recommend me a recirculating dump valve

[Paul Alexander]

hi folks,

the dump valve fitted to my elan is the whoosh type, but i want to change it for a recirculating dump valve. can anyone one recommend one?

cheers.

[Candles]

Hi,

I had a Bailey DV30 for ages, but then the piston started sticking so I replaced it with a champagne cork. Whilst this was 100% is keeping me on boost, it didn't do any dumping or recirculating, so I bought this:

DV on Amazon

It went in just the same as a DV30, recirculates and has 3 spring options. I can't comment on the longevity or pedigree of the part, but I can say that it is beautifully machined and works (I can hear it).

[Enright]

http://www.ebay.co.uk/itm/SAAB-900-9000 ... 28052b98f3

[Candles]

Or just take out all our 1990s technology and install this:

Isn't eBay ridiculous?

[HJ2]

Hey, that's bogus! It does not even have a turbo confabulator!
https://www.youtube.com/watch?v=yefVpB5GEio

[rip]

Hey, that's bogus! It does not even have a turbo confabulator!
https://www.youtube.com/watch?v=yefVpB5GEio

Lots of fancy nonsense jargon in there!

[lotusflasherman]

Getting back to the original request ..... Bailey DV30 very good but bit like 'rocking horse sh1t' these days.. cheaper options available but have no experience of those.

Fitted a Bailey DV30 to my Elan about 15 years ago . I got that from Bailey's - found I was driving past their place on a farm near Royston, Hertfordshire so called in. Guy came out and looked under bonnet of Elan, showed me 'the where and how' and supplied DV30 ( blue to match the car at no extra cost), fitting kit FK90 and a couple of extra bits for it to vent into the air filter housing so it's totally silent - well probably not, but I can't hear it working, just feel it, which is how I like it..

Test drove an Elan with the loudest BOV I've ever heard and the seller thought it wonderful ..

The DV30 has worked fine since but Oct 2013 bought another Elan and SORN'ed the original. New acquisition didn't have a dump valve and found Bailey DV30's seemed to be on 'back order' so 'borrowed' set up from SORN'ed Elan and started looking around at alternatives on ebay. Spotted another blue DV30 secondhand on ebay and that cost me £75 including p&p. You can get new ones made by others cheaper than that but I know where I am with DV30's. Pretty simple technology so don't understand Chip's problem.. Can I have the DV30 with the sticking piston please Chip?

Recently bought a FK90 so I'll be able to put the SORN'ed Elan back together sometime...

[rip]

Spotted another blue DV30 secondhand on ebay and that cost me £75 including p&p.

I didn't realise Bailey's cost that much.
I believe a Greddy RS BOV costs about £50. It is atmospheric but the outlet is a round hole so you can buy a recirculating adaptor for it. I have mine fitted but it does not recirculate: the output is hosed to a filter so the sound is muffled so much it is difficult to hear.
I used my BOV in atmospheric mode for a couple of months but then I got tired of the whoosh sound.

There is a subtle difference between a Blow off valve & Dump Valve: A BOV has an input from the engine side of the throttle. When this is closed, the pressure difference across it causes the valve to open. I believe a DV simply opens when the inlet pressure is too high.

[dapinky]

It's all down to budget, really.

Basically, the Bailey DV30 fitting (1" pipe) that you already have dictates the type to replace it with - i.e., replacing with a Greddy flange-type isn't as straight forward, but still do-able.

If you are on a limited budget, then the S/H SAAB units above will do the job.

Basically, the same unit is OE equipment on the SAAB, VW (and varients) 1.8 turbo and other cars - so that is the fitting-type required.

If you are going to buy S/H, then it may be worth bearing in mind that the Bailey units (whilst good when working), are not considered to be a 'servicable item' - although they do come apart.....

On the other hand, if you can find a S/H Forge DV007, you can get a service kit and re-build it to 'new' condition, with whatever springrate you require.

If there is more in the budget, then I would suggest a new Forge DV008

[Fredjohn]

I have a non-recirculating Forge fitted. I refurbed it with a service kit for a very reasonable amount. I also wrapped carb. filter foam around it to act as a very effective silencer. I'd certainly recommend the Forge brand, if only because of the ease of service.

[lotusflasherman]

Spotted another blue DV30 secondhand on ebay and that cost me £75 including p&p.

I didn't realise Bailey's cost that much.
I believe a Greddy RS BOV costs about £50. It is atmospheric but the outlet is a round hole so you can buy a recirculating adaptor for it. I have mine fitted but it does not recirculate: the output is hosed to a filter so the sound is muffled so much it is difficult to hear.
I used my BOV in atmospheric mode for a couple of months but then I got tired of the whoosh sound.

There is a subtle difference between a Blow off valve & Dump Valve: A BOV has an input from the engine side of the throttle. When this is closed, the pressure difference across it causes the valve to open. I believe a DV simply opens when the inlet pressure is too high.

