m20B20 to M20b23

[cyman1988]

Hello guys,

I have a 89 2 door bmw e30 with the M20B20 (160k Km on the clock).

I would like to know what should be done to increase the Hp of the engine.

For what i have read you can change the crankshaft and the conrods of the M20b20 from M20b23 and then you have a 2.3 l engine.

Given the fact that the engine is motronic 1.3 will this be better than the original M20b23?

Also adding headers and stainless exaust, chip and camshaft(272) what will be the expected Hp?

I have searched all over the web regarding increasing the hp of the M20b20 and all they say turbo it or swap to M20b25. I know that it costs and that the M20b25 will always be faster better and will have more torque please do not advice me to do so! i know it costs more but i want to increase the Hp of the current engine.

I know alpina C1 2.3L managed to have 170 Hp? ( i dont know their build).



Thank you.

[jimmyspeed]

Conrods are the same in both, pistons are different, cams different and the crankshaft is a longer stroke - i stripped my 323i after its snapped a rocker and the crank and pistons were hardly in great condition . That was about 10 years ago too!!!! There not exactly common either

Yes the motronic is better but yours is setup for a 320, so will need to be chipped or standalone ecu fitted - expensive

Your probably looking about stock 325 power if you tune it really well !

I looked in to the various combinations of parts and quite liked the thought off building a short stroked (320 crank) with 325 width pistons to make an over square revvy engine which is what the 320 is good at

I think the alpina's used a forged turbo diesel crankshaft and custom mahle pistons along with head work and other bits- there is info about online


If you want to build a period m20 theres tonnes of info and various combinations but if you want a fast cheap e30 stick an m52b28 in there

[ross_jsy]

Or just stick an m20b25 in. They have a lot more poke than a b20

[cyman1988]

Than you for the fast reply

So you say that it will be in the region of 155 Hp having spend like 3k Euro?(chip, headers, camshaft, etc,etc). so its better to swap to M20b20 with like 1200 euro(may need a rebuild as well)

[jimmyspeed]

no - heres what alpina managed with their skills

C1 2,3 E30 323i C1/1 125 kW (170 PS; 168 bhp) @ 6000 225 N·m (166 ft·lbf) @ 5000 1983”“1985

theres loads on here - https://en.wikipedia.org/wiki/Alpina

as for whats best? its your money

[bss325i]

No M20B23 used motronic 1.3 so no off the shelf ECU available.

The Alpina C1 2.3 used uprated Mahle pistons to raise compression ratio, a 268 degree cam and work to cylinder head.