Author Topic: Intake cam ajustment (Read 8490 times)

bmwconnect · « **on:** April 09, 2010, 10:23:04 PM »

I notice on the m42 I can advance or retard the cam timing without skipping a tooth. I was going to start playing around with it but I thought I would see if anybody on here has seen some gains with ajustment

Regards

flyinglizard · « **Reply #1 on:** April 09, 2010, 10:42:36 PM »

Back to -2 degrees, measured at the crank. gives more top end and a very smooth idle. Plus 2 gives a little tiny bit more mid range, idles comes and goes as the the box cycles O2 readings
Plus 5 gives a sometimes lumpy idle, more mid
Plus any more, and the idle gets weaker, power decreases over 5500
The best running car and midrange is about plus 2-3, fuel use gets better, as does mean dynamic compression at usable RPM of about 3600 or so .
Thats my experience with these cars. They are so weak that I mess with it. I have '93 cams .
Each crank notch is 6degrees FWIW. You need a good center line on the cams . The easiest way is too center the cam, move the crank.
I cant stand that my 400k Jetta 16v, kicks it all over the place.
They are about the same weight ( +-100#), the Motronic is supposed to be better than the M 1/ CIS VW system. The VW does have a knock sensor that the BMW does not have.

bmwconnect · « **Reply #2 on:** April 09, 2010, 11:28:09 PM »

Most interesting. I'm currently running 13psi on stock cams and 7000rpm limit but if I try and take it any further It's like hitting a wall so I guess the valves are floating. Would be neat if I could pull 7500rpm with some adjustment and not watch the boost drop. I could be dreaming though

bmwconnect · « **Reply #3 on:** April 09, 2010, 11:44:52 PM »

Quote from: flyinglizard;90654

Back to -2 degrees, measured at the crank. gives more top end and a very smooth idle. Plus 2 gives a little tiny bit more mid range, idles comes and goes as the the box cycles O2 readings
Plus 5 gives a sometimes lumpy idle, more mid
Plus any more, and the idle gets weaker, power decreases over 5500
The best running car and midrange is about plus 2-3, fuel use gets better, as does mean dynamic compression at usable RPM of about 3600 or so .
Thats my experience with these cars. They are so weak that I mess with it. I have '93 cams .
Each crank notch is 6degrees FWIW. You need a good center line on the cams . The easiest way is too center the cam, move the crank.
I cant stand that my 400k Jetta 16v, kicks it all over the place.
They are about the same weight ( +-100#), the Motronic is supposed to be better than the M 1/ CIS VW system. The VW does have a knock sensor that the BMW does not have.

Forgot to thank you

cristimm · « **Reply #4 on:** April 10, 2010, 10:18:02 AM »

Quote from: flyinglizard;90654

Back to -2 degrees, measured at the crank. gives more top end and a very smooth idle.

I am interested in a very smooth idle. What exactly means -2 degrees at the crank? How much should I turn the sprocket wheel and in what direction clockwise or counterclockwise?

Thank you.

bmwman91 · « **Reply #5 on:** April 11, 2010, 07:08:20 PM »

I played around with mine a few years ago & did not like it. You can move the power band around, but you won't see any gains overall. Aside form that, it didn't run very well at some RPM's since the ECU is not tuned for the changes, and my mileage dropped.

dinu.negrean · « **Reply #6 on:** April 12, 2010, 05:11:09 PM »

Very interesting flyinglizard, I was just discussing the problem of smooth idle with cristimm the other days and we figured out we have never seen an m42 run smooth. I am also interested in this matter, so if you could give us a few more details on the adjustment I would be most grateful.

When the flywheel is locked in place with the original locking pin, at TDC, and I put the cam locking tool on the cams is should be at 0 degrees, right? So -2 degrees means keep the cams locked in place, unlock the crank and rotate it 2 degrees counterclockwise?

bmwconnect · « **Reply #7 on:** April 12, 2010, 06:23:35 PM »

correct me if I'm wrong but wouldn't it just be easier to loosen them cam sprocket bolts and then move the crank + or -

flyinglizard · « **Reply #8 on:** April 12, 2010, 10:04:57 PM »

Just zero the cam and crank, loosen the bolts, tap the crank in the run direction, a little less than 1/2 a crank notch. Keeping the intake at zero. leave the xhaust at zero.(let it move with the crank)
The midrange goes softer and the upper picks up . The change is pretty discreet. The idle can smooth out a little if the injectors are tight/clean, along with good plugs and wires. It is common to retard the cam with a turbo to add some vacuum and lower the boost RPM a little.

I am going to bump mine back up a little to get some midrange, but the changes are very little. This car has a new chain and guides. The chain will get loose and the new guide will have some run in . Net result, is that the cam will get latter in the first 2Kor so. I will reset the cams at the next LOF. 5K

bmwconnect · « **Reply #9 on:** April 12, 2010, 10:20:11 PM »

Quote from: flyinglizard;90785

Just zero the cam and crank, loosen the bolts, tap the crank in the run direction, a little less than 1/2 a crank notch. Keeping the intake at zero. leave the xhaust at zero.(let it move with the crank)
The midrange goes softer and the upper picks up . The change is pretty discreet. The idle can smooth out a little if the injectors are tight/clean, along with good plugs and wires. It is common to retard the cam with a turbo to add some vacuum and lower the boost RPM a little.

I am going to bump mine back up a little to get some midrange, but the changes are very little. This car has a new chain and guides. The chain will get loose and the new guide will have some run in . Net result, is that the cam will get latter in the first 2Kor so. I will reset the cams at the next LOF. 5K

Thank you mike!

Choking Hazard · « **Reply #10 on:** April 16, 2010, 04:18:26 PM »

Best idle is from Mustang injectors. I put my cams back to stock.

Phreon · « **Reply #11 on:** April 23, 2010, 09:08:46 AM »

I drove my 93 318is from Florida to Baltimore last July, (80 degree weather), and got 35.5 MPG expressway mileage doing about 75 to 80 MPH.

I recently had to replace my profile gasket and of course the head came off to do it. I just made the same trip, now with with new spark plugs, and I only got 33.5 MPG at the same speeds. The only difference was the April temps are 60 to 65 degrees.

I am wondering if set my cams a degree or 2 differently when I reassembled them, or does 20 degree cooler outside temperatures make the difference.

Ryann · « **Reply #12 on:** April 23, 2010, 11:17:34 AM »

^checked your tire pressure lately?

bmwman91 · « **Reply #13 on:** April 23, 2010, 12:15:41 PM »

Quote from: flyinglizard;90785

I am going to bump mine back up a little to get some midrange, but the changes are very little. This car has a new chain and guides. The chain will get loose and the new guide will have some run in . Net result, is that the cam will get latter in the first 2Kor so. I will reset the cams at the next LOF. 5K

I totally forgot to do this! I changed the timing chain probably 40k miles ago, and I bet that I need to re-align the crank & cams. How much do you think the chain really stretches though?

flyinglizard · « **Reply #14 on:** April 24, 2010, 08:17:36 AM »

Funny. I set this car up last night. Both cams were a little late, enough to see with the eye.. I am pretty sure that the guide wears in a lot more than the stretch of the chain.
The car has run about 5k since chain/ slide replacement.
Bumped them both, idle speed came up a little, mid range, went from none to only weak.
Needs boost big time.

Re: air density correction is about 4-6 # of torque per 20* or more!!
My UL. plane leaves the ground in 125ft on a 75* day, and about 250 ft on a 90* day.

MM