Hey guys,
After installing the Eclipse GSX fuel pump (no other turbo mods yet), I noticed that my EGT's climbed from 1250 F to 1350 F during moderate-load, highway driving (usually with the A/C on, but not always).

Granted, I didn't run a lot of tests before I put on the new pump, but I don't ever remember the temps getting much above 1250 F.

The car runs great, and is having its best NA pickup ever (almost makes me want to keep it NA . . . nah smile.gif ), so I'm not worried.

However, I would like to know what range EGT should be in, and what indicated a lean condition.

thanks,
ac

 

You cannot really determine lean or rich from exhaust temperature. In some cases, being lean can make it cooler, while other times it can make it hotter. It depends on how lean/rich you really are...

Don't use it for that smile.gif

EGT's are a good indication of "emergency". If your EGT's climb higher than 1600F, it's time to shut down. If you're at full throttle and it sticks at 800F, it's time to shut down.

From the sounds of it, your car is running about right. Highway cruise (3000-3500 RPM) with A/C on should net around the 1200F mark, give or take a bit depending on the car.

 

I guess what worried me was the increase of 100 degrees F with the new fuel pump. I was worried about leaning out (although, if anything, the mixture should be richer).

It could just be the oppressive heat, maybe the gas I used, and I noticed that it is only at higher throttle positions (cruising at 65 had lower steady-state EGT's -- 1250 F; at 75 mph, the temps went up to 1350 F).

So maybe I'm just paranoid. I just want to make sure the car is good and ready for the forced air induction. smile.gif

thanks Red,
ac

 

Well, this is exactly why EGT makes a bad lean/rich indicator

Theory time!

If you're TOO lean, the fuel could entirely burn up and then have enough time left over to cool off before it's pumped out of the cylinder. (cold EGT under full load)

If you're TOO rich, there could be so much fuel that it's still burning when you're pumping it out of the cylinder. (hot EGT under partial load)

These EGT readings go against what the actual cylinder temperatures are, so it makes it confusing. The best way to go is a fast-acting CHT gauge along with an EGT gauge.

If the CHT rises dramatically when the EGT drops, you're running lean. (aha!) If your CHT drops through the floor and your EGT's skyrocket, you're running rich. (ooh!) If they rise and fall along the same lines, you may still be lean or rich but you're likely not into a danger zone until one of the gauges tips into the yellow...

You can also alter EGT by cam timing and ignition timing. Even certain octane ratings of gasoline will make it vary...