Low Boost Pressure?
Discussion
Morning guys,
I think i've got an issue with one of my turbos?
Basically all was well last night on the drive up to Warwickshire, but this morning the car felt slower.
The first thing I noticed was that I could hear the engine, but the turbos weren't making anywhere near as much noise as they usually do.
Boost pressure is down I think although it only occured to me to look at the boost gauge by the time I was at work ¬_¬
I've looked around the engine bay and can't see any obvious hoses that may have blown off.
The engine sounds healthy, and I was getting turbo noises from the left hand side of the car, but not the right. It almost seemed to drive like an NA.
Any ideas?
Car is a 2.5 GTO '02
Thanks
I think i've got an issue with one of my turbos?
Basically all was well last night on the drive up to Warwickshire, but this morning the car felt slower.
The first thing I noticed was that I could hear the engine, but the turbos weren't making anywhere near as much noise as they usually do.
Boost pressure is down I think although it only occured to me to look at the boost gauge by the time I was at work ¬_¬
I've looked around the engine bay and can't see any obvious hoses that may have blown off.
The engine sounds healthy, and I was getting turbo noises from the left hand side of the car, but not the right. It almost seemed to drive like an NA.
Any ideas?
Car is a 2.5 GTO '02
Thanks
Can't explain the temp thing but as far as boost pressure/performance, check that you haven't got a loose hose clip, rubbing boost hose (front turbo hose can rub on clam fastener bolts for e.g.), or even something perished that might be letting by. Also do you have a dump valve/BOV? If so, by losing the vac hose (with either a hole or it coming adrift somewhere, or even being blocked) the piston cannot hold itself closed under full boost and it gives the same feeling. Won't hold full boost and is worse/more noticeable, in higher gears.
Blu3R said:
Can't explain the temp thing but as far as boost pressure/performance, check that you haven't got a loose hose clip, rubbing boost hose (front turbo hose can rub on clam fastener bolts for e.g.), or even something perished that might be letting by. Also do you have a dump valve/BOV? If so, by losing the vac hose (with either a hole or it coming adrift somewhere, or even being blocked) the piston cannot hold itself closed under full boost and it gives the same feeling. Won't hold full boost and is worse/more noticeable, in higher gears.
Just checked again, I can't see/feel any loose hoses, I don't have a dump valve and can't see anything that's rubbed.I washed it yesterday. Could that have done anything bad?
To have no boost at all, it usually boils down to a few things:
1. Boost leak on the plumbing from the turbo outlets, through the intercooler, to the throttle body. To have zero boost, it's not a small leak, so you should be able to spot it fairly easily.
2. Something in the wastegate system. As Gadgeroonie said, check both wastegate actuators to make sure that they're still hooked up - if you look at your turbo, you should see a cylinder with a pushrod attached. That's your wastegate actuator. The pushrod should be attached to a lever on the turbo itself. The rear turbo is easy to check with a flashlight and a mirror-on-a-stick. You'll need to go under the car to check the front turbo. Also, make sure that the actuator is firmly bolted to the turbo - I just fixed a car where one of the bolts on the actuator bracket had fallen out, so the actuator was flopping around. While you're at it, hook a low pressure (you only need around 10 psi - if you go too high, you can destroy the actuator) source of compressed air, like a bicycle pump, to the vacuum line that runs into the actuator, and make sure the actuator moves freely when you apply the air. Sometimes turbo heat blankets will interfere with the movement of the wastegates, etc.
3. Broken turbo. With the engine cold and turned off, disconnect the inlet to the turbo (corrugated hose from the air filter), reach inside with a finger, and gently spin the compressor wheel. Should spin freely and smoothly, with very little axial play in the bearing. Fins should not have nicks, bends, scrapes, etc. Shouldn't be really oily, either.
Good luck!
1. Boost leak on the plumbing from the turbo outlets, through the intercooler, to the throttle body. To have zero boost, it's not a small leak, so you should be able to spot it fairly easily.
2. Something in the wastegate system. As Gadgeroonie said, check both wastegate actuators to make sure that they're still hooked up - if you look at your turbo, you should see a cylinder with a pushrod attached. That's your wastegate actuator. The pushrod should be attached to a lever on the turbo itself. The rear turbo is easy to check with a flashlight and a mirror-on-a-stick. You'll need to go under the car to check the front turbo. Also, make sure that the actuator is firmly bolted to the turbo - I just fixed a car where one of the bolts on the actuator bracket had fallen out, so the actuator was flopping around. While you're at it, hook a low pressure (you only need around 10 psi - if you go too high, you can destroy the actuator) source of compressed air, like a bicycle pump, to the vacuum line that runs into the actuator, and make sure the actuator moves freely when you apply the air. Sometimes turbo heat blankets will interfere with the movement of the wastegates, etc.
3. Broken turbo. With the engine cold and turned off, disconnect the inlet to the turbo (corrugated hose from the air filter), reach inside with a finger, and gently spin the compressor wheel. Should spin freely and smoothly, with very little axial play in the bearing. Fins should not have nicks, bends, scrapes, etc. Shouldn't be really oily, either.
Good luck!
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