MaSTeRofDZaSTeR

My mechanic fixed my idle after a while of having too low of an idle, but now he isn't recommending that I put a 160 stat in. He says stick with the stock thermo cuz the 160 would start the engine at too low of a temp to go into open loop mode so the engine will run correctly. Is this true? Obviously others can run with this easy, but he just suggests I keep my sys running cool through manual fans and other cooling procedures. Any opinions? Also he doesn't think I'd pass emissions out here in AZ with a 160 stat. :confused: (I know the engine burns hotter to burn carbons better for emissions but this seems too out of place.)


[Modified by MaSTeRofDZaSTeR, 10:15 AM 6/7/2002]

98NYFINESTVETTE

If you use a 160 thermastat, You will need the fans to come on sooner. I replaced my thermastat with a 180 last week. I feel that this made adifference. The car feels more crisp, does not run as hot, on the hwy it will maintain 179 to 183, local traffic it will go up but I have a switch for manual fans also. I feel the 180 is a great idea for a stock engine.

vader86

put the 160 in, every mechanic ive ever known will recommend the stock thermo, it might take a little longer to go into open loop but you wont have to worry about it running hot during summer.

Mike_88Z51

Do what your mechanic says. It never ceases to amaze me how many people go pay for good advice from a professional an then listen to someone who isn't a professional.

A 160 thermostat is FULLY OPEN at 160 dregrees. A 180 thermo is fully open at 180. The stock thermo is fully open at 195. When fully open all 3 tstats allow the same amount of fluid flow. This means that if your vette is already seeing temps above 195 on summer days the 160 tstat will do ALMOST NOTHING to help. (Granted, it will take a minute or two longer to get from 160 to above 195, but it will happen and the max temp reached will be the same.)

When you start the EFI vette engine cold, the system is in "open loop". No feedback from the O2 sensor. The ECM sets mixture control based upon predefined values. Once the engine reaches operasting temp the O2 sensor starts sending feedbak to the ECM and the system goes into "closed loop" since it has the O2 feedback to judge the results of its mixture mods. The sooner your vette goes into closed loop the better. Both for emissions and efficient engine operation. That is the reason for the stock 195 tstat.

Why do so many people recommend a 160 tstat? Because on a COOLER day or with a more effective cooling system the tstat will allow the temp to remain lower. This is only true however if the max temp was going to be BELOW 195 with the tstat wide open. So if you are racing and your cooling system is efficient enough, then you will have full fluid flow at 160 which tends to provide more HP at the cost of MPG and emissions. Important for racing not so much for stock. Remember, "heavy tracffic" to a race car is still at speeds over 100 mph. They have plenty of cooling air.

Example:
If your car is generating enough heat on a normal day so that with a fully open tstat it would reach a max temp of 183 degrees, then either a 160 or a 180 tstat will allow you to max out at 183 degrees. Both the 160 tstat and 180 tstat are wide open below (183) the max temp reached. Both are allowing max fluid flow. The final temp is dertermined by amount of heat carried away when the tstat is wide open. The 195 tstat will not be wide open at 183 so it will block flow until nearly 195 is reached.

Notice that the same effect (max temp 183) is obtained with a 180 tstat and with a 160 tstat in the above example. The 195 tstat is NOT fully open so it blocks flow at 183 degrees until 195 is reached.

If enough heat is generated that the car reaches 200 degrees, then all 3 tstats will be fully open at any temp above 195. No change in max temp because the limiting factor is cooling system efficiency.

Your problem is not the tstat, it's your cooling system limits. Go into the Tech Tips section and print out the tip on pulling and cleaning your radiator. I spent one Saturday morning (about 4 hours) doing mine. I scrubbed the radiator with Dawn detergent and straightened every single bent fin. BIG difference.

Next look into a manual fan switch, or if you have a secondary fan switch like on my 88 L98 with Z51 you can buy a replacement secondary switch from MidAmerica ($20) or other retailers that automatically turns the secondary fan on earlier. MAJOR improvement.

I promise that if you put a 160 tstat in and do nothing else, it will not change max temp on a hot Arizona day. I know, I have friends in Phoenix.

Long story short - listen to your mechanic, he knows what he's talking about.

Mike

Kieran Cox

I have the 180 in mine and Mike is right, no difference. Although the car does cool down lower between stoplights.


On the highway it runs at about 182 coolant and 195 oil. To be honest I don't like the coolant that cold for long periods. I think I am goin to get a 195 tstat.

RX7 KLR

I have a 160 in my 89', runs fine and passes AZ smog every time.

65Z01

I'm just across the TZ in W.Nyack, NY so our cars will be seeing similar temps.

I've been running a 160 deg stat for 1 1/2yrs and have had no problems with the ECM going into CLOSED loop mode quickly, not even in winter months.

Indeed when on the Garden State in 95deg weather engine temps will climb to maybe 175 but in 70 deg weather she runs at about 155deg. And yes throttle response and power are both better.

Two weeks ago on the way home from E-town my average mileage on the GSP was 31-32mpg so no problem there either.

Do the stat & fans, you'll like it.

pablocruise

160* here, no probs at all. Tried 180* also. Saw no difference really.

PeteL

Mine goes into closed loop at about 120*!

Robert Shaw high flow 180*, winter cruise temp about 170*, highest peak about 207* (just last week). Water temp on Pocono stayed around 200* . At 65 on the GSP in 95* weather I'll run about 185 with AC on. In stop and go it usually goes to 200 to 205.

Clean radiator, 200* aux fan switch, Craig Marcho chip 195* on 185 or so off. Running about 40% green / 60% distilled water. 16 psi cap. And lots of base advance. Engine is very happy!

TODDZWER

I live in IOWA today the temp was 88 with 76 per humidity, with the 160 therm and aux cooling fan switch it never got above 174 in the lanes. before the therm switch and the fan switch it stayed about 220. you make the choice :yesnod: