To the OP... if you can feel a difference from your butt dyno, than I would take it in. The mechanic should know what the car feels like accelerating and can run logs to make sure the boost is hanging in there and pushing the power it should. its a $55k car, its definitely worth it to make sure your 335 runs like a 335 and not a 328!!
If you get a tune (JB4 FTW!!), its only 300 or so bucks now a days, and you can easily tell if there are issues using that software. You can even make one of your gauges a faux boost gague!
The XI should make zero difference in speed. Maybe handling... but definitely not speed.
Quote:
Originally Posted by BMW_Belgier
Always the bashing on BMW...
Did you guys ever think about the concept of the N55? BMW mounted a small turbo because they wanted a lag-free response of the engine! They have a max torque curve starting at 1200 RPM and ending past 5000 RPM. That is the RPM you would normally use in a daily drive base...
They did NOT design the engine to be tuned past 400 hp and they did NOT design it for people driving it like bogus...
They really did an excellent job on the engine and they need respect for this!!!
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the n55 is a
bigger turbo than the twin turbos on the n54. the n54 definitely spools up faster and IMO is a better engine... however!!... the "twin scroll" of the bigger n55 turbo helps eliminate some turbo lag that bigger turbos usually have by restricting the airflow and pressure thus getting higer boost quicker, which leads to great torque at ~1500 rpms.
no bashing for sure! N55 is a great engine! but bigger turbos have their positives and their negatives regardless of the nameplate on the car.