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      09-25-2012, 04:13 PM   #21
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Drives: BMW F10 - Matte Blue
Join Date: Mar 2012
Location: Norway, Scandinavia

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I noticed that there seems to be a lot more torque, but the Prad (wheel horsepower) is only about 13hp more after the tune than std (461,9 vs 475,5).

The dyno pics shows that the frictional losses have risen from 89,2hp on the std run to 104,9hp on the tuned run, a difference of approximately 15hp (which seems quite a large increase in drivetrain losses - 20% more than the std car).

Also the correction numbers (Pmot/Pnorm) are much higher on the tuned run than on the std run. For std run the correction is from 551hp to 583hp (32hp ). For the tuned run the correction is from 580hp to 639hp (59hp).

The correction (Pnorm) is supposed to recalculate the hp to conform with the relevant standards (in this case EU directive 80/1269). This is things like temperature, air pressure etc. Meaning that on a run at 33 deg you will have quite a big correction of the Pnorm HP number (because a engine looses performance at high temperatures and the Pnorm HP is recalculated to be the estimated hp at 20 deg). On manufacturers dynos they have a tempered climate so that the engine operates at exactly the Pnorm parameters.

I noticed that the first run is done at 25deg and with a intake temperature of 52deg. The tuned run is done at a stated 33deg and a stated intake temperature of 72,7deg... (was this dyno session done in the UAE?)

This is probably also the reason the corrected numbers differ so much between the two runs. Ideally the runs should have been done with the same temperatures for comparison purposes. Because all we can really see from the two dyno runs is that the whp differs 13hp (the rest of the hp numbers are mathematical calculations to adjust for temperature differences and are therefor not "real" numbers)

I'm not saying PP have done anything wrong here, far from it.

It is however a source of concern on these kind of dynos that altering temperature inputs in to the dynos computer can give you the numbers you want. Tampering the sensors (or placing them somewhere warmer) to give you a very high intake temperature, and/or ambient temperature, reading for instance will give you a large correction factor from Pmot to Pnorm and hence boost your claimed hp numbers (and some tuners have done this in the past to boost their claimed numbers).

However, assuming correct temperature readings, the correction from Pmot to Pnorm is fairly accurate and, in this case, explains the large difference in correction numbers between the two runs (due to much higher temperatures in the last run).

Last edited by Boss330; 09-26-2012 at 06:20 AM.