Lot's of posts about removing the vacuum lines on the PSE valves for the 991.1 but I cannot seem to find any real feedback on the results. I have posted in a few different threads trying to get the answer to whether or not the PSE on off equates directly to the valves being opened and closed, some reading suggests even with PSE ON the valves still close at a certain RPM range which is exactly why I believe some users have pulled the plug.

Would really appreciate some feedback here - any noticeable loss of back pressure in the low RPM range or droaning?

 

I have done this on my non PSE, exhaust sounded awful. Put it all straight back together.
l've ordered the factory PSE 3 weeks ago, currently out of stock, ETA is about 6 weeks.

I've done this though, slight improvement.
Valve Shaft Collar clamp. You can adjust to whatever level you like.

Google this if you cannot copy and paste. It's on rennlist
"Let's talk about cheap exhaust valve mod options!"


https://rennlist.com/forums/718-gts-4-0-gt4-gt4rs-spyder-25th-anniversary/1215172-let-s-talk-about-cheap-exhaust-valve-mod-options-19.html

 

I was talking about the factory PSE not the valved center muffler on the "S". I have one ready to install I purchased from a forum member here but it will be on a base with no existing vacuum lines or COV so I am hesitant to install it as I cannot get any confirmation if the valves stay open throughout the rev range when PSE is ON. If using the PSE button truly sets the valves to hard open or hard closed there is no need for me to install the vacuum lines and COV as I would always have it on anyway. I have have experimented with a few different exhaust setups on my base 911.1 and the more back pressure I took away the worse it became mostly in the lower rpm range but it also affected the shift points on the PDK for me. I have another thread here posting an issue that appeared to be a slipping clutch but can no longer be reproduced after adding the factory center muffler back in. I am not sure if those two small center mufflers and smaller diameter bypass pipes will be enough to create the appropriate back pressure at low rpms or if Porsche has the valves close for a small part of the rev range even with PSE ON which would not be uncommon for Porsche to do.

 

Oh l see, l would assume that the valves would stay open 100% of the time without vacuum lines.