Supercharger clutch relay electric guru

[TurboRA28]

Hey all, i've been helping a mate tune his 4agze engine running a Microtech. We have set the supercharger clutch to 8' of mercury as per the factory ecu controls it.

Problem being that the factory ecu would leave the clutch engaged for 5 seconds once it dropped below 10' of mercury. So when you change gear the charger clutch stays engaged.

So currently its a bit laggy between gear changes.

Can't seem to find a way to do that with Microtech..

I was thinking of other ideas.. One being would it be possible to put a capacitor on the switching side of the relay, maybe with a diode before it so the current cannot flow back to the ecu. So the capacitor would remain changed and keep the relay on for a few seconds? How big of a capacitor would I need for this to work? Would it work at all?

Thanks
Joel

[brett_celicacoupe]

im assuming the ECU grounds the wire from the SC to engage it?


if it switches via a conventional relay then you may be able to connect a suitable capacitor in parallel with the relay coil terminals to hold the relay closed after the power is removed.

whats the resistance of the relay coil?

[TurboRA28]

Hey, yeah thats right the ECU grounds the relay to switch it on and give power to the SC clutch.
It is just your everyday 30amp bosch relay.

I'll measure the resistance of the coil.

[sideshow]

can u make it come on with rpm

on the std 4agze didnt they turn on the relay after 1500 rpm

instead of turning on with boost just make it turn on with rpm
and make it turn on just after idle rpm

i was always on the impression they turned on at 1500 anyway and not vacuum/boost on the std ecu

[TurboRA28]

Hey Jim, how are you going mate?

I was under the impression it worked like this -
"The ECU engages the supercharger based on intake manifold vacuum. When the vacuum drops below 8" the supercharger clutch is engaged. The clutch stays on untill the intake manifold vacuum has risen to over 10" for a period of 5 seconds. This time delay was added to avoid cycling of the clutch during shifts and momentary throttle transitions."

Thats what the intaweb tells me anyway

But maybe there is an RPM condition.

Setting it to say 1500rpm though, the thing is going to be on all the time even when just cruising around.. Thats why I liked the idea of turning it on based on vac.

Opinions?

Cheers
Joel

[Squid]

I was playing with something quite similar to this the other day, not for a car, but for a hydralic press, but none the less the gist of it was the same, we wanted the press to stay down for n number of seconds after the heat has been applied. We used a pre fabbed timer circuit which consisted of a 555 timer unit and a relay. I am sure River will be able to tell you exactly how of the top of his head!

It even had a dial in it, so it could be adjusted.

Question, what happens if you turn the car off?

[TurboRA28]

Awesome.. a timer circuit sounds good.

If you turn the car off shouldn't matter as it just means the clutch is engaged for a few seconds.

[Squid]

Yeah you are right, it shouldn't matter at all.

I say it is time to ask River or one of the other electronic gurus exactly how to hook it up...

or you could hit google it shouldn't be that complicated, just a matter of triggering the timer to start once power is cut, to keep the relay open till it counts down.

[The Witzl]

Joel, isnt there a hysterisis variable you can apply to the conditions of the output from the microtech? Doesnt it have dual logic parameters also?

** i ask because i dont know - the Megasquirt does tho


If there is no hysterisis, then yes, a simple 555 timer circuit should suffice to hold the relay to earth.
However.... you will want the circuit to have a quick response time (you dont want the relay closing and opening quickly, it will burn out the coil), or you'll want it to be active whilst the clutch is engaged, and to hold it's active output for the time delay once the input switches off.

... if you get what i mean?

[Hen]

I made a circuit up to give the delay you want.

Find it here

Let me know if anything isn't clear.

Hen

[The Witzl]

Teh Hen circuit doth work perfectly.