M50 vs M20.. for boost. whats your opinion?

[Cyrix2k]

M52tu any good? I hear good things about boring out the stock holes and using supra hardware.

isn't that an aluminum block? I wouldn't use it for boost. Some of the M52s are aluminum too (Z3 & all world market M52s?) and I would avoid those too.

[ak-]

isn't that an aluminum block? I wouldn't use it for boost. Some of the M52s are aluminum too (Z3 & all world market M52s?) and I would avoid those too.

I'd be scared to have a built aluminum block for boost, but I just want to know if there is plus side to it assuming everything is 100% on point.
I can't think of anything besides weight and heat dissipation opposed to iron.

[ak-]

I will look into the m52, but i dont like the sound of it being a obd2 n having to put it back to 1:( although... if it has forged internals, then there would be no point of building it! Which that is a plus on the $$$$ side:)
Thanks you guys for the info.

You don't have to. There are obd2 tuning solutions already.
Go bathe in bfc's forced induction section.

[einstein57]

So you guys are saying 335i motors are crap?

[Cyrix2k]

I'd be scared to have a built aluminum block for boost, but I just want to know if there is plus side to it assuming everything is 100% on point.
I can't think of anything besides weight and heat dissipation opposed to iron.

I *think* alusil actually wears better than the iron block bores too. I'll probably wind up boosting my 540 at some point which has an aluminum block, but it will be low boost. I'm not against boosted aluminum blocks, just high hp aluminum blocks.

[mr2peak]

So you guys are saying 335i motors are crap?

The hardware has a habit of stripping off the block, and the electronics make it more complicated. So I've heard.

[obrian]

My m20 with 200,000 miles could easily spin the tires at 60 mph with with 225 R comps on it. If your gona boost it I don't see the point in swapping motors except just because 24v motors are cooler. If the aluminum blocks are much lighter and just as strong then that might be worth it. But then again my m20 is blown up right now, lol. Point being, over like say 400hp and the returns on usable power are out there, and a m20 will do that no problem.

[Cyrix2k]

The hardware has a habit of stripping off the block, and the electronics make it more complicated. So I've heard.

I'm not too well versed on the N54/N55, but if I had to guess, BMW probably addressed that weakness to some extent. You can drill out the block to run larger studs on the M54 which helps. It's just a matter of what length you're willing to go to. An iron block M52 is ready to go as it sits.

My m20 with 200,000 miles could easily spin the tires at 60 mph with with 225 R comps on it. If your gona boost it I don't see the point in swapping motors except just because 24v motors are cooler. If the aluminum blocks are much lighter and just as strong then that might be worth it. But then again my m20 is blown up right now, lol. Point being, over like say 400hp and the returns on usable power are out there, and a m20 will do that no problem.

eh. I swapped to an M50 because I blew my M20 up. 24v motors are cheap now, possibly more so than the 12v motors. 24v motors make more power on low boost, are more efficient, require less maintenance, and easier to find parts for - even in the e30 chassis. The m20 isn't a bad motor by any means, but the 24v motors are better. Oh yeah, the 24v motors come with good ignition systems out of the box too!

[obrian]

I'm not too well versed on the N54/N55, but if I had to guess, BMW probably addressed that weakness to some extent. You can drill out the block to run larger studs on the M54 which helps. It's just a matter of what length you're willing to go to. An iron block M52 is ready to go as it sits.

eh. I swapped to an M50 because I blew my M20 up. 24v motors are cheap now, possibly more so than the 12v motors. 24v motors make more power on low boost, are more efficient, require less maintenance, and easier to find parts for - even in the e30 chassis. The m20 isn't a bad motor by any means, but the 24v motors are better. Oh yeah, the 24v motors come with good ignition systems out of the box too!

For sure, if ya gota bad m20 I think that would be the way to go.

[SwiftE30]

Better economy and more capable than an m20 as Nigel mentioned.
More displacement than an m50, forged crank and rods factory(idk if the m50 is the same), thicker walls in between cylinders so less probability of a HG going and room enough for O-rings, and priced pretty much the same as an m50.
Also 24v is backed up by so many tuning solutions check bfc.

Since yours going through the motor, it's as reliable as you make it.

COuldnt have said it better myself!

A stock M52 with a thicker headgasket and ARP's can handle 400rwhp all day long. No need to rebuild, plus you get the benefit of better gas mileage will not in boost.

Listen to Otis, He knows what he's talkin about! Followed his advice from the beginning and I havent been steered wrong. He's been a huge help, really easy to get a hold of, and just an all around good guy to know when you;re getting into to the FI world. COuldnt have done it without him. And I am one of the s52 guys youre looking for. COnverting to OBD1 was easy as pie. NO JOKE.

Waiting for the S5x crowd to chime in...3...2..1...

running stock internals on an s52(m50 manifold) convirted to obd1) with garret gt35 with Good and Tight manifold with minor accessories. (Tila 44mm WG and BOV. And holy balls, this combo could not be any more badass.


COnclusion: A 24v FI motor is Far greater than a FI m20. mind you, this possibility has a bit to do with cost. So if you are going to spend the money to do a full rebuild, do the full rebuild on a 24v and make it legit, so that people after you will want your advice. "Pay it forward" type mentality.

[MT325is]

Thank you all for your feedback. Very much appreciated!

I have a chance to buy an m50b25tu this weekend. Ready to be swapped in with harness, dme, etc... For I would say a god price. I'm pretty excited. And if everything checks out.. I'm buying it.
Again I will do a rebuild with forged internals, bore?, etc... So the question now sits is a m50tu a good platform to start my boost transformation? My power goal will be right about 400 to start, but that is capable of 500+ when I get bored of 400:) or should I wait around an go with the m52??

[einstein57]

According to r3v no to any aluminum blocks

[AbsorbantNut]

I'd say m20 because I have one & love it...but it seems that r3v says 24v is the way to go

[MT325is]

ha, honestly for me it dont matter... But like you stated 24v is what r3v says.. and r3v is smarter then me... in some ways.. lol :)
I have been searching m50s, and they are dirt cheap you can pick one up for the same price as a m20! so thats what i think i have decided to do... i didnt pick the one i had to chance to up cuz my m20 went to shit, so spent to much money getting that back on the road that i had no more for the m50:( ill still be looking! thank you guys! :bow:

[e30polak]

This argument has been beat to hell so many times, lol!

The decision between m20 turbo vs. 24v turbo should be decided by two factors - 1) budget & 2) power goals

M20 is cheaper - much cheaper if you're paying a shop to do the work.

However, the cost is the ONLY benefit an m20 has over a 24v build. The 24v motor, especially an m52, is WAY more efficient then any m20. The head flows MUCH better then an m20 at all rpms, the added displacement and VANOS help spool a larger turbo, earlier, and they simply make WAY more power, MUCH more efficiently.

I love all the m20 guys that say that an m20 can make 400whp too. Of course it can, BUT how will it make that power in comparison to a 400whp m52?

Take a good look at kamotors' 420whp dyno graph at 16 psi:



That power band is TERRIBLE!

Now let's take a look at an m52 graph - this is Brett's non-built m52 with a gt35r on 20psi. Makes power earlier and holds it all the way to redline!




CLIFF NOTES: m20 is only a better option because of the price, 24v FTW!!!