zzz

Which t-stat is best. I have the stock programming for now with the 185 degree aux fan switch. I'm concerned that with the 160 t-stat and in cold weather the car may not get into closed loop - is this true?

jackdaroofer

The thing to keep in mind is that once your engine reaches Thermo opening temps, it will probably stay there.

Here's what I mean. My 88 runs about 177 degrees on the road. With a 160 thermo, that means coolant is passing through the rad and the engine. With a 180 thermo, theoretically it is closed and coolant is not circulating.

But yet the engine is still running 177 degrees, regardless of the thermo setting.
In my case I have a small 1/16 " hole in the thermo flange which allows some coolant through at all times, but the principle remains...thermo preset really doesn't effect operating temps once the preset temps are reached.

vader86

That depends on how cold it gets where you live in winter.

In SC, it stays about 50F during winter, so i'm running a 160.

If i lived in VA, NY, MI, etc. where it gets snowy and cold, i'd prolly run a 180. Although most people up there put their vettes up for winter for the most part.

oldace84

Always change your thermostat to an 160 degree....it will still go uto operating temps.......but it will help in the long run....also change your temp. sensor.....to start at 200*, and off at 185*

You can't go wrong....parts available from Mid America.....Ecklers....CorvetteCentral.. or Zip products........read all the catalogs.....


Its all good....


any questions????


tony

oldace1@earthlink.net


I'll try to help....as everyone else will on this great forum....

Try it...you"ll like it...


:cool: :cool: :chevy :cool: :cool:

65Z01

I run a 160 deg stat year around in the Vette, with a 160 deg F aux fan sw wired to control both fans.

This evening I was racing in 41deg F weather and was launching at 155deg F, the same temp as on the drive home.

So long as the weather is in the 70s or lower coolant temp runs at 155-160deg; on hotter days it can climb to 175deg F on the highway and 190 deg in city traffic.

Each Christmass I drive from NY to OH in 30deg weather with coolant at 155deg and get over 30mpg; it goes closed loop at around 140-145 deg F.

You will definitely gain power from dropping to a 160deg F stat and fan sw. In warm weather my trap speed is always higher if I can launch at 145-155deg F compared with a launch at say 165-170deg F.

jfb

Early C4's had 195 thermostats and later C4's had 180. For everyday driving , use the thermostat your cooling system was designed for. In cold climates and winter, your cooling system can get rid of heat fast enough so the 160 stat can control the temperature and 160 is too low to operate an engine at. In summer temps, your cooling system cannot get rid of heat fast enough to maintain 160 and the 160 stat will always be wide open and you will run the same temps as with the factory stat (under 35 mph). This subject has been hashed many times in the past and some members claim better times at the track, but thermodynamics predicts lower hp with lower coolant temps. One member did a dyno run with a 160 and then a 180 stat and measured no difference. Continental Motors ran some small engines (40 hp) at different coolant temps and tore down the engines afterward and learned by actual measurement that the higher the coolant temperature, higher hp , lower specific fuel consumption and lower cylinder wear was measured. The C4 was not designed to operate at 160 and I see no compelling reason to install a 160 thermostat . But its your car and you can do whatever you want.

Ky_Vette

Why not run the AC/Delco PN 10220957 170 t-stat, that way you can get heat if you need it and run cool enough in the summer. That's what I've done, rather than switch to 180 for winter and 160 for summer (I'm running the Derale adj. stat controlling both fans.

zzz

Good info! Thank you! I didn't realize that GM had a 170 degree stat. I should have mentioned that I have an 86 in case that influences a choice. I'm not worried about the heater.

I recognize that thermodynamically the warmer block would produce more HP and have less ring friction. I was also concerned with heating the incoming air in the L98 runners reducing HP. I didn't know the lowest temperature that the car remains in closed loop too.


[Modified by zzz, 6:28 AM 11/2/2002]

C4ForGeeGee

Why not keep it stock?

gtsyellow

sort of but as said above times are better when the engine is colder, it's rather simple, the colder air is; the more oxygen it can carry with it. the word "dense" gets used a lot around here. anyway i have a drilled 160 in the car now & think i'm going to try a 170 straight for winter, & switch back to the 160 in the summer. it's a very simple job to change therm's so i might as well get the best of both worlds. i, like you have my fans come on at 185. a 180 therm is just too hot for that, your fans would never stop running

Ron78Z&66Vette

I decided to run the 170* for the same reason.

Lone Ranger

Please explain how higher coolant temps help increase hp when the extra heat will also make knock more likely thus resulting in retardation of timing (LT1/LT4). The cylinder wear issue found in the test of the 40hp engines is not comparable to an engine using an advanced multi-vis motor oil, especially something such as Mobil 1, not when you're only talking a difference of approx. 10 - 12 degrees on average with 160 tstat vs. 180. The C4 was only designed to operate at the higher temps for emissions reasons.

ShadowLP

Go with the 160. I've been running a Robert Shaw 1" for years in my 1986 Z-51. On the warmest days of the summer, with both fans running, the engine never gets over 185 degrees.

Corvette0096

I run the 180 in the winter time for a couple of reasons, Get the water hotter for the heater and get the oil hotter that way it cooks off the moisture in the oil faster..

jfb

C4 engines have knock sensors for extreme loads that cause pinging, not for typical operation at normal operating temperatures and spark is rarely retarded during normal operation. The thermal efficiency of ALL heat engines (and automobile engines are heat engines) is inversely proportional to the difference between the inlet and outlet temperatures. The larger the difference in these two temperatures, the less work (hp) the engine can do, partly because energy is lost in raising the inlet air/fuel temps to the combustion temperature and partly due to energy that was not extracted from the heat energy of the exhaust (if you could convert every calorie of the air/fuel mixture to mechanical hp, your exhaust temp would be the same as or lower than the inlet temperature). I am sure that Continental used modern engine oil in their test engines and that cylinder wear is comparable to running the exact tests with a V8 automobile engine.
Another reason to run C4 engines at higher temps is to allow a smaller radiator.

silver & red CE

The example you cite is a non-computer controller engine, the results don't really apply to an LT1/4 or a L98. While you have mentioned the knock sensors and spark retard, you have neglected the ECT's effect on A/F at WOT. The PCM will lower the A/F ratio as the ECT goes higher, only during WOT. When my 96 LT4's ECT exceeds 180*F, the PCM starts backing off the WOT A/F from 12.5:1 to as low as 9:1. The effect of this lower A/F ratio is at least a tenth second in the quarter mile.

Eric

Lone Ranger

Well, you can say what you want, but my '95 feels slightly more responsive and stronger since I put in the 160 tstat and bypassed the coolant from the flowing through the throttle body. Don't have track times, not a trackster, but my butt-o-meter is pretty well calibrated ;)