New IC

[Jay]

Jay - I am confused by your statements - the Wastegate (through the WGFV) uses the compressor boost pressure from the nipple on the turbo housing.

What have you done to your car? What spec is it? Have you removed the WGFV and just using the spring?

Yep, no WGFV and now take boost staight from before the throtle housing, this works because the compressor take off respond too quick to boost and causes surge (the sound you hear of the turbo spooling up and down) this is not controlled by the ECU!! the waste gate has more time to control boost but you do get a higher boost peak before waste gate control takes effect so becarefull on set up. If you shorten the inlet tract, e.g front mounted throtle I/M this helps overcome the surge. Surge is very damaging to the turbo so becareful!! you need to cure this ASAP

[S2central.net]

Martin this sounds odd to me.
Given the ECU takes the boost signal from the IM, if Mihnea setted boost to be 1.5 max then it should stay that way no matter of the pressure drop before the IM. If you have a bigger total pressure drop in the ilet tract (lets say 0.3 bar instead of 0.2) this only means your turbo will be forced to run at a PR of 2.8 instead of 2.7 (supposing P1=1000 mBar) to have the IM @ 1.5 bar relative.
Still confused on how our ECUs "brain" really behave.


Marco

Well AFAIK, boost pressure is controlled by modulation / duty-cycle on the WGFV. Lets say that a duty cycle of X% produces 1.5bar in the original configuration. The ECU will not, to my knowledge, use a higher duty cycle at the same place in the map to achieve the desired boost value of 1.5bar. The value in the WGFV map is the maximum that can be used at that point.

However, the converse is true - if the ECU produces 1.5bar before all of the duty cycle was required, the WGFV modulation would be reduced to keep pressure at or near the target value. This is often visible on a boost guage as slight wavering/wobbling of the needle. It means that WGFV is set too high, target boost is set too low, WG spring preload is too high or you have unmetered air getting into an otherwise healthy setup.

Paul

[Mihnea]

Paul, the ECU is adaptive in terms of increasing/decreasing boost pressure to reach target pressure. However, AFAIK this is only true on the ABY/AAN/ADU ECUs, not the 3Bs. If it figures target boost isn't reached, it will cycle the WGFV at higher duty cycles until it reaches target boost. However, this is long-term adaptation and you can't notice it in 30minutes...

HTH,

Mihnea

[S2central.net]

Jees - thats news to me !

What kind of %age increase/decrease will WGFV adaptation permit ?

Anyway - I would certainly not have noticed this because of the long term adaptation window.

But as Martins car is a 3B - my response to Marco is correct enough.... Yes or No ?


Paul

[Mihnea]

I'm not sure what the %age is, I think I remember it increases %age in small steps so boost increases in 50hPa steps at once, until target is reached. Now the main problem with noticing that is that in 2nd or 3rd gear for instance, it's gonna take very little time for boost to go up, and then it has to go down again because the revs increase and target boost goes down....

For the 3B it's still unknown to me if this function is true or not, can't see any reason why it wouldn't be, but have no proof of it. So your answer to marco is correct

Mihnea

[4WheelDrifter]

You could help me out here.
I had what i thought was a weird fault a while back. I was overtaking a line of cars (as you do) and the engine just cut out. As I backed off it came back. The car was obviously trying to overboost. When I got home I interrogated the ECU and the WGFV appeared to be at fault. All that had happened was the plug to the valve had come loose. I resecured the connection and the problem was solved. When I thought it got strange was, when I replaced my MAF to Turbo hose at a later date, the pressure lines to and from the WGFV were plugged. (!?)

[4WheelDrifter]

Maybe a Collin's bodge up?

[SteveH]

Martin, I'm not talking about your surging on throttle lift-off (compressor stall actually or something like this) but rather about the pulsing sound your turbo makes when on full boost at low revs.
Mihnea

Mik, I have this pulsing sound on my turbo too. Tom also had it on his old turbo setup. I couldn't hear it until I replaced the airbox with a foam filter.

[martinjs]

Ok, i understand what you mean marco/mihnea , to be honest ive had so many problems since ive owned this car with boost leaks and just about every other possible fault that can occur, and its only just recently when i finally got it properly mapped that it has run ok, well i thought so until mihnea noticed the strange noise (i didnt notice it to be honest).
so to cut a long story short i need to get this manifold finished to see if it cures it?

martin

[SteveH]

Martin, as I mentioned in my earlier post, I have this pulsing sound too. It must be caused by something other than your intercooler/hardware setup.
Mik, could the sound be the turbo hitting the surge line?

[martinjs]

What does all this surge line stuff mean, what actually makes the sound? im not that clued up on turbo dynamics

[SteveH]

Try this for a bit of bedtime reading....

http://www.automotivearticles.com/Turbo_Selection.shtml

[audiman]

Doug that video clip was when i had the Lamdba unplugged and it was making that noise. It doesnt do that anymore, its a more 'even' noise

[S2central.net]

Try this for a bit of bedtime reading....

http://www.automotivearticles.com/Turbo_Selection.shtml

and this one It shows example turbo maps running close to the surge line.

http://s2central.net/Turbology_v4.pdf

[Mihnea]

Steve, what RPMs and what boost levels are you running when it's doing that pulsing sound? I would think it could be that, although the RS2 turbo can run ****loads of boost in an RS2 or an ABY (Sal running 32 psi for instance) without doing that sort of sh*t....

So, young Thomas, your turbo actually sounds better when the lambda is connected rather than when it's disconnected? **** me if I know why that is so...