m42 Cam Timing Revisited

[Fraser]

Alright, so I've always got the feeling that the m42 is running out of breath at anything above 6k or so, and running it to the rev limit just seems useless unless you really need to bang the next gear.
How many of you have tweaked the cam timing on yer m42's? I remember the old Stu McHenry e3s writeup that briefly mentioned it, but IIRC, it wasn't incredibly specific.

I realize the m42 probably won't see any "gains" particularly, but I am interested in moving the powerband a little higher in the rev range. Will this so drasticly kill my mid-range grunt that it would be pointless?
I've also been thinking about acquiring an e30 m42 intake manifold for my motor (this is on the e36, with their stupid "trick" variable intake runners), does anyone have an extra?

Thanks guys!

[bmwman91]

My sister has a 1992 318iS and I noticed the differences in the intake manifold. Wouldn't the variable intake runners be a benefit? Why or why not?

[m42technic]

The DISA (differential air intake control) creats more low to mid range power. I understand the runners on the E30 M42 have a bit better high end punch.

Is this a track only car or something? It sounds like you dont care at all about low and mid range power...

[zenon]

the dead top-end could be valve float, the M42 has hydraulic lifters. If you can find some solid lifters which are compatible let us know...

[bmwman91]

Well, BMP sells a solid lifter kit for the M42...all you need is $2000

[zenon]

sweet, they do!
http://www.bmpdesign.com/bmw/parts/c...ngine_40.shtml

Don't forget that comes with a new cam kit too (retainers springs cams, maybe more!).

now, to do it on the cheap figure out which motor those lifters come from.
I promise you they have a BMW PN on another BMW motor (S14, euro S50 etc), and the solid lifters are compatible with a stock cam..... DannO just recently rebuilt his motor for track use, switched to solid lifters and kept his stock S52B32 cams.

[bmwman91]

Interesting....we should do a little research.

[m42technic]

You wouldnt be getting valve float at 6000 RPM. If he was, how can you know its the lifters and not the springs themselves?

[zenon]

hyd lifters typically pump up around the 6-6.5k mark or possibly higher, depending on valve springs.... if you switched to solid lifters I'd bet you can easily get another 500RPM w/o touching the spring force or the cams.


bmwman91, my suspicion is that they're just S14 buckets, if you're going to go lone ranger there's no point in going half assed, dig up an old conversation (either in the E30 or E30 M3 board [my guess is the M3 board]) between myself and JamesM3M5 there is a conversion that can be done to the S14 which upgrades its stock buckets with lighter ones off a totally different motor (a motorcycle actually IIRC)

[zenon]

I think this is the link:
http://216.242.91.254/forum/showthre...ighlight=james

enjoy, and keep me updated!

[Fraser]

I hope I'm not getting valve float at 6k...I've never had car with Hyd. Lifters, so I don't know much about 'em. If they float at 6k+ I'd probably be a bit more hesitant to bang the rev limit as often as I do.

I'm not incredibly concerned with loss of low and mid-range juice, as I feel like the damn thing has to be revved to the moon to get any power out of it at all. Maybe I'm just kidding myself into thinking that that loss of torque will be less significant than it really will be.
Are any of you guys running non-stock cam timing?
How about a stock motor (or modded, I suppose) dyno sheet? I'd love to compare an e30 m42 to an e36 one, to see what kind of a difference the manifold alone makes. Sometimes I swear to god I'm feeling a slight *loss* of power when the manifold switches over at 4-5k.

Thanks what you guys've offered so far- I would also be interested in a cost-efficient solid-lifter upgrade.

Fraser

BTW, thanks for letting this live here in e30- most of the e36 318 guys have given up on their m42's (or N/A ones at least) long ago.

[bmwman91]

Well, I think it is a damn shame that people think the M42 is some POS "economy motor." It performs quite well for what it is, and has some potential. It has always been quite pleasing to me...anyway, here's a dyno graph of mine WITH my mods...


This is uncorrected...with SAE correction standards it puts down 130WHP peak & 119.8ft-lbs peak.

