problems dont walk alone...

[prj]

I am very sure that you never got misfire. You are using the wrong word.
Before you were getting a fuel cut...

Are you 100% sure the wastegate spring is in stock condition and the wastegate is not screwed down? Try to run a hose from the turbo right to the wastegate without the N75 in between and check how much boost you will get.

[kirvis]

right, just got to work, and...
still a misfire...

[kirvis]

i have put that standard thingy back in

[prj]

i have took the bov out, and find that the hose that goes from head cover to the hose between MAF and turbo wasnt on. took it for a drive and it looks ok now. will se later on today when ill go to work as its longer journey and it will get more warmed up

I also recommend removing the BOV altogether, that way your car won't bog on gearchanges.

[kirvis]

i have took the bov out, and find that the hose that goes from head cover to the hose between MAF and turbo wasnt on. took it for a drive and it looks ok now. will se later on today when ill go to work as its longer journey and it will get more warmed up

[prj]

N75 disconnected?

[kirvis]

right guys... guess what...?

[prj]

It's ok, don't worry...
But let's get back on topic so kirvis can get his car fixed

[s2_bo]

Yeah your right. I got that completely wrong.. lol.

Sorry

[prj]

If there is no hose going to it then it will open just the same (at spring pressure). The hose is there to apply pressure to keep it closed longer allowing the turbo to make more boost.

Maybe the schematics make it look like the N75 is there to open the wastage. But in fact its there to keep it closed.

Sigh...
How will it open? What provides pressure? It opens because there is pressure going from the turbo to the lower chamber of the wastegate.
If there is no pressure going there, what will open the wastegate?

If you remove the N75 and just run a straight hose to the wastegate from the turbo then your boost will be limited by the spring pressure. If however there is no connection at all between the wastegate and the turbo, it won't open...

When the N75 is OFF, it does exactly that, it just runs air from the turbo into the lower chamber of the wastegate.
When it's ON, then it stops running air to the lower part of the wastegate, so the wastegate remains closed. If you don't connect anything to the lower part of the wastegate, it is like having the N75 ON all the time, thus no boost control.

P.S.
It's not the exhaust gas that opens the wastegate, it is the compressed air from the turbo.

[s2_bo]

If there is no hose going to it then it will open just the same (at spring pressure). The hose is there to apply pressure to keep it closed longer allowing the turbo to make more boost.

Maybe the schematics make it look like the N75 is there to open the wastage. But in fact its there to keep it closed.

[prj]

Can you explain that? If the N75 is unplugged you should only be getting spring pressure boost.

How much are you getting with it plugged in before it start to missfire?

Look at this schematic:

http://www.s2forum.com/forum/showthread.php?t=33383

If there is no hose going to the lower chamber of the wastegate from the turbo, how would it ever open?

[s2_bo]

hmmm... im a bit confused now... and you know you right as ive tried to run it with N75 disconnected from turbo, and couldnt feel any difference

Can you explain that? If the N75 is unplugged you should only be getting spring pressure boost.

How much are you getting with it plugged in before it starts to missfire?

[prj]

No no no, The BOV woant effect it at all! as it doesn't do anything different when the engine is under load then a normal diverter valve... The only time you will notice a diffrenct is just after gear change but its not that bad.
This sounds like way to big a power cut to be anything to do with the ECU having to adapt mixture due to the calculated air being dump to atmosphere.

Agree.

Just for reference, I have had BOVs on all my s2s and RS2 at some point and its never ever coursed something as bad as this.

Yes, but it will still flood engine on gearchange if the air is not recirculated. This is because air that escapes is not metered in any way...

Also if the N75 had lost a hose at worst you would only see .4bar boost. (1.4 bar on the digi gauge) as it would be not diverting pressure to the lower part of the wastegate and therefore the gate would open at spring pressure... Unless its the one going back to the maf hose, if thats off the you will be sucking in uncalculated air but such a small amount woant have such a big effect either...

Incorrect...looking at Paul's pdf, if you disconnect port 2 or port 3 of the N75, then the lower chamber of the WG will not be pressurised at all and the wastegate will never open, thus no boost control. You got it the wrong way around.

Lets get facts right here before we send Kirvis on a mission to undo things that dont need to be changed...

The BOV has nothing to do with the current problem at hand, it will just make the car not bog on gearchanges.

@ Kurvis
If you disconnected the N75 and did not notice any difference, then please check again that everything is connected correctly.

[kirvis]

No no no, The BOV woant effect it at all! as it doesn't do anything different when the engine is under load then a normal diverter valve... The only time you will notice a diffrenct is just after gear change but its not that bad.
This sounds like way to big a power cut to be anything to do with the ECU having to adapt mixture due to the calculated air being dump to atmosphere.

Just for reference, I have had BOVs on all my s2s and RS2 at some point and its never ever coursed something as bad as this.


Also if the N75 had lost a hose at worst you would only see .4bar boost. (1.4 bar on the digi gauge) as it would be not diverting pressure to the lower part of the wastegate and therefore the gate would open at spring pressure... Unless its the one going back to the maf hose, if thats off the you will be sucking in uncalculated air but such a small amount woant have such a big effect either...



Lets get facts right here before we send Kirvis on a mission to undo things that dont need to be changed...

hmmm... im a bit confused now... and you know you right as ive tried to run it with N75 disconnected from turbo, and couldnt feel any difference