SC14 electromagnetic clutch

[mic*]

hi ppl,

Am thinkin of running an manual "overide" switch to the electroclutch.

The idea is run a fused parallel circuit straight from the battery to the clutch, having it switched inside the cabin.

When switched on the S/C would be permanent drive, when off it would run the standard load based switch.

What i need to know that i dont have the tool to measure, is what is the operating amps of the clutch?

I need this to get the appropriate sized non-return diode to prevent feedback into the standard circuit under conditions where the switch is on, and the ECU tries to switch the clutch on too.

Does anyone know this, or can they see any flaws in the concept.

Forget about this bit, skip to the end. Need help. Feeling dumb.

[CrUZida]

Use a relay aswell

[Garth AE86]

wouldn't that annihilate fuel economy?

[mic*]

What i find annihilates fuel economy is the switch itself if your driving style has it flicking on and off a lot.

Every time it switches - bang - filthy rich mixture.

Its like being someone in an NA car who plants it when they lose a couple of km/hr approaching the top of a crest.

Maybe my ECU is not sensitive enough and is late switching but im forever driving, getting to half throttle to keep the "NA" 2.0L pulling a luxury sedan at a cruise as i hit a rise, then it kicks in, waste a shit load of fuel as it goes rich & boosted and im backing it off again just to keep my cruise speed.

Its up to me when i throw the switch on so ultimately worse fuel economy would be the fault of my own finger. I am interested to experiment coz i think i could get better fuel economy in some conditions, and certainly better driveability for short periods when i want it.


CruZ,

How do you mean for me to put a relay in this circuit? Have the accessories as the energizing circuit so i cant accidentally leave it on and kill my battery?

Anyone know the amps? Have searched a bit. Its a very specific thing to find. Not having much luck.

[Hen]

I checked a few years ago on an SC12 and seem to remember that it drew about 0.7 to 0.8 amps.

Run a relay. Though I don't think you'll need a diode. One side of the clutch gets "ON" 12V, the other is earthed by the ECU. Just add another wire that can be earthed by your relay, and have this relay controlled by a switch in the cabin. This would not require any diode protection.

Another way to play it would be to have a 3 position switch so you can have the SC always on, always off or switched as normal by the ECU. It'd take a little more wiring, but nothing hard.

Hen

[mic*]

okay,

i did not realise it was the earth that was switched.

I have not wired up my own relays before ay and am no expert on em.

So i am thinking i would run an additional earth wire with the contact side of the relay in it, using normally open contacts. The coil side is powered by my switch? on the right track?
So would you run a new circuit from the battery for the switch? I could tap an accesories wire couldnt i or does a relay coil draw too many amps?

Or else i could use a double throw relay in the original earth with second throw being permanent earth?

Henn, how would you wire the ON / AUTO / OFF setup you descibed? I only really know theory on most electrical and am starting to put it into practice. My practical experience is in the doof doof side of things - not too many relays needed to be touched by me there... So i need to be told what relay to use or i will fuck it up fer shizzle.

Trivial stuff: Is the sc12 clutch the same as the sc14? And the dash light that says SUPERCHARGER when it kicks in, do you know whether that is in the clutch circuit (meaning i would lose it when the S/C was being engaged by another circuit) or is it off manifold pressure or something?

[Hen]

OK, I am not 100% on the fact that the ECU pulls to earth to switch the SC, this should be checked. If it does, the following circuits should work.

In cabin on switch:


And now the 3 position: ON, ECU switched and OFF


Good luck
Hen

[mic*]

So the only new wiring is what iv marked yellow?



When you say your not sure if the ECU pulls to earth, the only other way i can see that it could be setup is the ECU between 12V-ON & the relay, rather than on the earth side. If that were the case, how does this look...



Where the blue dot is a non-return diode, rated to 1 amp?

I think i will leave the three position switch just for now. Can only see myself using it when i want my car in grandma mode for certain others that may drive my car - not often.

[Hen]

Yes, only the yellow wires are needed to be added.

I highly doubt the ECU switching is setup as shown in your second picture. The ECU almost always seems to pull to ground when it wants to activate something (eg injectors). And is basically an open circuit otherwise.

The best way to check would be to have the car running while the SC is not engaged (eg idling) and check the voltages on the two ends of the coil in the relay which controls the SC. If my guess that the ECU pulls to earth is true, then both ends of the coil should read 12V. Also the resistance between the ECU SC control pin and earth should be infinite.

A little harder to check is that when the SC is enagaged, there is no resistance between the ECU SC control pin and earth. Some revving and fiddling with a multimeter should be able to confirm this though.

Or more easily, check a wiring diagram.

Hen

[mic*]

I highly doubt the setup is shown in the second pic too.

If i have a voltage at the coil side when idling, thats enough for me. I cant see any possible way that a relay could be used in the circuit other than the two pics. If theres volts there which i fully expect there to be, then im jus gonna add the "yellow bits" in.

[mic*]

OK, now wait for it...

Where is the relay???

...on a 1G-GZE

even if a 4A-GZE owner can tell me where their relay is it would be a start. I feel really stupid here ppl, someone put me out of my misery please.

[TA22-3SGTE]

The ecu allways pulls to ground so all you need to do is tap into the s/c control wire at the ecu and run it through a switch to earth .

Trevor