As I understand it, the operator can calculate the transmission losses on the coast down. As soon as the clutch is dipped at max revs at the end of the power run, the drivetrain and rollers will coast down to zero. The dyno manufacturer will have calculated what the coast down will look like with no car on the rollers and any quicker coast down will be due to friction losses from the car on the rollers. IMHO, this seems perhaps like an imperfect science as things like tyre pressures will influence the result, yes? Some users and operators agree and accordingly compare rear wheel hp rather then flywheel horsepower. The most common dyno is the Dynojet 248C and its seems that most users/operators just say there is a 15% loss, so your 224.6rwhp divided by 0.85 gives 264.2fwhp!!! Surprisingly, the rwhp figure that Mike58 posted on the other thread had more than a 22% loss between fwhp and rwhp. This is why it is very hard to compare different dyno results on different days - even if the software adjusts for temp, pressure, altitude.
I think the best thing you can say is that you gained 22hp as a result of the remapping (great result) as dynos are very good for before/after comparisons. The ultimate hp numbers are probably best left to bar room debates - or forum debates !
I like the fact that many of us have used the WRC Technologies dyno as it gives a good base for more valid comparisons. It is also state of the art in terms of dyno technologies. The manufacturers of the Dyno Dynamics dyno have apparently worked with major manufacturers including Porsche to establish real fwhp calculated on engine dynos and then they have measured the real drivetrain losses. The software can then get much closer to working out a real fwhp figure. Talking to Steve Wong in the US, who sees hundreds of dyno plots for primarily 3.2s, he has noticed that Dyno Dynamics numbers are consistently about 5hp lower than other dynos, suggesting that the oft used 15% drivetrain loss number is a little too high for 911s. Admittedly with a much smaller sample, this seems to ring true. On the 3.2 dyno days at WRC, most 3.2s did no better than 220-225hp and even some CSs struggled to make 230hp. Steve Darnell's custom remapped CS made something like 240hp IIRC. Only Ian Highfield's car has confused things making 240hp with an exhaust mod and 255hp with custom remap as well. I have seen the same thing at JZM, where even healthy 3.2s made 225hp and a full H&S exhaust made "only" 229hp. On the other hand, Colin at 9M claims on his website to make 265hp from his std but blueprinted 3.2 running SSIs and MBE non-sequential engine management and has in mails to me claimed 270hp from the same engine with MOTEC management. Steve at JAZ claims to have seen 260hp from a Schofield mapped carefully blueprinted std 3.2 for club racing.
Now there is a lot of stuff we don't know about these engines and tests. For example, if you use race gas, octane booster or even just Optimax and push the timing maps really close to detonation, then you will make more hp, guaranteed, and this can be sustainable on the dyno on a nice cold day, but is not real world applicable for a hot June trackday at Spa. Dynos results can be manipulated to tell the story the operator wants to tell. For example, I have seen a 3.5 MFI engine make a scarcely believable 360rwhp - so over 420fwhp - on the dyno. The same engine was dialled back to 320rwhp for actual racing and still had to run on 100+ octane race gas. I believe that SW doesn't push the timing maps very far and concentrates on getting the AFRs close to perfect. He can and does make more hp for race applications. I still carry a couple of bottles of octane booster in the trunk for a really hot track day just in case.
HTH [
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