Getting More Out Of An M42

[Low Level E30]

I have seen in a couple places that people say an M42 is pretty well built-up straight from the factory, and that not much more can be gotten out of it - NA, of course.

Why is that, exactly?

What -can- be done with it, that's worthwhile? Would port'n'polishing the head do much? Extrude honing the intake manifold, like an M20? Can you stroke it much (I realize there's a factory 1.9 liter...) ? More compression? Cams?

Maybe Stu can answer this... ?

Thanks,

[Erick]

http://www.r3vlimited.com/Tech/318is.htm

Stu did answer this already ;)

[Low Level E30]

http://www.r3vlimited.com/Tech/318is.htm

Stu did answer this already ;)

Thanks for that --- good stuff!!

However - it does not answer some of the stuff I was lookin' to know about -- namely, port'n'polishing the head, honing the intake manifold, aftermarket cams (I realize the stock sprockets can be adjusted) - that kinda thing.

I've been around cars, and BMWs in particular, long enough to know the basics - light flywheels, chips, etc. I'm looking for the more M42-specific stuff.

Thanks again,

[Rob]

a good number of club racers use the m42, but as far as I know, the consensus is that you're not going to get much power without spending a ton of money, and when you do spend the $$$, it still wont make much power. ~200hp (crank) is on the upper limit of the motor, and thats in pretty track oriented setups...

[Stu]

Our non-conformist has finally seen the light of the 16v.

If you want to play games, you can get big power out of the M42. Schnitzer and Alpina both make forged stroker cranks, that will yield a 2.1L if larger bore pistons are used in conjunction. These crankshafts run $2000-2500 in the second-hand market. For pistons, go with 86mm. I am told that '95 M3 pistons will fit these motors fine, but you'll need to check the rod lengths and piston height to get the compression within reason (~10.5:1).

Stay away from the M44 crankshaft. It is not forged, and not even fully counterweighted. A true piece of shit that I wouldn't trust over 6500rpm.

The head can be worked a little, with the valve pockets expanded and some porting can be done. I don't see why you couldn't go as far as to Extrude Hone the intake manifold. Schrick sells cams ranging from 240* to 290+, with plenty of lift options.

Stock M42 injectors suck. They are single-pintal and only flow 13#/hr. Stock M50 injectors (4-pintal, 17#) would be a nice upgrade, but will require software.

The secondary throttle butterfly should be bored out roughly 3mm.

Ditch the AFM if you can. A piggyback system like an SMT-6 would probably be a good tuning tool if you build the motor up like this.

As for exhaust, I'm pretty sure the factory manifold is a pretty high-flowing piece, and it's stainless. I'm sure the S42 header is the real hot shit, but it's probably tuned to make power in the 6000-8000 range.

Just a few things to consider.

[Low Level E30]

Our non-conformist has finally seen the light of the 16v.

Hahahaha - our non-conformist!!

I like to think I am not constrained by the average person's need to be a sheep ;)

I'm asking because I will be getting a new assignment in a few months, and will likely be moving (I'm in the Air Force) --- I'm thinkin' about getting another E30, and since I already have a 325is, I thought I'd try some 16v power 8) - I like fun "toy" cars, and four-bangers with spirit are definitely fun!!

Yes, I do like four-cylinders. I used to have a 16v 2.0l VW GTI - prior to owning a VR6 Jetta ;) - I still think a 325i/is is the way to go, if you're only gonna get one non-M E30.

Thanks for the info, Stu. That's good stuff. I appreciate it.

Where do you pick up a higher-than-4.10 ratio LSD? What cars did they come out of, or are these a "custom" setup?

[OldUser1]

Where do you pick up a higher-than-4.10 ratio LSD? What cars did they come out of, or are these a "custom" setup?

Read Modding the M42 by Stu, the link is at the top of the page.

Rear end gear - The 318iS is equipped with a 4.10 limited slip from the factory, but you can do better. The desired gears out there are the 4.27 and the 4.45. You will find the 4.27 in E30 318i convertible 5 speed’s and the 4.45 is in E36 318i automatics. The 4.45 is a wicked, wicked street gear but will stick your RPM way up there on the highway. The 4.27 is a good compromise of performance and everyday use. It should be known that to make a 4.45 work, you have to swap the gearset into your E30’s differential, or find an automatic 318ti, which has a 4.45 and also has trailing arm rear suspension! So the E36 318ti 4.45 bolts right onto an E30, though finding an automatic 318ti with LSD may be difficult.

[Rob]

haha with all of that stu, you'll have what? 170? 180hp?


btw- stu, ask pete how high the stock valvetrain can go, RPM wise

[OldUser1]

btw- stu, ask pete how high the stock valvetrain can go, RPM wise

On B. Purcell's site is says that:
"The crank is forged (rather than cast) and is fitted with 8 counterweights. It can be used at revs up to 7200rpm."

http://www.esatclear.ie/~bpurcell/318isengine.html

[Stu]

There are a few things in the M42 that limit the max desired revs to about 7200:
-harmonic balancer
--E30 M42 one is good for 7200ish, E36 one is apparently stronger
-Hydraulic valvetrain.
--M42's use hydraulic lifters just like M50's. M50's have trouble with valve activation at around 7500, so this rule could probably be used for the M42 too.

There are probably other things, I just can't think of them right now.

For a rear end gear, look for:
-4.27 (small case, E30 318ic, limited-slip was an option)
-4.45 (small case, E36 318ti AUTOMATIC, unsure if limited slip was an option--kinda doubt it, automatic M42 in an E36 shouldn't have too much traction trouble. Then again, maybe a 'winter package' 318tiA would have the 4.45LS)

Low Level--- You'll have a blast with a 318is. Everyone I know that has owned one absolutely loves it. I don't suggest spending the kind of money it would cost to build a stroker M42, especially for a street car. You'll spend more on the motor than you did the car. ;) But, just to let you know, that is what can be done to the M42.

[Stu]

btw- stu, ask pete how high the stock valvetrain can go, RPM wise

On B. Purcell's site is says that:
"The crank is forged (rather than cast) and is fitted with 8 counterweights. It can be used at revs up to 7200rpm."

http://www.esatclear.ie/~bpurcell/318isengine.html

Correct. The M44 crank, even though it has 3mm more stroke, only has 4 counterweights, and is not forged.

[bimmerphile]

Tara's 318iS pwns j00

[e30Matt]

The 318iS is the most fun car I've owned to date. :up: :up:

[Rob]

i miss revs

[e9nine]

i miss revs

you miss FWD Ploughing too :P ???