I have an A-Spec turbo GT35R kit on a large street engine in the process of being tuned. The shop doing the tuning is telling me they are getting compressor surge on full throttle. Something about it making too much boost for the engine to take in. I'm running a straight pipe and an Apex'i GT exhaust so not much of any backpressure. They're saying that it may have too little backpressure and thus is making too much boost. These things they are telling me worry me (about their ability) or perhaps there's something I don't know. Too little backpressure on a turbo car? Too much boost too low? They're having this "compressor surge" problem up to 6,000rpms. Anyone out there with a similar setup (I'm sure there are) - straight through exhaust - large street port - GT35R ? Shop said they thought not due to too little backpressure... What they're telling me just doesn't make any sense. Any ideas? Thanks in advance.

 

what wastegate are you running? does it open up , not so sure but how do you get compressoe surge at WOT

 

I'm running a Tial 46mm wastegate. My spring was only a 6lb I'm trying to get higher lb spring. They were controlling boost via an AVCR. Compressor surge on boost seems to be mutually exclusive. The tuner said he's seen GT35's surge for a small amount of time but mine seems to be doing it though most of the RPM range.

 

According to the AVCR manual, the controller on can control about 75% more pressure than
your base spring pressure., 6lb spring = avcr controlling 11-12 psi. If your boost is higher than approx 12psi the avcr cant control and it surges!!. These are approx figures, I
run a 22lb spring for 32psi with avcr.

 

That sounds like it could be the problem. Only thing is they were running into this surging at 6psi and at 10psi runs. I want to run a spring close as possible to my street gas boost level (14psi?) and then have the AVCR tune up to the race gas level. Hopefully switching out the spring will help with this.

 

Is your BOV sourcing vacuum from it's own fitting?
You're not T'ing off of another vacuum hose by any chance?


-Ted

 

Sounds from the description like you are getting surge. Im most simplistic terms the compressor is spooling too quickly (if you look at the compressor map the surge line is on the left. You always want to be on the right of it. Causes of this are many, including

1. Turbine too small for compressor. hot side spools up before there is enough airflow for the compressor to work.

2. Wrong trim/size compressor. (compressor too big for turbine)

3. Air leak in inlet. (compressor has nothing to push against, so spins up quickly, like the secondary in a stock FD)

(2.) Seems odd for a large street port, so unless you can find a leak I would guess that your 35 hotside is too small. A GT40R or bigger seems to be recommended for big ports (no hands on to prove this mind)

 

I've got the same kit with a stock motor. The stock WG spring in that Tial is good for 15 psi, or so I've been told, which is what I'm running with no boost control. It spikes a teeny bit if I'm cruising with high RPMs then jam on it, otherwise, it's fine.

 

Yeah Tial has 2 diffrent springs from what I hear.. I think you can call them and they will give you or charge you for the 15lb spring.. just hear say tho so dont hold me to iT!

 

yo i have the same turbo kit from a-spec and the same exhaust and run stock ports
and the car move's just cant wait for this summer for higher boost and some c-16 then the real fun starts!!!

 

double check your blow off valve is sourced to after TB vacuum.

The 35R does have a compressor surge ring right?