Make 135 drive like or better than Z4

All,

I'll keep my question to the point and give you the background below: With a ECU remap or piggyback on the 135i, will it's *throttle* response behave equivalent or better than an N52-Z4? Also, is it possible, relatively "inexpensively", to get the 135i's handling and steering Z4-like?

I know what is possible with absolute numbers like torque and HP (see my link), but that doesn't always translate into "immediate fun" : http://blogs.insideline.com/roadtests/135.dyno.both.jpg

Background: About two years ago I drove a 2007 stick Z4, N52 engine and **loved** the everything about it ; it was the perfect balance of power, fun and drivability. But I read a lot of posts about the hydraulic lifters issue, didn't want to mess with it, got a good deal on a Z4-M coupe (no lifter issue) and have been loving it ever since. The Z4-M is a real monster.

Fast forward to today, just had a kid need need something more practical so I've had my heart set on the 135i. I drove one recently (twin-turbo model, stickshift) and found the throttle response to be too "filtered" -- it really felt like driving a numbed, newer generation 3-series. The 135i has more torque than the N52-Z4 I drove, yet the Z4 was definitely much quicker to respond to throttle and just *felt* more fun and connected to the road. That makes me think BMW "de-tuned" the throttle inputs and have low-pass filtered them too aggressively for my tastes on the 135i.

The suspension on the 135i also felt too soft and numbing, unlike my experience in the Z4. So what I'm hoping to find out is, with a decent budget of $4k-5k, can I make the 135i drive like the Z4?

Thanks.

I also drove and fell in love with a Z4M, but the practical side of me ended up going for a 135i. The throttle response in the z4m is fantastic and very aggressive in sport mode, I don't think you're going to get an n54 to have this type of response. There's just always going to be some turbo lag.

A friend of mine had jb4 on his 135i, and although I never drove it, he said throttle response was much crisper. It was also ridiculously fast, but you already know about the potentials I the n54.

One modification that would make the 135i MUCH MORE ENJOYABLE would be mechanical LSD. The car downright needs one. I dislike the factory e-diff, but have learned to live with it for the time being. Anyways, there's my .02.

FYI, what I just said is based on the N54 engine. As for the N55 engine in the brand new 135i, I hear tuning is substantially more limited.

Hi calvinboca,

Thanks for your response. The throttle response of the Z4-M is actually bordering on insane in sport mode. The Z4 (non-M) had a great balance which is what I was hoping to get on a 135i.

It sounds like your friend has good luck making these changes, so this is a good starting point.

Anyone else have any experiences or commentary?

Thank you!

We have both a Z4M and 135i. You won't get anywhere near the throttle response or linear throttle reaction that the S54 gives with an N54 (or N55 for that matter). You would have to remove the turbos, put in a light weight valve train and increase the rev limit to 8000RPM, add 5 more throttle bodies, etc, etc.

This will be the case for any turbo engine from lower RPMs before the turbo is fully spooled. On the other hand, you won't get the low RPM torque of the N54 in the S54 without putting a turbo or supercharger on it.

Different type of engine, different pros and cons.