No.1 Turbo not boosting correctly??

[Guest Bainesy36]

Hi there everyone,

 

I've just realised today that Tubby No.1 isn't spooling correctly. I've just been back out to try and get a good description of what it's doing for you to help me. This is an intermittent problem, but it doesn't make boost more often than it does.

 

When rolling on from low revs (1500'ish) with half throttle sometimes it will boost to 0.7Bar o.k. and as throttle increases this holds before No.2 takes over nice and strong up to 1.2Bar. Other times, boost will remain at 0.1-0.2Bar on No.1 and not build at all, with what I'd describe as a whirring noise from the engine. No.2 will usually pick up and boost o.k once the revs reach 4000rpm (not always though). If I put my foot flat on the floor from low revs, No.1 usually stays at approx' 0.1-0.2Bar, but when I release the throttle and re-apply quickly the car will suddenly build boost, but sometimes only to 0.5Bar.

 

I have checked the resistance of the IACV, EGCV, EGBV and Wastegate VSV's and they are all o.k. I have found a couple of split hoses (minor) in the engine bay (not 100% sure if they are all part of the turbo system) and repaired, but the problem is still there.

 

Any ideas as to what/where my leak or fault could lie and is the whirring noise something to worry about. I'd like to check anything you suggest this weekend before possibly visiting Chris Wilson with the car if I can't get to the bottom of it.

 

Thanks in advance,

Nige.

[JamesRZ]

weird im having exactly the same problem. Let me know if you find out what it is.

[Steviekid]

There is nothing mechanical stopping the first turbo from spinning up (unlike the second) so as far as I can see there can really only be one of three problems.

 

1. A duffed turbo. Unlikely with an intermittent problem like this where you're sometimes getting 0.7 bar ok.

 

2. The wastegate sticking open. Stick a foot pump directly onto one of the actuator pipes and block off the other one. It should start to open smoothly at 12psi and be fully open by 18psi.

 

3. A boost leak. Could be a hose, a sticky BOV, etc. Happy hunting!

[Guest Bainesy36]

Thanks for the replies.

 

I found the problem today and it has also cured my No.2 Turbo intermittent problem as well. The hose connections on the IACV VSV were fitted the wrong way round, causing the feed from the pressure tank to vent through the exhaust of the VSV and not hold pressure sufficiently to operate the IACV and EGCV actuators all the time (if I understand it correctly, but if I'm honest I still don't get it although it is definitely working now). No sucking noise when removing the hose from the pressure tank to the VSV rang alarm bells! Checked with the picture below and realised the hoses needing swapping. Once this was done and along with the other split hoses I've repaired in the past (one from EGBV VSV to Actuator), the car now boosts fine on both turbos. Phew!! :d

 

http://www.mkivsupra.net/vbb/attachment.php?attachmentid=13928&d=1112558665

 

The car has been like this since I've had it, but being new to everything, I wasn't always looking at the boost gauge at low to mid revs (just checking when full boost on No.2 for safety). With this sorted, I can safely say, these cars really do pull well from low down, much better than TTC now I've experienced both.

 

Good luck with your problem James, possibly something like this or more likely a split hose somewhere. You could try the TTC mod' quickly to prove some of the actuators and valves etc to narrow it down a bit. Plenty of advice on here.

 

Nige.

[JamesRZ]

yes it was a split hose on the IC, shouldnt have bought a cheap hosing kit for my FMIC!!