[Walker16]

Im thinking about the pure 600 or 750. ive ready they are 58mm and 62mm turbine.
Ive also seen the speedtech garrett kits that can get up 67mm.

I know bigger will mean slower spool but also less heat and wear (since i will never be able to max it out)

speedtech is more expensive but also comes with more stuff in the kit. Without considering price just looking for thoughts about a big pure turbo or a really big turbo.

I still leaning towards pure cause of price and the solid reputation but also looking to educate myself and see other opinions on the big aftermarket options since its pretty limited for the E chassis.

also is 550-600 still the agreed upon limit for the bottom end of our n55's? I seen some 600+ but that was the 135 version of the n55 and ive heard they are more solid on in the bottom end.

[wheela]

It's hard to say what the limit is. It's more about torque than power level. Power = (force x distance) / time, so the relationship in the motor is power = torque * rpm (along with some unit conversion factors). So the higher up the rpm range you make the torque, the more safely you can make big power. Bigger turbos can flow enough to move the torque higher in the rpm range, which makes more power than that same torque would at lower rpm.

I think this is the most power I've seen on a stock block n55 - 750 whp. Pretty intersting video if you haven't seen it before.

[wheela]

Also, the bottom end on 135i's I'd no different than a 335i n55 (or my X1 35i bottom end, or a 535i). An exception is the m2 n55 (and maybe the m235i, and very early X3 m40i?). The m2 n55 has lighter pistons based on the s55 pistons, and a lighter crank. I believe these changes are to support the marginally higher redline of that version of n55.

[Walker16]

hmmmmm... I got a buddy that is a master tech at a dealership and he didnt have a answer for me either.. He just said to buy a long block from a wrecked one, have it resurfaced and upgrade the rods pistons and bearings and we will just swap motors to eliminate downtime. lol
He loves to spend my money for me. Id rather attempt to bullet proof it instead of finding the point of failure when a rod goes through my block.
I think ill go the safe route with pure 750, upgrade fueling and detune it to keep it around 550 until i decide to mess with internals... hate to post a dyno pic and confirm the point my failed!... lol

right now im fbo with mhd, meth and lpfp upgrade. guess well get that hpfp done and see how it goes!