No boost with baily dv30

[T3rra]

Hi,

The standad dump vavle on my 88 turbo(250) was dignoosed as faulty. Iv removed it and checked the Diaphragm by forcing it up with my finger then covering the vac hose nipple with another finger and releasing. Diaphragm fails 2 stay up.

However the car runs well, builds boost about 2.8k rev and is reading 1.8 bar on the dash by 3.2k

Got hold off a 2nd hand baily dump vavle d30 the type recommended 4 stage 2. Which I will be at one day. Checked the baily and the diaphragm holds in place. However once on the car done build boost till about 4k revs and I'm only seeing 1.4 bar on the dash and the car is clearly much slower.

Checked all the vac small vac lines and put back the old dump vavle car builds boost again like b4. 1.8 bar( 0.8 bar )

At 1st I thought it could be the vac nipple and line getting pinched closed with the bonnet shut as it slightly higher and facing up wards, sealed the nipple over 2 an elbow and I'm still getting the same issue.

Iv taken apart the baily, found the spring 2 be 40mm could the spring be 2 strong? Or 2 weak?

Another thing I noticed with the baily is once car is turned off air remains in the vac line Cas it hissss when pulled off.


Thanks.

 

[944Turbo]

Not familiar witt the bailey, but sounds like the actual valve isn't sealing - as you say the spring could be too weak or the seat could be damaged.
Tony

 

[T3rra]

So would the valve be staying open rather then shut? Just boost build fine with the Bosch type that's clearly lost its resistance.


Thanks

 

[944Turbo]

Yes dumping the boost back into turbo inlet rather than allowing it to build,
Tony

 

[T3rra]

Iv spoke with baily today, they offer a rebuild service £37/8 however they currently have no tops and won't 4 a least 4 weeks. They think it's wear on the top and pistion, causing it 2 stick once hot.

Will try and return the bov and just fit bosch 993 one with the brass centre ring

 

[T3rra]

Just out off interested, what sort off boost build up are people seeing? Stock and none

 

[944Turbo]

Long time since I looked at standard BOV's but If my memory serves me, I think saabs use the same BOV as the 993 as well,
Tony

 

[944Turbo]

oh and for boost graphs http://www.cannell.co.uk/944%20UK%20League.htm

 

[T3rra]

Iv read Saab are upgrade over 993

 

[944 man]

Theyll run perfectly well without an air bypass valve Terry.

 

[T3rra]

Really? So if I ran with out bov would I get base reading that I could work from?

 

[T3rra]

944 man, what do u mean about running without? As I think that would make sense off why it's running ok with the faulty Bosch bov.

Once removed and tested the diapham don't hold. I tryed a baily and had the issues above. Thinking the baily was also faulty I got another Bosch type. But the Saab type with the brass ring. And now I'm getting same issues as b4 with the baily.

The Saab unit was used as it was easy 2 source and works off the car.

So could a wrong vac hose set up be possabile? I don't think there's anyleaks, hoses are new. And I swapped like 4 like position wise. Also with the Saab and baily I get a release off built up air when i pull the vac line off the top off the bov after the engine turned off.