crewchief264

Bbirdwell asked I make this post after we spoke on the phone about inclination angles:

I am fairly new (2 years) to the W211 Platform. However my car came with a Kleeman stage 2 kit. So Crank pulley Stock upper and mid lengths. I am not new however to Diagnostics and tuning. I have owned and still own some highly modified vehicles, that also have blowers.

That said my car was an auction special and I methodically restored and repaired the car in accordance with service data. One thing I didn't like was the super charger clutch engagement. At first I though it may be the TCC solenoid, however after a month of driving with live data on my scan tool, I was using an Launch X431 Pro v+, I focused in on the supercharger clutch.

You can easily open up live data and select the clutch PID and watch it engage and disengage.

When you start the car the clutch is disengaged. The clutch doesn't engage until you input about 20-30% throttle position and are moving. It then engages. The supercharger pulley does not disengage again until you come to full stop.

Now the supercharger will disengage if the ecu sees Intake temps through the roof.

So needless to say after trying to re-shim and even replacing the bearing in the clutch pulley. I put a Race IQ tune for 630cc injectors, 168 crank and 83 FSP. I run no belt wrap kit, and full UDP pullies with a stock RPM belt and have zero belt slip.

Ill never look back and solved the clutch engagement drivability issue that I didn't like.

Yes the blower is more noticeable at idle with a FSP, however you can use star and bump you idle up and its much less noticeable.

Yes your AIT at idle will be about 10-12 degrees over ambient temp. IMHO the drivability improvement is worth this.

Bottom line don't be worried about burning the bearings out in the blower, because your blower is spinning all the time anyways when you drive with a clutched pulley.

Respectful Discussion encouraged below:

GinDistiller

Totally agree. I've been running an FSP for years and will never look back! I'm in a cool climate too which helps.

bbirdwell

This is good info. I never wanted a fixed pulley as I worried about the 100 percent duty cycle affecting the rear bearings. If the car is already running 90-95 percent duty cycle I now don't believe it will make much difference. Now to look for a sale on a fixed pulley...

Alex e55

hi. maybe it is possible to programmatically program the clutch disengagement ?? did not study this question?

Alex e55

Please tell me what are the advantages of a fixed compressor pulley?

zerocat101

No more jerkiness from clutch engagement. Power on demand off idle. .The bad: makes supercharger rattle at idle but does not hurt anything u really don't hear it unless u have hood up. And you need COOLING. Inner chiller if you run smaller pulleys like 72mm. .

Jerseyjules

I am currently researching going with a fixed pulley also. Mainly cause I do not like the dead feeling I seem to get in some throttle positions. For example sometimes when says turning into traffic and the car goes into 2nd gear and I mash the title it occasionally does not downshift to the proper gear and get under boost. I just feel a traditional supercharger setup would feel more snappy in part throttle situations. Ok feel the current clutched set up feels like all in or nothing.

UncleBenz55

You can tune the pulley engagement and bypass valve, to get a smoother engagement. From what I understand a fixed pulley won't do much, since you still have the bypass valve.

Jerseyjules

So these box tunes they sell with the smaller pulley would do that for me? Next dilemma is what size pulley for a little extra madness while keeping the car mostly stock?

99lightning

83 pulley if your not doing long tube headers still i would split the intercooler and a underhood tank either vrp or at least a 03/04 cobra tank., Mk-ultra tcu tune and a good engine tune.

UncleBenz55

I'm not sure how these box tunes work. Personally I have no bypass valve and a stock pulley cause I want the car to feel more aggressive. It feels more aggressive but the clutch engagement is very noticeable now too.

A good tuner could make the clutch engage before closing the bypass valve, making the clutch unnoticeable.

Jerseyjules

I just ordered the 83 mm pulley with a tune. I'm not looking to go crazy on this car. My next mod will be the cooling pump and possibly an upgraded heat exchanger and I think possibly down the road delete the center resonator for a little extra sound. I don't want to make the car too much like a race car. I like the way it drives right now which is like a little more power and sound out of it.

CICBarkeep

I have an 83mm UPD fixed pulley which required the installation of a resistor "into the harness side of the supercharger plug so that clutch and ECU will think the clutch is engaged at all times." I find the rattle caused by the FSP annoying and am considering installing a clutched unit instead. Any idea where that resistor may be found and what steps (if needed) should be taken to disable / remove it? Thanks!

GinDistiller

There is minimal freeplay in the clutch wire harness so the plug should still be near the pulley on the passenger side. Normally it plugs in to the magnet just behind the pulley (magnet end of plug is a 1-2" long piece of black plastic that is slid onto a gold colored metal bracket).

Find the plug on the harness and just pull out the resistor, then plug back into the magnet.

NOTE: Some tuners set their tunes to not need a resistor, so if you find yours still plugged in then there's nothing you need to do. I believe the UPD instructions say a resistor is needed but that isn't always the case.