View Single Post
T77911S T77911S is offline
Registered User
 
T77911S's Avatar
 
Join Date: Oct 2006
Location: MYR S.C.
Posts: 13,546
my SYNAPSE DV is leaking

well i actually found a problem that made a real difference once fixed.

skip down for results:
i was wanting to try to adjust the DV so it opened for a certain pressure instead of being opened by vacuum. thought it might shorten the open time and not dump all the boost pressure between shifts. well i could not adjust it enough or make it consistent for opening pressure so i started checking the vacuum ports to see where they opened. neither port would hold vacuum!
finally i took it apart. nothing but a piston with some O rings inside. but i also found that the piston is not moving smoothly. its like something is out-of-round inside. i could also see what looks like a wear spot on one side of the body.
so i put some oil on the Orings and put it back together.
the ports still leaked of course but if i block one, it will work. as it would open i could see the piston sticking at the bad spot then popping open the rest of the way. so with bith ports connected together it looks like it is working despite it not opening smoothly.

result:
BIG drop in idle. my idle has been pretty steady at 950. it dropped to 800.
i did not check the mixture since it was late. drove it to work next day and the idle was the same all day. (in the past symptoms have changed. one drive it was better, the next drive worse).
the other big change is mixture. i am WAY TOO RICH. part of this is my fault.
i had exhausted all my ideas and was down to having the FD rebuilt. so since i was going to send it off anyway i bumped all ports up a tad in fuel flow. even after doing that before fixing this air leak my mixture was still in the 15's no matter what i did. now i am in the 12's. BUT. the mixture seems to be steady across the RPM range.
i have rasied my system pressure to 6.5bar and raised my control pressure to 4.1 bar and still very rich.
sometimes the engine would sound like it was running on 5 cylinders or like it had a slight miss to it. i think #4 injector had an intermittent fuel leak. yes, i check them with the engine running. (this made me think if that dumb a$$ post robby did the other day about silicon) so last night i was removing the fuel head and i noticed a very very slight trickle of fuel coming off #4. this was after the engine was shut off too.

so the plan is to check fuel flow of thehead tonight and adjust it back some. i am not ready to send it off since the weather has turned nice and everytime the weather is nice the car has been on stands.

oh, the synopse is only about a year and a half old so i am not too impressed with its condition.

iside the synopse:
its like there are 2 "seperate" chambers for vacuum. one is smaller than the other so i think one port would have more "pull" on the piston. the top of the piston looks like the inside of a cap off of a can a spray paint.
__________________
86 930 42kmiles [__] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD
88 BMW 325is 200K+ SOLD
05 BMW 330CI 130K:: [__] RUNNING: [__] NOT RUNNING:
08 VOLVO V70 190K:: [__] RUNNING: [__] NOT RUNNING:
90 B2200[__] RUNNING:[] NOT RUNNING:__2000 MER E320 WAGON [] WRECKED:[]RUNNING:

Last edited by T77911S; 10-29-2014 at 10:28 AM..
Old 10-29-2014, 07:23 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)