Random no boost on WOT

It's happened three times now, the first I put down to a hiccup in the system, but it's done it a further two times under the same circumstances so I thought I'd ask here for any pointers.

When travelling down the road at a steady pace off boost, if I drop a gear and give it full throttle, I get no boost at all......nothing. If I then take my foot off the accelerator and re-apply, it boosts fully as it should.

I've checked all the hoses, they are fine (they've all been replaced). I've just cleaned up the VSV's with some carb cleaner, but not re-tested yet, is there anything else I should look at.

Having searched a bit, I've come across this pressure tank thingy, I understand it's under the inlet manifold towards the rear of the engine? Could this be something I should look at?

That's one of the top VSVs causing that bud. Iirc it's the very small one right at the top of the engine. It's a very common problem. It doesn't react quick enough or something like that. Changing mine out cured the problem.

I would be surprised if it was the pressure tank. Quick way to check that is to put it into the temporary TTC mode. Take it for a quick on boost spin then check if the actuators are still open, if they are your pressure tank is fine.

Nice one scott, in the following pic, are you talking about number 7

If it not 7 or 10 it could be the wastegates them selves (or 1 of them) i have the same problem, on kick down, have you check for codes? If it niether of the vsv or waste gate, according to the manual it could be ecu

Number 10 is not connected on mine as I have a boost controller. The fact that they open when throttle is re-applied suggests it's not the wastegates.

I'll see if I can get a donor one and try it.

whoops, my bad, number 10 is connected, the boost controller connects to the thing in front of it.

I'll try the top one first and see how it goes, then go from there.

I asked paul about it and he said it most likely 10 or the wastegates stuck open, mine is looking to be the gates, did you check for codes?

no codes.

If the wastgates are sticking, then putting it in TTC mode would still produce the problem. TTC mode eliminates the VSV's. This is what I'll be trying next.

TTC mode is savage, no problems in TTC, so it's either iacv or egbr.

Yup, it was no.7 that was my issue bud. Try and borrow one to see if it fixes it.

Make sure you can re-create the fault with yours quite regularly though. When your dropping down a cog make sure you go from making next to no boost.. to 4krpm+ when you drop. 6th to 3rd always works well

TTC mode is savage, no problems in TTC, so it's either iacv or egbr.

Did the tank hold the actuators open ok once you had stopped?

yes, I got a sucking whooshing noise an hour after stopped, so the tank is still pressurised without leaks.

Should hopefully have some VSV's coming my way..........funnily enough, I've owned them before as they're from my old car

good info here. my old one used to do this but only sometimes, now i know, i will check as i have the same turbos and vsv's from my old engine installed