I've had my 06 E55 for most of the year now and just about got all the wear and tear items replaced and ready to start with power mods.
It already has a 77mm SC pulley, BWK and an EC tune. Came like that, but cooling mods are on the short list.

I've noticed for some time now that if I'm in manual mode and hold it in 1st it runs up through the RPMs and then at exactly 3200 it bucks pretty bad and then smooths out and continues on up in RPMs. This is not a sporadic thing either, it does it every time, hot or cold, morning or night, at exactly the same RPM, regardless of throttle percentage. At WOT its pretty dramatic, at part throttle its not as crazy. I tried this evening to see if it did anything weird in 2nd gear at that RPM and yes, it does it there too. Not as harsh as when in 1st, but still there. I ran it in Sport mode and at part throttle (50%?) I noticed it shifted to 2nd at that exact RPM. If I go WOT in Sport it stumbles there and then powers through up until it eventually shifts at whatever RPM it decides is appropriate. No other drivability issues besides this.

I don't think its the SC engaging, that RPM seems too high and I'm pretty sure I feel it closer to around 2000 or so. It doesn't seem like a trans issue either, but could be.
It really feels like the fuel just cuts out a that exact moment for a split second and then picks back up. I did get the fuel pump recall work done not too long ago, but this symptom existed before and after that, so I don't think its a fuel delivery issue. I don't have any data-logging capability right now but will look to get someone to pull some numbers for me.

Has anyone here experienced this issue or symptom? Any ideas what could be causing it to fall on its face at 3200 RPM... every time?
I've learned to drive around it but I know it's probably not a good thing and would like to get it addressed.

 

you could check the spacing between pulley/magnet should be around 0.30-0.40mm,if its to big it could cause severe bucking issues,not sure thats the problem in your case.
As you say check for fault codes and datalogg.

 

Welcome to junk aftermarket pulley upgrades.All these aftermarket ones makes the charge engage very hard.I'm a fan of cranks for stock blower,and upper for direct drive blowers.

 

So you think that's the SC clutch engaging at 3200 RPMs? I thought the clutch kicked in more around like 2000 RPMs?

 

depends on tps Load .also ,shiming not correct will effect this two.

 

The OP is saying there is a drop in power at 3200rpm, as if the SC is disengaging briefly then re-engages.. The title would be car is not pulling at all when he goes wot at low RPMS if it was the other way round.
Almost sounds like a hiccup or stumble of sorts you describing. I am presuming you have the clutched 77mm pulley and not the fixed pulley?

 

The clutched pulley will do that in mode depending on how he’s throttling the gas,I would try a sneaky reset but many think it resets the ecu .That reset will set the throttle values back to zero

 

Have you checked for any codes?

 

I had it checked for codes a couple times recently for other issues I was chasing down, nothing.
I do the ECU reset about every 3 days or so, I don't think that has any effect on this issue one way or the other.

Yes, it's a clutched 77mm pulley. I did go check the pulley to clutch clearance and it's pretty tight, way less than the .35mm min.
It's probably more like .1mm. The clutch still spins freely by hand so it's not binding up, but I suspect that being that close is causing an issue.
Would being too close cause the engagement to be more abrupt and cause more bucking, or would too much gap cause that?
Does the gap have anything to do with what RPM the clutch engages or is that more a function of load and speed?
In my mind the smaller gap would cause it to be more of an abrupt engagement as it doesn't have to travel as far to lock up, so more of an instant lock up, but maybe I'm wrong on that. I've been trying to imagine what symptoms the small vs. large gap scenario would create, but its all theory.
If anyone has any definitive information on this I'd appreciate the input.

Either way, gonna get some shims and pull it apart and try some different gaps and see what happens.

 

this why they call for a certain spec .fellow the spec and see if it changes .Ever think it might be your tune ?

 

I understand it calls for a certain spec, but what I don't know is what symptoms I'd get from too small of a gap vs too big of a gap.
Car came like this but I know its something I need to address.
Not sure what tune was on the car when I got it but I had it retuned with a EC tune. This problem existed before and after that tune so I don't think its that.

