Synapse BOV...does it just NOT work for some cars?

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Jun 18, 2009 | 10:12 AM

#16

Mad_SB

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From: Georgia

Quote:

Originally Posted by 05blue8

So I've read a ton since installing this thing Saturday night. The install was cake, I even kept my stock recirc hose and it fits perfectly. I have the Buschur upper pipe and intake so it fits perfectly in there. I T'd my wastegate to MBC hose for the C port, then used my old 9 DV vacuum hose for the A/B port split. First test drive right off the bat things didn't go so well. I took it out for a test drive and couldn't get it to release cleanly. I read around about trying just port A, just port B, even adjusting the preload spring. None of it helped. With just port B connected it was identical to A/B connected as far as flutter/surge release at part throttle or even at full throttle 29PSI. With just port A connected my car actually overboosted and I hit fuel cut at 32PSI. Needless to say even when I watched the gauge closely and hit 29PSI with just port A connected I got the same results, no clean release, flutter a few times. My first to second shift always 100% of the time results in over revving. When I get to say 7k in first and shift the car revs to 7500 or so like I never let off the gas. I haven't read much about that happening with the Synapse so I'm not sure if this valve just isn't going to work with my car or what. Any ideas from someone with similar problems that has actually gotten it to work properly? I know some parts just don't work on some cars so perhaps that's the situation here?

Thanks for any feedback you guys can offer!

Most of the time I have seen revs shoot up on lift shift it is because the recirc hose it pinched off a little bit (has a bend where it should not so it closes off the hose a bit on the bend) not allowing the released boost pressure to vent back to the intake quickly enough.

Had this exact problem when I put my VIII back to stockish condition for trade in, turned out to be the recirc hose was pinched off a bit because I did not have the pipes situated just right (stock VIII bov, hoses, and ic pipes). Loosed up all the connections, re seated everything, made sure the return line was not pinched any longer, tightened everything back up, problem was gone.

I think you guys are already on the right track with getting clean pressure and vacuum signals for the ports on the valve.

Last edited by Mad_SB; Jun 18, 2009 at 10:20 AM.

Jun 18, 2009 | 10:59 AM

#17

Fast_Freddie

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From: Lexington Park, MD

You need to utilize the nipple coming off the J-pipe (turbo outlet) for port C. If you look at the stock line that goes to the OEM BOV it runs straight back to the intake manifold, so use that line, and connect to port B or A your choice as they react a bit different...

Jun 18, 2009 | 12:24 PM

#18

05blue8

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From: Austin, TX

I'm running the buschur pipes with no nipple on them, of course...argh, running out of choices here, going to have to bite the bullet and get a nipple on there apparently

Jun 18, 2009 | 01:09 PM

#19

MOREPSiTEHBETT4

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From: Mitchigan

<--hates threads like this..if it doesn't work for most people..why buy it?

Jun 18, 2009 | 01:27 PM

#20

CharlieGsanD

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From: San Diego, Ca

Quote:

Originally Posted by MOREPSiTEHBETT4

<--hates threads like this..if it doesn't work for most people..why buy it?

because people typically post when there having problems more often than when things work as expected.

the fact is that the Synapse BOV is a good valve, it just operates differently than the OEM valve (Pull vs Push type) & requires a small modification (nipple in J pipe) to reference a boost source that the OEM BOV has incorporated into the valve itself. because of the fact its a pull valve & has such a faster reaction time than the OEM BOV means it can be more sensitive to car-car variations such as improperly Tee'd vacum/boost refrences that would have worked fine with a push type valve

Jun 18, 2009 | 01:38 PM

#21

CharlieGsanD

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From: San Diego, Ca

Quote:

Originally Posted by 05blue8

I'm running the buschur pipes with no nipple on them, of course...argh, running out of choices here, going to have to bite the bullet and get a nipple on there apparently

take it down to your local welding shop & they should be able to weld one on there for 25-50$

or you could try something like this

http://www.atpturbo.com/Merchant2/me..._Code=ATP-FTG1

myself, i just have a 1/8" pipe to hose adapter threded into the UICP

http://www.mcmaster.com/#barbed-hose-fittings/=2dhaao

Jun 19, 2009 | 09:30 AM

#22

Synapse

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From: San Diego, CA

There's a couple of rules of thumb when it comes to the Synchronic BOV:

1) Never put Vacuum to Port C. It needs to be boost-only. Otherwise it will never open. You're better off, running only vac to A&B until you can get a boost-only source.

If your MBC's boost source is coming off the intake manifold, it should be coming off a boost-only source anyhow. Same thing from your wastegate, you shouldn't be plumbing your wastegate with vacuum. There's been enough people we've dealt with over the years that have fixed their weird wastegate behavior (with any wastegate manufacturer) by switching from a vac to a boost-only source.

2) Specific to the EVO: Pulling a vacuum source from where the stock DV's vac source comes from isn't as stable as pulling it from a source at the back of the intake manifold. I've found through datalogging, that the source (for some odd reason) is much more stable from sources at the back of the intake manifold. I think that's why the OEM fuel pressure regulator gets it from this source.

Jun 19, 2009 | 09:45 AM

#23

Synapse

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From: San Diego, CA

Quote:

Originally Posted by LV///R

Also, if I get into boost, lets just say around 10psi and hold the throttle there steadily, my Synapse will just release the boost out of nowhere! My stock diverter valve never did that, not that it's a huge deal, but partial throttle boost needs to be there if I need it.

The BOV mirrors exactly what is happening behind the throttle plate. So, if you are holding throttle position (ie. pedaling it, cruise), turn your head over to the boost gauge, you'll find that the intake manifold has gone into vacuum and that's why the BOV opens up. This in effect, eliminates the turbo from having to build pressure against a throttle that is closed enough (<20%) to generate vacuum behind the throttle plate. Any time your car gets into -3" of vac, the BOV is closed and will close up to 125+ of pressure. So it isn't leaking boost at all.

But you have to make sure that you aren't running vacuum to Port C. For the Evo, running Port B to vac, Port A open to atmosphere and Port C to boost-only works best and will hold to 65+psi.

I know that Port C is a PITA, but it allows you to pull all the lines off the BOV and it acts like there is nothing on the pipe so that you can troubleshoot and make sure that the BOV is not the issue you may be facing. Why 2 ports to vac? Because every setup is different and having the ability to change response actually makes for a big difference. Pre-load adjustments alone don't do much on most BOVs so, that's why the 2 ports are there.

Jun 19, 2009 | 01:39 PM

#24

Fast_Freddie

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From: Lexington Park, MD

Just some info here, but when i first installed the synapse I had A&B connected with a "T" and C going to boost only. Now I am running only port B with A to atmosphere with zero preload and the car behaves much better, this is street driving BTW... I am taking it back to the track in a few weeks now that I have ironed out all of my other issues (NLTS glitch)...