I have no turbo boost. Where do I start?

[bmxJeff]

Hi All,

Finally got round to fitting my boost gauge. I've done this without fitting an MBC for now as I want to first diagnose the issue of the car feeling a bit sluggish (940 LPT) and the gauge will obviously aid me by giving me boost/vacuum info. I tapped into the vacuum hose just above the CBV. I also replaced this hose back to the intake manifold as it was a bit dry and brittle.

Thought it looked quite tidy:



Anyway, went for a test run and guess what.... no boost. 0psi under full load.

It seems to have what I presume is a healthy vacuum, about -20psi on idle which can creep to -25/30psi when engine braking etc. But when I put the pedal to the floor I get 0psi.

To be honest the car also has very little above 4000rpm in terms of power and doesn't seem to want to push past 5000rpm.

I recently discovered it has a tubo+ (plus) kit fitted. This will be bypassed/removed in the long run in favour of an MBC. I'm tempted to bypass it right away to simplify diagnosing the lack of boost.

The compressor bypass valve housing was weeping a little oil. I removed and cleaned but I know that needs a new seal. Diaphragm appears completely intact.

What else should I look for when diagnosing this problem?

[Steve940estate]

Have a look to see if the wastegate actuator rod is still attached to the wastegate. They have a little spring clip on them to stop the arm dropping off and this can rust away leaving the actuator arm to fall off. With the wategate flapping open at the slightest breeze you won't get any boost.

Make sure all of the hoses from the turbo to the intake manifold are connected properly and have no splits as well.

As you said it might be worth bypassing the Turbo + if there is nothing obviously wrong elsewhere.

[Pete940]

That explains a lot. Having had my actuator rod pop off many times recently, I thought there must've been something missing.

[Steve940estate]

You might not be able to see the small hole in the wastegate control arm if its full of rust and whats left of the clip. It should have a small R clip stopping the actuator arm dropping off.

[bmxJeff]

Originally Posted by Steve940estate

Have a look to see if the wastegate actuator rod is still attached to the wastegate. They have a little spring clip on them to stop the arm dropping off and this can rust away leaving the actuator arm to fall off. With the wategate flapping open at the slightest breeze you won't get any boost.

Make sure all of the hoses from the turbo to the intake manifold are connected properly and have no splits as well.

As you said it might be worth bypassing the Turbo + if there is nothing obviously wrong elsewhere.

Steve you brilliant man!

I checked all you advised today and waddaya know... actuator rod flapping in the wind!

Repaired with a split ring like so:



Now it pulls like a train. Can't believe I've been missing out on this all this time; It's like a new car. This is only at the stock 4psi, can't wait to get the MBC fitted

Thanks for your advice mate

[TonyS9]

If it had turbo+ it should be more than 4psi. Are you sure it has it. I plan to use a turbo+ modulator valve to turn the MBC on and off via a switch.

[bmxJeff]

Originally Posted by TonyS9

If it had turbo+ it should be more than 4psi. Are you sure it has it. I plan to use a turbo+ modulator valve to turn the MBC on and off via a switch.

Yeah I did wonder. To be honest I just assumed the turbo+ wasn't working.

It has the valve mounted to the front of the airbox with the 3 vacuum lines that intercept the hose between the wastegate actuator and turbo body. I haven't traced the loom from the plug on the valve to find the turbo+ ECU.

I assumed this was a turbo+ kit because I didn't know of anything else it could be.

[rogerthechorister]

Turboplus if working correctly should deliver at max 9psi, I think.

First question - you have to totally stamp on the loud pedal (at over 4,000 rpm) to get turboplus to click in. Are you sure you are stamping hard enough?

Second question - have you swapped the turboplus relay to check it? I THINK it's the same as a visually identical one on the inner wing on the opposite side - maybe (but maybe not) the radio suppression relay.

Bear in mind the turbo 2.3 litre HPT was on paper 161 bhp at full boost (I think 7PSI) and the turboplus 192 (at 9 psi) so you should certainly notice the difference over 4PSI.

[bmxJeff]

Originally Posted by rogerthechorister

Turboplus if working correctly should deliver at max 9psi, I think.

First question - you have to totally stamp on the loud pedal (at over 4,000 rpm) to get turboplus to click in. Are you sure you are stamping hard enough?

Second question - have you swapped the turboplus relay to check it? I THINK it's the same as a visually identical one on the inner wing on the opposite side - maybe (but maybe not) the radio suppression relay.

Bear in mind the turbo 2.3 litre HPT was on paper 161 bhp at full boost (I think 7PSI) and the turboplus 192 (at 9 psi) so you should certainly notice the difference over 4PSI.

I definitely stamped on the fun button hard at over 4000rpm bit I will double check today. I'll also have a hunt for that relay and get back when I have a chance. Thanks for the pointers