Huh??? In my world of engineering the words are interchangeable ... most of us hoover the carpet with a Dyson but life is too short to get hung up on semantics .

The Bailey DV30 (and that's DV for DUMP VALVE) has an input teed off between the manifold and gauge transducer so you're wrong on that definition. Same as 'pressure relief valve' and 'blow off valve' are interchangeable, the weight on top of a pressure cooker is a Blow Off Valve and I don't see a throttle on the pressure cooker.

[Elannewbie]

Does anyone know what the spring rates of the three springs supplied with the forge DV008 are off the top of their heads?

Or to put it another way which colour spring for what p.s.i of boost?

I say three springs as one is already in the valve, and there are blue and yellow springs supplied as alternatives.

The yellow Spring is "softer" than the blue.

Kind regards

Grahame.

[Fredjohn]

Grahame

Rather than confuse you with my explanation, try this link to Forge's own site and their definitions.

I have a Forge fitted and used their service kit with the appropriate spring included, after having a chat with them.

I think I have either the FMVD001 or 004 fitted, can't remember exactly, but I sent them photos and they identified it and supplied the right service kit.

[Elannewbie]

Ah brilliant! Thanks FredJohn that was pretty much the info I needed. I said In my post three Springs, and one being inside the valve, I'm guessing that is probably a green spring (weakest). Forge state that the spring rates do not directly relate to the boost pressure being run so, I think i'll start with no valve and note indicated boost pressure. Fit the valve and note indicated boost pressure with the green spring - if indicated boost is low (hence boost pressure opening valve with throttle open) then try the next strength spring until valve only opens when throttle is shut.

Kind regards

Grahame.

[dapinky]

Graham,

I'd start with the green spring and see how it goes. If you find that it is dumping too soon (or on slight throttle), then go up to the yellow one..... it's all a bit 'trial and error' really.

[Elannewbie]

Cheers Dave

Just got to wait to get my car back and then the "trial and error" begins...

Kind regards

Grahame

[dapinky]

Grahame,

just to expand on my last post a bit..... The DV008 (and 007, 006 previously!) are built as a 'universal' fitment item, but designed to be a straight swap for the standard item in VW, Audi, Porche, Saab, Seat etc etc engines.

As such, there is a 'right' and a 'wrong' way round to fit them - the 'correct' way is to fit it in an Elan (or any other aftermarket fittment) what looks sideways.... ie, the port on the side goes to the big pipe full off compressed inlet air, and the port on the bottom (opposite end to the vacuum fitting) goes either to atmosphere, or re-plumbed back into the air filter box.

This looks a bit wrong, but in this orientation the pressurised air will act to hold the piston closed until the manifold vacuum pulls it against the spring and opens it - this means that the maximum boost is maintained, and 'dumped' only when the throttle is released.

If you fit it the other way round (which looks right, but is actually wrong), it will still work the same, with the exception that the pressurised air is pushing against the piston and trying to open it..... as such, it is putting far more pressure on the spring to hold it closed, and if the spring is too weak for the boost, then as you build up the boost, the piston may open a bit, and you will lose the hard-won turbo effect (reduced boost pressure!).

Boy racers tend to prefer this way of fitting it as it makes more of the 'whoosh' sound on throttle release, but it is wasting the turbo effect and turning your car into an NA with a 'whoosh'.

All of the Forums say that if the appropriate spring is used, it will work either way round.... but Forge themselves say to use a weaker spring and fit it correctly for best performance. This is why the pressures listed for the spring have no direct correlation to the boost pressure developed from the turbo - it is merely limits the point at which the vacuum overcomes the spring to open the piston and the level of boost is immaterial.

As a rough guide, any 4-cyl engine develops the amount of vacuum for a green spring, a 6-cyl may need a yellow spring and an 8-cyl uses the blue spring - but that is purely a starting point!

(I'm on a green spring with no problems, running an Everest chip - if it was fitted the wrong way round it would probably need the Yellow spring to still hold full boost properly - unfortunately, I only found all of this out after I decided that my Bailey DV wasn't working properly due to a weak spring (which isn't user changable), so got an old Forge 007. The Forge was better but still leaked boost, until I fitted it the right way round.... I have since replaced it with a new 008 as the cost of servicing the old one, replacing the worn piston and a new spring made it an economical viability - - or so I convinced myself!). I have tried the old Bailey fitted correctly, and it's good as gold, so I could have got away with spending nowt at all, but never mind, ehh - It looks good

[epipete]

...... the 'correct' way is to fit it in an Elan (or any other aftermarket fittment) what looks sideways.... ie, the port on the side goes to the big pipe full off compressed inlet air, and the port on the bottom (opposite end to the vacuum fitting) goes either to atmosphere, or re-plumbed back into the air filter box.

