To start off with, the car is a 2001 Camaro SS M6.

Went to dyno this past weekend.. Added underdrive crank pulley and gutted my cats since last time I went, but removed my FTRA, but still have FRA. I was hoping to gain a couple hp. To my dismay, my car made the EXACT same power and torque from 2500 rpm (where dyno reading started) up through ~4200 rpm, then the power and torque was lower than before.. Around 4700 rpm both climbed back and matched the previous curves before falling off again around 5200 rpm and staying down through the end of the pull. The curve doesnt look quite as smooth, but its not so jagged I would think there is a problem either.

Before, with lid, S3, FTRA, and loudmouth, I made 342.6 rwhp and 355.3 rwtq.
Now, with same lid, S3, loudmouth, and the "new" SLP pulley, car makes 338.7 rwhp and 353.6 rwtq. Both sets of numbers are SAE corrected, and from the same place/same dyno.

My first thought was the SLP pulley was causing me to lose power, even though its supposedly been redesigned to prevent the high rpm false knock retard... However the car ET'd better and trapped higher consistently at the dragstrip with the pulley, and overall feels stronger and I have a noticeably more difficult time keeping traction which led me to believe there should have been some gains.

My second thought, maybe the FTRA made a difference on the dyno? Im going to put it back on this week and possibly try to dyno again this coming Thursday.

Another thought I had, since the curve doesnt look as smooth, maybe the car needs a plug change and its causing some high rpm misfire, so Im most likely going to put TR55s in before re-dyno also.

A friend brought up a point that I hadnt thought of... My car has an exhaust leak where the 2 sides of the y-pipe connect before merging together from where I broke a bolt on each side when I gutted my cats. He said maybe the exhaust leak is causing a power loss, which I dont see how, but then I thought maybe the leak is causing some sort of false knock? Im going to get new studs put in the ypipe and fix the exhaust leaks also mainly because its annoying as hell, but on the off chance that its causing a power loss. Anything is possible I guess.

Anyone have any input? After I change plugs, fix exhaust leaks, and put FTRA back on, if its still down on power I guess Im going to blame the pulley and replace it with an ASP. Id like to hear everyone's opinion though. Thanks for reading.

Later,
Chris

 

1.Car hasn't had time to re-learn after all this work.
2.Leak= Lean running = knocking may cause spark retard
3.Gutting cats may not help power on a stock engine
4.Let's see the 1/4 times, 60 ft and mph. THEN you can see how your power is coming along.

Mike

 

What was the weather like on both days?

A pulley usually doesn't show that much of a dyno gain. The gains are better seen in ET.

 

Car had plenty of time to relearn things, stuff had been on for a couple months.

Ive gotten my exhaust leaks fixed, changed my plugs, and put my FTRA back on.

True. I expected more from the pulley than the cats though.

With similar 60 foot times, my car gained appx. 2 tenths and 3 mph. However Im not sure if the DAs were similar or if one was in a much lower DA.

before pulley: 2.175 60'= 13.152 @ 109.50 in the summer though (mid june)
after pulley: 2.176 60'= 12.978 @ 112.03 in fall (mid october)

both runs were with FTRA.

The difference in ET and mph is why I expected to see hp gains.. but I guess they could be just as much due to the DA as to power gains. Track is closed around here, so dyno numbers are all I have until tracks open back up next spring.

 

Both runs were corrected to SAE... but one run was in May and the other was in December. Pretty big difference in weather, but with the correction it shouldnt matter.

 

if it trapped higher and got a better ET consistently after the pulley, then it could be just that the dyno results are off (either the before or the after). in either case, the car IS faster, proved by the timeslips, so you're good to go