Homefry RS2 Setup boost?

[newsh]

mine idles at -15psi and goes to -20psi when you shut off ,is this right,ialso seem to have a fair amount of oil in the boost pipe and pcv system
Theres plenty of boost up to 25psi when you floor it .

Theres actually no such thing as minus 20PSI, Atmospheric pressure is roughly 15PSI. Have a close look at your gauge the vac side is probably calibrated in inches of mercury (Hg)

[newsh]

Is that some kind of threat? I'm really not being that serious about this but here is a young man who has some issues with his car and you're giving him totally confusing advice. I apologise for my comments to you, which on re reading them were somewhat harsh and not my normal style. Might I suggest you apologise to Steve for confusing him.

[A80Avant]

i am not threating anyone newsh, i am merely saying that you wouldnt like me (or your doctor for that matter) to communicate to you in a similar manner that you do to me, simply because your knowledge in medicine would probably be inferior.

Apology accepted.

It appears though that i may also be confused about this matter.

Am i wrong that i am suggesting a possible boost leak to Steve? He is getting lower boost that what he should apparently.I do apologise about the vaccum, but my own experience mislead me as well then.

Which vaccum values on idle are normal then?

[s2_bo]

Glad that got sorted out between you two. I would say let john at it again. I'm sure he can sort it out. Good luck Steve

[Rusty]

Chilax people...

My understanding agrees with John here Vas:-

Under vacuum any leak will tend to suck air in, thus reducing the vacuum as the additional air is trying to equalise the pressure to atmosphere (14.5PSI ish).

Under positive pressure, boost will leak out and thus reduce the positive pressure, again trying to wqualise to atmosphere.

With no barrier in the way, two pockets of pressure will try and equalise to the mean pressure relative to the two masses of gas, teh atmophere can be assumed as infinite compared to an inlet system so it will always be trying to equalise to atmospheric pressre.

I've also done a bit of research into the N80 system and found that the breather line has a one-way valve in it, aka 'the flame trap' this means that on idle air is allowed into the inlet manifold when the IM is lower than atmospheric pressure at idle, taking the fumes from the N80 solenoid with it. However, on boost the breather system is only pressureised up to the one way valve (assuming it's in good condition and not leaking) and not beyond.

This would lead me to conclude that the contribution to poor running of a leaky breather system is minimal in terms of boost leaks, unless there is a leak up to the flame trap. It's only at idle that air entering the system and flowing into the inlet manifold, which is under vaccum, or at high engine speeds with air entering the inlet boot, which is at lower than atmospheric pressure due to the air moving at speed through the tube (bernoulli), that a poor breather circuit will cause poor running and even then, it wil be a minimal effect.

However, as I showed 2 years ago with the alpineweiss, every little bit adds up and if you want your car to be running absolutely correctly then all of these things have to be spot on, there is not point spending £000s on big turbos and exhausts if a £10 piece of pipe is leaking.

Just my 2p

[A80Avant]

thanks rusty. that explains things a lot

[T2Andy]

If any one has one of these as in Rustys pic in good working order i would like to
change mine to eliminate my problem .cheers .

[Rusty]

Won't be much new from Ben I'd guess.

[T2Andy]

Thinking about it i would be better with one of your catch tank kits

[stevieyid]

John ill drop you a pm. I have some Injector o rings somewhere which could explain the screeching noise on boost. There is a thread on here about screeching happening due to injector o rings. Next thing to change i think. Thanks again for your help

[quattro20v]

If i put, let's say 1bar of pressure to the maf hose. How long should the pressure hold?
Longer than 15sek.

Bad injector o-rings makes the screeching sound? Got to look in to that.

[s2_bo]

When you next do a boost leak test just spray some soapy water on to the injectors where they join the IM, it will soon show you if you have a boost leak there or not..


Just for reference the flame trap is actually not a one way valve, that's sits further up the pipeline. -

The flame trap is a ball shaped copper wire device bit like a ball of thick wirewool that is supposed to stop "fire" from leaving the crank case via the breather. In theory it would work very well, although I imagine that 90% of fitted flame traps are coated in oil and if you have a fire in your sump then its all bad news anyway

I think what Andy explains above also means that if the one way valve in the PVC system is letting pressure through you could also end up with a pressurized sump which can lead to blown gaskets etc.
Yet another reason to ditch it and fit one of his catch tanks

[s2_bo]

If i put, let's say 1bar of pressure to the maf hose. How long should the pressure hold?
Longer than 15sek.

Bad injector o-rings makes the screeching sound? Got to look in to that.

Thats hard to say tbh, there is no definitive answer to that for various reasons. Although i would say if it holds 1bar for a minute you can be pretty dam certain that its leak free.


Air can escape during a boost leak test with out even having a boost leak.
The most common place is the turbo oil seals. This normally gives of a bubbling sound as pressure is forced in to the maf hose.

Its not a problem if the turbo leaks air though through the oil seas as boost builds up after the turbine at the cold side outlet.

If you do a test try squirting some soapy water over all the pipe and hose connections, that is the best way by far to find leaks.

[quattro20v]

I forgot to write that, i had soapy water when i tested. About everywhere else but the injectors.

Thanks for the tip.

Btw. a flametrap of 7A

[stevieyid]

If i put, let's say 1bar of pressure to the maf hose. How long should the pressure hold?
Longer than 15sek.

Bad injector o-rings makes the screeching sound? Got to look in to that.

Here is the thread about the injector rings causing a whistling noise under boost:

http://www.s2forum.com/forum/showthread.php?t=37241&highlight=squeeling

Could explain my slightly low boost and also the noise im getting. So changing the injector O Riungs is my next mission