Boost goes up and car slows/dies? - What could this be?
#19
02-07-2010, 05:41 PM
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Don't worry, no offense takenI am by no means an expert on these cars so any help you can offer is appreciated
I remember I had the following faults with my car all around the same time.....
DVs, MAF, Boost leak, overboosting
But what I cannot remember is what caused and solved what issue
Would I be right in saying MAF would effect driveability and overboosting
Whilst a boost leak would effect driveability and also reduce available boost?
#20
02-07-2010, 06:04 PM
I don't know enough to figure how MAF could effect overboosting, but a boost leak would indeed reduce available boost, I belive that is corect
#21
02-07-2010, 09:18 PM
Seems logical - but could a sizeable leak on the intake side that adminsters unregulated air (not past the MAF) mixed with additional fuel injected by the ECU to compensate for the lean condition cause an increase in boost?
Pressure test is worth a punt IMHO - just read the DIY thread and seems straightforward.
Pressure test is worth a punt IMHO - just read the DIY thread and seems straightforward.
Seriously guys, you need a better handle on how the engine controls work, interact, and are reacted to. Additional air flowing around the MAF will result in a lean condition since the MAF never sees it. Boost leak is seen as a lack of boost which is compensated for by the turbos spinning harder to reach the target boost. Overspins the turbos, slow to boost, will run rich since the MAF saw the air and fueled for it. As target boost is reached the boost control solenoid allows the pressure lines to the W/G cans to see more boost - as the cans see boost they react and open the W/G allowing exhaust gas to pass AROUND the turbo and thus slow the turbo - this happens back and forth quickly so that the turbo maintains even boost. If an overboost is seen the boost solenoid opens fully - throws a code since it's out of duty cycle - and the e-throttle will close up the throttle to prevent engine damage. The closed throttle physically prevents air from getting past - results in a soggy throttle and motor that runs at WOT like it would at part throttle. I imagine the knock sensor might see knock at high pressures and retard timing or the ECU may retard at overboost to save the motor too - some of the tuners here could probably say.
Now, I am pretty sure that is correct or pretty close to correct. Most of this is from what I know from tuning on other cars and from what I've learned researching this one so I think it's close and ought to give SOME idea as to WTF happens. BAD MAF is one I'm not 100% sure about but unplugging it is a good troubleshoot and so is swapping which he's done. IMO it's overboosting and 4K is probbaly about the time his turbos are really spooling up so.....
#23
02-08-2010, 03:35 PM
Join Date: Dec 2009
Location: England
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I agree - great post!
So in that case what causes the 1.0 bar stock boost I'm now seeing (can relate to the shut down to protect as it feels like a rev limiter when it kicks in) - but What I don't understand is WHY it happens in the first place?
Car is bone stock and has only started doing this in the last few weeks..Its really lazy to drive now.
So in that case what causes the 1.0 bar stock boost I'm now seeing (can relate to the shut down to protect as it feels like a rev limiter when it kicks in) - but What I don't understand is WHY it happens in the first place?
Car is bone stock and has only started doing this in the last few weeks..Its really lazy to drive now.
No sorry, increased fueling might excite the turbos a bit more but that wouldn't effect boost. If anything a leak on the intake side would create a LEAN condition as unmetered air made it into the turbos.
Seriously guys, you need a better handle on how the engine controls work, interact, and are reacted to. Additional air flowing around the MAF will result in a lean condition since the MAF never sees it. Boost leak is seen as a lack of boost which is compensated for by the turbos spinning harder to reach the target boost. Overspins the turbos, slow to boost, will run rich since the MAF saw the air and fueled for it. As target boost is reached the boost control solenoid allows the pressure lines to the W/G cans to see more boost - as the cans see boost they react and open the W/G allowing exhaust gas to pass AROUND the turbo and thus slow the turbo - this happens back and forth quickly so that the turbo maintains even boost. If an overboost is seen the boost solenoid opens fully - throws a code since it's out of duty cycle - and the e-throttle will close up the throttle to prevent engine damage. The closed throttle physically prevents air from getting past - results in a soggy throttle and motor that runs at WOT like it would at part throttle. I imagine the knock sensor might see knock at high pressures and retard timing or the ECU may retard at overboost to save the motor too - some of the tuners here could probably say.
Now, I am pretty sure that is correct or pretty close to correct. Most of this is from what I know from tuning on other cars and from what I've learned researching this one so I think it's close and ought to give SOME idea as to WTF happens. BAD MAF is one I'm not 100% sure about but unplugging it is a good troubleshoot and so is swapping which he's done. IMO it's overboosting and 4K is probbaly about the time his turbos are really spooling up so.....
Seriously guys, you need a better handle on how the engine controls work, interact, and are reacted to. Additional air flowing around the MAF will result in a lean condition since the MAF never sees it. Boost leak is seen as a lack of boost which is compensated for by the turbos spinning harder to reach the target boost. Overspins the turbos, slow to boost, will run rich since the MAF saw the air and fueled for it. As target boost is reached the boost control solenoid allows the pressure lines to the W/G cans to see more boost - as the cans see boost they react and open the W/G allowing exhaust gas to pass AROUND the turbo and thus slow the turbo - this happens back and forth quickly so that the turbo maintains even boost. If an overboost is seen the boost solenoid opens fully - throws a code since it's out of duty cycle - and the e-throttle will close up the throttle to prevent engine damage. The closed throttle physically prevents air from getting past - results in a soggy throttle and motor that runs at WOT like it would at part throttle. I imagine the knock sensor might see knock at high pressures and retard timing or the ECU may retard at overboost to save the motor too - some of the tuners here could probably say.
