hmm, it's just weird because he did a bunch of pulls. we were tuning for 1.5 hours...

I'm not sure what you are talking about picking up on RPM, unless you are talking about those dynos where you clip on a sensor to a coil pack wire... this dyno is all load based so the RPM should be associated with the roller speed.

 

How about for $hits and giggles you go try out a different dyno and see how the rpm match up to what the dyno reports.

Edit: My reasoning is that it would be much much cheaper to diagnose for like $50 versus $5k for a swap or built tranny. Also you can record it and post it up to get some more help in to your issue on hand.

 

Switch the axis to road speed and if that fixes it then it was rpm pick up. You can do this in the dyno viewer software. No need to get the car on the roller again.

 

^^ exactly...

also, every dyno i've seen has an RPM pickup. If this one doesn't then there's no way it can be showing RPM accurately. There are just too many variables like wheel size, gear ratios, ect...

 

so your saying the cars rpm are off? like it think its redlining but its actually not. so the dyno rpm is right and the car is off?

 

Thats why you "calibrate" the dyno session to the vehicle. The dyno asks you to get the car up to 3000 RPM and hold it while it calibrates. It then uses that as a basis to calculate RPM. This calibration was done the same way in April and also back in october.. yet my most recent dyno plot shows up like this. I've been going to this guy for a long time and never had this issue. I've been on his dyno probably 10 separate times.

found this in the manual for the dyno:
Eng/Rl RPM Rt Engine / Roll RPM ratio –
measured ratio of engine RPM
to roll shaft RPM – can be used
to detect tire slip in manual
transmission vehicles, or
automatics when in torque
converter lockup.

Calculated From Roll Speed The engine RPM value is computed based on the
dynamometer’s measured speed. This input yields a very high
quality engine RPM value, but may not be accurate if wheel slip
is encountered, and can only be used in a single gear, and only
with manual transmissions.

Roll To Engine RPM
Conversion
If engine RPM is being calculated from the dynamometer’s
speed input, then this value represent the multiplier used to go
from dynamometer roll-shaft RPM to engine crankshaft RPM.
This value is the calibration value resulting from the calibration
routine discussed below

Calibrate Speed Based RPM This button will display a calibration screen used to calibrate the dynamometer’s roll shaft speed to the engine’s RPM. The
operator has only to specify the engine RPM value to calibrate
to, drive the vehicle in the gear that will be used for testing at
the specified RPM, and click the “OK” button.

just pulled it out of this document: http://www.mustangdyne.com/mustangdy...ers-Manual.pdf

 

I wonder if it could be the TC. Mine recently started to act up with 400+wtq.

 

I was thinking TC also but unable to verify.

 

Did you happen to change your rear end gearing up at all? Either way, get it to another dyno before you do anything drastic.

 

I installed a Quaife LSD, coming from an open diff.. but I'm pretty sure my last dyno (in april) had this on already... i'll have to review dates.

 

neither here nor there, but a properly running supercharger with the MUCH bigger damp'd crank pulley and a 2.87 jackshaft pulley should make WAY more than 10psi. I'd think closer to 15-17.

 

Is the fluid dampr larger than stock dia? Didn't know that. My setup had always produced low boost.. I think it's too free flowing. I have cams headers and ART pipes. I made 7.5 lbs on 3.13 pulley little over 10 with the 2.87

 

yes, its 3/4" bigger than stock. about the same as dropping 1 pulley size by itself.

 

oh damn, that is scary. I didn't factor that in when I was installing. hmmm come to think about it, the belt that I ordered did seem a bit small when I was installing it. I had to modify the belt tensioner to give it some more range. Won't a bigger crank pulley also then overspin the alternator/powersteering? why would they make it bigger thank stock?

 

What are you tuning with (EMS)? Are you hitting overboost fuel cut?

 

Uprev, no boost protection AFAIK

 

Bump

 

bump for what?

it was already told that the OP needed to look at road speed on the dyno to determine if it was trans slip.

Without that data, the best he can do it take it to a different dyno and go from there.

 

talked to the tuner today and he said that road speed was also off.. where does that leave us?

 

Get on a dyno with an actual RPM pickup. Dynojet if possible.