So here's my dilemma. This dyno (I've seen it before) shows the stock TDI making 153 HP. Either it's corrected or an optimistic dyno. Best it should be is 140 HP to show a good baseline. It's high by 9%. If that's correct, than it stands to reason that the 170 HP figure is also high by 9%, which makes it about 155 HP. So that's a 15 HP gain, not 27. Torque is about 4.5% off, so corrected the tuned torque would be about 285.
Even if you don't correct the high numbers, 153 to 170 is 17 HP, not 27.
This came to my attention at the last NEDD where we had two common rail cars run, one with a Stage 1 tune, one with Stage 2. They ran before I arrived so I don't recall who tuned them. However, the numbers were pretty low, somthing like a 10 HP increase for Stage 1 and 15 or so for Stage 2. We had a stock CR car there that established a baseline.
You have to look at the change within the power curve...it doesnt matter what the peak numbers are, just the change (differences don't change based on the dyno).
http://www.goapr.com/products/ecu_upgrade_20tdi_140hp.html EDIT - Does not past link referencing, above dyno graph click the 3rd tab for gains.
Things to know would be if the tuned cars were identical to the baseline vehicle as far as transmission and remaining driveline components go, i.e. same size wheels and tires, etc. and if they were back-to-back runs with the same correction factors and weather conditions. Another question is, does the dyno operator really know what he's doing?
There's no way a stock TDI can make 153HP at the wheels if it's rated at 140HP at the flyhweel (brake HP). There is friction loss in the drivetrain.
There's no way ANY engine can produce more HP at the wheels over it's brake HP.
Obviously no car can produce more at the wheels than at the crank. I think it is the case of an optimistic dyno or less actual drive train loss than corrected for, and VW/VAG always underratting their engines. FYI, the APR dynos (as stated) are corrected for crank numbers. I can't remember what their correction factor is off the top of my head.
The car on the dyno is the same one before/after the tune. APR uses several runs and averages them out vs just giving the lowest stock and highest tuned numbers/graphs.
I'm not arguing anyone is wrong here, just that there are viable options out there. I'm not affiliated with APR, just been really happy with their work in the past and know they have more experience with tuning VAG vehicles than anyone out there.
Two thoughts:
1) You can't trust peak numbers/single number gains (e.g. "25hp gain, 170hp peak, etc) to tell you anything- there is an obsession about peak numbers in this country...the power curve is what is most important.
2) If you are going to pay for a tune from a company, you need to see the difference/gain dynos...it drives me nuts that tuner just tell you the gains, don't show you the power curve or graphs. They have the dynos if they know the gains, so why not just show them?