ITB's?

[samuraibaz]

Have just started stripping down my m42 & was thinking of using itb's on the rebuild & was wondering if anyone had any info? Advantages/disadvantages? cheers baz

[ross_jsy]

Dbilas do a kit I believe.

I think an m42 would sing with appropriate headwork, cams, lightening and ITB's. Probably a lot better than an m20 on ITB's anyway

[jmc330i]

E36 M3 itbs can be used on the M42, although on the 1.8 they can lose you torque and don't really gain much bhp. If you're rebuilding your M42, I'd consider a 2.0 or 2.1 stroker build whilst you have it apart and then combine that with the S50 itbs.

If you're keeping it as a 1.8, you would ideally need smaller itbs than the S50 ones.

[capnmchl]

Sorry to hijack a bit, but what's the deal with a 2.0 or 2.1 stroker build? Simply a case of cobbling M20 parts together or is it a bit more complex?

[jmc330i]

M44 crank and rods with S50 pistons is a little under 2.0l - around 1950cc depending which S50 pistons are used.

M47 crank, M44 rods and S50 pistons is almost 2.1l - around 2050cc again depending on the S50 pistons.

IIRC, the block needs boring by 1mm to fit the S50 pistons, I think the pistons need decking (but I'm not 100% on that) and the M47 crank isnt a straight fit but its possible.

Its not quite as easy as its written above as there is compression ratios to worry about, but that gives an idea of whats involved.

[capnmchl]

Not really worth the expense unless you run in a limited engine size class or have all the bits/machinery sitting around then?

[jmc330i]

I guess it depends who you know...
As you say, might only be worth while if you need to stay under cc limits, although I'm considering it as I need to keep my touring a 4 pot and NA.

Other than cost, one downside with a stroker is that I think it loses some of the rev happy nature of the M42.

[smithysmith]

Itb's really need stand alone management (megasquirt, emerald or similar) to work properly. ive never seen anyone get a decent running setup that they were happy with on the IS though.

stroker builds : The simplest build is an m44 1.9 engine with m47d crank, this gives you 2 litres without a re bore. There is a good chart in the wiki showing different stroker builds for m42/44

[samuraibaz]

am gonna be looking @ switching cranks etc & adding aluminium flywheel, chip etc but will b sticking with m42 as it is much stronger & revs much better than m44 which suits my driving style was just looking @ getting it as quick as poss to about 120 as i hav 325i manual convertible for 6 cyl driving & was just curious if itb's or injection upgrades r the best route on m42.

[smithysmith]

am gonna be looking @ switching cranks etc & adding aluminium flywheel, chip etc but will b sticking with m42 as it is much stronger & revs much better than m44 which suits my driving style was just looking @ getting it as quick as poss to about 120 as i hav 325i manual convertible for 6 cyl driving & was just curious if itb's or injection upgrades r the best route on m42.

The m42 indeed has a stronger forged crank but as you will be changing it for the m47 one you may as well start with the m44 with its bigger bore and lighter rods. It also has a knock sensor and serpentine belt which are both of use should you want to supercharge at a later date.