Performance Upgrades for an M42?

[mattio523]

Hi everyone,

I own a 1976 BMW 2002 and I'm thinking about swapping in an M42. I was wondering what kind of performance upgrades I could do to the engine to get a little more power out of it; I'm looking for about 145-150 at the flywheel. Any and all suggestions are welcome.

Thanks!

[kwill22]

Ok, I guess I'll be the first to say try searching first. There's plenty of info on it on here. 150 is not that far off from stock so you'd probably be fine with a chip, supporting mods and an exhaust.

[mattio523]

Cool. I'll just do that :P

[cody_eppler]

Get Ford mustang injectors and a chip. you will have a lot of fun. Thats what im running in my car. I can rip my car to 60 mph in second gear. 90 to 95 in 3rd and ive gone over 130. Just saying its a good time

[TobyB]

Also see if you can get the E36 trans to fit- the ratios are a bit closer, and
it has a 1:1 5th. That, with a 3.91 diff will make it FEEL like a rocket.

Of course, you'll be turning 4k on the freeway...

t

[bmwman91]

Here's my take after 14 years of 318iS ownership and tinkering. The ONLY easy / bolt-on power mods are a chip (Conforti or MarkD) and a lighter flywheel (M20B25). Exhausts, intakes, different injectors and special ignition wires are all nonsense that will, at best, not cause you to lose power vs stock. More realistically these things will cost you a few HP and impact fuel economy negatively. I tried it all and besides a chip and flywheel, the M42 has NO low-hanging fruit to get at because BMW optimized the engine in the first place (which is why BMW charges a lot for their cars). I am dead serious, messing with anything on these cars will just cause reliability issues and probably lose you a few HP.

A particular point is this: The stock air box is best, and the stock AFM is not restrictive no matter what anyone tells you (and I designed and built my own MAF conversion only to discover that it does nothing for power on a stock M42). I mention this because everyone loves to put a "high performance" intake on their car because way too many car enthusiasts are convinced that some $50 pile of parts is better than something that auto engineers designed and optimized for the engine's intake resonance characteristics and to prevent hot air from being sucked in.

Getting meaningful power gains out of these cars takes $$$. A lot of $$$. We are talking about overboring, stroking, using hotter cams, using lighter weight internal components and running custom higher compression pistons. Don't forget that you will need to spend some time on a dyno getting a custom tune for it when you are done building it. The cost of this will far exceed an S50 engine swap, so you need to be dead sure that you want to stick with the M42 if you are going to do a build. I have a 205bhp 2.1L M42 in my car now, and for the money I could have bought a newer faster car that probably handled better, but I love the E30 318iS so I chose to dispose of some of my hard earned money on a very custom M42.

As far as handling mods, I have done damn near everything there is to do over the years and eventually returned to mostly-stock. H&R sport springs with Bilstein sport shocks are a great combo and I ran that for 5 years or so. After busting my oil pan in the middle of nowhere I went back to stock springs and Bilstein HD shocks, and honestly the car handled almost as well. The main difference between the two setups is that at stock height it looks like an off-road machine! I don't mind these days since it just makes the car that much more of a sleeper. Anyway, I HIGHLY recommend replacing all of the stock rubber bushings (which I can almost guarantee are blown out) with new OEM rubber bushings. The stock suspension handles remarkably well when it is in like-new condition, while still providing a quiet(ish) ride and absorbing road bumps. I ran all poly stuff for years and when I went back to new stock rubber parts, the car seemed to handle BETTER on the street since the little extra compliance in the suspension helped to absorb road bumps and keep the tires planted. Poly is superior for track conditions where the pavement is near-perfect, but you want some compliance on the street where the roads are not perfect.

The short story here is that spending money on nice new OEM parts for these cars is probably the best way to go. Seriously. BMW knew what it was doing, which is why their cars cost so damn much in the first place. If you want a car that sees insane gains from bolt-ons then you should probably start out with an American or Japanese econo-box as your platform.

Sorry if this takes the wind out of your sail. If you just want to blow some money and tinker, then by all means do the "usual" list of mods and have fun. I did for 10+ years, and while it was a complete waste of money in an absolute sense, I had a blast wrenching on things and learning all about cars.

[roguetoaster]

Sorry if this takes the wind out of your sail. If you just want to blow some money and tinker, then by all means do the "usual" list of mods and have fun. I did for 10+ years, and while it was a complete waste of money in an absolute sense, I had a blast wrenching on things and learning all about cars.

Some days I too think I would prefer stock (with new springs this time) to the H&R Sport/Bilstein Sport setup. To second, for a street car it should be rubber bushings all round. Of course some upgrades like solid (not missing material) RCABs, maybe stronger trans mounts (as I seem to kill them frequently) and 21mm/14.5mm stock bars with OE bushings are effective and street friendly.

So, what's your take on cams? They are expensive new, but not awful as regrinds. Any experience?

