I have an 88' iroc 350 tpi and i want to make the car run a little cooler and i know that stock is 195 degree. The car already runs a little rich but should i keep it at 195 or change it to like 165 0r 175. THANKS ANY SUGGESTIONS!!!!

 

a 180 would or under works great. I would reccoment actually drilling holes in it (this is, if it is only driven in warm temps) so even when the stat is closed it is still flows some. The best thing you can do though is get a fan switch.

 

I'd be careful when drilling holes into thermostats... you don't wanna get tiny metal particles in the coolant. Just go with a lower thermostat if it's that big of a deal, mine has a 160 (runs great in the summer...but try getting heat in the winter... not happening!!)

 

if your tpi runs to cold it won't go into closed loop. I would put in a 180deg stat and a jet fan switch. thats what I did and it worked great.

 

my personal choice is the robertshaw 160 degree. what makes you think a 160 thermostat wouldn't allow it to go into closed loop? it's quite warm enough for closed loop.

 

Actually, a 160* is to cold for computer controlled cars. Unless you mod the computer or a chip something like that. I would go with a 180*.

 

Zippy is right, a 160* is more than ample for the engine to go into closed loop. The problem is the temp causes a lot of little parameters in the eprom to think you are in "warm up mode" and you end up burning gas. In fact, the IAC Learn Temp is too low to "learn", which can cause an idle problem.

If you tune your eprom, it really doesn't matter which t-stat you use because an "optimized" eprom for each yield similar performance results. I personally prefer a 180* T-stat over a 160* T-stat as I have found that the 180* allows for more consistent tuning and you don't have to freeze your butt off in winter.

 

well ya, if you have made a new eprom you can put in a 160 but if you haven't you need to do a 180. also you have better heat in the winter.

 

Actually, the IAC Learn Temp needs to be changed even for a 180* T-stat or you loose "learn mode" on the IAC. There are temp settings in the eprom that require changes even for a 180* (if you want to be optimal).

My point is, if you do the eprom then it really doesn't matter which t-stat you use so you might as well use a warmer t-stat to keep warm. And if you aren't going to adjust the eprom, you are better off NOT going with a cold t-stat.

I use to be a strong advocate of 160* T-stats until I got into eprom burning and tested different types. But with "tuning" I found better consistency with a 180*.

 

i agree with you glen, the 160 in warm up mode is a richer a/f ratio and idle situations can arise, but most never have a problem. one nice advantage to the cooler thermostat aside from the power difference is the transmission (on automatics) temperature runs lower. with a slight advance in timing, the a/f is kinda a nice power difference.

 

Changing the thermostat wont make it run any cooler in situations where the car isnt getting much air, like city driving. The ECM turns the fan on at around ~220 degrees, so no matter what stat you use, around town it will still run hot. I'd suggest an auxiliary fan control thats adjustable. I have about 5 Hayden units on different cars around the house.

 

if you drive the car in winter then go with the 180 most definately, especially if you run on the freeway alot. i live in VA, not terribly cold and i can drive my car yr round but it does get cold in the winter and i run on the freeway at least 50%+ of the time i'm in the car. luckily i changed my thermostat from 160 to 180 and gained alot of personal warmth, it doesnt get extremely warm on the freeway but alot better for me then the 160 and in traffic it still doesnt get over 180 or so. oh i have a hypertech stage 2 chip so the fans turn on at 170 anyway.

 

I really think it depends on just how cold it gets where you live. I switched to a 180 T-stat awhile back and noticed a much improved engine thermo difference.

But now we are getting our cold spell and I THINK the cooler engine temps are causing the car to stay in open loop longer than usual. I say this because nothing else has changed but my gas mileage has dropped.

 

Zippy, with the cooler t-stat (and warm up mode) you get a "pump shot effect" (from the richer mixture) which can also be accomplished by tweaking the "pump shot" tables. This is what I did when I went to a 180.

However, the tranny is a good point. As I said before, I have ran a 160* t-stat for YEARS until I switched back to a 180* (because I've moved to a cooler climate). I know people are stunned to hear that I have over 200,000 miles on my original waterpump and all my hoses. I changed all my hoses last year because I just felt I was living on borrowed time and I plan to change the waterpump when I build up my engine this spring/summer.

Somehow, I think I recall a year or two ago us having a debate (when I still was advocating the 160*) and you were advocating a warmer t-stat. Seems we have come "full circle". This is not a criticism of any sort, just how people can change their opinions as they do more "playing/tuning".

What I do like about the 180* (over the 160*) is better consistent performance (once you get into the eprom) and it makes for more consistent fuel tables for SD cars. I think a person has to play with both to see how both react and what a person prefers.

BTW, are you still playing with eprom burning?

 

Are you running a relocated MAT sensor and/or the TB coolant bypassed? With SD cars, the MAT definitely affects the fuel trim. I found that I had to redo my entire MAT compensation table in the eprom (took a year of driving to tweak it) as I would notice that my BLM/INTs would dramatically drop (richen) during winter (reducing gas mileage). Tweaking that table in the eprom now makes my BLM/INTs very consistent around 128/128 and my gas mileage is the same in both hot and cold weather now.

 

I do have the IAT sensor relocated (if its the same thing). Never thought of your point though, and its a good one.

One of these days I will definitely get in to PROM burning. Too lazy. Heck, I even bought a used scan-computer and havent even hooked it up yet (used on other cars, just not this one).

 

Yes, the IAT is the MAT. MAT is the correct technical term GM uses on our vintage of cars.

And relocating definitely affects the fuel trim as you will be reading substantially lower ambient air temps. The stock MAT compensation tables in the eprom are expecting the MAT to be located in the plenum and to have coolant flowing through the TB. When you change those, the ECM will detect the cooler temps and start adding more fuel - which is the last thing you need as most cars tend to be overly rich as they are.

Another risk you run with a relocated MAT and really cold weather is you may trigger an SES O2 Rich code. Last year when it hit 0*F I triggered an SES code 45 - O2 Rich error a couple of times when I had my MAT relocated. Hooking up the stock MAT sensor cured the problem and that is when I dived into the eprom to find out why. Adjusting the "MAT Inverse Look-up Delta Multiplier" table fixed it and now I am always 128/128 on my BLM/INTs in all weather from just below 0*F to over 100*F ambient air temp.

 

I should add, that with a relocated MAT you also may cause the EGR to cease to function when the ambient air temp drops under 40*F (approximately). That too affects your gas mileage, even when driving in part-throttle in closed loop. You need to adjust the "EGR Enable Temp" to a very low number to ensure your EGR continues to function. Remember, GM never intended the MAT to read the actual ambient air temperatures, it's expecting the MAT to be reading the heated air in the plenum.

This problem also exists for MAF cars. The fuel correction is not a problem for MAF cars as the MAF actually detects the ambient air temp via the air flow. Relocating the MAT on a MAF car does nothing except causes the EGR to cease to function at ambient air temperatures under 40*F. It is actually a useless modification on a MAF car that causes the EGR to cease functioning (at cooler ambient air temps) with no benefits.

And lastly, on SD cars, the eprom will sometimes use the MAT reading instead of the CTS reading if the ECM thinks the CTS is in error. GM uses this logic is quite a few of their ECMs. I haven't dived into the MAF system enough to see if a similar "routine" exists. But I wouldn't be surprised if it does.