Exhaust cam timing mod

[M4YTY]

Im a BMW tech in the UK. Everyone knows the m44 runs a bit rough on idle. I was looking through the technical journals at work the other day and came across a mod for the M44 rough idle. It was to adjust the exhaust cam timing slightly using a BMW special tool. I was just wondering if anyone has heard of this before and if it makes a difference. Just before i start ripping my motor to bits to find out it doesnt really channge anything. Sorry BMW if this was a secret, but its out now! Cheers Matty

[roadrash]

Hmmm... I remember my mechanic mentioning something similar to that. He said that some engines benefit from adjusting the timing by 6 (?) degrees. Or something like that. I don't know which cam it was though. Does that sound like what you're referring to?

[blndweasel]

Wow, 6 degrees is a lot, I'd be wary... I would definitely find documentation to back this up.

[thesk8nmidget]

yeah maybe .6 but that is interesting.

my m44 did idle fine once i cleaned out my icv though. never had a problem with it

[roadrash]

Originally Posted by blndweasel

I would definitely find documentation to back this up.

Yeah, you definitely should not trust my vague memory of what my mechanic said months ago. But, I do remember him mentioning something similar.

[mohaughn]

To funny.. I read about this somewhere the other day... It was saying the M42 has adjustable cam timing. It was 6 degrees forward or back. Going one way gives a little boost to low end torque, the other way gives more high end horsepower.

Was basically saying it didn't make sense to buy m42 cams.

http://www.r3vlimited.com/Tech/318is.htm

I can't find what I was reading the other day, but I did find a few short blurbs. Everything mentions e30 318is.. Not sure about the e36 m42. There are some differences. One of our pro mechanics should know.

[M4YTY]

Found it again today. VIBRATIONS AT IDLE SPEED. PARTICULARLY NOTICEABLE WHEN IN THE SEAT WITH THE VEHICLE STATIONARY. Its says its due to " differing levels of residual gasses in the individual cylinders at idling speeds. This effect occurs at irregular intervals with differing intensity. Retard the intake cam timing by 6 degrees (=12 degrees crankshaft) to 116 degrees crank angle. Changing the valve timing in this manner does not lead to any perceptible drop in torque or output"

All make sense now? Haha! I might give it a try as i have all the special tools availabe being a bmw tech. Il let you all know if it makes a difference. My idle is not erratic or rough at all, just a touch lumpy. More noticeable after fitting my magnex exhaust.

[blndweasel]

That will be awesome to hear what happens... keep us in the loop!

[96cali]

FWIW my loping idle on my '96 was not present on my '99 that came with Dinan software.

[gimp]

Originally Posted by M4YTY

"Changing the valve timing in this manner does not lead to any perceptible drop in torque or output".

This leads me to believe that it does, in fact, reduce torque and/or output, but not enough where the average person will notice.

No thanks...

[ClubSport]

I've seen the adjustable sprockets on my 95 M42 when I had the valve cover off, but I haven't played with them. I didn't think the M44 had adjustable ones, but I could be wrong.

[anthonyl]

Originally Posted by thesk8nmidget

yeah maybe .6 but that is interesting.

my m44 did idle fine once i cleaned out my icv though. never had a problem with it

I also have a rough idle, however its not constant. Could this be due to a dirty icv? How do I get to the icv and what should I use to clean it?

[spidertri]

Apologies for bumping such an old thread but I was reading over on bf.c and searched here to see if there was any discussion on the subject.

Thread on bf.c
http://forums.bimmerforums.com/forum....php?t=1030801

Has anyone done this on the M42/44? On realOEM it appears that both engines have the crescent shaped holes that allow for adjustability. It wouldn't be a lot of fun to keep changing the valve cover gasket just to tweak the power band though.

[dave45056]

You don't need to change the VC gasket each time. M42's have adjustable sprokets on the intake and exhaust. But I'm not sure about the M44. I thought that engine has a fixed Intake sprocket, but I'm not sure.
Also if you are going to do this, use a degree wheel.

[Christian]

I spoke to Rennie at Redline BMW about this. He's really knowlegable on the M42/M44. He used to race a 318ti sponsored by Grassroots Motorsports magazine. In the race car he said they picked up 12 whp by advancing the intake cam and retarding the ust cam. He didn't recall how much adjustment was made, but it sounded moderate. This adjustment increases overlap, which, in general, can be good for naturally aspirated cars. If I had an N/A M44 I would I would start with +2 intake and -2 exhaust and work from there.

For cars with forced induction increasing overlap can cause a decrease in power. I would love to hear some results from someone with a DASC trying different cam timing settings.

In a previous car of mine (not a BMW) I picked up over 15 hp in the midrange of my power band doing the same thing. The car felt slower after the adjustment because the power band be came more gradual and less peaky, but I actually picked up .4 seconds in the quarter mile.