[Massimo]

H&R sport springs with Bilstein sport shocks are a great combo

This

Chip and light flywheel

FYI I did have a improvement with one of the air intakes from one of the guys here. but that is all.

[word is bond]

As far as handling mods, I have done damn near everything there is to do over the years and eventually returned to mostly-stock...

So which H&R Sport Springs did you run previously? Since there are so many different part numbers and some debate as to which fits M42 cars best. And how about sway bars?

[FL318is]

bmwman91 is spot on. I have chased the same rabbit only to realize, I don't work for BMW R&D.

I focus on exterior/interior upgrades. But, it was fun wrenching.

BTW, I too have a 76 2002.

[kwill22]

Chip and flywheel would be the way to go. I actually love the M42 though. Underpowered, yea but fun. Just have to know how to drive it. And I've never had an engine respond so different to the weather as my M42. You can really feel the difference on 60 degree days as opposed to 90. Florida life

[bmwman91]

Some days I too think I would prefer stock (with new springs this time) to the H&R Sport/Bilstein Sport setup. To second, for a street car it should be rubber bushings all round. Of course some upgrades like solid (not missing material) RCABs, maybe stronger trans mounts (as I seem to kill them frequently) and 21mm/14.5mm stock bars with OE bushings are effective and street friendly.

So, what's your take on cams? They are expensive new, but not awful as regrinds. Any experience?

Can you tell me more about the beefier 21/14.5mm stock sway bars? I have been thinking of getting rid of my Suspension Techniques 22/19mm bars since stiff ones on the street aren't super ideal, and I don't need another chassis bracket to rip out in the rear (or a front one to go)! After welding the rear bracket back onto the unibody I got a set of TMS reinforcement brackets, but I am still paranoid and it turns out that stiff bars aren't all that awesome for handling anyway!

I don't have direct experience with aftermarket cams actually. By the time I was in a position to afford cams and a tune, I blew my original M42 and went with a fully built MM 2.1L which included hotter cams as part of the package. From what I understand you can get some decent gains on a stock M42 with slightly hotter cams (as long as the grind is sensible and increases duration at all lifts, not just peak lift) and a couple of hours on tuning on a dyno.

So which H&R Sport Springs did you run previously? Since there are so many different part numbers and some debate as to which fits M42 cars best. And how about sway bars?

I don't recall which springs they were exactly. I bought the Bilstein Sport shocks & H&R sport springs as a kit from Turner Motorsport in 2002 or so, and ran those until late 2006.

[TobyB]

Getting meaningful power gains out of these cars takes

a turbocharger...

t

[roguetoaster]

Can you tell me more about the beefier 21/14.5mm stock sway bars? I have been thinking of getting rid of my Suspension Techniques 22/19mm bars since stiff ones on the street aren't super ideal, and I don't need another chassis bracket to rip out in the rear (or a front one to go)! After welding the rear bracket back onto the unibody I got a set of TMS reinforcement brackets, but I am still paranoid and it turns out that stiff bars aren't all that awesome for handling anyway!

I don't have direct experience with aftermarket cams actually. By the time I was in a position to afford cams and a tune, I blew my original M42 and went with a fully built MM 2.1L which included hotter cams as part of the package. From what I understand you can get some decent gains on a stock M42 with slightly hotter cams (as long as the grind is sensible and increases duration at all lifts, not just peak lift) and a couple of hours on tuning on a dyno.


I don't recall which springs they were exactly. I bought the Bilstein Sport shocks & H&R sport springs as a kit from Turner Motorsport in 2002 or so, and ran those until late 2006.

The reason I asked about cams was my recent purchase of a worked over head with new 279/274 Cat Cams included. I suppose I'll just find out in time.

In case you were wondering, my dBilas ITBs should be at my doorstep Friday and I plan to install them Sunday.

I have the large stock bars (new from where I bought them from) on my street car and they seem to be a perfect middle ground between smaller bars and the IE (previously on the Chump until it destroyed the rear tabs/rule changes happened)/ST setups that are so tempting to put on with too much preload and guarantee ripping tabs.

They provided a noticable difference as I put on my springs/shocks first and then did the sways on different days. Certainly flatter through hard cornering, but not "track ready" by any means. As you would imagine, the rear bar made the larger difference vs just the front and the old rear stock. They also have yet to rip a tab on either my daily or the Chump (it's totally a double secret M-Tech car). Frankly, I think those bars, H&R Sports and Bilstein Sports are the very best all around sporty street setup you can get for these little cars.

As far as springs any of the H&R Sports will be just fine for a 318. In fact, the OE Sports are probably the ones I would have bought if I were doing it again as they will keep you farther from things that will bump and grind on the oil pan.

[bmwman91]

Which model E30 has the larger bars stock? I think I am going to ditch the ST bars for a set of those (and might be able to trade someone!).