When Does the Supercharger Engage?
 

Does anyone know the specific conditions that must be met for the M113 supercharger clutch to engage?

At idle, whether the engine is hot or cold, my s/c is in motion indicating the rotors and such are free. This occurs whether the drive belt is on or off the engine. However, the clutch is not engaged; probably wouldn't be at idle. So under what conditions would the electronics engage the magnetic clutch? Thanks in advance.

Cheers,
Jeff

BUMP - OK, 202 views later... anyone have any information? Someone, especially the ECU guys, should have an idea when the s/c engages.
Cheers,
Jeff

The vehicle needs to be in drive and I believe it engages somewhere around 1500rpm's (almost want to say 1200rpm's but it's been a while since I've payed attention).

There are variables that would keep it from engaging to protect the engine. The only one I'm positive on is intake air temps (too high and the clutch won't engage, commonly caused by a faulty charge air coolant pump), although I wouldn't be suprised if there's some other items that, if out of spec, would inhibit the clutch from engaging.

Thanks! I didn't think the clutch would be engaged at idle and not while in 'D' makes sense. The RPM range is logical. I knew a faulty IC pump circuit would be a problem, but was unsure how it manifested itself (casing/oil temp or air temp). Not sure I even have a problem, per se, as I'm too new to the car. As a footnote, my fuse chart (MB p/n 000.545.18.00) does not list anything even remotely close to intercooler, air cooler, etc. However, there are 7 fuses listed under the nebulous heading of "Engine Management Unit". Guess they expect one to check all 7 fuses for any engine-related suspicion. Just trying to learn the compressor before I state whether there is or isn't a problem. Regardless, I'm one step closer to understanding. Thanks again.
Cheers,
Jeff
PS - Love the moniker (OldSchoolRice) in reference to the Datsun. They were fun lil' cars.

What are you experiencing that you think might or might not be an issue?

LOLx2 Good question. Writing frankly, I'm not sure. Still fairly new to the car and with each fix or maintenance item I complete, the car runs/sounds better. Steady improvement.

The engine is strong and seems to accelerate well, though needs plugs badly (that's this weekend's project). But as other threads of mine in this section point out, the supercharger was ridiculously low on oil. That's resolved, but the bearings - no doubt - have some damage. Hopefully, the gears are in good shape.

All that caused me to research the s/c, and that's where I found the intercooler issues others have experienced. This caused me to look for the infamous fuse, which the fuse chart does not clearly define. This all caused me to ponder, while watching the motor at idle with the s/c clutch disengaged, just when does it engage.

I think I feel it kick in on hard acceleration, but I want to change the plugs first before making a clear statement there. But the 'feel' isn't at a particular RPM point; seems more in-sync with the pedal position. Sort of like a transmission kick-down. That's a subjective feel which I want to drive a bit with your RPM range in mind.

Does all this drivel make sense? The technical side of my brain is really curious right about now. Thanks again for your thoughts and any others you think are valid here!

Cheers,
Jeff

Unless you're hearing noises coming from the supercharger, I wouldn't jump to the assumption that the bearings are bad.

I'm not familiar with the fuse you're talking about. With all of the pumps I've replaced (a lot), I can't ever recall having to replace any fuses.

The only noticible thing that commonly happens when the supercharger clutch engages is the "chirp" noise. Not all kompressor engines make the noise, some people didn't like it so MB came out with a revised clutch. The supercharger engagement/starting to boost and disengagement is very smooth due to the clutch and the bypass valve. It's not something that's going to be very noticable.

Cool. I do still have a bit of a grinding noise, though it's much reduced after the Jet Oil addition. I'm out for a spin to see if I can discern anything. See ya, my friend!
Cheers,
Jeff

OK... Changed the plugs and the beast is running real good. With fresh plugs, I sense a power increase/surge ~1500RPM. So I think the s/c kicks in.

Am going to try and hook up a volt meter to the s/c clutch to see if I can capture the engagement point.
Cheers,
Jeff

Hey man...I'm somewhat reviving this thread...lol...
Did you finish analyzing the supercharger issues/concerns/wonderings...

I have wondered the same thing...just curious if you were able to satisfy your curiosity.

Also, would you say your engine is "clickety-clackety" or vocal?
Cheers!

