Terrible dyno numbers

[Brickell gt500]

I just wanted to see what influences dyno numbers?

Best numbers: 689 hp/ 696 tq mileage 13k miles; mods vmp tb, off road x, pulley

20k miles on 666 hp/ 695 tq only change JLT 123

35k miles, went to the dyno to get a race tune. Did a base hit 626 hp 630 tq.

Trying to figure out what's gone wrong. The tuner said it feels like a dead spot in the tire that the car had a wobble to it. I had the gears and driveshaft repaired under warranty. (Stock gears)

What in the rear end might cause a drastic change at the dyno? The wobble went away at higher speeds so o doubt it's an axle. Open to any or all ideas of what might be causing this.

Thanks

 

[03MUSCLE]

Probibly the dyno or weather conditions. What dose the Butt Dyno say??

 

[1320 Junkie]

Are all dyno read outs from same dyno in same weather conditions?

 

[Brickell gt500]

Same dyno. FL

#1 hit was August
#2 in the month of November a year later
#3 was on December 17th

 

[Brickell gt500]

Got beat recently by a tuned 2015 M3 and a 997 TT. Both cars I could have slaughtered when I had the first run. I walked away from a 997 TTS with the same mods. This time a big L.

 

[1320 Junkie]

Time for a leak down test

 

[93 347 Cobra]

What belt are you running? When was the last time you had it changed out?

 

[Brickell gt500]

Junkie good suggestion .

Cobra, the same belt when the smaller pulley went on. Never changed it.

 

[1320 Junkie]

How do the plugs look?
Any oil consumption?
Where is the tensioner tab located with engine off?
Vaccum lines all connected good and tight?

Just some basics before you freak out.

 

[Softballer77]

Do you have any catch cans? If you don't and are getting oil up in there and into the intercooler, you can have a loss in power. Can you post a picture of the dyno sheet?

 

[R.D.P.]

So you definitely feel a loss of power? No chance it could be something going on with the Dyno? The fact that the best run was in Aug and the worst in Dec makes the situation even more concerning.

 

[sb03cobra]

What clutch? Miles?

 

[93 347 Cobra]

What belt are you running? When was the last time you had it changed out?

You're getting great inputs from the replies. How many miles on said belt?

My stock belt is slipping after 14K miles on stock pullies and stock boost. If you're pullied and have more than 8-10K miles since pulley you need a fresh belt.

 

[dotmpeg]

Clutch?

 

[Brickell gt500]

Same belt and stock clutch. Mileage 35,400.

 

[tvspower]

OP Did you lose the last races at the launch, mid run or top end? Clutch problem?

 

[Brickell gt500]

From a roll at 60. So very top end and no clutch slip detected.

 

[99SSls1]

When the warranty work was done did they reflash the pcm?

 

[Brickell gt500]

I don't believe their was a reflash. Ford didn't provide me with the receipts. They basically said I don't get them since its warranty work. Can a bad axle bearing be a culprit? Bad installation of the gears? Too tight?

 

[2011 gtcs]

If may not be feeling like the clutch is shipping, but it's very possible it's just not holding as good as it used to, I noticed a difference when I went to my Spec SS clutch. Also Invest in a gates blue belt from Van and do a leak down test just to insure everything is happy. I highly doubt you could have hurt the pistons. Also make sure your plugs are in good shape.