Lone Ranger

These hot days I can tell by SOTP the car feels stronger when the coolant temp is below 190 or so as it is coming up to operating temp, but it usually runs 197 F to 210 F as it's current operating temp zone and I can feel that some of the responsiveness that was there below 190 F or so seems to have faded.

Soooooooo I think I'll put in a 160 t-stat, after all I have a Hypertech Power Programmer III that will program my fans for the 160 stat.

I assume I need to drain the cooling system prior to this to avoid any risk of wetting my Opti-spark, right? Just had a coolant flush and fill three months ago, but if it must be done it must be done!

Any other special tricks or techniques that make the job go smooth? Thanks for any advice :D

0ski_dwn_it

30-40 minutes not including the mess you will have to clean up. Its pretty simple.

jtjerry

if you do not reprogram ecm, you will have bigger fuel consumption cause ecm at 160 still enrich air/fuel mixture.
I had for 2 years 160 stat and after replacing it with normal 195 my car burn less fuel and perhaps run better so. If you can reprogram point when fan start better change that only, do not change stat.

Jerry

lite blue

Be careful removing the two bolts that hold the housing to the manifold. One of mine was corroded pretty badly. I broke it off, and ended up removing the entire manifold to go get a helicoil put in. :mad
Learned a lot about how the TPI is put together, though. :)

Lone Ranger

1st time I've heard this info about ECM's reaction to engine operating w/ the 160 thermostat installed. Anyone else?

Knight Ryder

I just did mone today, actually. Took me 15 minutes, not counting the time spent going to the auto parts store to get a magnet to get a :cuss dropped bolt.
I didn't drain a thing, just threw a whole bunch o' towels over the offending area and yanked the ol' thing off. New t-stat drops in, cover on with two bolts, good to go! :yesnod:
It seems like it's easier if you pull off the hose on the t-stat housing. That way you know where all the poop will go (out the neck) and it gets everything out of the way.
Definitely need to reprogram fans, but it did drop temps. Sitting at idle for ~15 minute w/ A/C (and therefore fans) on, sat steady at 192!!

EDIT: Oh yeah, refill coolant tank... :bb Wouldn't that one be embarrassing?


[Modified by Knight Ryder, 10:52 PM 7/8/2002]

Lone Ranger

Did you also open the air-bleed brass valve to get all the air out while refilling the coolant tank (keep filling until she bleeds coolant steadily)?

Knight Ryder

Yep.

silver & red CE

This may be true for an L98, but the LT1/4 goes into closed loop at much lower temps (~95*). So no, don't worry, on an LT1/4 your fuel consumption won't be effected. BTW, your butt-o-meter is very accurate. The LT1/4 PCM will enrich the WOT A/F ratio when the coolant exceeds 180*. It can go as low as 9:1, that's will cause big losses in HP.

Eric

Lone Ranger

I do try to keep it calibrated :D

NE14SIN

Ryder, what temp T-stat did you go with? I have an LT4 too and I want to know what everyone else is running.

kkonen

You SHOULD have more gas consumption with a lower temp thermostat. If you don't, you have a problem. If the engine is running cooler, the air charge is denser, requiring more fuel to get the proper air/fuel ratio.

vms4evr

No big deal at all. Like the others said be careful with the 2 bolts on the housing. It is a machined part and doesn't like to be banged around. I had to flush mine. But if you drain off some coolant from the radiator and make sure the upper reservoir is below the tube that recycles the fluid then you won't make a big mess that can fall down on the Optispark.
Fill it back up from the reservoir until it looks full then open the bleeder and let some out to get rid of the air. Put a towel under the stat housing so it doesn't pee down on the Opti. You'll also have less mess on your engine that will stink for days...
Graham

silver & red CE

While this is true, the effect is much less than the problem Jerry is speaking of. In these days of computer controlled cars, the choke function is a computer program instead if a plate in a carb. On the older L98 the engine computer didn't go into closed loop mode until the coolant exceed ~150*. With a 160* t-stat and cold weather the choke function might never shut off. It's no different that if the choke is stuck on a carb, the gas mileage sucks.

On the LT1/4, the computer controller is more powerful and it looks for a couple of parameters, the two key ones being the O2 sensors are heated and the ECT is above ~95*. This change is due to an EPA mandate, lower emissions during the start up cycle.

Eric

Knight Ryder

I went with a 160*, but I have not yet reprogrammed the fans to come on earlier. The car definitely runs much cooler at speed, but still climbs in stop-and-go (flip on A/C to cool off). I was running about 173* this morning on the freeway. Seems to stay almost exactly 100* above outside air temp when cruising.
Definitely a BIG improvement. :seeya

Knight Ryder

:eek: :eek: Are you SERIOUS?? No wonder this is such a popular mod! :yesnod:


[Modified by Knight Ryder, 11:32 PM 7/9/2002]

Lone Ranger

I would have thought the PCM would lean the mixture for higher temps. I thought lower temps called for a richer mixture, higher temps for a leaner mixture?

kkonen

Lean mixtures result in higher combustion temperatures. Enriching the mixture is one way of cooling the engine. Airplanes have an adjustable mixture to compensate for altitude. There is a gauge in the cockpit that measures Exhaust Gas Temperature (EGT). You know the right mixture by reading the EGT. Too hot, enrich the mixture, too cool, lean the mixture.

Eric 96

I just did this on my '96. If you haven't already, you should do the Throttle Body Coolant Bypass while you are at it. Just take the elbow off of the passenger side of the throttle body, then move the hose from the driver's side of the throttle to the tube running up the passenger side of the plenum.

The Tstat is easy to swap....might as well do a drain and flush of the coolant while you are at it...I also changed my upper and lower radiator hoses.

silver & red CE

Exactly, the factory enriches to prevent detenation. If you go to the strip, do a simple test, run the 1/4 with the ECT reading @ 160, then do a run with the ECT @ 190. You'll see the cooler ECT run is better by 1-2 tenths. I have a scan tool and after the ECT exceeds 180, the PCM starts leaning out from 12:1 all the way down to 9:1. At 9:1 you are giving up big time HP. Addressing this issue is the #1 way an custom engine program can help performance on LT1/4 cars. BTW, Hypertech does nothing for this problem.

Eric