Alu M52 + boost

[Major]

I made a post on Bimmerforums about turbocharging the aluminium M52 we get here in SA, and the consensus is that it isn't the best platform for anything over 8 psi of boost, unless timesert'ing the block every few months sounds like fun.

I'd eventually like to run about 300whp. I have an aluminum M52B28 in my garage, should I use it, or find an M50B25-NV and steal the crank from the M52? I'd rather not worry constantly about my block cracking.

[erik325i]

I'd only use the aluminum block if I were building a lightweight stroker motor. If you're going for big boost, start with the standard iron block.

Erik

[Blackangusinc]

I'm also planning on boosting M52TUB28. However, I don't plan to exceed 8psi. My main concern is how to deal with the dual vanos. Aside from some minor machining, this is going to be a stock OBD I converted motor. Obviously we'll spend a lot of time tuning this thing, but I'd love to hear from anyone who has done this before. Off the top of my head, advancing the exhaust and retarding the intake under boost sounds like our best bet.

[Blackangusinc]

Bump

[hoveringuy]

I'm also planning on boosting M52TUB28. However, I don't plan to exceed 8psi. My main concern is how to deal with the dual vanos. Aside from some minor machining, this is going to be a stock OBD I converted motor. Obviously we'll spend a lot of time tuning this thing, but I'd love to hear from anyone who has done this before. Off the top of my head, advancing the exhaust and retarding the intake under boost sounds like our best bet.

I can help you control the dual VANOS, but all of my dyno time on it has been NA. That said, I think you're mostly correct. You do want some overlap but not so much that you're just blowing right throught.

I've heard you can use the dual VANOS effectively to quicken the spool considerably but I don't have direct experience.

[Blackangusinc]

I may just take you up on that. I'll be running the silver label 413 ecu with a war chip and (hopefully) your vanos controller.

So some amount of overlap is good under boost? Is this for more effective exhaust scavenging?

[hoveringuy]

The right amount of overlap is good. That amount changes for different motors, exhausts, intakes, etc. It's not a case of some is good, more is better for sure.

On the exhaust side, you can retard to get more overlap, but then you lose blowdown.

On the intake side, advancing too much gives you reversion.

My controller has an LCD panel where I can toggle through 10 different intake and 10 different exhaust profiles instantaneously. You'll just need to see what works best on the dyno. I get a rough guess on load from throttle position and rpm.