Anyone know what vaccum/preasure this valve should open at? Also how can you test to see if the valve is rattling or can you just hear it. Thanks JOW02
Don't know what the figures are but you should be able to open the valve by simply sucking on a suitable tube connected to the pipe on the diaphragm. On the second point, you can hear the rattle above normal engine noise but you can check things with the engine switched off by feeling for mechanical play in the linkage; I agree with 355spider - wear takes place between the butterly spindle and/or its bushings; altering the actuator rod length takes up this play (for a while anyway)......
Managed to dredge up JH355's post referred to by f355spider. Makes for very interesting reading. Dates from August 2004. www.ferrarichat.com/forum/showthread.php?t=26404
Nice find, you are making him famous! JH355 just stopped by my house yesterday to offer some Christmas greetings and a gift of a F355 oil change kit he purchased from Ricambi America.
You're famous too - you are in the same post! And look at all the contributions you have made since.....and are still making. Early Christmas greetings from me too!
Anyone know the size of the bypass valve nut size? I broke off a post in tightening a rattle. Thanks guys!
Took every thing off, made two full counter clockwise turns, put it all back and it still rattles just as bad. Pulled everything off again, did two more full turns (four now total) put everything back and it rattles just the same. How far can this be turned before it no longer will open properly? Anything else causing the rattle that lengthening the shaft by turning just wont fix? I can still quiet it down by depressing down on the shaft with a screwdriver so it seems like there is still some play in there.
OK just checking its the bypass for sure. Mine was starting also to rattle. I got one off ebay for $140 or something like that aftermarket that looks better then OEM. Had to do a slight mod to it but should be fine to use, Machined the id to 63mm or something like that so it fit perfect on the exhaust muffler.
The rattle is from the internal butterfly tapping the inside housing. Has nothing to do with the bearings. The fix is NOT to increase preload, it's a temp fix if at all. The fix is to SHORTEN the stem so that the butterfly is just open and no longer taps the inside housing. The threaded end of the stem may fully seat into the lower threaded holder and it may not yet be open a hair. So, you cut a few mm off the threads with a hacksaw until the valve is just barely open. Diaphragm not holding vacuum is a separate problem. Diagnosed by sucking on hose attached bypass unit. Does not require much vacuum to open.
I would suggest there are multiple issues that can be the problem. JH355 fixes one, yours fixes another. Increasing preload does seem to help and keeps the butterfly closed and from rattling. Yours is just another solution. One needs to be super careful they choose that method, to adjust it only to open just enough to stop the noise/rattle. If it is open too much, the thermoprobe will sense the valve is open when it shouldn't be, and set a "check engine" light. I went another route and simply bought the Capristo valve several years ago....it continues to work great.
I think i'll leave it for the Stoogefest at the end of the month and let the brain trust help me out.
https://www.fcpeuro.com/products/porsche-exhaust-valve-pierburg-99711168001 Is this the correct replacement? Looks identical. @f355spider
On my 2.7 I replaced the original diaphragm as its membrane was torn with one easily available online for something like 70€ and adjusted the rod accordingly. I added a clip to suppress lateral movement of the valve shaft. At low load I still get a slight rattle, at around the engine speed where the valve otherwise opens at high load, which I suspect is caused by the whole exhaust system reaching the rpm where exhaust pulses force the gases to flow through the valve rather than the lateral circuits. I suspect that my entirely catless set up does not help with the rattle but I'm happy to pay this price for a fully derestricted thus healthier set up, at least with a twin circuit muffler like the Capristo. Also when the valve is fully closed the plate is not in contact with the bore. There is minimal clearance but there is clearance. Since this is an exhaust element that is supposed to expand with heat I strongly doubt that it was designed with no clearance at all as suggested in earlier posts.
Can you confirm part number on yours? The one I have has a longer rod than 355’s. If I cut the rod from the bottom, there’s nothing to thread to. Only way is to cut the rod from the top, which would require opening up the unit, which doesn’t appear to be straight forward. Image Unavailable, Please Login
Only difference in the part numbers is the 355 unit ends in “10”, which I think implies version 1.0, while the Porsche unit ends in “20”, implying version 2.0. vacuum outlet also sits in a different position once mounted.
I'll take a look at it tomorrow for you. You could cut the rod and use a tap and die set to thread the end?
Found it already... 997.111.680.00 (from here https://www.ferrarichat.com/forum/threads/f355-355f1-parts-thread.333036/page-2 post 49)
