Baffling Boost

[newsh]

Ok well drive it in fourth gear flat out from 2000 rpm up to say 5000 if you've got the piece of road to do it, you should see a max of about 14psi or nearly 20 if the car has been chipped, 10psi is not enough.

[newsh]

Of course a turbo car always pauses slightly after you hit the loud pedal while the turbo spools up, this is known as turbo lag, as the pressure rises you'll see the boost gauge swing from the left hand vacuum side, through the zero and into the boost side and the car will start to take off. The lag on an S2 with the K24 is quite short, with a bigger turbo it would be worse. You should be seeing full boost by about 2500 rpm with the K24. On my car with the RS2 turbo I don't see full boost till around 3000 (but then I get more )

[nip]

Lol tell me about it hp muirt, i went to mrc saturday even doug was suprised at 1 time we went of the boost gauge in 6th over 25psi, i had a boost leak fixed that even changed the n75 valve but its still the same, as far as i know the map sensor is standard it dont always boost this high sometimes it hits 20 21 psi any ideas

[Big_kev]

Cheers for the input so far guys. I will try and take a short video of the gauge while driving from 2000rpm in fourth and post it. I will make the video small in size i promise.

[Big_kev]

Guys

Have managed to take a short video of the boost gauge while accelerating in 3th from 1500rpm. The gauge seems to rise to 10psi and stay there until i take my foot of the accelerator. I used full throttle while accelerating. Is this the correct reading for a standard wastegate. Maybe this isn't my problem after all but it may have eliminated a possible cause.

Here is the film.http://www.ksayers.com/boost1.wmv

[newsh]

No, thats not right, you should be getting around 20psi at full boost. Can you check that the WGFV is working? Start the car and pop the bonnet, get a finger on the WGFV if poss or listen carefully, blip the throttle hard, almost WOT for 1 second, you should feel / hear the valve clicking.
Another thing you could try, remove the fuses for the ECU in the fuse box for a few minutes to clear any faults.
Start looking for boost leaks although you should hear a leak if its that big..
Make sure the WGFV is actually plumbed in right.
Replace the DV if you haven't done so lately.

[Jas11n]

You sure John?
20psi on a 3B? thats 1.4 bar. (unless it's chipped and has a 2.5bar or higher MAP sensor?)

Vid looks to me to show 11-12psi = 0.8 bar or there abouts, stock for a 3B no?

[newsh]

You sure John?
20psi on a 3B? thats 1.4 bar. (unless it's chipped and has a 2.5bar or higher MAP sensor?)

Vid looks to me to show 11-12psi = 0.8 bar or there abouts, stock for a 3B no?

He says its chipped to 285 BHP, which would be similar to a home fry, yes? Also the boost seems to come up quite slowly, shouldn't the needle swing round faster than that? TBH its so long since mine was stock I can't remember but it used to pull hard above 2000rpms with the K24.
If its still on the original map sensor then yes, it would max at about 14psi.

[Jas11n]

Didn't see the chipped bit

[BrianSmith_S2]

He says its chipped to 285 BHP, which would be similar to a home fry, yes? Also the boost seems to come up quite slowly, shouldn't the needle swing round faster than that? TBH its so long since mine was stock I can't remember but it used to pull hard above 2000rpms with the K24.
If its still on the original map sensor then yes, it would max at about 14psi.

Your correct, that boost did climb sooooo slowly and peak low for a claimed 285bhp

Brian

[S2central.net]

Guys - that guage is in inches of Mercury (in Hg), not psi as it would appear everyone assumes, so do the math @

http://www.onlineconversion.com/pressure.htm

1bar = 29.5inHg = 14.5psi

So cold idling at -0.6bar should be ~18inHg (vacuum)
zero boost would be 0inHg (thank goodness)

0.4bar boost (max throttle with WGFV disconnected) would be ~12inHg boost
Double that for 0.8bar with WGFV connected
1.4bar boost would be ~41inHg boost assuming ECU has a 2.5bar MAP fitted

Judging by how slowly this car is boosting and that it never exceeds 12inHg I'd say the WGFV isn't working. Could be faulty or its fuse has blown. Do an output test with VAG-COM or blink method - you should hear it ticking !

psi indeed !!!!!!!!!


Paul

[S2central.net]

Thats fuse 24 for an ABY of course - is it idling funny by any chance as the ISV is on same circuit ? Should be a 10A fuse fitted.

If fuse is OK then do the output test - quick and easy way to check electrical integrity from ECU to WGFV. Of course it might be seized in the safe position and so the car only boosts to the mechnical limit set by WG spring (0.4bar or 12inHg for u).

I have a brand new WGFV spare if you need one in a desperate hurry.

[BrianSmith_S2]

You must have bloody good eysight ive been watching the vid up close in slow mo playback and squinting cross eyed on my 32 in monitor and it does look like -Hg, and above 0 in psi.

Brian

[S2central.net]

Actually my eyesight is rubbish, but the first JPGs posted originally are pretty clear to see inHg on the dial. Wish I'd caught the thread earlier and saved all the postulation !


Paul

[BrianSmith_S2]

Actually my eyesight is rubbish, but the first JPGs posted originally are pretty clear to see inHg on the dial. Wish I'd caught the thread earlier and saved all the postulation !


Paul

On his original jpg i can see HG below 0 'zero' but on boost its quite clearly in psi,

just like my gauge

Brian