Belt slap with DASC

[denglish318ti]

Hey all, my engine makes a gruff sound when I rev it from low revs and its because the belt is jumping and vibrating a bit. I Have got with the 2000's and have uploaded a video onto you tube (what an effort that was!).
http://www.youtube.com/watch?v=KIHLfSVp93s

Any idea what may be causing it? As it is between the alternator and the power steering pump might it be one of those two?

Cheers
Dylan

[xxxJohnBoyxxx]

Originally Posted by denglish318ti

Hey all, my engine makes a gruff sound when I rev it from low revs and its because the belt is jumping and vibrating a bit. I Have got with the 2000's and have uploaded a video onto you tube (what an effort that was!).
http://www.youtube.com/watch?v=KIHLfSVp93s

Any idea what may be causing it? As it is between the alternator and the power steering pump might it be one of those two?

Cheers
Dylan

Is you idler pulley in good condition or fairly new. I know mine failed soon after I installed my DASC and it is common to need a new idler pulley with a DASC. They need a fresh spring to keep the belt tenstion tight. Just a thought.

Only thing I can think of.

Good luck, John Smith

[denglish318ti]

Idler pulleys are pretty new. Think you are right about the belt tensioner, as when I build the revs slowly it doesnt do it. But when I crack open the throttle the tensioner moves a bit causing the belt to slap a bit.
Cheers for your help
Dylan

[denglish318ti]

Think I found out what it is, I replaced the tensioner and it was working, but not ideal. Since then the belt got chewed up and it lost one of the ribs. It was squealing a bit, but then it stopped and I noticed that the belt had skipped on the charger pulley.

The now 5 rib belt was running on the closest to the front of the car ribs on the alternator pulley, but was running on the back 5 ribs of the charger pulley. Therefore my charger must be about 1 or 2mm too far forward in relation to the rest of the pulleys. I do not think there is any play in either the bolts that mount the manifold to the engine, or the bolts that mount the charger to the manifold. Therefore I might have to get a mm machined off the back face of the pulley. Bit of a pain!

[JP422]

WAIT!!!

I'm almost done installing a DASC kit on my '97 Z3... (bought the DASC kit used), and during a test fit, my S/C pulley seemed a few mm's too far back (in relation to the rest of the pulleys). I believe it's a stock DA pulley (3.6" diameter or so).

Eh, before you machine anything, would you like to try swapping pulleys w/ my? I was thinkin of adding a spacer or something to bring the pullet forward.

Oh damn, You're in England. Uh, maybe forget the pulley swap idea, but I hope we can figure this misalignment thing out.



Btw, I haven't posted much here... but usually on bimmerforums.com (Joemamaman). Anyway, there's much more M44 info here, so hi all~

-Joe

[JP422]

OK... Just installed my DASC today, and was able to adjust the pulley to line up with all the other pulleys and idlers. Perfect alignment now.

The SC pulley is pressed on, but doesn't bottom out... just pull, or press the SC pulley till it lines up with the rest, and keeps the belt straight. Then put on the center nut, and make sure to use red loctite.

[xxxJohnBoyxxx]

So you are saying the SC pulley does not line up with you alternator pulley? That is odd. Is the SC kit for your car? I would take a close look at the alternator mounting bracket and ensure it is mounted correctly and tight. If you mill off the back of the pulley you will most likely need to take some off the S/C snout diameter too since the pulley diameter inside might hit by putting that pulley in closer to the S/C. 1mm is not much and you might be able to make that up by loosing the alternator mounting bracket and cocking in the direction you need then tighten it.

Just some half-brain suggestions before you take the hard route. If you have to mill the pulley then you can't ever change pulleys without milling them too. There has got to be something throwing that allignment out. Look hard for the problem before making a custom pulley to fix a problem that is somewhere else.

John S

Originally Posted by denglish318ti

Think I found out what it is, I replaced the tensioner and it was working, but not ideal. Since then the belt got chewed up and it lost one of the ribs. It was squealing a bit, but then it stopped and I noticed that the belt had skipped on the charger pulley.

The now 5 rib belt was running on the closest to the front of the car ribs on the alternator pulley, but was running on the back 5 ribs of the charger pulley. Therefore my charger must be about 1 or 2mm too far forward in relation to the rest of the pulleys. I do not think there is any play in either the bolts that mount the manifold to the engine, or the bolts that mount the charger to the manifold. Therefore I might have to get a mm machined off the back face of the pulley. Bit of a pain!

[xxxJohnBoyxxx]

Very dangerous if you are floating the pulley on the shaft on the keyway to make it allign. Better to pin it with a washer or shim on the back side and tighten that nut to secure the unit. It will shear the keyway under boost and jack-up your S/C shaft over time if that nut is not tight on the pulley and the pulley is not dead-head on the shaft.

If I'm wrong and your tightning the pulley bolt tight then carry on and ignore this post

Best, John S

Originally Posted by JP422

OK... Just installed my DASC today, and was able to adjust the pulley to line up with all the other pulleys and idlers. Perfect alignment now.

The SC pulley is pressed on, but doesn't bottom out... just pull, or press the SC pulley till it lines up with the rest, and keeps the belt straight. Then put on the center nut, and make sure to use red loctite.

