Leaky dump valve

[ailwyn]

I have a leaky dump valve (wait for all the humorous replies), which means it's cracking open well before it should.

Have accepted that I need a new dump valve, however it would strike on the eve of my jaunt to Scotland, a 1000 mile round trip.

I have sent off some begging PMs to people I think may be able to help in the timeframe I have, but my main question is am I going to get any major problems running the car as is.

Currently I can't get more than about .25 bar of boost and hear the air leaking out if I pick the revs up above 4k or push the throttle down a bit too fast. It will still cruise at over 80, which given I have a nervous passenger will probably be as fast as I go, but don't fancy knackering the engine because of it.

Any advice appreciated.

Ailwyn

[Monty]

Ailwyn,

What about removing the DV and put in a blanking plug until u get a new one.

[ailwyn]

I could take off the Dump Valve and be left with the T piece of the fitting kit, but any ideas what I could use to blank it?

[John_W]

I could take off the Dump Valve and be left with the T piece of the fitting kit, but any ideas what I could use to blank it?

I agree with Monty. Just take it off and blank off all holes. If you leave the samco hoses attaached, just stuff a bit of wooden dowel (a bit of broom handle?) up it and clamp the jubilee clip up to keep things airtight.

JOhn

[ailwyn]

Thanks both for the input. I have removed the valve and inserted the top off a plastic brush handle, looks like a solid piece to me, so should be airtight, and used the jubilee clip to clamp it up.

Further development though, while I was pondering how to blank off the "pressure" hose, where I tapped into the boost transducer hose, I noticed a split in the old hose. I have no way of repairing that tonight so as the dump valve was already out, I coiled up the thin samco hose and plugged the dump valve end onto the T-piece, so the boost transducer is now not connected, but there is a samco "loop" on two of the three points of the triangle. I have done this on the assumption that the boost transducer (on the R/H wing) is only used for the boost gauge and not used by the ECM.

Any advice, criticism or agreement for that course of action greatly received.

Thanks

Ailwyn

[Monty]

Should beable to get a vacuum hose from a motor factor shop, u want a 3mm bore. Or just cut up the one u was using for the dump valve

[ailwyn]

Monty,

Thanks for the advice, will probably hack up the hose I've currently got.

My immediate issue seems to be resolved though by what I've done, just took it for a run and she's back to her old self.

My question still stands, does the transducer on the R/H wing only supply the gauge or does it supply the ECU too, if it does supply the ECU I will be back in the engine bay at 5am, otherwise I'll leave it as-is until I get home and sort it all out properly.

Ailwyn

[Ultimatt]

Ailwyn,

The electric boost sensor only feeds the guage. I replaced mine recently with a more accurate air pressure guage rather than the electric original. I've had no problems.

And in response to one of the earlier questions, the Plenum is at atmospheric pressure when the engine is off and runs at about -0.5 to -1 bar when engine is idylling or on overun. When throttling up it goes into positive.

Matt

[ailwyn]

Matt,

Thanks for that, my bodge should last the weekend then without ill-effect.

Ailwyn

[ailwyn]

Ok, it's been about a month since I patched up my leaky dump valve so I thought it was about time I thought about removing the broom handle top that was stuffed in the hose and fix it properly.

I have fitted everything back as it should be, removed and re-fitted al the air hoses and still have a leak... I would like any thoughts on whether this sounds like a broken dump valve or leaky piping.

When the engine is idling the dump valve is open.. if I pinch the hose from the boost transducer to the bottom of the dump valve with my fingers, it closes.

If I pick up the revs, it closes.

When driving, I have no problem until the boost comes on and the dump valve opens.

My suspicion is that the dump valve is broken, but I'd just like other peoples thoughts before I shell out for a new one.

Thanks

Ailwyn

[John_W]

My suspicion is that the dump valve is broken, but I'd just like other peoples thoughts before I shell out for a new one.

Ailwyn,
That would be my guess too, but before spending that amount of money I'd like to eliminate everything else first. I don't know how you plumbed in the broom handle, but if that was a straight swap for the dump valve, with all piping remaining in place but blanked off, I'd say you have the culprit.

Or maybe you've stumbled upon a demon broom handle tweak which performs better than a dump valve.

If you can wait until Donington, you're welcome to try a swap for my Bailey DV30 to see if it performs as well as your go-faster broom handle. You never know, after this year's Donington maybe everybody will be running with a mountain chip and a broom handle. Do you intend to do any further development work, and if so will you offer the same sort of cheaper upgrade deal as Alan does for the chips? I could do some dyno comparisons for you if I get a special price.

John

[Monty]

Ailwyn,

What type of DV is it? Is it a recirculating type? Just wonder have u got it plumbed back to front as i can`t understand why it`s working in that way.

Can u take a pic of the DV in position and were the Vacuum hose is plumbed in?

[ailwyn]

Monty,

It's not a recirculated DV, just the straight to air one.

Main connector is plumbed into the plenum hose by using the Bailey fitting kit, the small connector is hooked by T into the hose that runs from the plenum to the boost transducer.

I think it's the spring in the dump valve has gone, which then explains why when at idle (and there is a vacuum) the small connector can draw the DV open, and when I pinch the small hose the DV closes - no vacuum means the spring can return the DV to closed.

As soon as boost comes on the spring must be giving out and letting the air escape.

John, Jay,

As the top of the broom handle is lighter than the dump valve, I guess it would be an upgrade, and Lotus approved - add lightness

I can supply in quantity for a very reasonable £30 + postage.... let me know if you're still interested

Ailwyn

PS John, thanks for the offer but I think I'll just go ahead and order one - I'm 99% certain it's the culprit.

[John_W]

It's not a recirculated DV, just the straight to air one... I think I'll just go ahead and order one...

Ailwyn,

This time why not get one of the recirculating types - Bailey DV30 or the Forge DV006 - as they are silent. Or are you wanting to do a Stevo (dump valve whooshes throughout the Callander Classic team autotest - in reverse).

John

PS: shame you've decided against the broom handle - I was going to suggest a group buy.

[GeoffSmith]

... I think I'll just go ahead and order one - I'm 99% certain it's the culprit.

Why don't you try taking it apart to see if you can fix it - far more fun, you've go the broom handle as a backup and you might be able to avoid paying out £100. Just think of the advantages - "Yes I know I spend a lot of time on LEC dear, but it's just saved us £100".

Thinking about it, bring it along tomorrow and we'll have a go. Oh, I forgot, you're not coming - who was it suggested Sundays!

Geoff

[dapinky]

Ailwyn,

I've got a DV24 sat in the corner doing nothing except gathering dust until I get round to fitting it. (not likely this side of Donny!)

I can stick it in the post to you if you want to give it a try to see if it is yours at fault?