ionlion
Probationary Member
- 5
- 0
- Apr 4, 2008
-
Burnaby,
I'm having a head-scratcher of a problem. 90 Tsi awd, totally stock with only 140,000 km on it. Only makes 8psi of boost. At first I suspected leaks, did a leak test, it's fine. Then I thought maybe it was pulling boost due to knock etc... Nope, that wasn't the case.
Then I tried disconnecting the BCS and running straight from the J pipe nipple to the wastegate, with the line that normally goes to the BCS feeding into my boost gauge. Still only 8psi.
I've been searching many sites for a while and the general consensus is that the stock wastegate should do 10psi or so left to it's own with no MBC or BCS hooked up.
Here is the issue; if this was a boost leak then my gauge reading directly after the turbo would show 10psi or so, while the reading in the normal spot (FPR solenoid line off the intake manifold) would reflect the leak and be lower, but they're exactly the same leading me to believe I'm not leaking. (that and the boost leak test) Also, it spools very quickly and always stops perfectly at 8psi; I've tried slowly rolling into it, sitting at 5-6psi on the highway and then quickly going WOT, either way it doesn't ever go even a hair past 8psi.
Furthermore, removing the pressure source from the wastegate and preventing it from opening will give me boost above 8psi easily, although I didn't go much past that it did get up to 13 psi before I stopped, so i know at the very least I *can* make that
So, there are two possibilities here that I can't answer: Either the wastegate spring is actually only set to 8psi, or I possibly have a pre-turbo exhaust leak of some kind? Would this make sense?
I guess the third possibility is that i'm missing something basic
.
I'm at the point where I am just going to run a MBC, but first i'm waiting for a logger cable so I can confirm that the BCS was simply broken and that the car is healthy, but I don't want to turn up the boost until I know that 8psi is a normal reading with this setup. If i'm supposed to be making 10, something is wrong.
Then I tried disconnecting the BCS and running straight from the J pipe nipple to the wastegate, with the line that normally goes to the BCS feeding into my boost gauge. Still only 8psi.
I've been searching many sites for a while and the general consensus is that the stock wastegate should do 10psi or so left to it's own with no MBC or BCS hooked up.
Here is the issue; if this was a boost leak then my gauge reading directly after the turbo would show 10psi or so, while the reading in the normal spot (FPR solenoid line off the intake manifold) would reflect the leak and be lower, but they're exactly the same leading me to believe I'm not leaking. (that and the boost leak test) Also, it spools very quickly and always stops perfectly at 8psi; I've tried slowly rolling into it, sitting at 5-6psi on the highway and then quickly going WOT, either way it doesn't ever go even a hair past 8psi.
Furthermore, removing the pressure source from the wastegate and preventing it from opening will give me boost above 8psi easily, although I didn't go much past that it did get up to 13 psi before I stopped, so i know at the very least I *can* make that
So, there are two possibilities here that I can't answer: Either the wastegate spring is actually only set to 8psi, or I possibly have a pre-turbo exhaust leak of some kind? Would this make sense?
I guess the third possibility is that i'm missing something basic
. I'm at the point where I am just going to run a MBC, but first i'm waiting for a logger cable so I can confirm that the BCS was simply broken and that the car is healthy, but I don't want to turn up the boost until I know that 8psi is a normal reading with this setup. If i'm supposed to be making 10, something is wrong.
