up 30 hp from cool (denser) air. This isn’t going to happen without extra fuel and timing. This is pretty much the same thing I’m trying to say about the 160 thermostat and lower coolant temperatures. You can add extra timing and maybe a little fuel and make more power. If you want to talk about a stock car with stock timing/fuel tables it would not surprise me to see a 20-30 hp increase for a car running nice and cool at 175 degrees coolant temp vs. one running at 225 degrees and pulling massive amounts of timing.

 

aaahhhh....the good usual, lots of good technical debat going both ways.

I've decided to do some hands-on, "field testing". I know I've been running at around 198 water temp on my normal drive home. I'm putting in the 160 degree thermostate and will see what the heck happens. Will report back since I started this.

But let's say it does run a "bit" cooler. So what. What does that do for me???? or to me????



Padrino

 

Just make sure you get your oil temps up over 200* whenever you drive the car. That's all that really matters for the purpose of this "debate".

Mine easily achieves that driving easy even with the little bit of driving I've done in 35* ambient temps, but that's just been my experience. Yours could differ. I didn't find my normal oil temps changed much at all before/after the Tstat and fan reprogram. I still normally run @ 210-220 oil temps cruising on the freeway.

Oil temps do not always directly correlate to coolant temp...if they did, there would be no sense in monitoring both. I can get my oil temps to 250 just as easy now with a 160 stat as I could with the stock Tstat...but that's all in how you drive the car.
No it won't happen with the cruise set at 55 in 6th gear, but run out 3rd gear to 7000rpm a couple times, and then see what your oil temp is at. ( - don't try that with a stock engine btw).

 

why waste money on a t=stat when a real radiator solves the problem ?

 

Solves what problem?

 

running at 235-240
with a real rad. you can run 192 all day Long at over over 100 degrees ambient

 

For better or worse, some folks want to run cooler than that.

 

I have a 160*F stat, and lowered the cooling fan temps. At highway speeds, the ECT is ~172*F-174*F.
In traffic with the AC on, the ECT is ~177*F-183*F.

Russ Kemp

 

I'd like to know the definition of an "Econo Tune"

 

it's for worse

 

Me too as I'm the one that posted that term herein.

My mech told me I'd see more MPG which is what I want. He did tell me a side issue though is that I'll also see more HP. Sounds like a win-win to me

Padrino

 

Great thread. I'm not going to debate the 160 degree stat at all, personally I am way to lazy to trade out the thermostat for summer conditions although I do try to keep my tires around 30psi hot. Makes perfect sense to me. I believe ET is saying the that if you want to keep your oil temps ideal, you would use the 160 degree stat only in summer conditions. At low ambient air conditions occuring during winter, the 160 degree stat would result in oil temps being too low which is undesirable.