Best M42 Mods

[bmwman91]

I don't take it personal I know this is a controversial subject and I've seen many threads saying the same thing that it doesn't work or not worth it. I don't claim to be a mechanical engineer by any means and pretty much the reason why I've always tweeked what was there on my cars to see if there is something that can be gained. In the case of my 318 I have to agree that BMW did have it pretty much spot on as the difference my mod makes is not drastic but it is noticeable. Whether it's worth the cost is subjective to the person. This has now become an experiment for me and I would like to gather some actual data since my car is basically stock at this point.

I plan on doing 3 tests :

1. Bone stock setup with paper filter
2. Inlet modification with paper filter
3. Inlet modification with K&N filter

Once I have some data I will share with everyone.

Are you going to dyno it with each configuration? If so, try to do it all at once while strapped to the dyno, swapping parts between pulls. The margin of error on those things is probably of about the same magnitude as the differences that the intake will make.

[Simon S]

headers !!

er.. wait.. nevermind..

[djmossm42]

Are you going to dyno it with each configuration? If so, try to do it all at once while strapped to the dyno, swapping parts between pulls. The margin of error on those things is probably of about the same magnitude as the differences that the intake will make.

Yes most likely at the Castro open house event in December they are doing 3 runs for $75. I want to get some baseline figs on my car anyway so I figure I could also use that time to find out what's really going on with my setup good or bad.

[bmwman91]

Sounds good. See if you can talk them into 3 runs per intake setup...you'll probably find +/- 3WHP variances between every run with the same setup, so it's helpful to gauge the margin of error that way.

[djmossm42]

Sounds good. See if you can talk them into 3 runs per intake setup...you'll probably find +/- 3WHP variances between every run with the same setup, so it's helpful to gauge the margin of error that way.

Yes, that would be ideal but I think this will at least tell me if there is a significant difference between the three setups and from there I can get more detailed data and setup more controls. There will be a lot of people there so I don't know how realistic getting that many runs in would be but maybe I'll be lucky.

Peace

[MazterDizazter]

Just to recap:

Bolt-on mods that work:
Chip - MarkD or Turner (Turner is like an hour from me, which helps)
Cat-back exhaust
Single mass, lightened flywheel (I drive a 10lb flywheel daily, so reduced driveability does not concern me too much. That said, I don't want to go below 15lbs)
SPAL fan to replace clutched fan
Different LSD's (I plan on keeping this stock anyway)

Bolt-on mods that miiiight work a little:
Intake cam advance (how much reduction in fuel economy are we talkin' here?)
Cold air intake (while I agree that zee Germans probably know how to tune an intake better than I do, factory induction systems are built with the compromise of sound in mind, thus I would be hard-pressed to believe that the factory induction box is the end-all, be-all of performance.)
COP conversion
19-22lb injectors (I assume I could take my car to Turner and have them tune the ECU specifically for these mods)

What about lightened pulleys? Mild cams? Aluminum or carbon fiber driveshaft? Others? Turbo would be nice but I don't think boosting a 200k M42 and trying to rely on it daily is a good choice.

[bmwman91]

Mazter,

Messing with the intake cam is lose-lose. Unless you get a custom chip burned with fuel, and more importantly ignition tables, tuned to the change in camming, no good comes from it, plain and simple.

CAIs do sound cool, but that truly is it. They also let in a lot more small particulate contamination which will not be nice to cylinder walls or valve guides. The stock paper filter protects your engine much better while having 2-4x more surface area than cone filters (which negates the more restrictive material).

The COP conversion is a good way to clean up the engine bay. No power is gained from it though. I am the one that actually developed the whole thing back in 2006, and I did it because I wanted room for a turbo at the time.

Bigger injectors do nothing on a stock M42. At all. I have a 205BHP Metric Mechanic M42 in my car and they even said that the stock 19# ones can juuuuuust barely handle 205BHP, although I am using 24# ones with it so that they won't be running at mad duty cycle. You need a custom chip to run properly with different injectors anyway.

The stock pulleys are plenty light. There is no gain there. Compared to the flywheel, they are insignificant. You would probably benefit more by removing the PS belt, and even that gives little to no gain.

A lighter driveshaft will likewise not be worth it. In the gears that matter, the driveshaft will be spinning 3-4x slower than the engine, and its relatively small diameter means that there is a very small area moment of inertia to deal with (much much less rotational inertia that say, the flywheel). The only bolt-on rotating mass that is worth lightening is the flywheel.

