EGT and Air Conditioning

[HGreen]

I have noticed since its gotten warmer and I am running the air conditioner, that my exhaust temperature does not fall below 325 (post turbo, I know, I need to go to pre-turbo) for a long time, like for 5 minutes when awaiting shutdown. If the airconditioner is off, it drops down in several minutes.



Does the air conditioner draw that much power that it keeps the fueling up at idle?

 

[pwr2tow]

I have noticed since its gotten warmer and I am running the air conditioner, that my exhaust temperature does not fall below 325 (post turbo, I know, I need to go to pre-turbo) for a long time, like for 5 minutes when awaiting shutdown. If the airconditioner is off, it drops down in several minutes.

Does the air conditioner draw that much power that it keeps the fueling up at idle?

Yes, the extra fuel to run your accessories will keep the EGT's higher and cool down longer due to the little extra fuel it takes to run them. Plus the little extra resistance caused to the engine. With the engine in gear but at idle, the EGT's will never go low enough for shut down due to the engine needing more fuel for the extra friction or strain on the engine.

 

[Lightman]

I have noticed since its gotten warmer and I am running the air conditioner, that my exhaust temperature does not fall below 325 (post turbo, I know, I need to go to pre-turbo) for a long time, like for 5 minutes when awaiting shutdown. If the airconditioner is off, it drops down in several minutes.



Does the air conditioner draw that much power that it keeps the fueling up at idle?

Not so much extra power but the condenser sets in front of the intercooler and puts hot air on the intercooler so it can't cool as well. It will also cause general EGT's to be higher.

 

[wcjp]

During cooldown have you tried an infrared temp gun? I wait for below 300deg preturbo. The temp gun is also handy for AC troubleshooting, bearings, brakes, home maintnance and whatever else.

 

[WCPoe]

For what it's worth, I have gotten in the habit of bumping the A/C switch off just before I pull in the driveway. You still get cool air for a minute or so and it really helps the EGT's come down with the A/C off.

Bill

 

[RMalone]

I also turn the a. c. off about a block from where I intend to stop. If my truck will get to 300deg in hot weather with a. c. on I don't have the patience or time to wait that long, in fact I shut down when egt drops below 330deg. It's sort of funny were told not to idle these engines for very long... but don't shut down until egt is below 300deg! Has anyone else noticed how much more you worry about your diesel than you EVER worried about your past gassers? Don't get me wrong I love my truck, but I have never had a vehicle that I adjust my life to like my CTD.

 

[CDonaldson]

Kind of contradictory - don't idle too much and wait for EGT's to go down. Glad I have gauges, but then it does make you worry more without them, another contradiction is when you put in gauges to protect your investment the dealers use that against you in warranty stuff. Loose-loose situations.



I think you are right RMalone, I don't recall EVER worrying about my gassers as much as I worry about this truck. When I turbo'd my Miata and installed gauges I did pay more attention to this stuff. Preparation for the diesel I guess. Also, I think when we start modding we also start worrying more, reading the forums doesn't help - so much all the time increases paranoia.



CD

 

[Vaughn MacKenzie]

For what it's worth, I have gotten in the habit of bumping the A/C switch off just before I pull in the driveway. You still get cool air for a minute or so and it really helps the EGT's come down with the A/C off.

Bill

I was told by an HVAC technician that shutting off your vehicle and starting it with the A/C on puts a lot more strain on the system than doing it while the vehicle is in motion. I've always done that with my trucks especially when it's in the 100s and maybe that's why the A/C still works great on my 405,000-mile '96.

 

[DeezelDood]

My Westach hangs at 400 with A/C on (when I forget to shut it off). I always shut off my a/c comp before I shut off the engine. Not sure why, someone told me a long time ago to avoid starting engine with compressor clutch engaged.