M20 tuning

[DoctorDrift]

Hello guys i just have a questions regarding MAF conversion.

I am aiming to tune my m20 2.5 to approx 200bhp. The numbers are less important than how the engine feels to drive and response etc. It is for my fast road/track car/sprint car for which there are strict regs. I want to keep it 2.5 for this reason otherwise i will go up a class. It must remain an m20 and i cant do a conversion.

I will aim to give the engine a freshen up, have some headwork done, BTB exhaust manifold and free flowing system and install a 274 or 288 cam.

I am hoping this will yield somewhere close to 200bhp but i want to be able to use every single one of those ponies.

The car will be made as light as possible within regs and already has full e36 M3 supsension and brakes so hopefully will be a useful weapon.

Do any of you have experience with the MIller MAF for example? Is it worth the money? Does it significantly improve throttle response and drivability?

Has anyone tried a standalone ECU eg OMEX with a set up similar to above?

Any input is much appreciated, thanks in advance

[reggid]

a mild cam (280ish) on a high 9.7:1 B25 is a decent prospect with some compression through light skimming or a 1.75mm gasket as opposed to the 2.05mm which are the replacement ones. check the piston and valve clearance for a clash though.

and piston to head clearance (squish) to improve the chamber mixture motion, around 0.040" to 0.050" is good


lightweight flywheel

[DoctorDrift]

thanks for your reply reggid, do you have much experience with afm delete option or standalone management on an m20?

[Speedtouch]

I fitted a Miller MAF to my 1988 325iSE (with high compression 25 6E engine, and Motronic 1.3 management) and it performed well - much smoother throttle response, and no noticeable loss of power, put it that way.

I also had a 1989 325i Sport Tech 2 with Megasquirt fitted by the previous owner, but it never performed as well, probably because it had the later low compression 25 6K engine.

Mind you, it was only 'tuned' using the AutoTune function; I daresay if it was properly mapped, it would improve things.

[Gunni]

go for a standalone system, all the flexibility you need to get the most amount of your engine.

[reggid]

standalone is very flexible but you want to use a system that is very common with lots of support and a good basemap to start from.

[jimbom30cab]

BBTB makes a huge difference to the way these drive, not sure it unlocks any extra horses but the mod is well worth it in my view. Maggspower on here can sort you out.

Would you consider 19lb injectors and the M30 AFM?

[MillRat]

Without opening the motor you can try the following;

I would also look at expanding the air intake to the head. Use a larger diameter intake boot (with as few section changes and bends as possible), replace the AFM with a MAF, fit a larger throttle body and buy an intake manifold/plenum which has been enlarged (you can do this yourself, but take care to ensure the plenum ports still match the head ports). A well designed exhaust is also an excellent idea to release hidden power.

I like the Miller WAR Chip and MAF and use then on my race car. In my opinion it offers excellent value for money and is effectively plug and play (something I understand is not always the case with a standalone control system). A standalone system would certainly offer you more advanced tuning possibilities however.

A light weight flywheel and clutch have been recommended and although they will not improve the power, directly, they will greatly improve throttle response which on a modified engine is vital. A short throw gear lever can also improve the feel of the car.

Larger injectors are good, but be careful not to go too big. I think that recommended 19lb injectors are a good option and are a popular choice.

A good differential is essential! Find a gear ratio that matches the track(s) you use the car on and buy a good one (there is good differential thread in the racecar section of this forum).

The most recent modification I did was fit a close ratio dog-leg box from an E21. This made a huge difference in the acceleration and alone reduced my lap times by seconds. I cannot recommend it highly enough (not a cheap option however and I was very lucky to buy mine "cheap" off a friend who was clearing out his shed).