Turbo - Lack of boost after changing gear.

[MartinF]

I'm experiencing a lack of boost after changing gear on my Rev1 turbo engine, which I thought was due to the wastegate sticking open but now not so sure.

I first noticed this last year with the original CT26 turbo when I was at Snetterton. As I lost a few impeller blades I replaced this with a CT20B and took some time to file down the edges of the wastegate flap and the inside of my Ebay downpipe until i was comfortable that it wasn't catching, this was without the exhaust gasket, so including the metal layered gasket when fitting there should have been even more clearance.

Unfortunately once I was back on the road the same thing was happening. Previously with the CT26 I just had stock boost control, now with the CT20B I have a Greddy Profec to try and keep boost limited to 1Bar. I see around 15PSI when WOT in say third gear, but as soon as I change up to fourth there is only around 2 or 3psi, unless i come off the throttle for a second or two and then when I go WOT again the boost will build to 14psi+.

Classic symptoms of a wastegate being stuck.

So I ordered a new downpipe from BRD and the design is a little different to the classic EBay ones, but still a little tight in the wastegate area. I fitted this today and have the exact same symptoms.

So i'm asking the collective wisdom if there is maybe something else that i'm overlooking as i'm struggling to believe it is is the wastegate sticking still.

I have checked my recirc valve and it is all clean and moves fine, the only thing I wonder is maybe if the spring is a little weak, I can move this easily by hand, and is maybe staying open after activating.

Has anybody else had anything similar before ?

[pbmr2]

we filmed the wastegate arm with a gopro to prove it wasn't sticking, once that was ruled out we found that the diaphragm on the actuator was weak. solved the problem.

the actuator arm had adjustment on the end link, so winding that in a bit (or a lot) for testing could help you pinpoint the issue.
is the actuator rod still quite stiff to move by hand?

the recirc could also be weak as you mention. could just block it off for testing.

[MartinF]

Thanks for posting your experience, trying to get a camera on the wastegate is a good idea.

I don't think it will be anything related to the actual actuator as the two different turbo's had their own actuators.

[SonicSW20]

Stock BOV?

Have you checked your VTV? This is crucial for correct operation of the BOV.

[androo007]

I was going to suggest that perhaps the actuator iteself could be at fault.

[MartinF]

Thanks guys, it was a good shout about the VTV as I wasn't aware of it's importance.

Unfortunately it tests OK (easy to blow one way, not so easy another way) and is plumbed in OK.

[MartinF]

Well today managed to get a camera on the wastegate rod and it was proven that it is actually closed when expected, and even at the times where not enough boost is being made, which has me a bit flumoxed.

Changed the recirc valve for another one, but they both checked out the same and didn't make any difference

Anybody else have any enlightening ideas?

[pbmr2]

It might not feel like it but that is progress, as now you know it's not the wastegate sticking. That's one thing eliminated.

Also swapping recirc valves proves another part, so 2 things down.

also the actuator has been ruled out as they were changed between turbos.

so then is it the fueling or ecu pulling timing for another reason?

Is the AFM 100%?
could the vacuum lines for the fpr or actuator or dv be colapsing or kinked?

is there another leak somewhere else? like the tvis actuator or another vacuum hose connection that is broken but not fully snapped off?

TPS, is it working properly?
how is the idle, good and steady?

Will have a think about it over lunch, see what pops into my head

[MartinF]

Is the AFM 100%?

I guess this is possible but a slim chance, but will take a closer look.

The idle is rock solid.

I did wonder if it was something to do with the TVIS activation, but not sure this would limit boost by quite so much if not working properly.

[pbmr2]

seen a few of the tvis actuators split inside so they basically boost leak. but spose you'd have trouble more of the time is this was the case.

if the TPS isn't working properly or has dead spots it could cause all sorts of issues. could test it by simply clamping the tvis vacuum hose so it never sees boost. would not be idea but ok for testing.

fuel pump on it's way out? hard to test without a gauge.

it does suggest one of the vacuum or boost solenoids/actuators is jamming or sticking until the system jiggled again.

you're sure the dump valve is closing properly after use?

[gips]

Check your boost solenoid. Basically, you probably have a very weak spring on the gate. Due to this the solenoid needs to bleed all the pressure to the air in order for the spring to actually hold boost. If the solenoid stuck sometimes, it won't bleed the air and the gate will receive the help of the boost from compressor on top of the pressure from the exhaust resulting in slow spool. Its a theory, but can happen. Just remove the vaccum from the wastegate and check ,if you now have boost all the time. It may build a bit more than required, but don't worry, even without the vaccum the gate will still open almost fully at around 18PSI and ,if theory is correct even less due to your weak spring in there.

[MartinF]

fuel pump on it's way out? hard to test without a gauge.

It's a brand new Walbro, and if it was on its way it would be more likely to cause issues at high boost, i.e. maximum fuel pressure.

you're sure the dump valve is closing properly after use?

Well this was one of my theories, hence why trying another, but it's really hard to test when driving.

[MartinF]

Check your boost solenoid. Basically, you probably have a very weak spring on the gate. Due to this the solenoid needs to bleed all the pressure to the air in order for the spring to actually hold boost. If the solenoid stuck sometimes, it won't bleed the air and the gate will receive the help of the boost from compressor on top of the pressure from the exhaust resulting in slow spool. Its a theory, but can happen. Just remove the vaccum from the wastegate and check ,if you now have boost all the time. It may build a bit more than required, but don't worry, even without the vaccum the gate will still open almost fully at around 18PSI and ,if theory is correct even less due to your weak spring in there.

Thanks, but this doesn't correlate as when I had the issue with the previous turn I was on standard boost control. Now with the CT20B i'm using a Greddy Profec.

However wiring the wastegate closed may further eliminate it as an issue, which i might try at the weekend and drive watching the boost gauge