Maximum power from a stock M42.

[bmwman91]

True. It's probably easy to get lumped into the "pretentious twat" category with a purchase like that. It's also probably a risk since there have been a number of high-profile E30 heists in the last 15 years. Randy Sparre is one of the first really sad cases IIRC. I suspect that a lot of them are either stripped, or stuffed into containers and shipped overseas.

[digger]

Yeah, as noted it is the MM Rally 2.1L. Their big thing is, according to them, making reliable DD engines that pull hard and have broad, useful powerbands. A lot of that comes down to the custom cam profiles that they developed. As for reliability, they say that the lightweight parts that are used contribute a lot to it, as well as machining things to "better than factory" tolerances.

And yes, the "205bhp" figure is from them, so it might not be entirely accurate. I have yet to get this onto a dyno since I am still looking for someone local that can tune Motronic 1.7, because I bet that there is a little more power to be squeezed out with a tune done on this specific engine. The chip that they sent was developed for this 2.1L engine design, but it was not tuned for it individually, and every engine differs a little.

Oh and yes it is a bank-buster. The price is almost embarrassing to mention, considering what you could do with an S50 for a heck of a lot less. But, I had wanted that engine since 2006 when I was a broke student, and by the time 2012 rolled around I was working and happened to have some cash in the bank, so I decided to get the MM engine instead of a newer, more reliable car lol.



digger, I did talk to them about exhaust and whatnot. They said that the stock header and other parts of the system were best left stock to maintain the broad powerband for street use. They also cautioned against boring out the throttle body. My data logging on here shows that the AFM is also not harming anything. So really, the head and cams are the big bottleneck for the M42, which MM does a lot of work on. Anyway, I always assumed that there was some degree of "marketing speak" going on regarding statements of absolute numbers. Regardless, it pulls pretty well for a 2.1L, and I pulled ~1/2 a car length on a 2007 Infiniti G35 from 0-65MPH (with my wife in the car holding groceries...the guy in the Infiniti looked pissed lol). The nice part is that it pulls solidly from 3K RPM, which is nice around town, and it just keeps on pulling all the way to 7700RPM. Then again, for the prices they charge, it had better run strong.

I was talking in general about MM engines not specific to the m42 as I’m not that familiar with theirs spec in particular. most engines are basically the same and need the same things to make better torque and power.

There is a lot of marketing speak without much basis as they don’t prove a lot of their claims. Their product quality, machining is fantastic and I wouldn’t hesitate to buy individual parts or sub-assemblies and will continue to do so as needed.

But their complete engines leave a lot on the table it seems they just have some wacky ideas that don't seem to be as good as they think.

[RCtheRed]

Been reading through the thread and I'm honestly surprised the length some people go to to make the M42 more powerful! Not trying to bash I'm honestly quite impressed because that is a size able investment. Personally I enjoy my M42, and between looking into turbo builds that put it above 200+hp and NA builds it's crazy the amount of customization and improvements that BMW left out at the time of release of engine.

On a side note, there is an ITB kit that is being sold for a little over 1k (average price of turbo build) by racehead and with a proper boring of the engine, sport cams, exhaust upgrade and proper tuning would put the NA capabilities of the M42 close to if not over 200hp.

There's a wide variety of improvements and modifications out there and it is my believe the M42 has capabilities to be a lot more than what it is when BMW released it for the streets.

[fresh_TD]

Been reading through the thread and I'm honestly surprised the length some people go to to make the M42 more powerful! Not trying to bash I'm honestly quite impressed because that is a size able investment. Personally I enjoy my M42, and between looking into turbo builds that put it above 200+hp and NA builds it's crazy the amount of customization and improvements that BMW left out at the time of release of engine.

On a side note, there is an ITB kit that is being sold for a little over 1k (average price of turbo build) by racehead and with a proper boring of the engine, sport cams, exhaust upgrade and proper tuning would put the NA capabilities of the M42 close to if not over 200hp.

There's a wide variety of improvements and modifications out there and it is my believe the M42 has capabilities to be a lot more than what it is when BMW released it for the streets.

an itb kit, sport cams, boring of engine, exhaust, and tunning. The $1k will multiply itself real quick :-) ..it's just so expensive to get power out of the M42 going NA route:-( that's why mine is still stock

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[RCtheRed]

Sorry to thread jack but @bmwman91, thoughts on changing out the stock fuel injectors for mustang 4-pintle ones? Worthwhile improvement or is the change even noticeable?

As for weight reduction delete AC, remove spare tire wheel well, tear out carpet if it's the heavier padded one, remove tools from trunk lid and ship to me, and that's all I can think of for that.

[fresh_TD]

Lol

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[fresh_TD]

Sorry to thread jack but @bmwman91, thoughts on changing out the stock fuel injectors for mustang 4-pintle ones? Worthwhile improvement or is the change even noticeable?

