EGT's w/ exhaust systems, input wanted for comparison

[john8662]

First off, the purpose of this post is to allow me to compare my EGT readings and systems characteristics with others here on the forum.

The vehicle:

-1995 4x4 Suburban K2500
-4.10 gears (2400RPM @ 70 - 245/75 R16E)
-Pinnacle 4" Mandrel system (5" chrome tip)
-Stock computer chip
-Stock Turbo system/boost (WOT 9psi)
-97 cooling, 98 airbox (paper filter), gauges.
-New injectors (less than 500 miles on em)

Anyways, I wanted to hear from others concerning sustained EGT running empty running down the highway with similar configurations.

Before exhaust system and injectors,
600 deg PRE-turbo at 70MPH (2400 RPM)
-no wind
-flat ground
-outside temp 75 degrees night
-empty (just me, I'm not THAT fat).

After exhaust system and injectors (same time, doh!)
500/550 deg PRE-turbo at 70 (2400 RPM)
-no wind
-flat ground
-outside temp 75 degrees night
-empty (just me, I'm not THAT fat).

The reason for all this is I don't think that instaling an exhaust system is all its cracked up to be, or my factory system wasn't really all that bad. I did have trouble pulling hills loaded with a trailor, I always drove by the pyrometer, haven't gotten the same opportunity yet. I just read before I bought an exhaust system that most people were seeing 200 to 300 degree differences in EGT's? I don't see that. But on a positive note, the EGT's rise slower than before, but I can still punch it and get 1250 EGT empty towards 75mph from a dead stop.

So, does all this sound right, or is something wrong? Because I can't imagine installing a chip and trying to pull anything if I will always see high EGT's. I do know there is some room for improvement in my configuration, but small changes (air filter). Or an intercooler, but I am waiting for an intercooler design in front of the radiator/condensor.

Just enter:

-Type Of Rig (SUB, CC, etc.)
-EGT @ SPEED @ RPM
-Stock, Chipped, Boost
-Load, Temp, Terrain
-Exhaust size & Vendor.

THANKS

[ 09-30-2004, 01:40 PM: Message edited by: john8662 ]

[DmaxMaverick]

Under your circumstances, your EGT decrease is substantial.

You won't see a huge decrease until you get much closer to max power output. Try the same thing with a heavy load and a grade. Then you will see the big difference. EGT's are a good indicator of the work load put on an engine. A larger exhaust increases the envelope you can operate in. There is, however a point of diminished returns. 4" is beyond that, especially in your case.

Add the intercooler and more fuel to take advantage of it. If you are not after more power, then you haven't hurt anything. Exhaust overkill on a turbo engine doesn't hurt anything, except maybe your ears and wallet.

[Dvldog 8793]

Howdy
1999 CC longbox SRW-Type Of Rig (SUB, CC, etc.)
350* @ 70 @ 1800-EGT @ SPEED @ RPM
MANY mods, 5psi @ 70 -Stock, Chipped, Boost
Empty 70* flat-Load, Temp, Terrain
3.5 JK Muff backwards :D -Exhaust size & Vendor.
I have to REALLY work my truck to get over 1000* My probe is mounted about 6inches after the turbo
I have to agree that you wont see a huge difference until you start to pull. However, my exhaust was the first mod I did and it turned my truck into a whole different machine! Granted my down pipe was fairly smashed and the factory exhaust is restrictive but I never had a cat.
I am really surprised that you didn't see a bigger seat of the pants factor, maybe opening up the other end will help.
L8r
Conley

[autocrosser]

Just took a trip this weekend pulling a camper weighing about 8k. My 96 GMC EGTs were around 600 at 70mph measured right after turbo. Boost was running at around 9lbs. I never saw over 900 even when pulling up a hill running in 3rd gear. I just installed the Heath reprogramed ECM and what a difference it made. I thought raising my boost and the exhaust without the cat made a difference but this was really a difference. My injectors have 100k on them also with no sign of any problems. I have used a additive since the truck was new so they are lubed and kept clean.

[john8662]

350 degrees? I can see that, you probe is post turbo, mine is pre turbo. You do lose 200 degrees in the turbo coming out in the downpipe. I was just curious if it made a big difference in exhaust temp, I was suprised my exhaust upgrade didn't make THAT much difference. I'll order an Amsoil air filter, and see what that gets me. I do want more power, just don't feel i can make it safely.

[FarmerDale]

Checked it today - SRW long bed
70 mph - 2400 RPM - 600* Pre turbo
4" pinnacle system
Stock engine management

I saw a 100* reduction preturbo going from stock exhaust to 4" system. This was driving empty and keeps me around 400* most of the time. Pulling a load at 70 will push me around 700 on the level, and a slight incline will run up to 900 quickly.

[markrinker]

(Here are my results - #2 truck has 3" Heath exhaust and sender is in the downtube.)

No trailer - 450 degrees at 75mph, 7psi nominal boost.

Empty trailer - 600 degrees at 70mph, 9psi nominal boost.

5K average load - 750 degres at 65mph, 11psi nominal boost.

12 full load - 850 degrees at 60mph, 12psi nominal boost.

[Kennedy]

When comparing temps, if you want good data, you'll need to use the same gauge/probe setup, and even then minute differences can occur. Thermocouples are the biggest variable...

[john8662]

Thanks for the replies, looks like most of you are using a post-turbo install for your pyro. Kennedy has a point though. My gauges are ISSPRO, and there will be variation between ISSPRO and AUTOMETER, etc. I think I got the picture though, that the exhaust upgrade (heh, upgrade) doesn't make that much difference running empty on these rigs, but will on pulling. The only thing I changed so far is I'll loose my hearing by this time next year if I don't get a new muffler mentioned in another post. I guess the main exhaust restriction in these systems is just the turbo :mad: and I guess I need a stinking intercooler!

[markrinker]

If you plan to tow more than 10,000# with frequency, an intercooler would be a very good idea.

[Turbine Doc]

IC for heavy tow is a must IMO,

I never get much over 650 unless getting hard on it, with my Banks 3.5, before IC I'd easily hit 800-850 F when "gittin it" only time I get in that ballpark now is towing fully loaded GN trailer.

[DA BIG ONE]

580 deg pre turbo @ 70 mph, and 6 lbs boost, outside temp 93 deg, level roads.