Loss of 29 HP with upgrades?

[goldcup]

Title says it all in 2007 2001 GTS was dynoed at 438.57 hp/481.79 torque,at the time car had straight exhaust ,no cats or mufflers.
2008 car was dynoed at 409.93 hp/445.67 torque
Changes since 2007:
3.55 gears
3" highflow cats/catback exhaust
roe sct flash
An additional 3-5 thousand miles
One other note plugs and wires were changed before run in 2007 have not been changed since.
I won the prestigious KCVCA's runt of the litter award,and while I am honored I would prefer not to repeat

[Russ M]

Your car is an 01 which means its a creampuff, so your original reading of 438/481 was just wrong. An honest dyno will show 395-405 for any 2000+ gen 2 in stock form, any more than that and I suggest going to a different dyno shop.

Your new dyno runs are in line with a 2000+ with slight mods. Also don't forget it is not uncommon to loose 5-10rwhp with shorter gears.

[goldcup]

open to anything but the car was run several times and these numbers were consistent.
several other 2000 + cars were run the same day and their numbers were reasonably close to this cars numbers,for what it is worth

[johnk]

So the first number is with straight pipes, no mufflers, no cats, and then you installed mufflers and cats and lost 29 HP (on different dynos and different years) ? Are you suprized? Installing cats and mufflers to a straight pipe exhaust isn't an "upgrade" it's a "downgrade".

[MTGTS]

same dyno? and what kind?

[triblk6spd]

Yep, besids the variant in dynos you are going to LOSE some power when going from NO exhaust to cats and mufflers. Add that to the fact that you LOSE a few with the addition of gears and there you have your answer. You may have gained a few torque. Did you?

[plumcrazy]

and a leakdown test should be done if you're really worried about it. but id bet its a different dyno and the temp was warmer

[dave6666]

Originally Posted by Russ M

Your car is an 01 which means its a creampuff, so your original reading of 438/481 was just wrong. An honest dyno will show 395-405 for any 2000+ gen 2 in stock form, any more than that and I suggest going to a different dyno shop.

Your new dyno runs are in line with a 2000+ with slight mods. Also don't forget it is not uncommon to loose 5-10rwhp with shorter gears.

I'm officially arguing with you on the stock Gen 2 numbers you think should be correct.

My near stock Gen 2... (tubes, filters, cat-back)

Baseline '01 GTS - I'm running rich?

[jamie furman]

Originally Posted by johnk

So the first number is with straight pipes, no mufflers, no cats, and then you installed mufflers and cats and lost 29 HP (on different dynos and different years) ? Are you suprized? Installing cats and mufflers to a straight pipe exhaust isn't an "upgrade" it's a "downgrade".

I agree it has the be the exhaust, thats where the 29hp went no doubt!

[ViperJohn]

I agree: Cats and gears. The other possibility is that one set of results is corrected and the other is not. That can have an effect on the horsepower reading.

[redtanrt10]

Back to back the 3:55's reduce the dyno hp by 3%

[Dom426h]

+4 on the exhaust 'downgrade'

both runs were done on the same dyno?

[CROM]

Originally Posted by goldcup

Title says it all in 2007 2001 GTS was dynoed at 438.57 hp/481.79 torque,at the time car had straight exhaust ,no cats or mufflers.
2008 car was dynoed at 409.93 hp/445.67 torque
Changes since 2007:
3.55 gears
3" highflow cats/catback exhaust
roe sct flash
An additional 3-5 thousand miles
One other note plugs and wires were changed before run in 2007 have not been changed since.
I won the prestigious KCVCA's runt of the litter award,and while I am honored I would prefer not to repeat

438whp/480tq is a lot for a creampuff, or any year Viper, with just a straight through 2.5" exhaust system and nothing else. The STOCK numbers for that car should have been 395whp/440tq or so. 43whp and 41tq just from removing the cats and mufflers...seems sketchy. I almost guarantee these numbers are uncorrected numbers.

Fast forward to your recent run. Your numbers are almost exactly what my 98 car made with K&Ns and Smooth Tubes, w/ stock exhaust. If the SCT tune does what the tuners say it should be doing your power curve should have a lot more meat in the low and mid range, but your peak numbers should only be up 10-15whp. Do you have both dyno charts? As others have said you will experience a loss in WHP on the dyno with the gear change. I think something is a little off, but not way off. You should currently be making right around your inflated numbers from your first set of dyno runs in 2007.

[Doug Supercharged Vipers]

I suspect the exhaust may have traded off some horsepower and the gears will scrub some of the hp numbers as well.

I would suggest to take a trip back to the dyno and see if you can remove the SCT program, dyno the car, and then reflash the PCM with the SCT and re-dyno.

This will provide you with better +/- comparison hp numbers "same day, same place"

Best of luck!

Doug

[goldcup]

Thanks for the info,car will go back in the next couple of weeks and I am going to remove the program and run etc...The dyno is the same dyno/location as last year temps etc were nearly identical.I know nothing about dyno's so I can only take everyones advice and start w/o program and work up from there.The new run does show car making power earlier and then tapering off,which explains the feeling of the car being stronger.

[Camfab]

I've had two 2000 ACR's built on the same day. The first car made 424 RWHP with a Corsa cat back only. The second car had a Corsa cat back + high flow cats + 3:55 gears and made 424 RWHP as well. I think the the 3:55's offset the gain at the cats. With my current conf. the removal of the high flow cats only netted 5 RWHP at 585 RWHP! Really no good reason not to run cats. Corsa claims about 18 RWHP on a 2000 GTS. That puts both cars at 406 RWHP bone stock, if you want to believe Corsa.

[DEADEYE]

It's the gears! When my car dyno'd 604 rwhp on 3:73 gears Sean Roe told me it would dyno closer to 640 on the stock ratio. The gears change the way the dyno reads your power on the rollers. It also shows an increase in torque