Mike in CA

I did the PSE vacuum actuator bypass mod today that was discussed at length in the "Mesh for front wheels" thread. Thought I would post a new thread rather than further hijack that previous one.

What It Does
Normally when the engine is started vacuum is supplied to an actuator which closes a flapper valve in the exhaust stream and routes all exhaust through the side mufflers. Pressing the PSE button triggers a solenoid to shut off vacuum, allowing the flapper valve to return to it's default open position and providing a straight shot to the center muffler. Even when the PSE button is engaged the flapper valve is still controlled by vacuum in certain situations until revs rise above 3000 RPM. Plugging the vacuum line to the actuator which operates the flapper valve allows for the valve to be open at all times. The PSE button is no longer functional so the exhaust sound cannot be muted.

How to Do It
The mod itself is straight forward. Simply remove the short piece of hose that connects the actuator (one on each side of the center muffler) and vacuum line and substitute 3/16" Hypalon plugs. Hypalon is a synthetic rubber that is heat and chemical resistant. A selection of Hypalon plugs is available from Amazon here:
http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1
I bought this package because I didn't know for sure what size plugs would be needed, but you only need 4-3/16" plugs for this mod so you may want to make a trip to a store locally. The plugs fit quite snugly over the vacuum line and reasonably snugly over the nipple on the actuator. The plug on the actuator is no more than a cap to keep out moisture and dirt.

Removing the existing clamps on the connecting hoses is a bit of a PITA unless you have a screwdriver that is small enough to fit into the small pry-opening on the clamp. I ruined one of my small detail-work screwdrivers getting the clamps off. The clamps aren't really re-useable so feel free to waste them if necessary. An alternative is to simply cut off the small pieces of hose as they are easily replaceable

Once the vacuum line and actuator are plugged, the vacuum line should be secured so it can't move around. I found the easiest way to do this was to take a piece of galvanized wire and secure the lines to the actuators.

So Does It Work and Does It Make a Difference in Sound?
It definitely works. PSE sound is now available at all times, in all rev ranges, and without having to press the PSE button, which now still lights up if you do press it, but changes nothing.

As for the difference in sound, I've posted a video below of the before and after result. Honestly, the vid is inconclusive but I took the trouble to make it so I figured, what the heck, I'd post it. There is clearly something inhibiting the engine when it is in neutral. It cannot be revved over 4000 RPM, for example, so at no time in the vid do you hear revs higher than that. IMO, however, the vid does not tell the whole story.

When running up through the gears, or when maneuvering at slow speeds there is very definitely a throatier sound from the exhaust from idle to 3000 RPM than there was before the mod. I know that aural comparisons made even a few minutes apart are suspect which is why audio equipment comparisons are made as instantly as possible. Still I'm hearing a difference and the exhaust note from idle seems both louder, deeper and more uniform up through the rev range, especially below 3000 RPM. Call me crazy.

So, I like the mod. Even if there were no sound improvement (I swear there is), I like the fact that the exhaust is always "sporty" and I don't have to reach for that button every time I start the car.

Video Here
The vid shows a comparison between having the PSE switch engaged and having the vacuum line plugged.



[/QUOTE]

<3mph

Nice job and nice description!!

Maverick787

Sorry Mike I don't follow the extra benefit? Does it basically removes the need to depress the sport button? Therefore your sports exhaust stays 100% engaged? Good video.

Mike in CA

Correct, Maverick, the sport exhaust stays 100% engaged without having to depress the sport exhaust button. Whether everyone sees that as a benefit is a matter of preference.

The video only captures exhaust sound at idle and when blipping the throttle; admittedly it's not conclusive. In actual driving though, where before the engine computer seemed to modulate control of the bypass valve below 3000 RPM even with the sport exhaust button depressed, the exhaust is fuller and louder at low rpm. Sam had the same mod done by his mechanic and also feels that the exhaust is different at low rpm.

It's an easy mod to try. If someone isn't convinced it makes a difference it's also easy to reverse. TEHO.

silverrules

Thanks Mike. I asked my dealer to plug up my 0.2 and they had the plug on hand.

Mike in CA

Thanks for the tip on posting the vid!

Jimmy-D

Mike - appreciate you posting and sharing this with all. Some thing for me to consider. I just have to see how loud cold start is normally because I may freak the neighbors

SamFromTX

Good work, Mike and much cleaner job than what I had professionally done. Thanks for taking the time and effort to make and post this. Now, if you like this, a third muffler bypass makes the difference much more pronounced. (No affiliation with any maker.)

orthojoe

Thanks for the DIY, Mike. Simple and useful.

neanicu

Good job Mike!

Sierra Mike

Nice work Mike!

I've ordered the following from Carnewal for my 997.2 GT3:

http://www.carnewal.com/products/P97...Manual-Control


I think this version will do the 991 GT3 but worth checking first:
http://www.carnewal.com/products/P91...ust-via-Remote

It's pretty cool - can't wait to try it out and especially as I'm doing it in conjunction with a Sharkwerks muffler bypass.

Mike in CA

Nice stuff, Capt! I did my little mod on the cheap....

Macca

Mike. Great stuff. I will give this a go when Im back in NZ with the car. I have SW bypass so hoping it wont make it "too loud" but I suspect not :-)

silverrules

It's very easy to put the hose back if it's too loud.

Macca

Good point. 20 mins around the block and a few cold starts and I think it would become clear if it's neighbour friendly or not. Listening to mikes videos and reading his commentary I don't think it's going to be an issue at all until drive is engaged and throttle position is above 35% in which case it's not going to be an issue for early morning driveway manouvours. Sure would be nice not having to remember that button tho!