SRT Dyno Results - Before and After Valve Replacement

[GR8_ASP]

Completed a second dyno test on my SRT. I did a dyno test 1 week before replacing the intake valves and a second set 1 week after the repair. The graph is not easy to read but the 3 lower curves are the "before" condition and the top 3 are after. The last run, number 6 (red), was done with the air filters removed. I wanted to see how much restriction the filters provide. The effect was minimal. I do not see any significant gain in changing the filters alone.

More to come for sure but I needed a baseline. You may note I did not gain 25 hp or 40 lb-ft. I gained about 20 RWHP and 22 RWTQ. The RWHP gain was close, considering driveline losses. The torque stills seems a little low to me.

I continue to see the significant variability in the graphs. It is fairly repeatable with the peaks around 100 rpm apart. Any ideas what is causing this? Tests of Gen I and Gen II just before and after my first 3 runs did not show this variation.

 

[GONABITE]

What were your air fuel ratios do you have a graph. Maybe there is a need for more timing in the mid range area or more fuel. These companys are always trying to make the emissions folks happy.

 

[Jack B]

Viper SRt:

Rerun the graph and use a smoothing of either 2 or 3, it will clear up considerably. Also have the operator reset the bottom axis to zero, not 350, you will get a better prospective.

As was noted previously, you need the a/f on the same graph to analyze any problems. If the dyno operator didn't suggest doing a/f his capacity to help you is probably limited. There seems to be something wrong with the dyno. Most Vipers have the hp and torque cross at approximately 5200. In addition, a typical run that shows a valley in the the torque will also show a a similar (but smaller) deviation in the hp, you have a major drop in torque at 3200 and no matching drop in hp. I would look at the dyno for the problem. You hp does not look bad at all, 450/.85 = 529


.

 

[GR8_ASP]

Okay, a few points of explanation. I exported the dyno data into excel to allow me to analyze it more. I previously posted the dyno graph provided by Dynojet. I evaluated it under all smoothing functions. None provided a significant amount of smoothing. On the day I ran prior to the new valves several other Gen I and II Vipers ran same day, same settings and had smooth curves. I do not believe it is a dyno or data graphing issue.

Here was the initial graph produced by Dynojet:

I normally plot the torque on a reduced scale to better show it. Here is what it looks like with a comnmon scale. Yo will now note that the lines cross at 5252 where they should.

I can upload the graph with all 6 curves, but I need to scan it first. But the curves look the same. Just less clear due to scanning and a weak original graph (light lines). Plus, Dynojet does not allow you to start an axis at a number higher than zero. Thus the total graph gets compressed vertically. On screen at the dyno facility the differences between Gen I/II and the SRT were very obvious. This is not a graphing technique effect.

 

[Torquemonster]

VIPER-SRT - I do not know what is causing those ragged lines but I would be concerned enough about them to get some expert advice. It is not normal.

It could be electrical - something eratic in the ECU, it could even be valve springs.... though I'd be surprised, it could be detonation. The engine needs some diagnostics to sort out what it is - because an engine that spikes like that is unlikely to run forever IMHO... I may be wrong, but if it were mine - I'd want it sorted to a satisfactory conclusion.

It would be interesting to compare an aftermarket tuneable ECU to see if that eradicated the problem.

 

[GR8_ASP]

Torquemonster - I agree, hence my posting and inquiry.

Thanks

 

[Torquemonster]

I think it does need to be said however that the power figures are very impressive for a stock car!!!

 

[Hans Christian]

What does dodge say - anybody raised this question directly with them and gotten some feedback ????

What about the owners question section - anything ???

What about our president joe can't he raise it with PVO ???