Dynoed GTS after mods/very disappointed...

[VEETENN]

My 98 GTS with only smooth tubes and K&N's dynoed 4 months ago at 411.6hp and 453.4 torque. Now as many of you know I added Belanger headers, 3" Random Tech high flow cats, and 3" Corsa cat back. I dynoed it today after driving it 350 miles and the best it did was 426.7hp and 466.1 torque. Only a 15hp increase what the heck is that!? A stock 97 GTS with K&N's only, did 427hp! A 2000 with K&N's and smooth tubes only, did 420hp! WHAT'S WRONG! It was suggested I may need the Mopar performance computer. At max power about 5500rpm air fuel ratio was about 12.5.

Do any of the experts out there know what's wrong? Thanks for any help you can give me.

 

[GTS Dean]

Are you running oxygenated/reformulated gasoline?

 

[ronviper]

Brad do not judge your car by the dyno numbers only, how does it feel. Look at some of the previous posts 1badgts said many times the dyno numbers can vary from dyno to dyno and the conditions. Take it to the track or race someone you raced before see how it reacts or performs under those conditions, it may surprise you.

 

[VEETENN]

GTS Dean, yes in CA 91 octane, but everyone else had to run the same thing.

ronviper & Rick, I don't think the dyno was at fault other cars such as that 97 GTS did well.

 

[VEETENN]

Also Ben Treynor reminded me his car (2001) pulled 515hp on the same dyno with the stock ECU so I shouldn't need a Mopar Performance ECU I would think.

 

[David Jenkins]

How do you know the a/f ratio was 12.5? How do your before and after number compare to other cars the were dyno'ed before and after modifications?dj

 

[Gerald]

Brad,

from what you should have been reading on this board.. The MOPAR Hi-Po computer for some reason robs alot of HP, put the stock one back on.. See if that helps.


Gerald

 

[JonB]

-How old are the plugs? Over 5000-7000 cost HP.
-How old are the wires? Over 15K?
-How clean are the K+Ns?
-Are your Throttle bodies opening fully?
- mats?
- cable adjust?
-Are your injectors clean?
-Any chance your intake sys is flawed? ie droopy cones or shrunken hoses?

The results do sound low to me

{ I do not think you need a MPP ECU/PCM }

 

[VEETENN]

David Jenkins: The Dyno Jet readout shows the air fuel ratio. At 2000rpm AFR=15, 2500rpm AFR=14, 3500rpm AFR=13.5 4500rpm AFR=13.5, 5000rpm AFR=13 5500rpm AFR=12.5, 5800rpm AFR=12

Gerald: I have the stock ECU on, it was suggested that I might try the Mopar ECU.

illy: I have never felt any detonation and they never told me it was detonating, the car only has 10,000 miles.

JonB: I did not change the wires or plugs, I checked only the #1 plug before dynoing and it looked like new, only 10k miles. I cleaned the K&N's and checked throttle bodies for full open before dynoing. Don't know about the injectors but with 10k miles I would think their clean. Can not see any obvious flaw in intake system (smooth tubes are hard plastic can't collapse)

 

[BurnR8]

JonB,

I gotta say I really hate droopy cones and shrunken hoses....

this should be avoided at all costs....

 

[VEETENN]

The same dyno used both times. No changes other than exhaust mods I mentioned. Same temp and both readouts are corrected hp.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by 1bad gts:
Definitely not the computer(I have a highly made over 560 to the wheels on motor using the stock computer and stock fuel system. ) Before and after did you use the same dyno? Did you make any changes like gears? Was motor run at the same operating temp? In each instance are you comparing corrected horsepower?
<HR></BLOCKQUOTE>