Too little boost, solenoid, MAP or something else?

[jimmydanny]

Hiya\'ll!

 I got a FC3C TII, S5. Before, I got my 7-9 PSI, whatever is stock, but now I only get 4-5, which means the duty solenoid controlling the boost isn\'t working somehow. It is clicking, so in that manner it works.

 What can cause this to happen? The possible causes that I can think of are these:
 Solenoid, wastegate, MAP, vac lines to solenoid, or my intake being straight instead of the S-shaped rubber one.

 Any other ideas/ways to test?

 Does it matter what way the solenoid is plugged on the vac lines?

[Prof]

If you replaced the intake section, there are a couple of small vac lines that go into it from the vac rack.  It\'s quite likely you have introduced a leak that\'s enough to stop it making full boost.

[TiddlesRX7]

Also check the actuator arm on the turbo is still connected. They have a habbit of loosing their C clip and falling off the wastegate.

Ade

[jimmydanny]

The actuator arm MUST be connected, else I wouldn\'t have that low pressure, I would have too high as the wastegate would never open.

As for the two vac lines, one goes to the solenoid, the other goes to the crank case ventilation, both are connected.

[jimmydanny]

Feck, anyone got convertible window motors lying around to sell? Cheaper the better I need both LHS and RHS.

[m1tch]

The actuator may be connected but how old is it? I changed mine for an upratd HKS unit so that I know the spring was strong enough to increase the boost. I have also seen on another forum where the actuator rod was slightly loose, when I had a look at the back of my turbo the different between closed and \'fully open\' was a matter of about 5mms before it hit the back plate on the turbo (silly design lol) so if its loose then it might be the fact that its simply worn. Also 5psi is the stock spring pressure ie what you would get if you didn\'t connect up any boost controller, might be an idea to check the vac line going to the actuator and the solinoid (they usually click when working).

[TiddlesRX7]

The actuator arm MUST be connected, else I wouldn\'t have that low pressure, I would have too high as the wastegate would never open.

As for the two vac lines, one goes to the solenoid, the other goes to the crank case ventilation, both are connected.

Not true. On mine when it fell off I got a really steady boost up to around 0.5 bar and then it just levelled off as the turbo pressure forced the wastegate flap open.

[Prof]

Feck, anyone got convertible window motors lying around to sell? Cheaper the better I need both LHS and RHS.

I have both sides available.  They are heavy so I will weigh one and then let you know how much they weigh and the likely cost of shipping - I don\'t think they will be cheap to ship.
 
Let me know if you are interested - I\'ll probably want £50 for the pair of motors, so it will be that plus shipping.

[Prof]

Not true. On mine when it fell off I got a really steady boost up to around 0.5 bar and then it just levelled off as the turbo pressure forced the wastegate flap open.

^^^ What he said ^^^ with the flapper disconnected, the exhaust gas can just push around the turbine and open the flapper easily.  You\'ll get some boost, but not a lot.
 
When you changed from the plastic double 90 degree induction piping (stock) to your straight intake, what have lines have you got connected to that intake ?  Got any pictures that might help ?

[jimmydanny]

Prof, I got contact with a guy in the US with two motors, but he is charging 100 per motor, which is 60£ per motor, so I\'d go for yours. Only demand is that you can check and confirm that all screws are loose enough to be opened, in case I need to repair or so.

I got both of the vac lines to the intake, removed the return from the stock BOV as I run to atmosphere anyways. Worst case is that I have to drill a hole and find a nipple that fits or weld a 25mm tube to it.


This is an old photo before I drilled up the holes for the nipples, but they sit on the straight part before the turbo.

[Prof]

Are you using the stock BOV like a vent to atmosphere one ?
 
You may run into some issues if you do, as they are a bit \'leaky\' providing some bypass air for idle.  It\'s not an issue when they are setup as a recirc, but you may want a proper after market bov that has twin piston setup so it can seal off the intake to air leakage under vacuum.  For the same reason people have issues with some dump valves.
 
With the stock boost solenoid, the actuator is fed from the output of the compressor, but the line that feeds it has a \'T\' junction, which goes off to the duty/boost solenoid and then vented back to the induction.  The idea is that some of the boost is bled off so the actuator doesn\'t see the full boost, causing it to allow higher boost to be built before it opens the wastegate, all under control of the ECU.
 
Normally, with a good flowing exhaust, and intake such as yours, simply piping the compressor output to the actuator will probably get you 8psi of boost easily, but the actuator spring is weak, and if the wastegate has been ported to allow larger bypass flow, then the flap area that the exhaust gas works against is much larger (upto 50% more area) so will open more easily.  This causes the boost to bleed off.  If you don\'t port the wastegate you run into the opposite problem of boost spikes or boost creep which is just as bad.
 
 
The best way to fix it is:
 

• Port the wastegate - if you want to run higher boost you\'ll need the flow
• Upgrade the actuator - the stock one isn\'t really much cop - the HKS actuator is a good replacement
• Remove the stock boost/duty solenoid and fit an aftermarket controller
• Use either an FCD (not so good) or a piggy back or standalone ECU to control the fuelling and remove the boost fuel cut

You\'ll need to do all of those things to get more boost than stock and keep control of it, but the effort is worth it.  Don\'t forget the stock solenoids are old and tired now, and probably not working as well as when they were originally fitted.
 
With regard to the \'screws\' on the hood motors - which ones?  The units came off a car I scavanged parts off, and I tested both motors were working at the time.

[Prof]

Jimmy,
 
I misread your post earlier - it\'s window motors you wanted, not hood motors !
 
I have those also, and they would be cheaper to ship !
 
I will test them on the car before I take them off, and can video it to show they are working.  I hope to start taking bits off as soon as it stops raining - so give me a couple of days !!
 
Dave

[jimmydanny]

Price? I really really need them, my dad is paying to get my car sealed before the next storm comes in here, which it usually does pretty fast

Hood motors? WTF is that?

[jimmydanny]

Btw, you don\'t have a idle regulator? What its called? idle control valve? Anyways, S5 TII engine, JDM, if that matters.

[Prof]

Sorry don\'t have a spare BAC valve...