 

This does not sound like a SC engagement issue. I mean, I would toss a shim in behind that pulley since you know it is out of spec, but I think it's a long shot that it will fix what you are describing, might make the friction rings on the sc clutch last longer though. Your problem sounds like a tune issue to me.

I would flash the stock tune back on and see if the issue goes away.

EDIT: Just saw you already got a different tune and the problem existed before and after. Are you monitoring boost pressure? I wonder if you are having belt slippage or SC clutch issues. If you aren't using anything to datalog already, the EC software they gave you has some data logging. I would take a look at what your boost pressure is doing and make sure nothing abnormal is happening. Also you can check for black dust on the SC pulley and on the bottom of the plastic engine cover over the pulley.

 

This the thing ,every car acts different with gaps .On mine ,to small ran like ****,when I shimmmed it to 3.65 it still was there but not as bad .The after market pulleys do this there all junk imo .I’m a big believer in only crank setups they make more tq ,spool harder and faster ,and it will make more power then any upper (compared size etc ).

 

Yeah, maybe I'll try that too. The guy who did my tune is doing a heat exchanger for me next week so maybe I'll see if he can reflash it and a least prove/disprove that theory.
So you don't think the gap (too little or too much) has an effect on drivability, just an effect on longevity of the parts involved. i.e.. clutch, friction rings, pulley springs, etc?

 

I have not had mine undergapped, I wouldn't think so but it looks like that other guy has had issues with it from experience. Still 3200 RPM is a strange RPM to be having issues under all conditions from the SC pulley. Check my edit, are you logging boost?

 

Well, everything I've read on the 55K series, they all have SC engagement harshness, even with the stock pulleys. A little is OK and expected based on the design, but I'm just trying to figure out if my current gap is what's causing my particular issue or not. I'm going to try a couple different things to try to figure this out, just needed some ideas from the board here.
Drothgeb suggestion to try to the stock tune is on the list, as well as adjusting the gap. If neither of those work then I'll keep looking.

 

No logging capability right now, but that's on my list as well. I agree the 3200 RPM is what has me thinking it's not the SC pulley, I would think it would already be engaged at that point.
I just went out a did a standing start WOT in M, shifting about 5500 1-2 and 2-3 and it was smooth as silk, weird. Then I stopped and did like a 30% throttle and held 1st and it did the bucking bronco routine again. Who knows? I think I have a good list of things to troubleshoot and try to solve this issue. At the very least I'll know whether it's tune related, pulley related, or neither.

 

You can use the eurocharged software

It looks like you can only log MAP pressure in kPa with it. You can multiply by .145 and subtract 14.7 to get gauge pressure in PSI if you want but either way you can just see if there are any abnormal dips/spikes to make sure your clutch/belt aren't doing anything strange. A slight rise through the RPM range is normal, shouldn't be any sudden jumping around any where (except for shift points).

Also if you end up data logging a pull, make sure you aren't spinning tires. From my own experience I believe the ECU opens the SC bypass valve to reduce torque for traction control. I've noticed that on logged pulls I never hit as high of peak boost numbers if I trigger traction control as when I don't. That's just my own speculation though.

 

Take the supercharger belt off , if it goes away guess what ,it’s your s/c engaging at a much higher speed then designed ,that’s your bucking

 

Sheeesh man, frustrating. Spanner in the works now, you say a recent run with wot was smooth as silk yet next run at part throttle bucking bronco.. Feeling like this is becoming a tune issue as its part throttle. Easy enough to flash stock tune file if you have one seeing as you bought the car already tuned, start there.

 

Yeah, that's probably the quickest and easiest thing to start with. Prove/disprove and then go from there.
I'll report back but it may be a few days.

 

Starting to become a pain in the rear, for sure.

 

Ever get this sorted? I've been having similar problems at lower RPM which I've so far proven is SC clutch related. Was thinking of trying FSP and tune but don't know who to trust here in Sydney Australia.