Alchemist

I've always heard that if you drop below a 180° thermostat, it's necessary to reprogram (or change the chip).

This is probably a dumb question....but Why??? :confused:

Paul T

No, the chip just kicks the fans on and off.. The reason the 160 is put in is with aftermarket chips they mostly turn the fans on at 180 and off at 170. You can put in a 160 and run a stock chip without a problem.. not much benefit though I would say..

vader86

It wont hurt anything if you run the stock chip with the 160. Sometimes people here have said that their car dont run right without the chip, which doesnt make sense, all they do is turn the fans on sooner.

Alchemist

That's kinna what i thought too....which was why i was confused.

Kizmo

I had the guy at my local NAPA telling me that if I ran a 160* thermo that my gas milage would suffer. He ssid that I would have to have the computer reprogramed. Is this true?

Thanks.

65Z01

I've heard some people say the same thing but think they just don't understand our EFI systems.

If your O2 sensor(s) are functioning properly, along with certain other sensors, gas mileage won't suffer. Well except at WOT because you will be burning a little more fuel to produce that extra HP liberated by lower coolant temps.

I run a 160 deg stat with fan sw and typically get 31-32mph on a long trip. This is even better than when the car was bone stock two years ago.

No Go

I believe the concern is when the car switches from 'cold start mode' to accepting information from the various sensors.

My understanding is when car is first started it resorts to set settings that are on rich side (like choke on carburetor). When set temp is hit, it switches to O2 sensor adjustments, etc.

If the car is too cold it won't come out of cold start. This causes poor gas mileage and probably decrease engine longevity...now if you could change this program switch...

The terms are probably not accurate nor do I know the temps, etc, but makes sense as my LT4 runs quite well when on cold start, but when it is hot the idles gets really rough (leaned out). My 91 ran fine on 160 and stock program as is my current LT4 with 160...course your experiences may be different.

:)

abigfoot

I dealt with this thermostat problem or question for years. Basically all the 160 thermostat does is open at 160(duh). This is fine for racing or if your not going to run your engine for extended periods. It will stay cool. If you drive on a hot day the engine will heat up. The small block will run at approximately 194. (For arguments sake we will assume the fans are on continuously). If we use the 160 logic, running no thermostat would keep it real cool, not the case. The water needs time to filter through the radiator. If it travels to fast it does not cool. Any temp thermostat will cause some necessary back pressure in the system to keep the flow at an optimum level. A 160 degree thermostat just extends the amount of time it takes to get to the design running temp. :cheers:

Mr Mojo

Simple sloution, put in a manual fan switch, that's what I'm gonna do.

KYVette90

Without getting scientific on this one, just get the low temp fan switch if you use the 160. It will work perfectly. :cheers:

JasonL

No Go, the "cold start" mode you're referring to is usually called open loop. I need to consult my service manual again, but I believe once the coolant temp hits 130F, the PCM goes to closed loop and will start using the O2 sensors, etc.

I have heard that keeping the 180 thermo while running fan programming intended for a 160 thermo can be bad. Reason being the thermo will never fully open, while the fans will still be trying to cool the car. The result is that the fans run continuosly and may burn out sooner.

Running a 160 thermo w/ stock programming shouldn't be harmful, I have done it before. Although your coolant temps will swing a wide range, from 170 on the freeway to 220+ in traffic. I don't know if this extra heat cycling is bad for parts or not.

Fastguy

That is how mine is now. I just added the 160* TS and I have a stock computer. It runs at 165-170 on the highway but still gets to 220-230 in traffic with the AC on.

No Go

Didn't realize the temp was that low (130). Don't know why our engines would ever come close to that when operating...but even DRM suggested against the 160 that I purchased from them for that very reason. I'm not having any problems though.

:)

JasonL

I need to correct my previous statement. The manual says the PCM goes out of open loop when the O2s are hot enough to operate, the ECT sensor is above a certain temp, and after a certain amount of engine run time. Goes on to say these exact values vary for each engine.

Not sure how I came up with the 130F figure, but I always imagined the PCM goes into closed loop well before the normal operating temps :confused:

90EXPVette

Or keep an eye out on e-bay, I picked up a new Hypertech thermomaster for $55.00 including shipping

Joe