VICS operation
 

I have a 95 car .. now with a 99 engine.

I don't see where or what to connect the RPM switch to.
I have identified the butterfly actuator .. which I assume is linked to VICS .. but i don't see any plugs or wires or anything to connect the RPM switch to .. what am i missing or not seeing?

more on the VICS .. since i have a turbo system on my car. is the VICS RPM switch actually even needed? If i understand it correctly, the purpose of the RPM switch is to keep the butterflies closed normally, then open them at a predetermined RPM (people say around 5200-5600). With this process in mind .. if i connected a vacuum hose to the butterfly actuator .. wouldn't it keep the butterflies closed during vacuum and open under boost .. which is essentially what i need?

You're missing the vacuum solenoid.

The 99 has a vacuum reservoir in the manifold itself. It is fed from the plenum via a hose with a check valve. In the 99 motor this check valve is green and white, and is hidden from view. Between the vacuum reservoir and the actuator, will be your solenoid.

i think i found a source for the vacuum solenoid. that should arrive in a week or so.

i also see the green and white check valve. on the throttle body side of the check valve, there's a T connection - one side goes to the check valve, the other is open. is this the end that is supposed to connect to the vacuum solenoid? the other side of the check valve doesn't appear to have a free vacuum line. Is that T connection a special vacuum line, or a line just like any other on the intake manifold?

You're not trying to make your butterflies closed during vacuum and open during boost; you're trying to make your butterflies closed below about 3500rpm and open above about 3500 rpm.

You guys need to stop pulling shit out of assholes:

Attachment 189640

to determine the best crossover point: do two dyno runs, one with it open and one with it closed. The point where the curves cross is where you set the change. You'll find it to be very close to 5200RPM.

Ahh I was wrong that the vac chamber is inside the mani.

On 3 different cars the best crossover point was closer to 5600 RPM. Both NA and turbo.

My comment wasn't really directed at anyone, but just wanted to show the source ;)

But then I might get consipated? :dunno:

Just to confirm- when vacuum is present, the valve is closed (idle, below 5200rpm), and then no vacuum is when it opens for 5200rpm+. the little diagram shows a little arrow next to the actuator in the closed position, i assume that's what it means.

I wonder how much vacuum the canister can store to allow the butterflies to close going above and below 5200 numerous times without pulling more vacuum. I assume the solenoid purges the vacuum stored between it and the actuator...then sources vacuum from the canister when it drops back below 5200.

brain .. thanks for the picture .. that makes understanding the VICS so much better.

just for my curiosity .. is the actual function of the VICS solenoid to allow vacuum to pass (or not pass) from the VICS vacuum chamber (which is built into the manifold) to the VICS actuator?

yeah it allows vacuum to suck the actuator inward, closing the butterflies. The chamber allows it to maintain vacuum where it otherwise wouldn't exist.

then to open butterflies, it release the vacuum and the actuator extends, opening the resonate chamber.

when it releases the vacuum .. any idea if it releases vacuum only from the actuator side, or from the chamber also? cause if it doesn't empty out the chamber each time ... bouncing above and below 5200 rpms may take a while to empty the chamber.. but either way .. as soon as the car sees vacuum .. shouldn't the chamber almost immediately fill back up?

on another note .. the purpose of a check valve on a vacuum line is to prevent boosted pressure from passing, correct?

yeah I have no idea how that part works. too little brain.


and correct, check valve prevents boost from entering.

The check valve allows vacuum to stay in the little reservoir.
Whenever mani vacuum is higher than that in the reservoir, air flows from the reservoir into the mani, increasing the vacuum in the reservoir.

now i'm going to feel like an idiot here ...

but looking at the picture that brain posted and at my intake manifold.. i'm not exactly sure which line is the VICS chamber exit line. i see the check valve and the line entering the VICS chamber on the frontside of the chamber, but on the backside of the chamber, there is no line coming directly out. i see two lines, one at the top of the intake manifold, which looks like it's too far away from the chamber, as it's high up... and the second line i see is coming off the bottom, by the rear. the picture looks like there should be a line out the rear directly behind the VICS chamber .. but i don't see this. is the VICS chamber exit line actually the one coming off the bottom??

manifold, check valve, chamber, solenoid, actuator.

i understand that ... what i don't easily see is what vacuum line leaves the chamber, as there doesn't appear to be a line coming out of the chamber area on the firewall side of the intake manifold like it looks in the picture

pictures are worth 1000 words?

ok .. here:

Attachment 189617

the left most black tube is actually coming off the bottom of the manifold .. but i guess it's the closest to the chamber .. and the line from the actuator is going to the same-ish area .. so maybe it's the right one?