[The Nerd]

Originally Posted by Poochie

Thanks a lot for sharing this letter, it explains what all this hoopla about the 'power lost' is about.

Here in the US, there is no emission standards at full throttle (85%+). This exception was made so car manufactures could deliver maximum power when it is needed the most and the overall effect on emissions would be small, since people rarely drive at full throttle.

Thus, at high RPMs, the O2 sensors go into an "open loop" state and is taken out of the system so the fuel system can be enriched for maximum power, without the needed to abide by any federal emission standard, since it's exempt.

It seems in the early M340i, the ECU mapping was programmed in error to place the O2 sensor in a "open loop" state at lower power band, instead where it belong, at WOT.

This new software update places the power back in the higher RPM to meet allowed emission standards. So the addition power wasn't taken away, it was just move to higher band in the RPM.

This aftermarket tune just brings back original lower end power band.

Thanks for the info....2 questions.

1) Where did you learn of the info you shared regarding this power loop, emissions standards, etc, etc? I'd like to read more about that as it pertains to the m340i.

2) If what you're saying is true (no power lost, it was just moved to lower rpm ranges)....then, wouldn't Mission Performance's peak WHP #s from their dyno remain relatively the same from earlier model to late model....albeit at different rpms? Because on their dyno, their was a 50-60 WHP LOSS....that sounds like actual power being robbed.

And by the way, I do understand that a car's performance is about the total area under the horsepower and torque curves, not just peak #s. However, a horsepower loss is a horsepower loss.....and it would be nice to truly get to the bottom of this. Thx again for sharing....