Sweet87Camaro

I'm fairly new at programming my ECM. My engine is pretty mild. I have done some slight modifications to the spark tables and updated my injector settings. I have switched over to a 6e mask upgrade and I've pretty much figured out where everything is with the exception of my thermostat settings. I have installed a 160 degree thermostat and I need to know what prom settings to change to reflect the new lower temp thermostat. I searched the existing threads but couldn't find the information I was looking for. Can anyone help me out?

Grim Reaper

The biggest changes will be in your fan settings. Stock, the fans kick in around 210* and stop around 200*. With a 160, you need the fans to start kicking in around 175-180* and stop at 165-170*.

Remember that thermostats are "roughly" 160, they are not "exactly" 160. A 160* thermostat will BEGIN to open anywhere from 150-165* (sometimes even broader variations if it is made with "Chinesium", fully open anywhere from 155*-170* and begin to close 155-165* and be fully closed 150-160*.

If you can determine the EXACT temperature your thermostat begins to open, is fully opened, begins to close and is fully closed; then you can adjust your fan temp to within just a few degrees of those temps and keep your coolant temperature as constant as possible. You want your fan to stop working BEFORE the t-stat begins to close and you don't want it kicking in before the t-stat is fully opened.

As well, double check the temperature your converter locks if you have an automatic as well as some other temp settings which I forget at this moment and the temperature that your ECM goes into "normal" operation.

You MAY find that the cooler settings may require some tweaking of the MAF Scalar Tables as the overall amount of fuel based on the air flow has changed slightly due to the cooler combustion chamber. This is best done with using a WideBand O2 sensor...but your primary concern will be your fan speeds.

PS: A 160* was a bit too cool for optimal operation. This whole idea of using a 160* t-stat came back in the "old days" when people did not know how to adjust the ECM and it was primarily a "trick" to get the ECM to give more fuel. 160* is a bit too cool for optimal combustion. You REALLY want a VERY COOL incoming air intake with a VERY HOT combustion chamber. With today's ability to properly program the eprom, none of these "tricks" are necessary (or really desired).

If you MUST use a cooler t-stat, I suggest a 180*. It maintains a reasonable temp for combustion (and your heater) yet does have a slightly cooler temp.

Do some searching as I and others discussed this in detail a couple of years ago and I have a lot more info regarding "what to set" (if you MUST use a cooler t-stat) as well as discussions on the pros & cons of various t-stats.

The biggest thing to know, is the true temp you t-stat begins to open, is fully open, begins to close and fully closed. You can get this data with a good scantool that can data log. I found doing the tests on VERY cold mornings; and going up and down steep mountain roads the best way to determine this.

You'll notice things like when the t-stat firsts opens, the cold water from the radiator will cause your coolant temp to drop to the point where it closes again. Then it will begin to rise (this is your "begin to open") and stablilze to a maximum (this is your "fully open").

And, when you go down hills, you will notice that the temperature will drop until it hits a lower temp from your "normal cruising" temp. This is your "begin to close" temp. Again, your "better quality" t-stats will have very close temps within a degree or two from each other and very close to the rated temp.

Your cheaper t-stats from Sprawl-Mart will have wider variations between the opening and closing temps...and not necessarily very close to the rated temp. However, you would be amazed how bad some "expensive" t-stats were too. Things you notice when you have a scantool and log lots of driving.

Sweet87Camaro

Thanks for the input Grim Reaper. A lot of areas to take into account, but at least I know where to start now. The t-stat is a higher end model, but as you pointed out, that doesn't always make them better. I will run some test like you recommended and adjust the settings accordingly. Thanks again for your input.

Grim Reaper

Again, most of the "technical info" suggest that a HOT ENGINE is the best setup for performance. The "cooler t-stat" came about because of all the metal the TPI setup has, as well as the use of the radiator as your tranny cooler and the coolant used to cool the oil too.

Most of the guys who have built their engine, stick with a hotter t-stat for the engine (to maintain the hottest combustion chamber possible) and then a separate tranny & oil cooler, to stop the "strain" the stock setup puts on the cooling system.

For a "stock setup" (tranny cooled through the rad and coolant used to cool the oil), I still think the 180* is the better setup. I found it gave better overall performance than the 160* as well didn't freeze your butt in winter.

If you ever go to the SD setup, it is possible to control BOTH fans with the ECM and then you can easily maintain a stable coolant temp. Do some searching on "Operating Both Fans", it involves crossing a wire (which I forget at this time) to cause Fan2 to become operable by the ECM. This avoids having to use the special temp switch to operate Fan2 (stock is around 220*) or install a manual switch.

With that setup, I prefer to use Fan2 as my "primary" and Fan1 as my secondary. Fan1 is used when the A/C is on and the vehicle speed is under a set amount. This way with Fan2 as your primary, you can get additional cooling if your car is in stop-n-go traffic with the A/C on. With the normal setup, you only get Fan2 to operate if you have the "special temp switch", manaul switch or your engine is as very hot conditions (around 220*).

And lastly, whatever you do, as long as you have the MAF setup, don't waste your money on the relocated IAT/MAT. It's completely useless on a MAF car (something some vendors never tell you).

graebz28

iTrader: (5)

Great post. Grim, would you ever recommend running a 195, esp with a TBI to keep the manifold hotter. I know you are recommending the 180, which I am currently running, but would a 195 be better.

Grim Reaper

Many hot rodders, especially with a "wet manifold" type system believe "the hotter the better", and I'm inclined to agree as the heat does assist with atomization.

TPI, with it's massive "heat sink" and "dry system" may actually benefit from a "slightly cooler" intake charge but that is because of the "heat sink" and the LONG travel of the dry air. And, from my testing, I see no benefits running cooler than 180*.

thermodix

Yeah most of the "technical info" suggest that a HOT ENGINE is the best setup for best performance...



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Thermostat

Lucid

iTrader: (4)

Vader's post on Thermostats and Operating Temperatures :

https://www.thirdgen.org/forums/tech...-persists.html

You can do it on the MAF dual fan cars as well, you run a jumper wire from the green wire from the primary fan relay to the green wire on the secondary coolant fan relay. This effectively bypasses the temp switch in the head and will energize the relay(s) whenever the ECM grounds the wire.

The only drawback (or advantage) is that both fans come on at the same time and are not controlled independently.