GTS DYNO - Need help...

[OKViper]

Well, I had my '99 GTS dyno'ed here in OKC and don't know what to make of it...

First, Car has 10,000 miles with the following mods: Henn. headers, High-flow cats (from Jon B.) and Borla cat-back, 1.7 T&D RR, Mopar PCM, K&N filters inside stock box with larger smooth tubes going to 65MM throttle bodies. The only thing I had done was the headers and cats, everything else was previous owner.
Second, the following dyno graph was with the stock PCM, The Mopar PCM gave 411HP with 465TQ with the same AF's and curve.
I have a couple of questions: Isn't this EXTREMELY low for this car and do you guys think that it is in dire need of a tune? I live in Oklahoma and there are no Viper tuners here, so I would try to find someone close. And, what should this car be making? I really expected 450+ and 490+.
The car idles and drives perfectly and is crisp in response and pulls strong - it spins third gear with the stock 3.07's. I just didn't expect this...
So, where do I go from here? Please help this new Viper owner...

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[apun]

Isn't your AFR pretty lean?

Alex

 

[Gerald Levin]

My 96 STOCK GTS (no extras, no smooth tubes, no K & N, etc) dynoed at
416.7 HP 461.45 TQ so I'm guessing its on the low side.

 

[Casey]

It's low. Tune it up and try again!

 

[KenH]

SAE corrected and on a dynojet, I would expect to see the 450RWHP/490RWTQ number that you are looking for. It is unclear if this graph is SAE corrected or what type of dyno it is and that could account for quite a bit of the difference you are seeing.

Your A/F does look a little lean to me and you may be losing some power there.

 

[Jack B]

A couple of observations:

1. The correction factor is STD, that is going to read higher than SAE, which has been the most common for this board. This basically means your numbers are even lower.

2. On the positive side, the torque holds horizontal till almost 5000, that is very nice.

3. The a/f is approximately 10% high (lean), there is hp to be had by fixing the a/f.

4. When my car had the same mods, if the STD factor was used, it would consistently put down 460-470 hp.

5. If you have the file you can change the STD to SAE and see what those numbers are.

6. With the a/f and timing massaged you will probably go from 400 to 420-425, but, there seems to be a bit missing somewhere.

 

[Joseph Dell]

Change plugs and wires and go back again. Also, tell us if the O2 **** (for the Wide Band) was in the tail pipe (which I bet it was) vs. in a dedicated **** after the headers.

If the w/b was in the tailpipe, expect it to read 1 pt leaner than normal (due to the cats).

finally, we've seen cars w/ TB's loose power. i wouldn't be surprised if this was part of the culprit.

numbers aren't _that_ bad... i've seen Gen2's make less power with more mods. the rockers might not be adjusted very well so i'd consider re-adjusting those too...

JD

 

[OKViper]

This was on a dynojet and this graph shows the factory PCM with the sensors at the tail of the exhaust. With the Mopar PCM, Torque was up 10 lbs. and the HP was the same. I also think it was fatter but I don't have the graph in hand.

Will changing plugs and wires open up some lost HP? The car only has 10K miles, but has that been problems for others? I am just really dissappointed with these results. I just added those high-flow cats and headers and was really hoping to see something exciting, not depressing...

I was thinking I might need to find someone to do some tuning with a VEC II and see if we can't figure this out...

Any more thoughts?

 

[GTS Bruce]

Dynoed my car Monday 01 GTS.Headers,no cats,corsa,smooth tubes/filters,jesel 1.7 rockers stock pcm.442/479.From 2500 up AF averaged around 11.Should do better when leaned out.How was your fuel pressure?Do a search.Mopar performance pcm usualy worthless and larger tb's on a stock engine often a detriment.Something realy wrong with your AF if graph is correct.Should be in the high 14's when cruising with almost no pedal but not at WOT . Good luck. GTS Bruce

 

[Joseph Dell]

The A/F is NOT wrong if you are taking a reading after the cats at the tailpipe. don't worry about that part!!!

yes, the plugs and wires will make a difference. sure, you can get more power w/ a vec2, but enough to warrant the cost? maybe... maybe not.

just my .02... and i've used a VEC2 to get 50rwhp and 75rwtq out of a stock viper.

JD

 

[Jack B]

Joe:

Just as bad is the method by which the tail pipe sniffer works, on a short/large OD exhaust system the likelyhood of air contaminating the sniffer input is good.

All you have to do is remove the front oem O2 sensor and use it for the dyno then change it back afterwards.

 

[Joseph Dell]

What Jack said. Do it!

JD

Joe:

Just as bad is the method by which the tail pipe sniffer works, on a short/large OD exhaust system the likelyhood of air contaminating the sniffer input is good.

All you have to do is remove the front oem O2 sensor and use it for the dyno then change it back afterwards.

 

[OKViper]

Thanks for the suggestions, I just ordered ab's wires and new plugs hoping that that may be part of it.

Any more suggestions? I'm at a loss...

 

[pdmracing]

Dell, what plugs do you suggest?

 

[Jack B]

Try the Gen III plugs or the Gen II oem plug.

 

[Joseph Dell]

Dell uses 1 step colder than stock on supercharged and TT cars. NGK part R-5671A-8 (stock #4554) .

JD