I went to the Tune Time Performance car show today in Lakewood, NJ, and had the car put on their Mustang Dyno. As you can see the car is all over the place. Anyone have any idea what the cause may be? I even threw in some race gas to prevent the timing from being pulled.The car was dyno tuned a couple of months ago and the graph was smooth back then. It's got me baffled why it is running so bad. If the car ran smooth it would have been even more impressive with the HP results. It does idle smoothly. Car has the GT350 Intake manifold and CAI, and Kooks Headers and 3 In Exhaust w/ high flow cats.

 

No idea why it looks like a cardiograph, but don't worry so much about the numbers, as Mustang Dyno's are notoriously stingy compared to other makes of dynos.

 

I dont worry much about the numbers, even though 418 whp is decent for a mustang dyno. I'm just worried about the way the car breaks up during wot.

 

Pulling time is when it detects knocking, and has to. When's the last time the
plugs were changed? Also, since you are tuned, and ut's pulling time, you may
need to gap them a little closer. I have a turbo vehicle, and the gap should be
.032, but with the boost module, had to gap them at .028 and use 91 octane fuel.

With a tune, both VVT and SPARK advance will be more aggressive. If you left
the plugs at the factory gap, it could work for a bit, but maybe they were at the
wear point, and now they need replaced.

300-500HP = 0.032-0.035
500-700HP = 0.029-0.031
700HP + = 0.026-0.028

That, or cam riming is being pulled...

If you have not replaced your plugs, and are upwards of 40,000 miles, and you are
tuned, maybe replacing them would help.

 

It looks like they just didn't put any smoothing in. Worst case, the car wasn't all the way tight on the rollers and was moving forward and backwards slightly during the pull, making it look jerky on the graph.

 

Nevermind, I just saw that you said the car is actually running badly. Could be a spark issue or a fuel issue. And of course the tune touches both of those things. Do you have an aftermarket tune?

 

I should learn how to read when I'm multi-tasking, haha. Your tuner should probably be your first stop and they'll probably want data logs from a WOT pull to diagnose it. That would be from 0% throttle to 100% throttle with as little time in-between as possible. He can tell you any shortcomings in your systems through those logs.