m50b25 non-vanos questions... fuel efficiency?

[e30_325es]

I was getting ~25mpg highway with an s50/zf/2.93lsd and schrick cams, high comp pistons, trm tune. ~20 average and ~18 on it alot.

[GunMetalGrey]

So are you guys saying that a NV is bad for boosting?

[pantelones]

So are you guys saying that a NV is bad for boosting?

to my knowledge, its not bad to boost a m50 nv, but its not that bad to boost a vanos motor which will make more torque than a nv. the easy way out is just to avoid the "problem" all together and get rid of it. the only difference between boosting a nv vs. a vanos is having a proper tune to effectively use the vanos to your advantage, and not cause a headache. i believe that you need a stand alone or piggy back to run boost+vanos right? the extra rotating mass of the nv rods and crank play a roll in some peoples decision, but a m52 short block with the nv m50 head will solve that weight weenie issue. in the end it really doesn’t matter what motor your boosting, its just if you can FULLY comprehend how your motor works and how boost is going to affect it. or loads of cash works as well...

someone with actual hands on knowledge correct me if im wrong...

[pr0craztinazn]

how do you like that setup? i would imagine that it would still be pretty quick and fun to drive right? i just bought an 87 325e which is geared similar and i like the way it pulls, but just wish it were a little faster.

my current dilemma is what to do with the motor. ive been leaning toward putting a 731 head on my rebuilt m20b27 and use 1.3 motronic with all i related parts needed, but i realized today that the cost and amount of work is almost the same as doing a m50 swap. so now i need to look into building a m50 and decide what i would want to do with it, and how much it would cost.

i am also leaning toward no boost, and just making a really efficient N/A motor. the car is just going to be a spirited daily driver, not a track rat. the hassle of making euro itb's clear the vanos solenoid is enough to make me go non-vanos. to me itbs = throttle response, and that makes your car feel more responsive/faster even though your not making any more power.

It responds way faster and smoother than my eta ever did (with the Mark D chip or when it was stock), although the eta had a smidge more torque from a standstill. If you want a little faster, the NV will do it. I keep finding exhaust leaks pre-o2 sensor due to hitting all sorts of stuff while driving in DC (terrible roads are terrible), so it should feel faster whenever it's all sealed up. I don't regret my swap at all; it's fast enough to get into trouble, but economical enough that I could idle around in 5th gear at 35mph in medium highway traffic like I did with my eta without lugging.