Hey all,

I figured I would start a new thread because I didn't want to de-rail the guy's thread below me with the DV fluttering, nor could I find a concrete answer in other threads.

So I have had the Synapse BOV (port C delete) for over a year now and really no complaints what so ever. I didn't start to notice any issues, until I started to road race and got a lot of 1/2, 3/4 throttle flutter over 18 psi or so. Well long story short, I adjusted the BOV a bunch and got the least amount of part throttle flutter with port B connected, Port A vented, and the screw backed all the way out. Better, but still some part throttle flutter above 20 psi. Did a bunch of research decided to change my MBC from a "T" into the bov and intake manifold boost source, to just running the MBC to the wastegate and turbo nipple right after the turbo on the licp side. This solved almost all my part throttle flutter, I am a happy man.

BUT, in all this testing I started to see the BOV was fluttering at WOT in 4th gear and 5th gear ONLY. As soon as it would hit full boost (25 psi) and would continue till about 4000 rpms or so, then would be smooth and normal. Now it was always doing this a little, but I never really concentrated on it because I have been trying to solve the part throttle issue. Now I wouldn't really care but I am consistently getting 5-6 counts of knock every time this happens. I am not 100% sure this has to be the reason for the knock as I am no expert, but I have been tuning this car for a couple years now and the tune is very concervative. Not sure if the knock sensor is picking up noise from the BOV (unlikely) or turbulance in air flow is causing the knock. No knock in 3rd gear at the same rpms, but 4th and 5th. It doesn't matter where I start the pull in these two gears, as long as the car hits full boost below 4000 rpms it will flutter will it reaches the 4000 rpm mark.

So I feel like I have almost done everything to the BOV possible to solve this issue (since they are pretty basic devices). I have read bits and pieces about removing the spring in the BOV all together, but was a little unsure because I couldn't find a diagram or description, nor did I know if this would even solve anything. I am just trying to see if there is anything else I have overlooked or something else I could give a try. I am going to try to swap BOV's with my buddies metal IX this week to see if I can narrow it down to the synapse causing my issues. I really like this BOV and would like to keep it but this has really been an annoyance as of late.

Oh an btw because I am sure it will come up...Mods to car:
HKS 272's
Full exhaust
MBC set to 25psi
Injen intake pipe
Injen UPIC, MUSE LICP, ETS 3.5 core


Thanks in advance for your time!

 

i have the same issue i swapped out my spring and run port A only and this is my less fluttering setup...I'm thinking of trying the divter valve they have out now...It sucks not to partial boost when trying switch lanes knowin it will flutter at 15psi ....

 

Well the above 15 psi part throttle fluttering I have got under control for the most part. It's the WOT flutter at full boost that I am having an issue with.

Anyone else shed any insight on this issue?

 

Well I finally got around to switching the bov's and it was still doing the same exact thing. So it is obviously not the bov causing the issue. I'm thinking possibly its related to the mbc and bleeding off boost but I'm not sure. I have just never seems boost fluction like this before. Any input would be helpful. Thanks!

 

I only read the first post so not sure if you have corrected it or what tips you might have received. I had I close setup to yours with the older synapse bov and mine did the same. It would have no problems in 1st through 3rd but if I was on the highway and wot it would flutter at mid rpms then fix it self higher on. I was also having problems with being leaner with it. A buddy of mine had another bov laying around and I tried it. Sure enough it stopped doing that when I switched.

 

Yeah what you described sounds exactly the issue I am having. The only thing is I switched BOV with my friends stock metal IX and it was doing the exact same thing, so I'm leaning towards not bov related but still unsure. What I have gathered from the logs is the load is all over the place when this is occuring. Without looking at the log I believe it was going from 280 load all the way up to 310, back and forth till around 4k rpm is hit. Wideband looks fine, timing is fine till this occurs and starts pulling timing because of knock (4+ counts)...

Out of curiousity which BOV did you switch to that solved your problem?

 

I borrowed a buddies forge. A while back when I first got my car I was having trouble with fluttering and I couldn't find out why. Thought maybe I had a boost leak, did a test but didn't hear any. Took all my piping out and put them back in checking all couplers and tightening the hell out of them and it fixed the problem. As far as the tuning goes, that's all greek to me.

 

What mbc are you running btw?

 

I am running a standard Hallman. The car has no boost leak, as that was the first thing I checked when I started to notice the problem. Can a mbc go bad? In my eyes, the mbc could be the only thing that it is causing the problem. As said, I know that the purpose of a mbc is to bleed boost, but I was under the impression not so violently. I have never owned another mbc and this is the first turbo car I have owned, so I really have nothing to compare to...

 

So it still only flutters in 4th and 5th? How do you have your vacuum lines routed?

 

Bump to see if you get the problem fixed. I'm having basically the same issue.

 

I had the lines originally routed the traditional way (bov t'd into mbc and intake manifold boost source. Licp nipple capped off and wastegate to the mbc) I switched over to having bov to intake manifold only and running the mbc to the wastegate and licp boost source. There was no difference in "flutter" at wot in the situation I described above. Connecting it the second way did eliminate all partial throttle flutter, which solved half my problem.

Glad I'm not the only one with this issue!

 

I will tell you I had the SAME issues with my Synapse. It absolutely frustrated me to no end as it wasn't enjoyable driving my evo on the highway.

However, once I switched my stock ignition out for the Spoolin' Up COP, there is ABSOLUTELY NO flutter no matter how hard I try to induce it. Are you guys still on the stock ignition? If so, how many miles on it?


EDIT: This is more related to partial throttle/getting into boost where I'd get the fluttering. Not WOT/full boost situations, so my advice may be irrelevant.

 

I tried to switching to port A in Push Mode with port B VTA and that seems to have fixed my flutter problem at WOT/full boost. However, now I'm getting flutter anytime I shift with little to no boost. I'm waiting on Synapse to get back to me on their recommendations but I think I'll try adding some preload to see if that fixes my new flutter problem.

As a side note, I do have a Spoolin Up COP and I did not have any issues with partial throttle when I was using port B in Push mode with A VTA. The car felt great during daily driving! It was only under WOT that I had a problem. Sure would be nice if I could figure out how to get the best of both worlds.