The M42 was a well designed engine. Again, there is a reason why a BMW retails for 3-4x many other cars on the market. It would be an embarrassment to their engineering department if it was so easy to get huge power gains from simple bolt-ons. They did all the tweaking for us. If you want to make a LOT more power, you need to build a strung-out NA engine, or go FI. That's the simple truth here.

[MazterDizazter]

I'm a little disappointed to be stuck with less than 150hp but also glad at the same time, because now I don't have to waste any money on bolt-ons. I can find a better use for that money elsewhere, like making the car is mechanically and cosmetically 100%. Thanks!

[oldmann]

I'm a little disappointed to be stuck with less than 150hp but also glad at the same time, because now I don't have to waste any money on bolt-ons. I can find a better use for that money elsewhere, like making the car is mechanically and cosmetically 100%. Thanks!

Keep the car as light as u can. With good suspension you won't be dissapointed.

Best DD I've ever had. Decent fuel mileage, fun to drive.

[unevolved]

The M42 was a well designed engine. Again, there is a reason why a BMW retails for 3-4x many other cars on the market. It would be an embarrassment to their engineering department if it was so easy to get huge power gains from simple bolt-ons. They did all the tweaking for us. If you want to make a LOT more power, you need to build a strung-out NA engine, or go FI. That's the simple truth here.

Why would BMW not go with sequential injection? The M20 has it, I can't understand why a seemingly high-performance 4 cylinder wouldn't have full control over it's injectors.

On a related note, has anyone ever documented the gains in power and efficiency from nothing but a standalone?

[bmwman91]

Why would BMW not go with sequential injection? The M20 has it, I can't understand why a seemingly high-performance 4 cylinder wouldn't have full control over it's injectors.

On a related note, has anyone ever documented the gains in power and efficiency from nothing but a standalone?

The M20 does not use sequential injection. It uses 3/3 batched injection. The M42 uses 2/2 batched injection. It has all the control that it needs over the fuel system. Sequential injection requires higher flow rate injectors, and there are not really any massive benefits to it versus batched injection, unless it is being injected directly into the combustion chamber. In fact, direct injection engines are having big problems with carbon & gunk build-up on th eback of intake valves since there is no fuel spraying & washing things. It has been a big issue on BMW's N5X engines.

Gains from stand-alone ECUs.....
Well, yes & no. The stock M42 tuning was actually very conservative, to the point that it looks like BMW intentionally crippled the ignition tables to make sure that the 318iS would not bite into the more expensive 325 models' sales volumes. A performance chip with a stock Motronic 173 ECU will yield very nice gains. Unless you think you can out-tune Jim Conforti or Mark D, you won't make more power with a stand-alone. Now, there are other benefits. I believe that the stock ECU is part of the culprit for the relatively slow throttle response the M42 has. Something newer & faster can probably help that out a bit. Additionally, more modern ones allow you to use a MAF and a Wide Band O2 sensor which give all sorts of tuning options, as well as the ability to run lean at low-load conditions to improve fuel economy.

[future rs]

So lets say a MSII setup with ITB's and supporting mods. I would like to make close to 200hp. And no I don't want to swap the engine. I like the idea of keeping it high rev 4 cyl.

Also with tuning what can these motors be rev'ed to?

[bmwman91]

You will not hit 200BHP unless you bore, stroke and cam it. It could use some head work to breathe better too. You will also have to "work hard" for that 200BHP when driving as it will be sort of a peaky power curve. ITBs will only exacerbate this. It is a fun setup no doubt, but it would get old on the street.

How high you can rev it depends on your desired longevity. With stock internals, I think that you can rev it to 7200RPM all day long. The MM Rally engine I have is software limited to 7700RPM since I told them that I want to drive this thing for another 20 years. The engine has substantially lighter (everything) in the crank and valve trains. I believe that they said that the setup can withstand brief 9000RPM mis-shifts. The main limitation with the M42 is the hydraulic lifters. You'll get valve float if you go much above 7200RPM with the stock ones and stock springs. MM said that they can go over 10k RPM with solid lifters on some race engines, but I don't know how long-lived those are.

[InNeedOfBoost]

Just been browsing through here for ideas...sorry to bring this back from the dead but its been giving me ideas.

Whats everyone's opinions on the M20 clutch and flywheel kits as far as brands? Or do you normally just run the OE M20 ones?

Are they direct bolt on to the M42's or do they require any kind of modification.

Not looking to make a bunch of extra power, just want the car to feel a bit more responsive.

[bmwman91]

OEM M20 clutch and flywheel parts are fine. There is some variance in which throw out bearing to use, but I am running all M20 parts with no issues.

You will need to do a little grinding on the upper oil pan to get the M20 flywheel to clear it, or have it lightened to remove the interfering part.