Turbo c5 won’t make full boost
03-19-2018, 04:30 PM
#1
Turbo c5 won’t make full boost
Hi,
I have searched thread after thread on all different types of forums trying to get some insight but haven’t found anything. If this specific situation has been addressed feel free to post a link.
I just finished building a c5 z06 turbo rearmount
78mm comp oilless .9ar
stock ls6 w/ ls7 cam
3 inch exhaust to turbo
2.5inch coldpiping to intercooler
deka 60# injectors
walbro 450
treadstone 1300 hp intercooler.
Race port 50mm external wg
turbo smart/a&a corvette bov
The car will not make more than 3lbs of boost. It spools “quickly” and makes the peak boost before 4K rpm then remains constant until redline. It will spoil and flutter when I let off even at very partial throttle so the turbo does seem responsive.
The car is currently running a 50mm turbosmart Raceport with a 10lb spring, directly hooked to the compressor housing. I have disconnected the wg line to ensure it stays closed and it still levels out at 3lbs. I also visually checked to make sure the wg was not opening from exhaust pressure. The BOV seems to be functioning but I screwed it all the way tight for the time being to ensure it isn’t opening too.
I plan to run a pressure check on the cold side ASAP.
Does it sound reasonable that a leak could be bleeding that much air somehow?
Has anybody else run into something similar?
The car builds boost then levels off.
Sign of a potentially failing turbo? Was just rebuilt by vengeance so I would be surprised if that was issue as it looks and feels perfect and tight.
ANY input or suggestions would be greatly appreciated!
thanks,
Ryan
I have searched thread after thread on all different types of forums trying to get some insight but haven’t found anything. If this specific situation has been addressed feel free to post a link.
I just finished building a c5 z06 turbo rearmount
78mm comp oilless .9ar
stock ls6 w/ ls7 cam
3 inch exhaust to turbo
2.5inch coldpiping to intercooler
deka 60# injectors
walbro 450
treadstone 1300 hp intercooler.
Race port 50mm external wg
turbo smart/a&a corvette bov
The car will not make more than 3lbs of boost. It spools “quickly” and makes the peak boost before 4K rpm then remains constant until redline. It will spoil and flutter when I let off even at very partial throttle so the turbo does seem responsive.
The car is currently running a 50mm turbosmart Raceport with a 10lb spring, directly hooked to the compressor housing. I have disconnected the wg line to ensure it stays closed and it still levels out at 3lbs. I also visually checked to make sure the wg was not opening from exhaust pressure. The BOV seems to be functioning but I screwed it all the way tight for the time being to ensure it isn’t opening too.
I plan to run a pressure check on the cold side ASAP.
Does it sound reasonable that a leak could be bleeding that much air somehow?
Has anybody else run into something similar?
The car builds boost then levels off.
Sign of a potentially failing turbo? Was just rebuilt by vengeance so I would be surprised if that was issue as it looks and feels perfect and tight.
ANY input or suggestions would be greatly appreciated!
thanks,
Ryan
03-19-2018, 08:20 PM
#2
Melting Slicks
When was the last time it did make the correct boost ?
What, if anything changed or what work was done prior to this problem occurring ?
history is all important
What, if anything changed or what work was done prior to this problem occurring ?
history is all important
03-19-2018, 09:42 PM
#3
Thanks.
03-20-2018, 07:07 AM
#4
Melting Slicks
So it has never made the boost ?
Start with the obvious...check for leaks, pressure test the cold side, BOV etc. Ensure no exhaust leaks....primarily ensure the wastegate is not leaking.
Does it vent to atmos or does it re-enter the exhaust ? If the former it should be easy to see if it is leaking at idle etc.
With pressure loss in the system, you probably will see lower boost when referencing off the compressor also at the rear, but that could easily be accommodated with stiffer w/g springs.
Although with signal pipe off the gate you'd expect to see some sort of change.
Also, where are you measuring boost from and how ?
Start with the obvious...check for leaks, pressure test the cold side, BOV etc. Ensure no exhaust leaks....primarily ensure the wastegate is not leaking.
Does it vent to atmos or does it re-enter the exhaust ? If the former it should be easy to see if it is leaking at idle etc.
With pressure loss in the system, you probably will see lower boost when referencing off the compressor also at the rear, but that could easily be accommodated with stiffer w/g springs.
Although with signal pipe off the gate you'd expect to see some sort of change.
Also, where are you measuring boost from and how ?
03-20-2018, 03:47 PM
#5
So it has never made the boost ?
Start with the obvious...check for leaks, pressure test the cold side, BOV etc. Ensure no exhaust leaks....primarily ensure the wastegate is not leaking.
Does it vent to atmos or does it re-enter the exhaust ? If the former it should be easy to see if it is leaking at idle etc.
With pressure loss in the system, you probably will see lower boost when referencing off the compressor also at the rear, but that could easily be accommodated with stiffer w/g springs.
Although with signal pipe off the gate you'd expect to see some sort of change.
Also, where are you measuring boost from and how ?
Start with the obvious...check for leaks, pressure test the cold side, BOV etc. Ensure no exhaust leaks....primarily ensure the wastegate is not leaking.
Does it vent to atmos or does it re-enter the exhaust ? If the former it should be easy to see if it is leaking at idle etc.
With pressure loss in the system, you probably will see lower boost when referencing off the compressor also at the rear, but that could easily be accommodated with stiffer w/g springs.
Although with signal pipe off the gate you'd expect to see some sort of change.
Also, where are you measuring boost from and how ?
I just got together the stuff to pressure check the cold side so I will do that next.
I have been measuring boost entirely off of the map sensor on the dyno. I have a boost gauge uninstalled that I will install if I find the suspect part/leak and need to verify that it is the only issue.
im just figuring with the amount of exhaust/boost that I must be losing it will be an obvious issue once I stumble upon it.
thanks.
03-20-2018, 06:35 PM
#6
Burning Brakes
Common issue with wastegate springs is that they are meant to be stacked. If your gate came with 3 springs, say 7, 11, 14 PSI springs, they are meant to be added to the 7 PSI spring to increase boost and not as replacements (this is why they are different diameters).
If you pulled out the small spring and added a larger one, you're likely only really running 3 PSI worth of gate spring.
If you pulled out the small spring and added a larger one, you're likely only really running 3 PSI worth of gate spring.
03-20-2018, 10:43 PM
#8
03-20-2018, 10:44 PM
#9
04-15-2018, 05:15 PM
#10
Update. Fixed my boost issue. Pressure tested the cold side and there was a coupler halfway on big enough to get a couple fingers in right next to the turbo. Fixed that it spools about a thousand rpm faster and the wastegate opened for the first time. Tuner spent like 2 hours checking my entire exhaust and coldside while the car was in the air when we first ran into this problem and I made my first post. Guaranteed me that the turbo was bad because comp is a bad company and nothing leaked and everything else worked fine. Might have to have a little chat about all of that. Thanks for the help guys.