Volumex vent pipes

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dglitten
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Joined: October 9th, 2008, 4:46 pm

Volumex vent pipes

Post by dglitten » March 19th, 2011, 9:05 pm

Hi Guy

Chasing a leak in my manifold I pulled the engine out for easier access. The only leaks I found was related to the hoses connected to the 2 vent pipes and blower vent pump. Unfortunately I also found that the vent pipes does not seal up in the housings. Both pipes leaks around the upper side pipe (picture).

Is it possible to remove the pipes, clean the bores in the housing and refit without dismantling the supercharger? I have read the topic “Volumex Rotor Condition” and the pictures point in the direction that a dismantle is needed.

Best regards

Dennis
Attachments
volumex_leak.JPG
volumex_leak.JPG (176.65 KiB) Viewed 1573 times
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Guy Croft
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Re: Volumex vent pipes

Post by Guy Croft » March 22nd, 2011, 9:15 am

You can remove them, at the back end (RH) you need to remove the rear M8 nut. You should lever them out gently between the horizontal 'T' section pipes where they are strongest. If you bend them they will split.

They are supposed to be sealed in place just with a bit of silicone sealant on the ribbed tails of the T sections.

How clean the vent galleries are inside is another matter.

G
Attachments
VX vents.jpg
here you can see the vent gallery that gets blocked with carbon thus allowing gas & fuel vapor from main casing into the rear bearing pack
VX vents.jpg (64.79 KiB) Viewed 1536 times
VX vent tube.jpg
refitting the rear vent tube as described above
VX vent tube.jpg (115.09 KiB) Viewed 1536 times
VX F&R bearing housings as-is.jpg
those above are cleaned ones, though of course they look like this or worse when you strip them down, and sometimes I see them were carbon has filled the entire region behind the seals rendering the vent system ineffective.
VX F&R bearing housings as-is.jpg (118.09 KiB) Viewed 1536 times

cstorry
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Re: Volumex vent pipes

Post by cstorry » March 22nd, 2011, 4:22 pm

Can you refresh my memory why they are needed again ?

I seem to recall that they are used to evacuate any fumes from the compressor housing following a switch-off ?

What I mean is - can't they just be blocked off ?

I note that the bigger blowers (e.g. R10 Volumetrico) don't have any such venting.

Thanks
Chuck
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Guy Croft
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Re: Volumex vent pipes

Post by Guy Croft » March 23rd, 2011, 3:07 pm

Hi Chuck

Here is what I figure these mysterious things do - if you leave them open.

1. On closed throttle they suck in
2. On boost they blow out

Case (1) they will suck pure air into the casing.

Case (2) they will tend to blow fuel/air/misfire products into the bearing housings - the seals there are oriented to keep the oil (front) and grease (rear) where it belongs. Whether the seals are strong enough to prevent this I doubt, judging by the level of carbon I find in there on overhauls.

How much boost is lost by allowing them to blow out I don't know but on VX units I've driven it certainly didn't impact on the performance and the diligent owner might well route them back into the air cleaner.

Over to you..?

G

cstorry
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Re: Volumex vent pipes

Post by cstorry » March 24th, 2011, 4:41 pm

I guess since the air and fuel are mixed/metered upstream of the compressor that it would not be a good idea to mess with that by leaving those tubes open.

I'd have to dig out a manual for one of the volumex cars but I think the tubes attach to an evacuation pump that is operated by some sort of timer immediately after the engine is switched off - resulting in the pipes normally being closed off during running.

My guess is that most of the pumps no longer work - mine certainly didn't and I didn't bother to replace it.

I was just thinking that if you were faced with the inability to repair or find replacement tubes that blocking the holes in the compressor (tap and some sort of plug) might be perfectly acceptable.

Chuck
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