New Dyno Numbers....what happened?

[GeneralLee]

So I have a 97 GTS and dynoed it about 5 months back, it was stock except for a muffler delete and K&N drop in filters....thats run 1 on the sheet. It was 72 Degree air according to the dyno readings.

Run 2 is 1 7/8 B&B Headers, Cat Deletes, B&B cat back, AccuFab TBs, smooth tubes, Roes big airbox. 87 Degree air.

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So what went wrong, if anything? I've heard like 30-40 HP with removing the stock cast manifold. Is that not accurate? The car feels much better, and other cars there seemed to be on their numbers, so any ideas? Or is it all in my head? I put in a few gallons of 100 octane just because, do you think that had adverse affects?

I knew my bottom end torque would move up the RPM range with the bigger headers, but I was hoping for some better HP numbers.

 

[DrDJ]

I'm not sure what happened, but you had a helluva dyno run with just the K&Ns and muffler delete!

The big airbox shouldn't make a difference (Vipair maybe?) The TB change could have actually cost you HP. Headers should have helped a 97. Cat delete should have definitely helped. Did they record your A/F during the runs?

DrDJ

 

[GeneralLee]

No, forgot to add that..their A/F meter was acting up, so it was not available. Also, these were at the same place on the same dyno.

 

[00SVTdubs]

weather was warmer and you dont know a/f. I bet it was a combo of hot air and rich a/f's. Did you run it at the track before? Id go there again for some real world numbers!

 

[GeneralLee]

I have run at the track....

I ran 12.1 at 118 with the first dyno set up. That was with original PS1s with no tread....2.2 60'

I did try once with the new setup in Memphis about a month back, but it was like 105 degrees and 100% humidity. Ran a 12.4 but the conditions were so bad I dont count them as a good comparison. Im gonna try to get to the track at least once more this season to try again. Plus now I have SSRs and new PS2s....

 

[00SVTdubs]

so many variables... thats why dyno numbers dont mean squat, its just for tuning really. Id go back to another one that has a properly working a/f gauge and see whats going on. Dont be too concerned with the numbers, just make sure its good and safe and hit the track again! Good luck!

 

[GeneralLee]

Yeah, I agree dynos arent the real world answer, and the car does feel much better(not to mention that it sounds amazing now!) I wasa just expecting more than a 9 HP from the exhaust...and there isnt even a gain under the curve! O well, Ill see what happens at the track.

Thanks all!

 

[jcaspar1]

I would guess you gained 20 with the headers and lost 10 with the throttle bodies.

 

[FE 065]

Did you enlarge the intake manifold behind the larger TBs?

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[GTS Bruce]

Run 1 seems very optimistic while run 2 is probably correct.

 

[GeneralLee]

The manifold is stock. No porting or anything. Im going to try dynoing with the stock TBs to see if it makes a difference. But I do wanna get back to the track for some real world numbers.

 

[FE 065]

Adding larger TBs without opening the hole in the intake's TB mounting flange equal to the new TB bore size would have to almost guarantee no gain.

I know some people who've done it on the car with adequate safeguards against shavings & dust making their way further back in the intake manifold..

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[-FROG-]

I was gonna say TB's too....

 

[BLWNGTS]

A couple of things coming from a tuner.
First off.. what was your tire psi?! suprisingly that can have an effect on the numbers. Second... never use 100 octane unless your car is tuned for it. It actually does no good and can hurt performance figures for a car tuned for 91 or 93 octane.
Third, is take off the throttle bodies. You can always try and swap them between runs to see if you get a difference but I would say that is hurting you also. try those and dyno again. I promise you will be suprised with the difference!!

 

[GeneralLee]

The tire pressure was 35psi, and yeah I know that filling the tires up more will help, so I guess you could say this was a "real world" run... I actually forgot to add some air, but oh well. As for the 100, that is my guess too. I know that it could possibly hurt, and I knew it for sure wouldnt add any, but it smells so good without cats..... so Ill try again with regular 93. Im gonna go back and try with 93 and the big TBs on, then put the stockers on and try again. I do like the improved throttle response with the big TBs, but if they are hurting performance Ill take em off.....