[m42technic]

Originally posted by zenon
hyd lifters typically pump up around the 6-6.5k mark or possibly higher, depending on valve springs.... if you switched to solid lifters I'd bet you can easily get another 500RPM w/o touching the spring force or the cams.

What do you mean by "pump up?"

[Rob]

$2200 for the cam kit, damn.

[zenon]

325bEater, it's not floating per say... actually bmwman91's graph doesn't look as bad as what I'm used to seeing. @ this point they're just pumping up @ most, not totally floating.

when a lifter pumps up it is floating ever so slightly but due to the hydraulic lashless design, the lifter now takes up this slack. Problem is when the valve closes back up @ high RPM the lifter can't "bleed down" fast enough and it won't totally seal.

the other side of the coin is a lifter that "bottom's out" (sorry the technical name has escaped me right now) @ high RPMs where the force of opening the valve bleeds out oil and you now don't have the valve opening as much as it could.... and it will also contact the seat while following a portion of the cam's ramp that is closing more quickly than it should and therefore "slams" into the seat. (if you search on the net for fast bleed lifters you may find V8 guys saying they wouldn't want to run their fast bleed lifters @ high revs for much longer than reaching for shifts, this is what they’re hearing)

[m42technic]

Usually when you say a lifter has "pumped up," it means that they dont have any slack in them (they are fully pressurized with oil).

[BimmerToad]

The later M42 valvetrain (93 or 94-95) should be able to withstand higher RPMs, because of the lighter weight valve design (6mm valve stems as opposed to 7mm stems).

Would it be possible to work with the DISA and simply port the higher RPM runner, but keep the lower RPM runner stock to retain the nice low/mid torque?

I assume the solid lifter conversion is off of a S50Euro, since the M42 is essentially an M50 engine, minus 2 cylinders and Vanos.

What about a slightly higher duration camshaft with increased lift for streetable torque?

It does seem like revving my '95 318ti past 5.5k has no performance advantage, besides holding a gear longer before a turn. . .

[BimmerToad]

When I get access to a scanner, I'll upload my dyno graph of a stock '95 M42 w/ DISA.

It was dynoed at 126 rwhp and 117 rw trq.

[Fraser]

Great BimmerToad, you basically are in the same boat I am. That'd be great to compare your dyno graph with BMWMAN91's.

I may look into porting the high rev intake runner alone. Ultimately I wouldn't mind running a shrick or at least advancing the stock cams a bit, but I'd like a little real world info before I go and do something stupid like completely kill the driveability of the car.

The DOHC 4 motors I'm used to (Honda/Nissan) seem to typically have kind of "frantic last pull" to redline, whereas the m42 becomes pretty undramatic (aside from the noise!) at anything past 6k.

Thanks again guys!

[bmwman91]

Well, I don't know if that "frantic last pull" to redline is all that great of a thing. It is definitely fun, but I guess I do not really like a motor that has really crappy low/midrange power (aka most 4 bangers). The M42 pulls decently on the low end for its size & has pretty decent midrange power too. If I had scaled the dyno-chart out more (so the torque's minimum was at 0 instead of 40) its power curbe would look a lot more flat than it doe szoomed in. I dunno, I guess I fail to see the point of revving it to 8K when the first 4K are useless. My $.02

[supa7]

Would it be possible to work with the DISA and simply port the higher RPM runner, but keep the lower RPM runner stock to retain the nice low/mid torque?

I would think that porting the higher rpm runner would hurt low end performance because the air charge at low rpm will still pass through the short runners anyway.

In theory, the airflow would lose some velocity. Whether it's significant or not is something I can't figure out. Did you ever try it?

I should buy a spare intake manifold and experiment

[bmwman91]

Wow, talk about being resurrected from the dead! I was a dumbass college sophomore when I last posted here.

The M42 is still an OK motor, but you won't get anything much from it without boring, stroking & porting it. Oh, and custom tuning. Messing with the intake manifold won't help much of anything, the bottleneck is in the head.