boost problem

[frazz]

hi,
I've just plumbed up my boost gauge to the pipe from the ecu and took it on a test drive and i've found that it's only boosting at 0.5 bar when it's on idle the needle sits at -8 vac, does anyone know what s2's boost at standard or what problems i might be having. I've always thought that it was down on power.

[vcosmin]

I think that 0.8bar on 3b, and about a liitle more on ABY 1-1.2 . You have to check, with vagcom, check n75 WGFV, and the check the pipe conected to MAP, check knock sensor. There can be a lot of possible problems, but you have to check them one at a time. PS. i suppose u used a T connecto for pipe to MAP for conecting boost gauge ? right ?

[frazz]

i've fitted it using a t piece, it's had afew quid thrown at it over the last 12 months to try and sort the problem. it's been on a code reader and the only fault it came up with a speed sensor fault on the gearbox but i was told that it wont cause this.

[vcosmin]

i've fitted it using a t piece, it's had afew quid thrown at it over the last 12 months to try and sort the problem. it's been on a code reader and the only fault it came up with a speed sensor fault on the gearbox but i was told that it wont cause this.

Speed sensor ? if the engine was turned off, its normal. There are lots of possible causes, just check them one at a time, it will be great if u had some sparte parts, or a friend with working car, to swap compenents (N75, ECU, etc), a see what is wrong with yours.

[frazz]

don't know anyone close by as far as i know i am the only person in town with an s2. al start by by passing the n75 valve. i've got the wastegate wound in quite abit what if i stretched the w/g spring would that help

[vcosmin]

If you bybpas the n75, the ecu will go in limp mode, no more than mechanical boost, which is given by the spring, 0.4bari is stock. If you increase mecnical boost, by using a firmer spring, you rish to damage your engine, not so good ideea.
http://forums.audiworld.com/s4s6/msgs/150222.phtml

[frazz]

just an update, i've had a mate come out with me on a test drive to look at the boost gauge closely, in 1st and 2nd on full throttle it goes to 0.5 bar then in 3rd 4th and 5th it goes right up to 0.8 bar then comes down and rests around 0.5 bar again at around 5500-6000 rpm, is this normal.

[newsh]

I'd say, as you've tightened the spring down already, there's a very good chance your WGFV is not working

[frazz]

I'd say, as you've tightened the spring down already, there's a very good chance your WGFV is not working

is the WGFV the n75 valve, do you know what the standard boost is, i took it out again today and it doesn't actually go to 0.8 as i said earlier it only goes to 0.7 bar on full throttle and drops off to 0.4 the further up the rev range it goes

[newsh]

Yes its the N75, you wont know what the boost will be cos you've adjusted the spring but basically you should get a step in booost when the throttle reaches WOT and the WGFV comes into play. Anything up to 90% throttle will be at one boost level (0.4-0-6Bar depending on the spring tension) Then when you floor it the WGFV opens and allows the wastegate to close, raising the boost to around 1 Bar or more.
You can do a quick check of the valve, start the car and allow to idle, under the bonnet open the throttle all the way briefly not allowing the engine to rev too much, you should hear the valve tick, if you can get your finger on it you should feel it pulse.
You can test it with VAGCOM too if you have it and hear it clicking with the engine not running..
Oh yes, make sure the throttle is actually opening all the way otherwise the ECU won't get the WOT signal.
I've had this stuff on my car, when I first got it the WGFV was unplugged, that was a nice surprise when I plugged it back in. :

[frazz]

i've always thought that my car was holding back and feels like it has more to give, the n75 valve is that the one on the airbox side of the engine near the DV. so it should boost up to around 1 bar on a stock ecu

[newsh]

Yes, its plumbed into the MAF hose with one small hose to the turbo and another to the Wastegate.

[frazz]

after checking the n75 valve i found it to be working, i found that the throttle cable was pretty slack so i removed the c clip and adjusted it as tight it would go without reving the engine, it now pulls really well untill around 3500 revs and boosts at 0.8 bar then it feels like it misfires and puts black smoke out of the exhaust. i've tried adjusting both the throttle and w/g spring to find a happy medium but the only way i can get to run without missing is to have it how it was. is it possible that w/g spring is worn and can't cope with alot of boost.


i've just been out test driving the car further and i've found the misfire only happens on full throttle, if you keep it at 3/4 way down it's fine and if you back off the throttle when it starts to miss and apply it again it powers through the miss.

[newsh]

OK cool, best way to check the throttle is to get someone to floor the pedal inside the car and then adjust the cable just tight enough so its at WOT, if ts set too tight you might break the plastic quadrant when you floor it.

Is this car a 3b? If so you need to check your static timing.

[frazz]

yes mate, it's a 3b how do you check the static timing, you reckon that an incorrect throttle set up is the cause of this misfire, oh yer and what does WOT stand for