Why am I so down on power??

[drbobvs]

Went to the Mustang Dyno again since I had my JDM and VMP tunes "updated". Justin from VMP added 2% more fuel this time and the JDM hesitation issue has been fixed.

The weather was about 15 degrees warmer this time and the oil temp was 190 degrees at startup. I had just gotten back from giving someone a "demo ride" too, so the car was driven hard before the run.

Since my last run I added BBK shortys and a new tensioner. Here's the sheet from 4/24 and the 2 sheets from yesterday RPM vs MPH.

Now I know heat can deplete power but at some points I'm down nearly 40 Ft-lbs!! The boost is down about .4 psi, perhaps from the heat too but maybe partially due to the headers also. I've emailed JDM to get the AFR into place, so hopefully they can do that this week.

Does heat really make that much of a difference day to day?? The car sure feels strong but I just can't believe the sheets. What do you guys think?

 

[stkjock]

Rob - the boost IMO is down due to the headers for sure. Less restriction = less boost pressure to read

As far as the power looks down about 5%, IMO the heat and humdity we had yesterday can account for a lot of that, if not all. on a % basis its not that great.

 

[Steedman07]

+1 on the ambient temps...Especially if you had just drove it hard then put it on the dyno..Heat soak sucks..

 

[08GOGT]

heat and humidity and the Barometric Pressure have huge effects on power. Also since you were running the car hard everything was heat soaked.

I would find a shop with an actual dynojet and have the car run with ambient conditions logged. This way you will see actual and SAE numbers plus the conditions on the sheet for each pull.

 

[MattP343]

You're on a mustang dyno?

 

[drbobvs]

Yes, Realspeed has a MD Mustang Dyno. I like to figure 10% difference on average to a Dynojet, although the owner of the shop has told me he's seen anywhere from 8-14% difference from his MD to various Dynojets in the tri-state area.