Now, I am pretty sure that is correct or pretty close to correct. Most of this is from what I know from tuning on other cars and from what I've learned researching this one so I think it's close and ought to give SOME idea as to WTF happens. BAD MAF is one I'm not 100% sure about but unplugging it is a good troubleshoot and so is swapping which he's done. IMO it's overboosting and 4K is probbaly about the time his turbos are really spooling up so.....
#24
02-08-2010, 03:40 PM
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Ok Jim
Not and endless list, but these are some of the things I think should be checked
Pressure test
MAF sensor
DVs
Boost control solenoid
Wastegates & vacuum hoses
Spark plugs
Coils
I'll add others if I think of any
Not and endless list, but these are some of the things I think should be checked
Pressure test
MAF sensor
DVs
Boost control solenoid
Wastegates & vacuum hoses
Spark plugs
Coils
I'll add others if I think of any
#25
02-09-2010, 01:12 PM
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Ok guys - Jim and I have just spent the last two hours trying to free one of his wastegates
The actuator itself is ok but the wastegate is seized solid
It's been blasted with a cans worth of WD40 but it's still stuck
Does anyone know where they usually seize (inside or out) and whether it can be free'd without having to remove the turbo?
The actuator itself is ok but the wastegate is seized solid
It's been blasted with a cans worth of WD40 but it's still stuck
Does anyone know where they usually seize (inside or out) and whether it can be free'd without having to remove the turbo?
#26
02-10-2010, 08:50 AM
hehehe.... 
No sorry, increased fueling might excite the turbos a bit more but that wouldn't effect boost. If anything a leak on the intake side would create a LEAN condition as unmetered air made it into the turbos.
Seriously guys, you need a better handle on how the engine controls work, interact, and are reacted to. Additional air flowing around the MAF will result in a lean condition since the MAF never sees it. Boost leak is seen as a lack of boost which is compensated for by the turbos spinning harder to reach the target boost. Overspins the turbos, slow to boost, will run rich since the MAF saw the air and fueled for it. As target boost is reached the boost control solenoid allows the pressure lines to the W/G cans to see more boost - as the cans see boost they react and open the W/G allowing exhaust gas to pass AROUND the turbo and thus slow the turbo - this happens back and forth quickly so that the turbo maintains even boost. If an overboost is seen the boost solenoid opens fully - throws a code since it's out of duty cycle - and the e-throttle will close up the throttle to prevent engine damage. The closed throttle physically prevents air from getting past - results in a soggy throttle and motor that runs at WOT like it would at part throttle. I imagine the knock sensor might see knock at high pressures and retard timing or the ECU may retard at overboost to save the motor too - some of the tuners here could probably say.
Now, I am pretty sure that is correct or pretty close to correct. Most of this is from what I know from tuning on other cars and from what I've learned researching this one so I think it's close and ought to give SOME idea as to WTF happens. BAD MAF is one I'm not 100% sure about but unplugging it is a good troubleshoot and so is swapping which he's done. IMO it's overboosting and 4K is probbaly about the time his turbos are really spooling up so.....
Seriously guys, you need a better handle on how the engine controls work, interact, and are reacted to. Additional air flowing around the MAF will result in a lean condition since the MAF never sees it. Boost leak is seen as a lack of boost which is compensated for by the turbos spinning harder to reach the target boost. Overspins the turbos, slow to boost, will run rich since the MAF saw the air and fueled for it. As target boost is reached the boost control solenoid allows the pressure lines to the W/G cans to see more boost - as the cans see boost they react and open the W/G allowing exhaust gas to pass AROUND the turbo and thus slow the turbo - this happens back and forth quickly so that the turbo maintains even boost. If an overboost is seen the boost solenoid opens fully - throws a code since it's out of duty cycle - and the e-throttle will close up the throttle to prevent engine damage. The closed throttle physically prevents air from getting past - results in a soggy throttle and motor that runs at WOT like it would at part throttle. I imagine the knock sensor might see knock at high pressures and retard timing or the ECU may retard at overboost to save the motor too - some of the tuners here could probably say.
Now, I am pretty sure that is correct or pretty close to correct. Most of this is from what I know from tuning on other cars and from what I've learned researching this one so I think it's close and ought to give SOME idea as to WTF happens. BAD MAF is one I'm not 100% sure about but unplugging it is a good troubleshoot and so is swapping which he's done. IMO it's overboosting and 4K is probbaly about the time his turbos are really spooling up so.....
#27
02-10-2010, 08:52 AM
Damn... how long did the car sit?
You can try to drop the exhaust and inspect from there, although it's a bear to get in there in the first place.
justin
You can try to drop the exhaust and inspect from there, although it's a bear to get in there in the first place.
justin
Ok guys - Jim and I have just spent the last two hours trying to free one of his wastegates
The actuator itself is ok but the wastegate is seized solid
It's been blasted with a cans worth of WD40 but it's still stuck
Does anyone know where they usually seize (inside or out) and whether it can be free'd without having to remove the turbo?
The actuator itself is ok but the wastegate is seized solid
It's been blasted with a cans worth of WD40 but it's still stuck
Does anyone know where they usually seize (inside or out) and whether it can be free'd without having to remove the turbo?
#28
02-11-2010, 03:59 PM
Join Date: Dec 2009
Location: England
Posts: 120
Rep Power: 22 
Carb cleaner and GT40 is coming out on Sat..
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