If you blocked off the DV....then that could not be causing the problem. I think that it could be the WGA, the EBC setup, or the tune. How much WG spring pressure are you running anyway?

 

I'm running the amount of preload recommended by FP. The car did this with both an aftermarket EBC and a 3-port and also with a variety of tuning changes. I'm suspecting a boost leak and my next step is to make a new tester that will fit this turbo. I was also planning to add preload and try that. Finally, I have an MBC that I can throw on to try.

 

a boost leak would fix compressor surge. you need either less boost or more mass flow at the points you are getting surge. I'd work on the boost control and tune it out.

I'd suppose it's possible that if you had a leaky/fluttery wastegate you could get some surge that wouldn't otherwise be there , i.e. not enough energy going into the turbine wheel to drive the compressor causing the surge.

 

point taken.

 

Could you elaborate on this a little? Don't think I've heard this discussed

 

I did a boost leak test and didn't find any leaks, except that when I pass through 15 psi -- the changeover point for the pneumatic Mac valve on my Dejon Tool Leak Stop Kit -- there is a sizable leak from an open port on the valve itself. The leak is transient though and it seals back up as soon as I pressurize past 15 psi. My surging problem doesn't occur until into the low 20s psi though, so I'm guessing this isn't the issue. I guess the next thing to try is tightening the WGA arm preload. Not fun on my car since there's very little room to get in there (extra thick radiator).

 

Had the same problem with a local car here, so we changed the springs in the tial 50mm bov and it didnt help a bit. I thought tuning may have been a issue also, but if you wait till 4500 to kick it, it wouldnt do it. So I am kind of puzzled about it also.

 

everyones fp red and blacks will surge in 5th at around 26-30psi if you're just on the highway and go wot, but i never heard of 4th gear really doing it........ unless you're at like super low rpm and going wot.. there should never be a situation where you have to go that low in rpm tho.

 

Check out post 3. This is happening in the 3700-4700 rpm range. It will even do it briefly in 3rd when the cutout is open. I'm wondering if the wastegate is getting blown open from the exhaust side due to my 18 psi spring or too little preload.

 

is your clutch slipping at all?

 

Ok, is your FP Black ported? how about the exhaust manifold?

 

What is your target boost under these scenarios and are you hitting boost or load limits ?

 

Just catching up...

Clutch is a new Exedy Twin with less than 2K and no launches.

My fuel cut is well above the problem area. I disabled boost error correction and it still happens.

Target boost when this happens is anything above 21 psi or so. My normal tune shoots for 30 psi at 4200 or so in 4th (tephra v7).

Exhaust manifold and turbo are both ported by Buschur.

 

Well nothing there. There must be something our cars have in common about the build making this happen. hmm... doesn't look like it though

 

just give it less preload. how big is your vacuum line going to the wastegate actuator?