Monte0704

Hey guys. I have a new to me GSL-SE that was running about 2 years ago. They guy just ripped a bunch of stuff off, welded the mechanical advance wide open, introduced vac leaks, etc. The timing pulley was 180 degrees off, all sorts of fun stuff. Then it sat for more than a year after it wouldn't start, then he sold it to me.

I've nearly got it all put back to stock. All the vacuum lines are new, the OMP is properly blocked off to run premix, the ACV is blocked off properly, etc etc.

The last thing I need to figure out is the 5 and 6 port port actuators. I know they use exhaust pressure to open, but the guy also removed every cat and straight piped the 7 after the factory header.

Do you think there is even enough pressure to actuate them even if I figure out how to tap the exhaust to pressurize the system?

Hoping someone has any idea .

In my brain, the car will at least start and run with the system unhooked, just fall on its face up high.

I've also seen the electronic version, with the RPM switch and everything, but thats pretty involved to just get the car to run right.

mjm4jc

I am not sure if that setup will have enough back pressure to open up the aux ports. My gut says no. Perhaps some of the other guys who have experimented with different exhaust setups may be able to confirm.

mjm4jc

I have a situation also with the aux ports. I no longer have the air pump or the air control valve, but I do have the Racing Beat exhaust which has the tube that comes off the pipe to open the aux ports. What I have found is that the back pressure is too inconsistent. The ports do not seem to open at the same rmp all the time.

I am wondering if it is possible to come straight off of the stock air pump (stepping down the hose in size to eventually 3.5 mm) which then goes to one of the rat's nest solenoids that would be controlled by an RPM switch? So you would have constant air from the air pump going to the solenoid which would open up when the RPM swiitch triggers at the proper RPM. To me this would be consistent. Can anyone confirm that this would be possible?

Monte0704

Here's what I know.

The actuators need pressure to open. On the S5 6port, it does use the air pump.

For the older S4, we need pressure from somewhere, and even the RB exhaust doesn't accurately actuate the ports.

The best fix seems to be a pressure/vac switch wired up to an MSD rpm activated switch .

You use a factory vacuum relay to do this. There are three ports on a factory switch. Vacuum, no vacuum/atmosphere and output to your device. When supplied with 12v, the relay moves from the vacuum to no vacuum on the output .

If we take off the atmosphere port filter, and put 5psi there, vacuum where it normally goes and the 5th and 6th port actuators on the output.

Then you have it switch at whatever RPM, and since it's vac to pressure, they snap open instead of slowly trying to open as exhaust pressure builds.

The only problem is where to get your 5psi.

I've seen 12v pumps hot wired it with a relay, I've seen the air pump used, etc.

You could just make your passenger blow really hard above certian rpms, lol.

mjm4jc

When you say "vacuum pessure switch" are you referring to one of the solenoids in the rats nest or something else? Vacuum relay???? Please explain.

LongDuck

As the guys have mentioned, the 5/6 ports need about 5psi of PRESSURE to activate - meaning to open the port entirely. The port actuators need a lot of volume to reach that pressure and anyone thats tried to blow into a port actuator to see if it will open will know this; it won't. Your lungs and mouth can't generate the pressures required.

sure, the S5 cars used the air pump, but must be using some kind of air pressure volume compensator or the ports would not open smoothly. You want smooth operation with slowly increasing backpressure (from the exhaust) because if they slam open, you'll kill the port air column velocity and the resultant flat torque curve. Remember that the SE has a torque peak at about 3500-4000 RPM, and stays mostly flat to redline. This is partly what makes an S3 engine and intake special in the 1st Gen. Point being, even RB knew that their presilencer would need a flared mouth on the pipe inside to "catch" enough air pressure to work the valves. Look into the engine side of the presilencer to see this.

if you want to preserve the driveability and uniqueness of the S3 intake, fix the exhaust based port actuation by putting the port co trol system back to stock (...or RB, factory Lower Intake manifold, etc.) If you don't care about driveability, do what a lot of dweebs do and wire the ports open and kill your nice smooth torque curve, make the power peaky, and it will feel just like a 12A car.

most guys never touch the port actuators and their gaskets during maintenance, and they can develop air leaks over time, preventing their proper operation. It doesn't use that much pressure, so any lost to atmosphere will prevent proper operation.

Monte0704

Ahhhh, this all makes sense. So scratch the idea of having it slam open. Instead I'll probably let the pump build pressure against the actuators...should mimic the backpressure system fairly well .

The issue I've heard is that the RB exhaust doesn't always actuate reliably.

In response to the other guy, yes, a vacuum solenoid switch from the rats nest. The two on the firewall on the passenger side are not used with the air pump removrd.

I guess nothing can really perfectly mimic the exhaust pressure though.

If I hit 6k RPM, then lift until 4500 then accelerate again, the exhaust system would open, close, open, while the electric system would just open

cpt_gloval

iTrader: (1)

No reason to have them open when you lift throttle though