4" exhaust dyno results

[TST Tech]

Here are some dyno results that we did on a 2003 Duramax automatic. All of the tests were done on the same truck and on the same day. We put it on the dyno, ran it stock and then installed a 4' system. All the test were ran at a constant speed of 55 m.p.h, tow haul mode, overdrive off. Here are the results;

Stock Power and Exhaust
h.p 200
torque 221
boost 20 psi
exh temp 1140

Power level 4 Stock Exhaust
h.p. 256
torque 275
boost 24 psi
exh temp 1200

Stock Power 4 inch Exhaust
H.p. 218
torque 248
boost 24 psi
exh. temp 1100

Power level 4 4 inch exhaust
h.p 274
torque 290
boost 26 psi
exh. temps 1130

After seeing these results on the dyno,I'd say the larger exhaust is a great ideal on the Duramax. I'd say most of the restriction was in the stock muffler. I don't know this for a fact though. The air box was completly stock. On one dyno run we took the airbox completly off and didn't seem to make any difference. However, on our 2001, it did pick up 4 more psi of boost with the airbox removed. The 2002 and 2003 must have a better design on the the stock airbox. Have a great day, Greg

[FISHDMAX]

TET TECH, which 4" exhaust was tested???

[GMCTRUCK]

Got any full load peak #s stock and modded? What box was being used? Did exhaust have any impact on peak #s? Details. Come on Greg crack those knuckles and start typing. If I hadn't asked somebody was bound to. ;)

[Paintdude]

Thanks for the comparo numbers.. smile.gif

[ski]

i thought the whole idea behind a 4" exhaust was to reduce EGTs' any power gains were an added bonus. Most manufacturers advertise 75 - 200 degrees cooler, dont see near that here. Am I just off base ? Can you go into more detail about the specs on the exhaust ?

[Maverick]

Those stock numbers seem very low. I suppose it varies with the dyno and area. My bone stock 01 Duramax 3500 put down 258 rwhp and 477 lb ft on BD's dyno in BC.

[GMCTRUCK]

Maverick, if you read TST's post again you will see those numbers were taken at a steady speed of 55mph on the drum. They are not peak, wide open throttle numbers but, power to the ground at a steady cruise. Although I'm not quite sure how that works.

[Maverick]

Needing 200 hp to cruise at 55 would be pathetic. He must have both rear brake calipars dragging then.

All the dyno runs on Allison trucks were done in 4th gear (except Kennedy's-He had Tech II help). Thats in the 55 mph range.

[TST Tech]

Hi guys!
I'll try to answer a few questions here. The exhaust system used was called Diamond Eve. It's nothing special by any means but it does the job. It starts at the end of the turbo downpipe and goes all the way back. It does have a muffler, but it's not doing much. I personally couldn't tell a difference in sound , with or without it. It is an aluminized system. Of course the box used was a TST Powermax. Anything else and I'd probably get fired! :D As ( Ski ) had mentioned, there isn't much of an egt reduction at that particular speed. We do see more of a reduction when we go to higher speeds.Overall we saw a reduction of 120 degrees. The reason we use constant speed is so we can duplicate spd and h.p. for a given temprature. On a typical 60 second dyno run the pyro usually doesn't stay still long enough to get an accurate reading. That's why we do constant speed tests. The dyno will not let the truck go over 55 m.p.h. with foot all the way to the floor. It's like simulating pulling a 40k lb tralior up a 7% grade. Maverick, I'd say you have very accurate dyno number on you truck. Our 01 put out 252 h.p. and 452 torque to the rear wheels. That's totally stock power and exhaust. We haven't tried a 5" exhaust, but I suspected there isn't a big difference between it and the 4". I believe that alot of the restriction is in the stock muffler. Guys, gotta go do some programming now, have a great day.! Greg

[ski]

greg

thanks for the added details and taking the time to post some numbers. do you have any full throttle run numbers for the same 03 truck ?