Celica ST205 -- not boosting properly?
Discussion
My '95 GT-Four ST205 developed an interesting issue the other week, while on a long drive down to Portsmouth.
I was accelerating on the motorway and my boost controller's gauge showed me as getting to a peak of 1.12 bar (which is roughly where I have it set as the max boost -- it's a Blitz SBC-iD III boost controller and power meter)
As soon as it hit 1.12, the car kind of "jerked" a bit as if the boost had suddenly dropped off, and from that point on, it will now not boost over 0.5 bar in any gear and struggles to even get there in 3rd-5th. The boost controller screen didn't flash red in the same way that it does when I hit my warning threshold.
What's likely to be the cause of this? I'm assuming if the turbo itself had screwed itself up, that I would hear all sorts of horrible noises coming from the engine bay, so I'm hoping that it's just that a hose popped off under the boost pressure or something like that.
The car is running on stock internals, except for a Blitz Access ECU, the aforementioned boost controller (with TVSV disabled) and a HKS SSQV blow-off valve.
Seems unlikely that I would have hit fuel-cut, but if I have, do I need to disconnect the battery to reset it? No engine management light came on, so I'm assuming there's no error codes stored.
I was accelerating on the motorway and my boost controller's gauge showed me as getting to a peak of 1.12 bar (which is roughly where I have it set as the max boost -- it's a Blitz SBC-iD III boost controller and power meter)
As soon as it hit 1.12, the car kind of "jerked" a bit as if the boost had suddenly dropped off, and from that point on, it will now not boost over 0.5 bar in any gear and struggles to even get there in 3rd-5th. The boost controller screen didn't flash red in the same way that it does when I hit my warning threshold.
What's likely to be the cause of this? I'm assuming if the turbo itself had screwed itself up, that I would hear all sorts of horrible noises coming from the engine bay, so I'm hoping that it's just that a hose popped off under the boost pressure or something like that.
The car is running on stock internals, except for a Blitz Access ECU, the aforementioned boost controller (with TVSV disabled) and a HKS SSQV blow-off valve.
Seems unlikely that I would have hit fuel-cut, but if I have, do I need to disconnect the battery to reset it? No engine management light came on, so I'm assuming there's no error codes stored.
Did you get it sorted?
Bit of mis-information here. From memory the Blitz Access ECU has a raised fuel cut limit and 1.1 bar isnt near enough to trigger fuel cut so I would discount that. Likewise suggestions of I/C water pump causing limited boost is not correct, especially as the car has a Blitz SBC so removes the stock boost circuit so the ECU has no control over boost. I would guess (with 15+ years as a Supra / GT4 / MR2 specialist) it's maybe popped a vacuum hose off (maybe one off the chargecooler / inlet manifold) or more likely developed a split in a chargercooler hose. Have you checked the one from the turbo to chargecooler and the charge cooler to inlet? Could also be a turbo inbalance where the impeller is rubbing on the turbo housing but unlikely.
HTH
C
ChrisPackit said:
Did you get it sorted?
Not yet, no. Only picked the car up today (been having the Castrol livery refreshed by Mook @ Skewer!) but it still wasn't boosting properly on the way home, so definitely need to get under the bonnet and see if I can figure it out.ChrisPackit said:
Bit of mis-information here. From memory the Blitz Access ECU has a raised fuel cut limit and 1.1 bar isnt near enough to trigger fuel cut so I would discount that.
I thought that was the case, but I couldn't remember! Thank you 
ChrisPackit said:
Likewise suggestions of I/C water pump causing limited boost is not correct, especially as the car has a Blitz SBC so removes the stock boost circuit so the ECU has no control over boost.
Yeah, it was a long shot, but the battery was disconnected and reattached and it still didn't boost fully so definitely not a limp mode thing.[quote]I would guess (with 15+ years as a Supra / GT4 / MR2 specialist) it's maybe popped a vacuum hose off (maybe one off the chargecooler / inlet manifold) or more likely developed a split in a chargercooler hose. Have you checked the one from the turbo to chargecooler and the charge cooler to inlet? Could also be a turbo inbalance where the impeller is rubbing on the turbo housing but unlikely.
It's a shame that a lot of the technical docs on the GT4OC are no longer available, that was an invaluable resource when it was still there!
Took it into a local garage this week for them to have a quick look.
Seems like the actuator arm to the wastegate is corroded/cracked and seized up, meaning that the wastegate is stuck in the position it's in, I think he said there was a couple of mm of gap or something.
They couldn't investigate further without risking damage as the whole area seemed to be corroded and they were worried bolts would round off or snap.
So, not sure what the best way forward is now. Replace the actuator, or just go the whole hog and replace the whole turbo for a reconditioned one?
Seems like the actuator arm to the wastegate is corroded/cracked and seized up, meaning that the wastegate is stuck in the position it's in, I think he said there was a couple of mm of gap or something.
They couldn't investigate further without risking damage as the whole area seemed to be corroded and they were worried bolts would round off or snap.
So, not sure what the best way forward is now. Replace the actuator, or just go the whole hog and replace the whole turbo for a reconditioned one?
gazchap said:
Took it into a local garage this week for them to have a quick look.
Seems like the actuator arm to the wastegate is corroded/cracked and seized up, meaning that the wastegate is stuck in the position it's in, I think he said there was a couple of mm of gap or something.
They couldn't investigate further without risking damage as the whole area seemed to be corroded and they were worried bolts would round off or snap.
So, not sure what the best way forward is now. Replace the actuator, or just go the whole hog and replace the whole turbo for a reconditioned one?
The actuator on them is a relatively easy swap, only 2 bolts hold it on and Ive never known them to seize with a bit of WD first. Could swap it without taking the whole turbo off, just the C clip to the wastegateb arm is tricky. I would expect an actuator to be < £100 and an hour or two to fit, then test.Seems like the actuator arm to the wastegate is corroded/cracked and seized up, meaning that the wastegate is stuck in the position it's in, I think he said there was a couple of mm of gap or something.
They couldn't investigate further without risking damage as the whole area seemed to be corroded and they were worried bolts would round off or snap.
So, not sure what the best way forward is now. Replace the actuator, or just go the whole hog and replace the whole turbo for a reconditioned one?
C
mine always hit fuel cut when running 1.1Bar and it got colder in Autumn. Had to turn down to 1.05 over winter. COld air going in, being cooled..just too much cold air in there!
mine always threw an error code - 54 iirc - charge cooler fluid level error. you THINK it's full, but just 0.5ml off and it would limp mode again. fill it right up and off it went happily again.
or yours has somethign else - hope it's a simple/cheap fix.
mine always threw an error code - 54 iirc - charge cooler fluid level error. you THINK it's full, but just 0.5ml off and it would limp mode again. fill it right up and off it went happily again.
or yours has somethign else - hope it's a simple/cheap fix.
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