As for weight reduction delete AC, remove spare tire wheel well, tear out carpet if it's the heavier padded one, remove tools from trunk lid and ship to me, and that's all I can think of for that.

Just looked at the itbs..they really look good

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[digger]

i wouldn't waste time with fancy injectors unless you have emissions tests to pass. you just a need a set the proper size and that function correctly (i.e like new) . the only people who say they do anything are those coming from using poorly running units so of course they work better than a part operating incorrectly.

[5Toes]

FWIW my m42 I installed m52/s52 pink top injectors and they fit great. the spray pattern is superior and I got them for a great deal rebuilt. they flow with 5% of stock m42 ones so with a good o2 sensor the engine could learn them easily.

[fresh_TD]

FWIW my m42 I installed m52/s52 pink top injectors and they fit great. the spray pattern is superior and I got them for a great deal rebuilt. they flow with 5% of stock m42 ones so with a good o2 sensor the engine could learn them easily.

I have a set of these laying around..hmmm

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[bmwman91]

Regarding injectors, IMO clean stock ones are best. If yours are old and nasty, get some nice clean ones. I think that at least one member here offers cleaning service.

Why stock?
First, they flow more than enough for the stock engine, and according to MM they are good for ~180bhp. There has been much contention over the years about what the actual flow rate of them is. Based on a big chart of Bosch injectors by PN, the M42 ones are rated at 214 cc/minute, or 21 #/hr. A number of people are convinced that the M42 injectors flow 19 #/hr. I think that the 19 #/hr value might be based on a 2.5 BAR fuel pressure, but the M42 uses 3.0 BAR. Based on my actual measurements of air flow into a stock M42 and my 2.1L, the 2.1L flows ~40% more air, but the injectors MM sent are rated at 24 #/hr which is only ~14% more than stock (40% more air, only 14% higher flow injectors). The M42 injectors are also used on the M30 engine, which has nearly twice the displacement. Anyway, it should be fairly clear that flow rate is not a limiting factor with the stock ones.

Second, the atomization properties of the stock ones are fine. A good amount of the injected fuel ends up on the port walls and valve head which is then vaporized by the engine heat and passing air anyway. While the later 4-pintle type would seem to have a clear advantage in terms of atomization, nobody knows how the spray pattern compares to the stock ones and they may very well shoot even more gasoline onto the manifold and port walls.

Lastly, injectors with a different flow rate are going to mess with the AFR. The DME is programmed with a specific flow rate in mind, along with corrections for the injector opening- and closing-times. Chances are that the fancy newer ones will have different open/close timing characteristics, which further throws-off the mixture from the base maps. While the O2 sensor will be able to correct for small changes like this, assuming that the injectors are within 10% of the flow rate, I think that there is a good chance that the WOT AFR will be off since the DME goes into open loop mode. Dyno runs I did a decade ago with a stock M42 + Conforti chip showed no signs of lean running at 7000RPM. IIRC the AFR was around 13.5:1.


I hope that this was helpful. Just remember, the whole reason BMW charges so much of a premium for their cars is because they have engineers being paid a lot to know what they are doing. There is a reason why most bolt-ons either do nothing beneficial, or simply improve one thing while being detrimental to another (example: light flywheel...lots of fun, but makes the idle rough and makes the tranny rattle). The one exception in the M42's case is the stock tune. It is so conservative that it had to be intentional on BMW's part, probably for business reasons (like wanting to sell off the remaining M20 models before the M50/E36 era so they de-tuned the M42 to make the M20 cars look more appealing at their higher price).

[mjimport]

I just found out today via Pelican that the oem m42 injector is NLA, part number 0280150714.
Just an FYI to help those searching for injectors.

[bmwman91]

FYI the current BMW part number for the M42 injector is 13641706176. RM European and other parts suppliers have them still.

[mjimport]

Thanks! I'll check that out.

[digger]

new ones are 120-130 bucks a pop from ECS/FCP ouch

good point about the injector characteristics, dead times etc. rated flow is merely one aspect of an injector. its like thinking the camshaft advertised duration is the be all and end all

like you say nobody can tell you without very expensive testing which injectors have superior flow pattern. some engines like having fuel vaporized by the hot valve and port, while some other engines prefer the the fuel is injected during inlet valve open period around highest port velocity and it would vary with load, rpm and spec. Newer injectors are probably developed for fully sequential injection to.

So if the stock injectors are good condition then might as well make use of what BMW and Bosch knew about fuel injection. same with running higher fuel pressure people think it atomizes fuel better = more power and economy. ive seen lab tests that showed the opposite at certain loads and rpms due to a change in spray pattern when the pressure is increased. You can be sure that engines running higher fuel pressure than 3b have had serious multi million $$$ R&D programs to reap any benefit

With a heavily modified engine and different ECU then all of that is out the window though.