AC WOT CUT-OUT SWITCH

[TandW]

Do any of our GM 8.1 litre techs know if the ECM has within it a function for cutting-out AC operation during periods of high demand on the engine. If so, is this function performed by monitoring intake pressure, or does it monitor throttle position. Finally, if this function hasn't been included or enabled, is there a shade tree mechanic work-around. I'm counting on steady Eddie here for an answer. You listenin'?

[TandW]

Do any of our GM 8.1 litre techs know if the ECM has within it a function for cutting-out AC operation during periods of high demand on the engine. If so, is this function performed by monitoring intake pressure, or does it monitor throttle position. Finally, if this function hasn't been included or enabled, is there a shade tree mechanic work-around. I'm counting on steady Eddie here for an answer. You listenin'?

[tech@brazelsrv]

well I'm not steady eddie, but I will tell you that the a/c cutout is controlled by the throttle position sensor (TPS). On the 8.1L it is set at the factory to 100% which means it never cuts out even under WOT. When we tune that engine we set it to cut out at 95% TPS.

[TandW]

Thanks for the comeback, Steve. Now may I ask why or if it can be set for say,50% open throttle. I'm sure there would be a measurable performance increase and less downshifting on most of the grades we encounter. What say you?

[kennersonf]

OK I give, what's WOT

[dieselclacker]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Fred K:
OK I give, what's WOT </div></BLOCKQUOTE>

How about Wide Open Throttle, Fred.

Dieselclacker

[kennersonf]

I figured it out just after sending the message. Thanks..

[cannon man]

my m/h has a switch on dash to turn ac on or off. works good too.

[TandW]

That's a good thing to have cannon man. I want my WOT AC cut-out switch to function. As Steve Brazel mentioned, it does not. Since I believe in reserving horsepower for hill climbing and EPA long ago recognized this device as the only viable fuel-saving add-on I intend to get mine working. What good is the technology if you don't use it. So I ask again if their is a way to change the setting to 50% throttle position. Or perhaps someone knows of an adjustable vacuum operated switch. How about it guys?!

[BellaBo]

Three thoughts....

1. It seems that if you were going to get your engine reprogrammed to 50%, you might as well get the performance tune and wouldn't need to worry about the cutout.
2. I also think 50% is too low of a setting anyway. Your A/C would be going on and off and probably putting more load on the engine when it engages than you would save.

3. Turn your A/C off and use the roof air to save the load.

[tech@brazelsrv]

Light to moderate driving at 60mph runs at about 50% throttle position, our feeling is that under WOT situations which are usually of short duration, you want as much power as you can get so we set it to 95%. If you want it to cut-out at a lighter throttle that would tend to shut it off too much, defeating the purpose of your a/c....obviously, if you don't need the a/c cycling you can manually shut it off. BTW, the a/c cycles with the defroster on as well.

[Brazels RV Performance]

We can program your ECM anyway you want it,we're like Burger King that way.So let's get you an UltraPower tune for you coach!!

[max49]

I want mine at 100%. I don't need no 'stinkin' WH making any more decisions for me. I want to be the captain of my ship, afterall it is mine and I'll decide if I want the AC running or not.
Who would design this cut off anyway? Actia? Most of the time when you get the 'reduced engine power' or 'limp mode' there is nothing wrong with the engine anyway except the computer that puts it into limp mode.
Your asking for for more troubles, IMO,
Please spare me.

[TandW]

Steve. Please elaborate again. As built, is the AC WOT cut-out switch enabled or disabled. And why do you reset it to function at 95%. Please explain further.