M20b20 turbo conversion

[Dannysimmse30]

I have just brought an e30, 1990, 320i.

I'm fairly confident with the majority of the parts I will need except the engine management system.

I see a lot of people using things such as mega squirt and vems, but I don't understand how these work in terms of: are they able to be tuned by myself, or will they have to be mapped by a professional?

If anyone knows any other ways of doing the turbo conversions on the 2 litre, 6 cylinder engine please let me know as I need all the information I can get, as I know that I don't know enough to start ripping the car to bits!

[Dannysimmse30]

Iv been looking into this, not totally sure whether it would work! But I'll see if anyone knows if it would

http://www.diyautotune.com/catalog/diyp ... p-385.html

[ross2009]

imo i wouldnt even bother with the b20 just swap a b25 in and turbo that

[jmc330i]

Welcome You should be able to find the info you need on here somewhere!

Any particular reason for turboing a 320i? Because the first bit of advice everyone will give you is to find yourself a B25 engine. The B20 isn't the best place to start as it will probably need the compression ratio lowering to be turbocharged with any real gains, and even then it wouldn't be worth the work - a late low comp B25 can be boosted to 240-250bhp without touching the internals (maybe some arp rod bolts).

[ross2009]

Welcome You should be able to find the info you need on here somewhere!

Any particular reason for turboing a 320i? Because the first bit of advice everyone will give you is to find yourself a B25 engine. The B20 isn't the best place to start as it will probably need the compression ratio lowering to be turbocharged with any real gains - a late low comp B25 can be boosted to 240-250bhp without touching the internals (maybe some arp rod bolts).

ha beat you too it

[jmc330i]

Damn, I was almost as slow as a B20 turbo

[ross2009]

Damn, I was almost as slow as a B20 turbo

ha ha ha

[Dannysimmse30]

When you say the compression ratio needs to be lowered are you saying it would have to have the head skimmed to spaced out? And just thought I'd work with what iv got

[ross_jsy]

You will have to drop it with either an MLS head gasket or ideally with different pistons or rods. B20's are relatively high compression.

Later b25's are relatively low compression which is pretty suitable for low levels of boost, plus you have the advantage of an engine that's already 25% larger to begin with, thus more power.

[Dannysimmse30]

Fair point, is it worth having the b20 bored out? Or better to just buy a b25 head as I'm thinking this would basically do the same?

[ross_jsy]

There are apparently advantages to boring out a b20, something to do with water holes in the b25 block that aren't there in the b20, thus making it stronger. Plus you would have perfect bores, always a nice starting point but I would just buy a know good b25 and start from there

[Dannysimmse30]

Iv been looking at the m20b25's and I'm struggling to find one with the gearbox.
Would a more modern engine work with custom mounts maybe. Like the e36 or e46 2.5?

[maxfield]

A 2.0L gearbox will fit a 2.5, they're just not as strong.

An E36 2.5 M50 is a fairly simple conversion, and will take up to 500hp on stock internals. Have a read through the M50/M52 section to learn about the conversion.

[ross_jsy]

Iv been looking at the m20b25's and I'm struggling to find one with the gearbox.
Would a more modern engine work with custom mounts maybe. Like the e36 or e46 2.5?

Yes, just use an m50. They love boost and are a very strong engine.

Check out Craig's build thread for ideas.