low boost "m52b30" stroker questions

[diptenkrom]

i have a 98 328i with m52b28. i have sourced a m54b30 engine and will be building a stroker "m52b30" with m54 intake cam, m50 intake mani, and an m50nv intake cam as exhaust. the question i have is that if i use the m52 forged rods, ARP studs, and a good mls headgasket and a small (t25/t28ish) turbo, what is a safe boost level and respective hp rating?

thinking like 7-8psi and 320hp maybe? i know you should lower compression, but i want quicker spool for acceleration, not high top end. just looking for something that would be fun to drive, and good for something like autocross where large turbo lag would be a detriment.

[MKovac]

Building for response and no lag doesn't have to necessarily involve high compression. Properly sizing your turbine housing, manifold and collector, gear ratio etc will make a bigger difference. Not to toot my own horn but I was able to achieve this with the correct hardware and 9:1 comp ratio. From experience, and everyone will agree with me here that you will always want more boost than you initially anticipate. Get a dbb 6262 vband .82 or twin scroll gt30/5r and drop you CR with a .10 or .12. Find a happy medium with the gasket because you are going to want to turn up the boost eventually.

[diptenkrom]

Thanks for the response. It isn't that I want high compression so much as not wanting to lower it. I've had a 10:1 comp and a t28 on a 2.0 fwd Nissan. I'm not opposed to a thicker hg but I don't want to change pistons to drop it. Also it will give me decent off boost performance if it stays around 10:1...

I have a t25g Garrett turbo already. Is it to small to do anything? What kind of a/r numbers would I be looking for?

The twin turbo 300zx was using 2 t25 turbos in a 3.0L so I'm thinking it is too small. Unless I can source another.

Another question is, is it really that hard to run bottom mount turbo on the e36 m52?

[PowerKraut]

I have a t25g Garrett turbo already. Is it to small to do anything? What kind of a/r numbers would I be looking for?

Way to small imho. A/R depends on the charger. As a rule of thumb i would get nothing smaller than T3 0.63 on a 3 liter.

The twin turbo 300zx was using 2 t25 turbos in a 3.0L so I'm thinking it is too small. Unless I can source another.

Fitting twin T28s would be cool though

is it really that hard to run bottom mount turbo on the e36 m52?

Been done many times. Look up a few bottom mount build threads. WG positioning, oil return, intake and intercooler piping can be tough. But not impossible.

[papiichulo]

Do the m52b30, get a ces cutring/copper spacer and arp studs and call it a day.
Then find yourself a gt30 and other turbo accessories.
Then to put the cherry on to, get an rk tune.

Bam you're done.

[diptenkrom]

Yeah mentioning WG placement. I was wondering why all the manifolds seem to be designed for external wastegate, is there a problem running internal ones? Or is it a clearance problem?

[PowerKraut]

Not that much of a clearance problem on internal ones. Just in most cases internal ones dont flow that good and are pretty tiny, givin you a fair amount of boost creep or even over boosting. And external ones are more or less easily adjustable via different springs.

[diptenkrom]

Way to small imho. A/R depends on the charger. As a rule of thumb i would get nothing smaller than T3 0.63 on a 3 liter.

Fitting twin T28s would be cool though

Would love twin turbos. Can't weld so I can't make my own manifolds and custom ones cost way too much. My actual first thought was sequential turbos like a t25/28 and then a larger t3 based one. Or a rx7 FD style unit. But lots of money and space required for that. Also I decided not to shoot for that much boost.

I'll have to talk to some people and see if I can get someone to help me with the welding part. I could still do a t25 and a t28... Quick spool and wider powerband.