Hey I am running a fp green on a forged 2ltr.
The car drives great if driving flat out. But if in high gears and low rpm i get boost fluctuation or surge sometimes its not too bad but sometimes the whole car nearly shakes.

I will just give my spec which anyone that can help may want to know.
The engine is running 9 to 1 comp pistons and a 1.2mm head gasket, the head is ported and polished and running piper 285 cams. The turbo is a standard fp green with uprated actuator, I have a 4" shroud on it with a 4" intake on it with k&n cone filter made by neverneverman. I have a mynes exhaust manifold and a standard elbow with 3" blueflame exhaust.
My ecu is autronic and its mapped for 95 plus half a bottle of nf booster.

I am 2bar peak boost on setting a on my boost controller and 1.6bar on setting b. I only get this issue on high boost settings.

So I decided to try run more preload which did not help at all it made things way worse I could not even boost over 1.8bar and it was like I was hitting rev limiter or something.

So I tried it with fp's recommendations of 3 full turns from zero or 6 half turns which ever is easiest to understand but that did not make things any better so I set it back to what I had the car tuned on.

If changing preload on a actuator should you really have a remap to suit?
Also having never drven my car in cold weather I drove it tonight and the surge was a whole lot worse when the car was boosting it was shaking and you could really feels it fluctuating on boost but as I drove for longer and the exhaust and turbo obviously got warmer the surge wasnt as bad is this normal?

So lads what do you think?

 

It sounds to me as a boost creep problem. The surge might be boost peaks that trigger boost cut in your engine management? For those high boost applications I would use an external wastegate or at least port the internal. But before doing any major work I would make sure there are no boost leaks around

 

I have also heard of this problem with the FP green. Do you have the upgraded WG for the FP green?

 

Ya I have the 1.4bar actuator.
I am actually thinking of converting the turbo to external wastegate a guy from greece on the MLR has done it with great effect.

 

The surge which you are experiencing is not a characteristic of most FP EvoGreen turbos. Your turbo's surge line diverts from that of a standard FP EvoGreen comressor as a result of the enlarged , modified 4" compressor inlet which alters and distorts radial compressor inlet flow, leading to cavitation and compressor stall at low rotor speeds. The larger suction volume is not characteristic of a "standard" EvoGreen compressor. You have, as a practical matter, altered the pressure ratio. You've gone and made your Green funky.

 

Sorry for the double post!

 

Would you be so kind as to post a link to the Green with remote gate please!

I don't think that your problem is a wastegate issue, since you state that it only occurs at low revs. The wastegate only comes into play at peak boost levels.

I think that your problem is either related to the DV/BOV circuit, your method of boost control, or is a result of altered compressor pressure ratios due to the 4" compressor inlet. Other than the 4" inlet bell and the Autronics ECM, your Evo is fairly representative of most Green equipped Evos in the U.S.

 

Just a update guys.

The more I taught about my problem I figured it couldnt be surge as it only happened in high bust and not when starting to spool but high up the revs.
From reading other posts I figured I may be missfiring from spark being blown out at high boost.
So cosidering the coils on my car are old I decided to purchase the tm works direct coil on plug setup.

It arrived today and I fiited it and what do you know the car is fine no more juddering or missing its great.

 

Glad you found the problem. ; )

 

mine had the same problem

 

So let me see if I completely understand what you are saying. You had, what you thought was mid range compressor surge but it turned out to be spark blow out? I have low to mid range compressor surge if I lean into it a little bit from highway cruise speeds (65-80 or so). I see that it is almost hitting full boost but obviously I am not at WOT. Now I am running a stock 05 VIII 16G. Do you think mine is actual compressor surge? I have the mods in my signature.

Josh

 

Hmmm...I had surging issues, but it always high gear low RPM while spooling up.