Yes. Found some basic information in MB document GF09.50-P3001AM (Supercharger control function),which is a very basic tutorial. As we know, the s/c is engaged through the s/c magnetic clutch. The mag clutch is activated as defined by the performance map in the ME-SFI module (N3/10). The performance map receives input from accelerator pedal position(B37), boost pressure (B28), intake air temperature (B17/18), and RPM via the CPS(L5). Based upon these 4 inputs, the engine control module continually controls the throttle valve actuator (M16/6)and activates, as required, the s/c magnetic clutch (Y2/1). The document suggests the clutch is activated by application of ground via “terminal 15 secured”. This means the clutch should always have 12v present on it, even if it isn’t activated.

The s/c is never engaged at engine idle or with the vehicle stationary (no ground speed). This suggests there is also input from either the transmission (drive shaft speed)or one or more of the wheel sensors. The document makes no mention. One other non-activation condition – battery voltage below 9v.

The document states the s/c is engaged “during the thrust phase of the engine. This avoids any delay in the actuation during the changeover from thrust phase to the pulling phase.” When the engine is required for heavy torque, the s/c is engaged. Sadly, the document does not quantify what is ‘heavy torque’. The ME performance map would define.

Regardless of the performance map, the s/c mag clutch is activated at all times above 3500 RPM for what the document says are “technical reasons”. No further explanation is given, though I suspect is simply a matter of keeping the engine fed with sheer volume of air at that RPM. Remember, the roots blower will have some natural obstruction to air flow by its very design…until the roots are forced to move at high speed, the entire assembly is a big air flow restriction.

One other source I found was a pair of webpages (written in German) that goes into some pretty good s/c stuff. For me, I asked Google to translate these two webpages…
www.hehlhans.de/motorg55-7.htm
www.hehlhans.de/tab-wisg55amgk.htm
But the pictures alone are worth the visit.

Regarding my specific situation, the s/c does kick in; I can feel it. But the thing sucks up Mobil Jet Oil II like no other! I serendipitously found the front s/c bearing seals leaking very badly when I happen to park the S55 on an incline (nose down). Opened the hood and saw the lube dripping from the front of the s/c. Other than that, the engine is real strong. Odd noises have all faded away long ago after new plugs, s/c lube, cleaning the injectors, etc.

Cheers,
Jeff

[Regarding my specific situation, the s/c does kick in; I can feel it. But the thing sucks up Mobil Jet Oil II like no other! I serendipitously found the front s/c bearing seals leaking very badly when I happen to park the S55 on an incline (nose down). Opened the hood and saw the lube dripping from the front of the s/c. Other than that, the engine is real strong. Odd noises have all faded away long ago after new plugs, s/c lube, cleaning the injectors, etc.

Cheers,
Jeff[/QUOTE]

Thanks for the super technical response!!! Definitely helps me understand what is going with the s/c.

Just out of curiosity, how long have you had your S55? How many miles have you put on it? What is the current mileage? Any difference in engine power/response as it has aged?
Thanks!

[/QUOTE] ...out of curiosity, how long have you had your S55? How many miles have you put on it? What is the current mileage? Any difference in engine power/response as it has aged?
Thanks![/QUOTE]

Had the car ~2 years. The car was a piece of meat when I got it; but I went in with my eyes open and knew what it was. Engine performance has improved considerably after plugs and such. I'm a huge fan of Techron and Seafoam as a gas additive, so after all this time, the injectors shoot smooth. Picked it up at ~49K miles and have ~80K. These cars are designed for interstate driving and IMHO, really helps them in the long run. Supercharger appears to be a very solid design. Frankly, I love this car.
Cheers,
Jeff

I wouldve thought THERE IS NO CLUTCH !
BUT assuming there is; how does the air get thru two -2 or 3 lobe rotors mated to each other with very close tolerances?
IF there is a clutch that engages the SC when NEEDED, then why is there such things as bypass valves that are partially open under partial throttle conditions and fully close when you get closer to full throttle?
OR am i quoting the engineering from 2 different MB SC systems?

Im told i have a groaning noise MB mech says is either a SC or motor mount.
He never said maybe doesnt know if its the SC itself or a problem with bypass valve
who knows i just got this car and it still has electrical issues to figure out before i ponder the SC.

Go to the hehlhans.de links above and read. Your question on the bypass valve vs. throttle valve will be answered. Plus a lot more