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Thanks for posting chart. The very lean afr reading with the SSI has never looked right. With the stock chip, it should actually go very rich at the upper rpms so I suspect it is not accurate - possibly a vacuum leak at the wideband lambda sensor of the dyno at the time, or possibly even an exhaust leak. The fact that with the new headers displays richer seems to confirm it because a freer exhaust will always dyno leaner and require more fuel, the opposite of what is showing here.
The dyno numbers that are referenced on the hp chart posted by 911st are normalized to a Superflow engine type dyno, which should be closer to the factory numbers. I have found and suspect over the years that the loss at the wheels on a 911 for a Dynojet SAE corrected is closer to 11-12%, not 15. I have a set of hundreds, maybe a thousand Dynojet runs accumulated from a probably a few hundred different Porsches, from 3.2 to present, undergoing various stages of modification that I'm using as a basis. For example, a 2007-2008 GT3 is rated at 415 HP, while my completely stock GT3 dynoed 371 at the wheels on Vision's Dynojet, in line with what others have gotten. I don't think the factory really underrates their motors, so using a 11% loss ( divide by 0.89 ) comes to 417 HP. Therefore a motor that dynos 221 at the rear wheels is actually closer to 248-251 at the flywheel. Chip tuning Bill's car with more ignition timing for 91-93 octane pump gas should bring about another 8-10 hp.
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