[xxxJohnBoyxxx]

Guys and I'm speaking to anyone with a S/C allignment issue. Are you sure your Alternator is mounted correctly. Ensure the top bolt on your alternator is tight since this bolt goes through a flaoting bushing and alligns the alternator. Also you can adjust the alternator in/out at this point with washers in the right area but I don't suggest it unless you are sure your have an allignment issue.

Good luck, John S

[JP422]

Thanks for the info on the alternator! That's good to know.

As for mine, I never touched the Alt, so it's in the same position for the last 100k miles... and I'm assuming it's aligned fine.

When I removed the SC pulley, it has a slot machined through it for the woodruff key. Besides that, it's machined through, and there's nothing to position it (front to rear) except the tight fit.

I just pressed the pulley into place, and screwed on the pulley nut (with red loctite of course). As I screwed the nut on, it let me go untill I had it aligned perfectly with the rest of the pulleys. I have to admit this is an odd method, but I guess it works. If you tighten the nut until it bottoms out, the pulley might be contacting the nose of the SC, and it will also be WAY out of alignment with the rest of the pulleys.

The SC pulley is on tight enough (I had to use a puller to remove it, and the nut to install it), that I'm going to assume it's fine.

I wonder how the aftermarket DASC pulleys are made? How do they fit, and do they bottom out with perfect pulley alignment?

[xxxJohnBoyxxx]

Originally Posted by JP422

Thanks for the info on the alternator! That's good to know.

As for mine, I never touched the Alt, so it's in the same position for the last 100k miles... and I'm assuming it's aligned fine.

When I removed the SC pulley, it has a slot machined through it for the woodruff key. Besides that, it's machined through, and there's nothing to position it (front to rear) except the tight fit.

I just pressed the pulley into place, and screwed on the pulley nut (with red loctite of course). As I screwed the nut on, it let me go untill I had it aligned perfectly with the rest of the pulleys. I have to admit this is an odd method, but I guess it works. If you tighten the nut until it bottoms out, the pulley might be contacting the nose of the SC, and it will also be WAY out of alignment with the rest of the pulleys.

The SC pulley is on tight enough (I had to use a puller to remove it, and the nut to install it), that I'm going to assume it's fine.

I wonder how the aftermarket DASC pulleys are made? How do they fit, and do they bottom out with perfect pulley alignment?

Yes the pulley is suppose to botton out on the S/C shaft. If the pulley is tight then sand a little on the inside. When they anodize it the black anodize can get a little thick and cause it to be tight. You can call Magnuson superchargers since they make the DASC supercharger and ask them if floating a pulley on the woodruff is ok, see what they tell you. It might be ok but I'm just going from experience and the school of hard knocks.

My opinion is that pulley might be tight now but there is a large amount of torque to turn a S/C and it will loosen on that shaft start to float and bang that key until it is all jacked up. S/C can take up to 40% of your HP to turn them, that is a lot of twist. Remember that pulley is spinning close to 13,000rpm at WOT so it will be ugly if it starts floating on the shaft.

Only a opinion and I hope it works out for you.

[JP422]

Jeebus... that's what I was afraid to hear. Normally I feel it needs to bottom out too (floating pulley seems a bit odd to me), but if I crank it on more.. it goes back past the pulley alignment point. I have to admit I haven't seen what where a full bottomed out pulley will sit, but I also didn't notice any stops.

Anyway, I fired up the motor last night, only to find I stupidly forgot to double check the fitting on the coolant flange (under the intake mani), so I'll be disassembling everything once again.


At least I know the motor starts

Meanwhile, I'll take another look at the pulley and try to see what full lock will do. Also gonna swap out some old sensors while I'm in there.

[xxxJohnBoyxxx]

Originally Posted by JP422

Jeebus... that's what I was afraid to hear. Normally I feel it needs to bottom out too (floating pulley seems a bit odd to me), but if I crank it on more.. it goes back past the pulley alignment point. I have to admit I haven't seen what where a full bottomed out pulley will sit, but I also didn't notice any stops.

Anyway, I fired up the motor last night, only to find I stupidly forgot to double check the fitting on the coolant flange (under the intake mani), so I'll be disassembling everything once again.


At least I know the motor starts

Meanwhile, I'll take another look at the pulley and try to see what full lock will do. Also gonna swap out some old sensors while I'm in there.

Find a washer that is the right size to pin the pulley where you want it. If you sand the anodize off the inside of the pulley it will slide on and off the S/C shaft nicely like it's suppose to. I've had to sand 2 of my 5 pulleys when I was DASC.

I damaged a pulley by accidental "floating it" for less then 20 miles with a loose S/C nut. <---School of hard knocks.

Can't sell that pulley it just sits on a shelf as a reminder of stupidity...$90 down the drain

[JP422]

Ahh.. excellent advice. Looks like I'll be using washers to help bottom it out. I kind of like how tight the pulley is, and using the puller is cake, so I'll leave the anodizing (let it wear off on its own)... but I'll definitely take out the float.

Thanks John!

[xxxJohnBoyxxx]

Make sure the washer outside diameter does not go past the pulley bottom out diameter or it will scrub the S/C bearing and make it leak oil. This is important.

You can also use a little teflon tape on there and test fit to see how far off you are. Might just be a micro or maybe a CH. PM me for CH measurement