Cnchavez8674

Good morning. I am currently replacing my exhaust and am running into a problem. when I start the car the PSE valves remain fully open. I thought I might have a bad change over valve so i switched them out there was no fix. Am I doing something wrong? do the valves close at a certain speed? I'm lost. I know its not a lot of info. I just don't know how to put it all in words. lol. Basically, can someone tell the basics of the PSE?

stellman

Did the car come from the factory with PSE?

Are you going to an aftermarket exhaust?

Cnchavez8674

Thank you for the reply. Yes, the car came with the PSE from the factory. I am replacing with aftermarket exhaust. It seems on startup the valves remain open. I can actuate the valves by hand and it gets super quiet. when i switch on sports plus mode nothing happens. This is all done in the garage not on the road. I didn't know if there was a speed or RPM trigger for the activation.

SilverSFR

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Cnchavez8674

thanks for the reply and clarification. there does not seem to be any vacuum it appears to be neutral. I did switch to a different change over valve and the results were the same. i am wondering if i have a couple of bad changeovers or there is a problem with the vacuum lines.

SilverSFR

My question was to the wider group. Do change over values when PSE active open and pass vacuum or close and stop vacuum and cause positive/neutral pressure? You would think active change over valves pass vacuum but I am not positive that they do.

Cnchavez8674

well in order for them to work properly they have to create vacuum. the way the exhaust valves are structured, vacuum is the only way for them to work.

SilverSFR

You would think.

Cnchavez8674

No vacuum keeps them open. Quiet.

SilverSFR

So explain closed = loud at start/45 seconds of idle. Before vacuum has been built. That is the part that I scratch my head with.

Cnchavez8674

The valves are not working. That tells me its not getting vacuum.

dannyk304

Not to create an argument, I think you're all creating some confusion about how the valves work. I hope this helps clarify: The valves are operated by vacuum, as you all know. Vacuum does take a few revolutions of the engine to build up as a natural function of an ICE, so yes, regardless of the mode you're in upon start-up the valves have no vacuum and are open - LOUD - and when vacuum builds they close - QUIET. By default, PSE is active (loud) with the absence of vacuum and the valves are open. When the valves are open, the exhaust routes through the center muffler and out through the two inner tips, as well as some residual going out to the side mufflers and then out the two outer tips as well. When the valves are closed (QUIET) the exhaust is routed into the center and then pushed out to the sides and out the two outer tips only. So, with no vacuum, all tips are functioning and exhaust is running through the center and out of the car (LOUD). When closed, goes through the center and out to the sides and then out of the car - QUIET. Even when PSE is off, QUIET, the valves open after about 4000 RPM as the heat and pressure can damage the sides and more breathing is needed in this situation. When valves are open, and exhaust can go out through the center some exhaust does creep out to the sides and outer tips, but when closed the inner tips do not do anything.

Cnchavez - there may be several reasons the valves are not getting vacuum - one could be a vacuum leak which would likely result in a CEL (related to coolant system fault strangely enough, but that's because of the way coolant relies on vacuum and so it just sets off this warning), another is of course bad COV but that would lead to a leak and aforementioned CEL. More likely, if you don't have this CEL, it is a power related problem - no power to the COV means it doesn't turn on and vacuum doesn't divert to the valves. Another issue, perhaps - if the car came with PSE from factory and you bought it used, perhaps the former owner wanted only loud mode and thus plugged the vacuum line somewhere between the PSE COV and the actuating valves. if PSE was added afterwards, maybe the power was never hooked up (it is complicated, requires some interior dismantling,) and as is in my case, there seems to be an issue with the DME not directing the COV to activate.

biggreek

I'm in the same boat with my 991.2 GTS. I installed a new aftermarket exhaust and the exhaust flaps are backwards from OEM (normally closed instead of normally open. Vacuum is supposed to close the valve and now vacuum opens the valve). I'm trying figure out a solution currently.... No matter what, the exhaust now closes at 4k rpm and above ..not ideal.

SilverSFR

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dannyk304

SilverSFR, you are confused, it's opposite to what you say. Valves open means LOUD, valves closed means QUIET. The actuating valves are, by default, under spring tension in the open position and in the absence of vacuum will remain open and LOUD. When the COV diverts vacuum to the valves they will close - quieten the exhaust. The actuating valves regulate whether the exhaust goes straight through the center and out or pushed to the two side mufflers before they go out. Think about it, if the exhaust flows straight through it will be louder than going through an additional muffler (meant to muffle) thereby making it quieter. So, to make it clear - when the valves are open, as they are by default, the exhaust goes through the center and out of the car through the two inner tips (and some residual does circulate to the outside ones as well) but when the valves are closed, the exhaust goes into the center from the headers but instead of exiting the system it gets circulated out to the two sides before exiting through the two outer tips, the two inner tips are CLOSED out of the loop. The reason you have 45 seconds when igniting the engine, in LOUD (OPEN) is because the engine needs a few revolutions to generate vacuum to then operate and close the valves to quieten the exhaust. There can be no vacuum generated without a running engine and it doesn't happen instantaneously. When you put it in sport or hit the PSE button, you're telling the COV to divert vacuum AWAY from the actuating valves - removing the vacuum - thereby allowing the spring tension and opening the actuating valves, allowing both banks to mix in the center muffler and go straight out through the two inner tips making it LOUD. When there's vacuum, both banks remain separated from one another in the two chambers and forced out to the two side mufflers, making it QUIET. So, to recap - valves open is LOUD, occurs when vacuum is not present and valves closed is QUIET, which occurs when vacuum is present in the actuating valves.

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