I need help from you all!

I'm encountering a very odd problem with my 2005 VIII. My synapse bov keeps opening during high boost low RPM in 4th, 5th gear with ecu based boost control. When the 3 port solenoid start to work at WOT fuill boost, the BOV open and shuts repeatly with the quick pressure variations in the intake manifold. Synapse is so sensitive that it opens near every time the BCS has a pulse. It happens even if my boost is tuned very tight and don't vary too much.
The problem isn't present in 1-2-3 gears.

The problem is that the synapse action time (about 30ms) is faster than the BCS pulse frequency. It is really annoying. I dont want to get rid of this problem by raising preload on my bov, as it will probably cause surging...

I tought about three solutions which I don't know if any will solve the problem:

Solution 1: Changing the wastegate to a 18 psi wastegate. So the WGDC at full boost (23psi) will be more like in the 15-20 area, instead of 50-60 which will give less time to the BOV to act (theorically) .

Solution 2: Finding a way, I don't know if it is possible, to raise the WGDC pulse width frequency with ecuflash/grimmspeed. Higher frequency with the same duty cycle would not allow enough time to open the BOV.

Solution 3: Changing the synapse BOV spring for a weaker spring rate as some members do to help surging with that BOV. With the weaker spring, I could give it some preload to raise the opening pressure just a little over pressure variation at WOT full boost. I fear that this would cause a part throttle surging...


Is there anyone that can help me with my problem?
I'm open to comments and brainstorming to find the best solution!
Thanks guys!!

FYI: Synapse vacuum is connected to the intake manifold, stock bov location / 3 port boost source on the turbo housing (stock solenoid location)

 

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This is not related to my problem, this act to how often the ecu check Error and
applies the boost error correction table. This will change very very slightly the WGDC
which won't affect much the quick pressure variations in the intake manifold.
Thanks anyway for your idea.

I need some other ideas guys please!

 

I actually agree with this. If you lower the interval the BCS will go hyperactive trying to chase the target load/psi and you'll get pressure spikes IMO. If you raise the interval the BCS will mellow out and not try to chase so aggressively.

It sounds like your WGDC is setup for your lower gears and you're relying on your correction factor for the same psi in higher gears. Post logs with psi, WGDC, load error, and WGDC correction.

And you can try to zero out the correction (to stop it from correcting) and see if the same problem reoccurs. But try the previous first.

 

I would not say that a BCS that varies from 1 or 2 WGDC is "hyperactive"
This correction has little to nothing to do with the Base WGDC. My boost
error correction table is set from -1.5 to +1,0 so WGDC is on target.

Anyway I'll try it and come back with an answer...

 

Domyz, are you going to the tuning seminar at Perry in early March? If so and this isn't solved by then I could give it a shot after seeing in person how it behaves.

 

is the latest small synapse bov or is it the larger unit? = slightly smaller than a coke can.

 

I would also recommend zeroing out the Boost Error Correction Tables to see if that fixes the problem. I was having the exact same problem with the same set up (Synapse DV and Grimmspeed 3 port EBCS) and that's what I had to do to fix it.

 

Thanks I'll try it, I'll post results.


It's the larger unit, but the latest one without "C" port.


I didn't have the intention to go there but if the problem isn't solved in march, it probably won't occur anymore. I forgot to specify that this seems to happen only on cold weather (under 10F). If this is enough cold outside at this time, I should go there to get your help, it would be great from you.

 

Posting a log with the WGDC, MAP, correction and load error would definitely help.

 

If it only happens when cold it could be the WGDC vs IAT correction table that isn't adjusted properly and causes the ECU to have too many adjustments to make.

 

I think you have a completely different problem. You have your wastegate/BCS and BOV on the same pressure source such that when the BCS is regulating boost pressure to your wastegate it is causing your bov to open.

Hook the BOV up correctly and it will work correctly.

 

No they are okay I already wrote it at the end if my thread.

 

No as I said the only adjustment the ecu can make jf boost isnt on target is applying the boost error correction table which give very mild change to the wgdc: Its set from -1.5 to 1.
Its think my problem is more hardware related.

 

sorry I was thrown off by your grammar. I thought you were saying the stock bov port on the manifold was "plugged", not "plugged into" What you describe is compressor surge. definitely not your bov opening and closing at 30hz.

None of your proposed solutions will fix compressor surge. reduce your boost target at low rpm, or drive around it by not getting into boost at low rpm.

...or search the forums for the 8000 other threads on how to solve compressor surge.