That video shows the valve in perfect function under acceleration and throttle off decceleration where it functions just fine, but doesn't show any of the light to mid load, throttle modulation scenarios that you will encounter while throttle steering a car around a circuit track.

My camera was dead today along with a downpour of a rainy day otherwise I'd have my own in-car footage of exactly what is happening while driving the car spiritedly on a track, or in todays case, aggresive back road driving. This also happens on long upgrade hills, where you're in 4th-5th gear just bopping along with your foot on the gas partial throttle and boom, small pressure differential in the plenum causes the valve to kick open.

Like I said, the Syncronic works fine for on/off types of throttle input as any other valve, but with faster reaction(a good thing). It however does not solve the issue that myself(Eric) and so many other track course driven Evo's face right now with ANY bypass valve installed.

 

Post #23. After BoxerSix's experience with the valve on my Evo, my guess is that Evo IX does not have upgraded cams installed.

 

I thought I would give you an update. Yesterday I finished installing my GM 3port BCS. I figured I'd swap in the stock plastic BPV for the hell of it. Guess what? Its gone! No stumble no shudder... nothing! Problem is it wont hold 21psi if I roll into 5th. So I traded one big problem a minor one.

 

Stock Evo 8 plastic valve still does it here. It's what Eric put back in after sending the Forge BOV back, and before putting in an MR valve(which did it too)......

 

I'm taking the World Tour of Evo DVs...

 

Its crazy, I think the electronic thingy (yeah thats a technical term!) may be the way forward.

 

I'll have mine made in about a week if you want to hold off a bit so I can test it here.

 

I'll be watching.

 

Truth is I don't know whether to chuckle about this, or go run and hide in shame

 

Adam- With only Port B connected, you eliminated the DV flutter altogether, right? Basically, the valve was no longer opening at part throttle/high rpm/boost? But you still had the bucking?

The car on the video that I was testing with, was cammed for intake and exhaust. I left the setup to still DV flutter. However, on that car, it wasn't unstable when it would DV flutter. But I also was not driving the car very hard when it would flutter.

 

Interesting - do you know what cams? I'm running HKS 272/272.


No shame - you've only been the travel agent for one stop of many.

 

The valve still opens.....and again I don't believe it to be your valve, but rather a very sensitive combination of the fast spooling stock turbocharger coupled with aggressive camshafts that change the intake reversion pulses in the plenum.

I really think the valves are picking up on this and causing this havoc. It's the ONLY turbocharged car that I've ever had this associated problem with, and I can account for at least ten Evo's here that have this problem. Each and every one of them are modified in various forms from another, yet EVERY single one of them has camshafts installed...........

The best way I can say to replicate this problem is to get cruising up a long hill about 50 mph in 3rd and try to maintain that speed while lightly modulating the throttle light you're throttle steering the car.. Mid rpm range(~4K). Doing just that, you'll notice on a vac/boost gauge that the engine plenum goes through a ~10hg to ~5-7psi differential range as it should while modulating the throttle as you would be doing trying to hold a line through a tight corner. Going up the hill provides the light load that the engine is under as it would be at WGI going through the esses or coming out of turn 7. It's during this time that the valve is highly sensitive to plenum changes due to the very small vac/boost differential that's happening during this very light throttle modulation. It's a weird scenario. Either way it's causing and instability of the flow into the plenum, causing this bucking.

I went through every possible combination to hook your valve up(there's like a bazzillion different ways) but unfortunately it didn't eliminate this issue. The valve actually works best, and lessens this issue the greatest, when port C has boost and both ports A+B are to post throttle vacuum.....

I did get your message here on the forums so please feel free to give me a call anytime tomorrow or during the work week. I won't be working on Erics car until the remaining parts arrive, but will be very near it

Best regards,

-Adam Hennessy

 

I dont even have to be on the track.. my BPV does this during normal throttle adjustments keeping up with the flow of traffic.

 

I think that we're getting down to the root cause of this issue, we all know that it is down to the cams.

