I have an issue with my set-up where in 4th gear it will sometimes flutter at WOT in 4th gear as boost is spooling up and get stuck at a particular boost level (~22 psi) on its way to full boost (26 psi at the moment). I can hear the fluttering in the car and it goes really rich when this happens. Once this happens the car will not build any more boost. Something is not holding shut and the boost is escaping.

Does this sound like a BOV or Wastegate actuator problem?

It doesn't happen in the lower gears. I have a 1G BOV with the Dejon Tool leak stop kit (uncrushed) and an 18 psi FP actuator on my FP Black.

Any suggestions?

Thanks!

p.s. For those with an FP Black and the 25 psi actuator, what boost do you see at wastegate pressure?

 

I had this happen with my new turbo thought the bov was leaking.It turned out to be my Hallman boost controller,i had it plumbed to the intake mani,changed to the turbo nipple and the flutter went away.

 

Thanks. I'm using a Grimmspeed 3-port for boost control.

 

comp surge, leaky BOV, weak BOV

 

+1

changing to the turbo nipple usually solves this

 

Sounds like you're entering genuine comp. surge at that particular boost/rpm range.

If the boost range is above your wastegate spring load u can dial down the boost if your ebc allows RPM based maps.

Otherwise your options are limited to
1) Turbo a/r or comp wheel change
2) Get a controller that can vent surge thru the BOV.
3) Do an el cheapo fixed artificial leak with a brass plumbing ball valve on your intake, post turbo, be sure to recirc if u're MAF.

#3 will work but it will also delay your spool a bit. But comp surge at 22psi will kill your turbo. It's a decent stopgap until u decide u got the $$$ to do something permanent. Just think of it as having a leaky stock BOV.

 

I can turn the boost down in 4th in that RPM range by just changing my tune (courtesty of gear-dependent Tephra v7 boost control), but that seems like a band aid. I really think something is not right with my BOV or actuator. Just not sure which...

 

It is hard for me to imagine that what you are experiencing could actually be compressor surge. Off the top of my head, I can't recall anyone else complaining of compressor surge with the FP Black turbo. For one thing there is the Black's anti-surge compressor cover.

From my perspective it would have to be a DV, MAF/intake, BCS, or WGA related issue. It also might be in the tune, or a combination of the above. Anything, just not compressor surge.

EDIT: Someone please educate me. Doesn't compressor surge usually occur at partially open, or closed throttle positions and not at WOT? Maybe I am not understanding the phenomenon.

 

My old FP red with 64mm cover did the same thing but much worse. The dyno of it briefly flatlining in 4th is on here somewhere. I'm suspecting the BOV because it goes rich when this happens (though the AFR in 3rd in those same cells is okay).

I just don't understand why a BOV problem would only occur in higher gears and at such a low boost level.

Lowering the WGDC does tame the issue in the affected RPM range.

 

I just had this problem with my car and after messing around it ended up being a weak spring in the bov. it actually binded up and got stuck in one position from driving it like that for so long and caused me to only get 12 psi vs 27. I took the bov apart and freed it up and stretched out the spring put back together and had all my boost back.

 

dont bog the car

 

Well, if that worked you had comp. surge.

Now, just why u had comp. surge stems from 2 much CFM for the motor at that RPM.

In order to verify that u have a genuine over cfm prob. u need to check the CFM produced by the turbo at that boost in it's comp. map. Then workout your engine consumption at that RPM & VE. If the CFM exceeds the calc'd consumption then dialing down the boost for the RPM is the solution.

If your calc's show that the CFM does NOT exceed the expected engine consumption you can start hunting the problem. I'd look at things like if your TPS shows fully open, or perhaps your variable valve cams aren't coming in properly. Or maybe a kinked/obstructed post turbo intake hose.

Have u done any breathing upgrades l8ly? Like better intake, BOV or exhaust? Such ups. could push the comp. past the surge line.

 

I was prepping the field for my brothers 2000+ horsepower mud racer and i like to bog the car. its fun as hell. thats why i bought an evo. it does an amazing job in a muddy corn field lemme tell ya.

 

Compressor surge occurs when the CFM produced by the turbo cannot be consumed by the engine, either because of engine volumetric eff. limitations or some kind of obstruction post turbo. Comp. surge causes the comp turbine to 'slip' and the air flow is reversed, thereby placing strain on the turbo bearings & turbine wheel. Further, the MAF can be disturbed by the flow reversal and will cause fueling transients. Then the BOV will suddenly see rapid pressure fluctuations and start firing off , chasing it's tail and compounding the problem.

Compressor surge can therefore occur anytime. at any RPM, even WOT if the turbo is oversized or an obstruction occurs. Usually WOT comp. surge would implicate limited Cv (fluid flow) in the vehicles intake tract. Larger diameter, mandrel bent, intake piping could help here, esp. if the run is long due to a FMIC.
Sometimes the FMIC flow is the restriction.

In industrial terms we are looking at debottlenecking the system to optimise total results.