problems dont walk alone...

[prj]

ok ill put the standard bov back on. so u recon it should change straight away?

In standard form there is no BOV.
There is a bypass. Big difference.

Also check your wastegate, is the nut overtightened? Is there a different spring?
From what you described it sounds like you have no boost control at all.

[kirvis]

In standard form there is no BOV.
There is a bypass. Big difference.

Also check your wastegate, is the nut overtightened? Is there a different spring?
From what you described it sounds like you have no boost control at all.

going to have my breakfast and will check it

[newsh]

Maybe a hose came off the N75? Or its connected wrong.

[prj]

Maybe a hose came off the N75? Or its connected wrong.

+1, check that too.
But even if that solves the problem, get rid of the BOV... it still floods engine on every gearchange.

[kirvis]

+1, check that too.
But even if that solves the problem, get rid of the BOV... it still floods engine on every gearchange.

well just like i mentioned i changed N75 to solve the problem, as it was the same with the standard one
ill take the BOV off and let you know is there any changes

[prj]

well just like i mentioned i changed N75 to solve the problem, as it was the same with the standard one
ill take the BOV off and let you know is there any changes

I doubt there will be... the BOV just totally screws up your mixture on gearchange...

Are you really really sure the N75 is connected correctly? Search this forum for "Boost control essentials" by Paul, read that document, and make 100% sure you have connected everything exactly as needed.

As I said, if you have 1 bar boost at part throttle, you have no boost control! Check that the wastegate can open... make sure the spring is not completely screwed down.

[s2_bo]

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...

[kirvis]

well when i fitted the N75 i looked at the thread with fitting instructions. so im pretty sure i fitted it ok.
ok going to do it now. wish me luck

[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

[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.

[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]

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]

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]

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]

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

Sorry