Here's 2 tests you can do to root cause this issue finally, that is unrelated to this BOV but will get you closer to a solution:

1) Pull all signal lines off of the Synchronic BOV. Since it is a pull-type, it won't open and will only stay closed. In effect, it is like being able to test as though you don't have a BOV in the system at all.

If you are getting any of the same bucking with this scenario, then there is no amount of bypass valving (or DV) that will fix the issue. Ultimately, this will be proof that this is a bonified case of exceeding the compressor surge line. I've never seen this compressor map, but I'm thinking that this is a compressor map where the surge line is shifted far to the right at higher pressure ratios and flow rates. So, for all of the additional flow demands that the cams introduce, the compressor/turbine just can't keep up.

2) After you have done #1 and you are still getting bucking: Only put the boost only source to Port C, with Ports A&B to atmosphere.

The BOV will start to act like a compressor based wastegate and regulate boost at 7 psi. Test at part throttle/high RPM and see if this issue still exists. When I was performing some testing, I noticed that the issue was worse as you ran more boost into the part throttle/high rpm scenario.

If you find that the bucking no longer is a problem after you do #2, then we might have a solution. The EVO has such a fast spooling turbo, that a late spooler probably wouldn't see this issue, but then you lose that which we want, fast spooler with good power down low. I think that ultimately, this has to become an excercise in perfect turbo matching. But I bet that a late spooler would mask this problem because you would never make high boost at part throttle/high RPM like the stock EVO turbo.

If #2 does seem to kill the problem, then this means that there are only 3 bottom-line solutions:

1) Get a different turbo that will flow the demands of these cams
2) Wastegate more at part throttle/high RPM to lower the boost just at that range
3) Compressor bypass to lower boost only at part throttle/high RPM

You could achieve #3 by building a circuit with a 3 way solenoid valve that hides boost/vacuum from ports A&B at part throttle/high RPM.

Does anybody here have an external wastegate setup that is having this issue? We might be able to setup a different test.

 

I just read this thread in it's entirety now. I haven't seen it until just now, but I would like to add a few comments/questions that may help to fix this issue.

Obviously, take Synapse's advice above on testing whether this is truely compressor surge or not. It's always good to get definitive answers and facts straightened out to eliminate most of the guesswork. However, looking at the compressor map and plugging in some test numbers, I would imagine it would be nearly impossible to get surge on a stock turbo. But, depending on the exact setup/conditions, who knows.

Anyway, when I first started reading this thread, it reminded me of my old Greddy Type-S DV that I had on my Eclipse years ago. That DV had two nipples...one for a vac/boost source on the top to open/close the valve and one boost only source on the side to open the valve, along with an adjustable spring within the valve body. This dual chamber design worked flawlessly for me and made the most sense as normal pull type DVs wouldn't allow for operation under part-throttle lift off conditions and would cause this DV flutter effect/bucking.

I haven't read your patent nor seen the internal design of the Synapse DV, but I am assuming that there are different chambers for the three nipples, with one nipple for boost, and the other two for vac/boost? Also, I think I read that the spring inside is also adjustable?

If so, I wonder if BoxerSix could try this:

1. Connect a boost only source to the intended nipple (I think C, if I read correctly)
2. Connect the vac/boost nipples to post throttle plate IM.
3. Adjust the spring to it's tightest tension or add a spring that is stiffer.

The pre throttle body boost source, if possible, should be as close to the throttle plate as feasible, to minimize the differential in boost pressure pre and post throttle plate. If not possible, then the adjusted spring tension should help.

The adjusted spring to it's tightest setting (or a heavier spring) will keep the DV from reacting to small pressure changes during your part throttle driving, but should still allow the DV to react if the differential is enough (this is where the 'testing' of the right spring tension, etc, will come into play).

So, ultimately the goal is to have the DV react quickly during transitions that are high enough where you want it to react, but to keep seated during transitions/part throttle where the differentials are small enough where you don't want the DV to react at all.

Make sense?



Eric