Do these boost pressure test figures look ok?

[Jonas_R]

Block of WG. block off PVC system (running with a catch tank)

Pump up the system to 2 bar:

This is the time that elapsed each time the pressure dropped 0,1 bar:
2-1,9bar = 23 sek
1,9-1,8bar = 54 sek
1,8-1,7 bar = 1min and 17 sek
1,7-1,6 bar = 1 min and 40 sek
1,6-1,5 bar = 1 min and 56 sek

I cant hear any air escaping.

But is this oki? I am going to run around 1,6-1,7 bar peak.

Seems a bit strange that it cant hold the boost pressure, but I guess it just cant. Tried going up 2.2 bar, but that made the bund pop, not nice

/Jonas R.

[S2central.net]

Impossible to say...

Only way to reliably pressure test the inlet system is to apply pressure to the hose which connects to turbo output, whilst the throttle body hose is bunged solid (including the ISV link) - this should be airtight and avoids the PCV and WG system.

Pressurising at the MAF hose is OK as long as you know there is possibility of blowing air past the oil seals in the turbo - this is what mine currently does (gives a bubbling noise in sump - weird).


Paul

[Jonas_R]

Sorry I did not make myself clear then.

I have bunged off PVC system, and hose to WG.
Then I have a bung into the MAF and a bung at the throttle body hose, as you described. But I cant pressure at the output of the turbo, dont have a bung that fits there.

But if I understand you correctly then, air can escape through the turbo oil seals? When I did the pressure test at 2 bar, I could not hear air escaping anywhere, there where no sounds, other the me breathing

/Jonas

[S2central.net]

Thats the problem with pressure test at MAF hose... Impossible to know if air is leaking past oil seals (unless loud enough like on my old old turbo) With all the bungs you have in place it should be airtight. Suggest you pressurise from turbo output hose - although I know it needs an abnormal bung - BUT its the only way to know that your intercooler, pressure pipes and connecting hoses are airtight.

I have a collection of bungs that I got made up so I could pressurise the system from different places.

I suppose the only other alternative for you is to bung the oil lines where they connect to turbo but thats potentially rather messy and you need fittings the right size to do it properly.


Paul

[Greg_S]

Jonas, if you wanted to check if the air is escaping through the turbo seals you could seal off after the turbo to double check

[Jonas_R]

Yeah I guess you are right, but ic, and all hoses are new samco's so they should be fine.

But I aint getting any cutoff's and car pulls fine, so maybe I should get it a rest

[Jonas_R]

Greg:
The turbo have just been refurbed, so should air be escaping on a refurbed turbo?
But I dont have any bungs to plug off the hose

But on the other hand air could be escaping through the MAF bung, I mean at 2.2 bar the system blow off the MAF bung And at 1.5 bar the MAF bung is starting to slide off the hose, but I cant hear any air escaping.

Perhaps I should try with some soap or is water to see if there are bubles anywhere?

/Jonas R.

[S2central.net]

Gregs idea is sound also... My bets you have air going past the oil seals - normal enough though i have seen some cars airtight thru them !

I've just remembered that I have a recently rebuilt RS2 turbo (with cracked hotside) that I could test with - be interesting to see if the oil seals on that are airtight.

Just need some old hoses, clips and bungs and kick the compressor into life....

Mmmmmm - I love being off work !!!!


Paul

[dkw_dude]

Block of WG. block off PVC system (running with a catch tank)

Pump up the system to 2 bar:

This is the time that elapsed each time the pressure dropped 0,1 bar:
2-1,9bar = 23 sek
1,9-1,8bar = 54 sek
1,8-1,7 bar = 1min and 17 sek
1,7-1,6 bar = 1 min and 40 sek
1,6-1,5 bar = 1 min and 56 sek

I cant hear any air escaping.

But is this oki? I am going to run around 1,6-1,7 bar peak.

Seems a bit strange that it cant hold the boost pressure, but I guess it just cant. Tried going up 2.2 bar, but that made the bund pop, not nice

/Jonas R.

Sounds like it is in better shape than mine.
I pressure tested my 3B a while ago the same way (blocked WG hose and PVC system) plugged the turbo to IC hose and inserted compressed air. It dropped from ~2Bar to ~1Bar in 12 seconds or so , at the same time there was hissing noises from the intake area couldn't find any leak (sprayed the area with soap water). Sounds like the rings are worn? Did a compression test test, it was 12-12-12-12-11,? Bar so that should be ok.

[S2central.net]

Air will always escape past rings if you don't bung pressure pipe at the TB hose...

You just need to verify the boost hoses and intercooler are airtight with a pressure test.

Need to test PCV, breather and WG separately... Assumes TBV is airtight ofcourse and all the pesky narrow guage hoses.

Paul

[newsh]

Air will also leak at the TB pivot.

I'd say your times are pretty impressive, my reasonably new RS2 turbo leaks past the seals faster than that. I get no bubbling noise though, must leak on the return side, after testing I get a lot of oil in the exhaust which smokes like mad when I start up, shocking for my carbon footprint..

[S2central.net]

Just for the record... I rigged up my boost leak kit and various bungs to the cold side of a couple of turbos tonight. The first was a recently rebuilt RS2. The 2nd was a big mileage S2 turbo.

Used factory MAF hose attached to cold side inlet - all bunged with air coming in from where the MAF connects and factory hose to the intercooler which I bunged as well. Did this just on the bench with nothing else connected to turbos.

Both leak air past the oil seal(s) - I could hear the air getting into the centre housing of the turbo at the oil galleries... With my fingers blocking the galleries, I could obtain a little more pressure at the MAF hose, but the damn bung popped out before hitting 1bar... I was using an old hose clip that I didnt trust to tighten too much.

Impossible to say that the newly rebuilt turbo behaved any better in this regard - I can't see how an ordinary oil seal would ever be airtight when in this test mode. Don't forget its a bit of an unfair test as the MAF hose is *always* under vacuum so in the real world we dont present the trubo oil seals with pressurised air.

I can see how an oil seal failure in the trubo would cause oil to be sucked into the engine though !

Paul