gkstar

Has anyone thought of trying to connect a led to the S/C relay in the fuse box? The box is on the driver side under the hood, so routing a wire would not be that hard. I would like to know if S/C is on or off, it may also help optimize fuel economy when cruising long distances.

flush

you can't tell if your SC is on or off already? it's pretty audible and you can feel it, plus, look at your RPMs.

Yacht Master

I was going to do that on my E55. Just for the reason you listed, at highway speed I can't tell if it is engaged or not. I know at highway cruise it should be disengaged but don't know at what higher speed it will re-engage. Our E55 also have a blower bypass valve that may open under conditions of low loads and low RPMs with the S/C still engaged, so some have told me the way to tell is with a boost / vacuum gage in the car.
If you try it post the out come here TIA.

Fifth Ring

I can't say I have ever been able to tell the transition from off-to-on. It might be a useful diagnostic tool. What we'd really need is a light indicating when the clutch for the S/C is engaged or not. I'm not sure if that can be "tapped" via the fusebox.

Expat

I think it's a great idea especially for those (like me) who are trying to work out if they are having I/C pump issues.

Eurocharged Rick

you can tell the difference with a vacuum gauge hooked up very easily...

i also thought about hooking up a switch to the supercharger clutch wiring so i could manually turn it off and on...purely for better fuel economy

Yacht Master

I was going to tap it at the S/C plug, and run the wire around the fuse block then up to the trailing edge of the hood and hot glue the LED just under the edge. Then if it works (and looks cool) go the distance and put a LED in the cluster and wire it up nice.

gkstar

Yes, I am referring to the relay that controls the clutch, it is in the fuse box under the hood and I can tell which specific relay it is when I get back home - I have the schematics. I do not believe the added minuscule LED load will interfere at all given the clutch likely consumes quite a bit more.

gkstar

Be carefully with this though. The computer knows how to avoid stress on the belts and pulleys and can choose the right time to switch S/C on or off.

If you do not switch back and forth while driving (but only during complete stop), then it should be safe.

Zeppelin

I think this would be a waste of time. Even if you know when the SC is engaged and when it is not is not going to save any gas. The SC engages above 2900rpm for several reasons - one being that the engine cannot breath through the SC without it turning at higher RPMs (like 3000 and above).

So if you disable the SC above 2900rpms you will see a huge performance drop over even a C320. Gas mileage will suffer as well.

You can try this by un-plugging the SC clutch and going for a drive. The car feels like a C320 below 3000rpm, but above that it falls on its face.

msheredy

That is too funny, as I was thinking of the same thing. It would make for a cool conversation piece too. I'd guess it would be easy to do?

Eurowow

very interesting idea, I was going to install a Start up Button & apexi indglow boost gauge in to my c32. Got the idea from my s2k, I wouldn't mind spending a lil more time to install a S/C on/off switch.

PeterTheFish

I'm resurrecting this thread in hopes of getting some help on a project I've been contemplating since my wife has started nagging to drive the car more often.

I'm planning on running a switch to either the S/C relay or the SC Plug on the clutch itself, depending on what lends itself to ease / reliability. Preferred location would be the glovebox, so I can lock it off and put a blank key blade in my wife's remote. However, need to know what relay controls the S/C? I haven't been able to find a map / diagram anywhere - help!?

Montero Cruz

were you ever successful?? I know its been 11 years haha, just picked one up and had the same idea