Update on my low boost issue

[89mulletbird]

I posted awhile back that I was only making about 15psi in 2nd and 19psi in 3rd no matter how much I cranked down on my manual boost controller. 4th gear seemed to respond to the controller, as I was able to get up to 25psi by adjusting the controller.

I thought maybe I had an exhaust leak so I removed all the exhaust system, flattened all the mating surfaces and put everything back together. No change to how the boost responds.

Today, I disconnected the vacuum line going to the wastegate actuator and did a WOT run in 2nd gear. The turbo still only made 19psi.

So... do you think the wastegate puck is leaking? Should I try to install a new HD actuator? I'm running the 12psi actuator now. The puck is well-centered on the wastegate hole so it's not an alignment issue.

 

[89mulletbird]

Further update. I wired the wastegate puck shut and still only makes 19psi in 2nd gear at WOT. The boost spools fairly quickly and abruptly stops at 19psi.

 

[89mulletbird]

Further update, I hooked my boost gauge up to the turbo outlet and it is matching my plenum pressure at WOT so it's not a pressure drop issue through the IC. I think I may just be maxxing out the flow of the 6152?

 

[Pronto]

Just a guess, too much back pressure in the exhaust?

 

[Mr.Spool]

I had some thoughts but looking at your sig 1/8 et and mph you cant be bp limited or out of compressor.turbine runs off exhaust maybe due a compression test on the motor.which ex housing is on the turbo?

 

[bison]

Do you have a catalytic converter on the car? You won't run that turbo out till your engine is swallowing over 60lbs/min. That's mid 10's. What converter is in the car ?

 

[89mulletbird]

No cat on the car, I have a THDP and 3" mandrel all the way back. My 1/8 mile times may look a little bad because the track here is poorly prepped and slightly uphill. Its in the parking lot of Chargers stadium. Also I have a 9" Carr LU converter that is probably eating some HP up top. I have a PTC waiting to be installed. I'm going to take it to Fontana 1/4 mile tomorrow, that should be a better gauge of where I'm currently at.

Bison - let's say the car was running out of turbo, is this the symptom you would see? Low boost, but increasing in each gear? I'm running about 70% duty cycle on 60lb injectors with around 45psi line off fuel pressure. I'm also running about 10.5:1 spraying methanol. Attached is a data log showing the boost jump up when I shift into 4th.

 

[bison]

You would see the opposite. High boost then falling as rpm increases. Flash stall would be the highest then it would taper downward from there. That's if it's out of compressor or drive energy can't turn the compressor fast enough. Usually backpressure spikes and manifold pressure drops. If the compressor cover is the problem it will usually spike then fall off like I described before. Switching compressor covers can drop backpressure and increase manifold pressure in some instances. If it were to run out of it's efficiency zone you would see a huge spike in charge air temp.

 

[89mulletbird]

I have a .63 exhaust housing and a .70 inlet housing.

Is there any data I can collect that would further help figure this out? My IAT sensor is currently in the air filter. I could put a thermocouple in the uppipe before the alky to measure inlet temp.

 

[bison]

Ex pressure vs boost pressure. Can you post pics of the compressor /turbine also?

 

[bison]

What is the stall at full boost?

 

[89mulletbird]

What is the stall at full boost?

Do you mean of the housing, or the actual turbine blades?

By stall at full boost do you mean what RPM does it reach with the transbrake applied at 20psi?

 

[bison]

What is the rpm after the 2-3 shift?

 

[89mulletbird]

Do you mean of the housing, or the actual turbine blades?

By stall at full boost do you mean what RPM does it reach with the transbrake applied at 20psi?

 

[89mulletbird]

With both the 9/11 and the ptc 9.5", after shifting 2-3 at 6000RPM the RPM drops to 4700.

HOWEVER! I think I fixed the boost issue. I hadn't cleaned my air filter in several years. It turned a 5gal bucket of water totally black. I took the car to the strip today and here is the data log. I got a full 25psi in 2nd, near red line it dropped to about 18, then came back up to 25 in 3rd and stayed solid at 25. (see attached photo)

Now does it look like I'm running out of turbo as I wind up the RPM? I ran an 11.11 today at 118MPH, but didn't log that run.

 

[Mr.Spool]

I don't think your out of wheel, I drove a 61 turbo combo that went 130 mph and ran 10's,my old 49 turbo did 120 mph at 3800 lbs on just a stock motor with a mild port head pump gas alky and over 98 mph in the 1/8.gotta be something else.like I suggested earlier compression test the motor.

 

[bison]

With both the 9/11 and the ptc 9.5", after shifting 2-3 at 6000RPM the RPM drops to 4700.

HOWEVER! I think I fixed the boost issue. I hadn't cleaned my air filter in several years. It turned a 5gal bucket of water totally black. I took the car to the strip today and here is the data log. I got a full 25psi in 2nd, near red line it dropped to about 18, then came back up to 25 in 3rd and stayed solid at 25. (see attached photo)

Now does it look like I'm running out of turbo as I wind up the RPM? I ran an 11.11 today at 118MPH, but didn't log that run.

It seems as you are based on the log but you shouldn't be out of wheel yet. You shouldn't be over 5600 unless it will pull past that in third also

 

[89mulletbird]

What do you mean by "You shouldn't be over 5600 unless it will pull past that in third also"?

I do have a small exhaust leak on my passenger header flange, I tried to file it flat but still leaks so I'm going to throw a gasket on it. I'll see if that helps the spooling.

 

[89mulletbird]

Mr Spool - I'll run a compression test when I throw a header flange gasket in this week, thanks.