Boost question for the boost junkies?
 

I took the car out for few test runs at the track today and for some reason the car seemed sluggish to get to max boost and then would not pass 15 psi.

The day before I had it tuned up to 20 pounds no problem car pulling strong and hard.

My afrs are at 11.0 from 15-20 psi. The car is far from being done on the tuning side of things but why couldn't I get passed 15psi?

The only thing that happend at the track was that my brake booster hose popped off so I put it back on and nothing. Couldn't get passed 15psi.

I eliminated the possibility of the boost controller being the culprit as I replaced it with another one and still the same symptoms.

Any advice on where to check next.

As for specs:

-13bt S4
-GT45 turbo
-no intercooler just water pre-turbo
-Tial 38mm wastegate
-Greddy blow off valve
-3" inch downpipe and exhaust
-accel 300 cdi box on leading only
-4x1000cc injectors from RC eng
-Megasquirt 2 ECU

pressure test

pressure test is good advice.

perhaps either a front end leak (though you would generally hear it if it is that much leakage) or a back end restriction in your exhaust

or a turbo problem.

BTW, 4000 CC of fuel injector delivery is good for about 440 rw rotary hp assuming you limit duty to 85% so i would be very careful.

hc

this might sound stupid but how do i pressure test the front side of turbo? is there a tool i can rent for this?

If your getting 15psi, its not a bad leak. That said, a pressure test is going to be your best bet.

hey thanks guys but how do i go about the pressure test? I know its noobie but just a lil guidance to doing this.

purchase or make a pressure tester like this

www.boostpro.net/prodtester.html (universal tester at bottom) . then you will need a coupler to attach it to the turbo inlet, probably a 4" --> 3" reducer. then you can hook up an air compressor to it. slowly raise the pressure through the regulator then listen and feel around for leak. sometimes it helps to spray slightly soapy water around the engine bay to look for bubbles. Don't focus so much on how much pressure the system holds (because it will leak out the exhaust anyway) but rather just find leaks like bad gaskets, split hoses, etc.

I just purchased that tester, can't wait for it to come, you won't find one cheaper as I did quite a bit of searching.

I'm still hitting my boost limit (set at 18psi) but down like 50 whp from when i was tuned.

hopefully my engine didn't take a crap on me :(

Ok heres an update...There were 2 loose bolts that hold the turbo to the turbo manifold. I tightened them up but it seems to still be loosing boost. Not too sure though...there is too much traffic here in chicago with all this dumb construction lol.

could that alone be the main cause?

Ok here's an update...

Took apart the the turbo and manifold and all that good stuff and the T4 gasket was blown.
Now here's another question for you gurus...I was told that people run without the gaskets because the T4 gasket was prone to blowing. That it actually seals better. This was coming from a shop I called when looking for the gasket.

Is anyone running without a gasket?

Well I replaced the gasket with a new one and still doesn't wanna pass 15-17 psi. I'm stumped. The boost response does feel better though just won't pass 15psi.

What were the results of the boost leak pressure test?

If it happens again;

http://www.turblown.net/store/index.php?productID=80

Chances are you have a boost leak. When you turn the boost up past 18psi its pretty common to start blowing apart connections, vacuum hoses etc.

This must be a chinese Gt45? I cannot see water only pre compressor keeping the intake temps low enough for 20psi on a real GT45R...

Well I don't have a pressure tester right now so couldn't get a reading for that. I'm looking into getting one soon. I guess this means I should dial in low kpa low rpm mid kpa and mid rpm to get the car running smooth.

I guess this means you should pressure test. First.

Can I ask what your temps with water injection are? Maybe I shouldnt post this but the datalog I saw maybe 165 degrees F but it was hot out here. I have seen as high as 220 degrees F and the car runs like a pig. I can't afford an intercooler right now so not sure what else I can do to drop the temp.

Is there a place I can rent this tester right now? Or is it a fabbed up tool I have to order online?

You can make one for like $4.

Replace the water with alcohol and retune ( after finding the leak). Maybe you should take your air filter off and look at your compressor wheel while you are it...

What kind of alcohol? meth? Will that be ok for the compressor wheel? Right now it's just water.


And thanks siguy. I'm going to try and make one with a tire valve in it.

Ok found the leak. It's the lower intake gasket. I have 6 port steel gasket and I cut the secondaries so it wouldn't restrict airflow and it's leaking by the rotor housing.

Update:

Changed out the gasket for a new one and it's still leaking. I was leaning toward a cracked manifold but then again it's leaking by the other rotor housing too. This is weird.

Is your mating surfaces clean? Did you torque it correctly? O-rings installed correctly?

Is there a correct sequence to torquing the manifold down?