legendr34

Mainline DynoLog Chassis Dyno:

404.5 RWHP
430.1 FtLb

The owner said the same car on a Dyno jet, it would read 15% higher, and even higher on a Mustang (~20%)

Calculated for DynoJet:

466.17 RWHP
494.61 FtLb

But for some reason, the car would downshift to 3rd (for a split second) when we hammered it in 4th on M mode

The E55 is 100% stock

Timeless

If it is stock, you were probably hitting the speed limiter (155 MPH I believe).

enzom

Congrats, but I think the dyno operator is wrong. Mustang dynos read lower than DynoJet dynos by about 10 percent. And the estimated readings on a Dynojet are a bit too high unless you are looking at uncorrected numbers run in Michigan in February. The average corrected DynoJet run for an E55 is about 420 rwhp and 460 rwtq. I think the strongest has come in at under 440rwhp.

Not an attack on you my friend, just sharing some observations. Enjoy the ride!