Best M42 Mods

[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.

[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?

[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.

[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!

[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]

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.

[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

[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]

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.

[Simon S]

headers !!

er.. wait.. nevermind..

[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.

[djmossm42]

"Designed" When I think of that word with respect to an automotive air intake, I think:

What is the helmholtz resonance frequency of the inlet snout / airbox volume (including the impedance presented by the air filter element)? At which RPMs does this result in positive pressure waves impinging on the intake valves, and which RPMs does this leave rarefied waves impinging on them? What is the net gain in volumetric efficiency and energy output when integrating the power curve from min-to-max RPM? What is the net change in temperature for the induced air/fuel charge that is pulled into the combustion chamber? How is the atomization of fuel effected by a change in inlet air temperature?

Home-Depot'ing car mods is fun, no denying that, and it can be a real learning experience. At the end of the day though, you do need to keep in mind that you are trying to improve upon a design that was optimized by a bunch of German PhD's and engineers that probably solve the wave equations* for the optimal air intake on the back of napkins for fun when they are out having bier with their friends. They have already taken into account everything you can imagine, and about 3x as many things that most normal enthusiasts have never even heard of, when designing the air intake system. Messing with it really only makes some aspects of the system different, not better. The whole reason BMWs are "good" cars that carry a big price premium is because they are designed well enough that $30 in parts from Home Depot CANNOT improve them!

With the exception of the stock chip, there is no "free" low-hanging fruit. As far as I can tell, the stock M42 software was severely crippled so that the M42 models would not eat into the more expensive M20 models' sales volumes. A chip is the only power mod worth its price, really. A light flywheel is nice too, but it comes at the expense of a rough idle, slightly degraded driveability and probably reduced transmission life. The heavy flywheel was another case of "the best option with all things considered."

This isn't a personal attack directed at you specifically or anything. It's just my usual tirade about "cold air intakes." I wasted all sorts of time and money on them a decade ago before I knew better too. Hell, I am glad I did. It drove me to study mechanical engineering, which is the only reason that I know better now anyway lol.

*(probably sounds simple...look it up).

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.

[getouth]

I agree that the only mods worth it are the flywheel and chip. Mark D or Turner motorsports and I highly recommend removing the fan clutch and installing a 16" spal electric fan! It takes a load off the engine and improve acceleration and economy. I've owned M42's for the last 5 yrs four total. My $0.02

[Martin C.]

What about the Dinan chip? AS far as I know they only produced the one with no software updates (I called them).

[bmwman91]

CAIs work as long as it's designed right...

"Designed" When I think of that word with respect to an automotive air intake, I think:

What is the helmholtz resonance frequency of the inlet snout / airbox volume (including the impedance presented by the air filter element)? At which RPMs does this result in positive pressure waves impinging on the intake valves, and which RPMs does this leave rarefied waves impinging on them? What is the net gain in volumetric efficiency and energy output when integrating the power curve from min-to-max RPM? What is the net change in temperature for the induced air/fuel charge that is pulled into the combustion chamber? How is the atomization of fuel effected by a change in inlet air temperature?

Home-Depot'ing car mods is fun, no denying that, and it can be a real learning experience. At the end of the day though, you do need to keep in mind that you are trying to improve upon a design that was optimized by a bunch of German PhD's and engineers that probably solve the wave equations* for the optimal air intake on the back of napkins for fun when they are out having bier with their friends. They have already taken into account everything you can imagine, and about 3x as many things that most normal enthusiasts have never even heard of, when designing the air intake system. Messing with it really only makes some aspects of the system different, not better. The whole reason BMWs are "good" cars that carry a big price premium is because they are designed well enough that $30 in parts from Home Depot CANNOT improve them!

With the exception of the stock chip, there is no "free" low-hanging fruit. As far as I can tell, the stock M42 software was severely crippled so that the M42 models would not eat into the more expensive M20 models' sales volumes. A chip is the only power mod worth its price, really. A light flywheel is nice too, but it comes at the expense of a rough idle, slightly degraded driveability and probably reduced transmission life. The heavy flywheel was another case of "the best option with all things considered."

This isn't a personal attack directed at you specifically or anything. It's just my usual tirade about "cold air intakes." I wasted all sorts of time and money on them a decade ago before I knew better too. Hell, I am glad I did. It drove me to study mechanical engineering, which is the only reason that I know better now anyway lol.

*(probably sounds simple...look it up).