[ebirotedu]

No, your math is right. I ballparked it in my head going the other way.

The base 390 hp peak number threw me off. That dyno might read high assuming the 40hp peak increase is accurate.

10-12% loss seems about right.

Originally Posted by SpeedyATL

I think i used 12% loss, which is about what dinan uses on their site for a '20 M340i.

390 ÷ .88 is 443hp.

Did i back into it incorrectly?

Dinan shows 393whp for their stock 2020 m340i....

https://www.dinancars.com/products/s.../D900-B58-G-S1