So this is the wrong way round? Furthermore I have a small pipe going to the Plenum IIRC.

[dapinky]

So this is the wrong way round? Furthermore I have a small pipe going to the Plenum IIRC.

Pete, I can't see what make of valve you have, but I have to assume that they are all pretty much the same design, so yes, according to Forge (for the information as disclosed above) it is wrong...... (now comes the long-winded explanation - because i know you've got the time to read it).....

.... but it will still work (mainly) as intended, but will open sooner than it should due to the fact that the boosted air is pushing against the piston/spring.

Let me try to explain it in simple terms (because it's how I understand things!).

Now, the numbers I am using are just random ones from the top of my head - all units and values are just for example.

Lets say that the green spring has a value of 5 units, yellow is 7 units, and blue is 9 units - when the valve is standing in atmospheric air, any spring will hold it in the closed position - but some more firmly than others....

the small pipe to the plennum you mention is the vacuum operation pipe - when you open the throttle air is sucked in to the engine, and a partial vacuum is formed in the plennum due to the lower pressure ('coz the air is now in the cylinders!). This lower pressure drops the pressure in the DV by the same amount (due to the hose between them) - but only on one side of the piston seal.

Lets assume that the vacuum pressent in atmosperic conditions are 1 unit - when you have light throttle, that increases to 2, 3 or 4 units - but as it is less than even the lowest spring value, the piston remains closed.

When you floor the throttle and the pressure drops in the manifold, the vacuum may then go up to 6,7 or 8 units. If you have the blue spring fitted it will remain closed, as the spring still exceeds the vacuum, but if you have the yellow or green springs, the valve will open - lets say 10% open for the yellow spring, and 50% open for the green one.... okay so far? (This is just in NA mode - the turbo isn't doing anything at this point).

Hence you need the correct spring rate for the car/engine - nowt to do with turbo boost.

Okay, so if the spring is too weak, and the valve partially opens at full throttle, what does that mean in practical terms? - no great effect on the operation of the engine, but the open valve will allow unfiltered air from the engine bay to get sucked in to the manifold to fill the vacuum void (via the DV) - in the case of a recirculating valve, it will pull air from the unfiltered side of the airbox - again, not the end of the world, but not ideal.

Thus a DV can be fitted to ANY car (not just a charged one) - and is the premise that the kiddies with their Vauxhall Saxos use to get the whooshy noise in McDonalds car park - they just fit a weak spring and let it make 'fast noises' when they push/lift off the throttle.

Anyway, enough of the 'Modified Vehicle Brigade' - back to your physics lesson.....

Once you have selected the right spring rate for the maximum vacuum you will develop (as stated, I use a Green spring) we need to consider what the turbo pressure brings to the table..... sod it, whilst we're still on spring selection, lets leave the theory and do something practical.... "How do you decide which spring to use to start with - other than total Trial & Error?".....

Firstly, see what other people have used in the same application (Green!), then see how it works in your car.....

....Fit the vacuum pipe to the valve and hold it in your hand (this assumes that you have no valve fitted already, and have yet to cut the intake pipe - but if you already have the pipe adapter fitted you'll need to fit the DV to it (the right way round!) so that the flat end of the piston is visible & accessible. Use a small length of wood (a flat end of a pencil is ideal), push against the piston and feel the spring tension - it should be quite firmly held closed.

Now start the engine and let it idle - push the pencil again and you should see that it takes less effort to open the piston a bit (spring pressure remains at 5 units, but vacuum has changed from 1 unit to 2 units, so there is only 3 units to overcome with the pencil) - gently rev the engine to a steady 3K revs (or whatever) and see how much the pencil now needs - it should get a tad easier, but not much.

Using your third hand (or an assitant in the car?) rev the engine a few times whilst holding the pencil against the piston - you will actually feel the difference in pressure required to move the piston as this happens.... Maximum vacuum is achieved at maximum accelleration rate (of the pistons in the engine, not necessarily the car!) - not the maximum speed of those pistons - although max accelleration occurrs just before maximum speed (well, it doesn't really, but without going into the dynamics of the whole thing, it can be taken as pretty much that, for our purposes).

Basically, get the assistant to floor the throttle whilst you hold the pencil - if the piston in the valve moves a lot, you need a stronger spring - if you still can't push it open with reasonable finger pressure, you need a weaker spring - if it 'just about' starts to open on its own, perfect - (or with minimal 'push' from you).

Right, enough playing - back to the theory....

With the right spring fitted, the valve will remain somewhere between firmly shut (engine off), and just-about shut (*maximum* vacuum) - - so it's like spending a hundred quid on nowt at all ... but then the magic happens - we add some extra pressure to the inlet charge from the turbo.

We all appreciate that when the turbo spools up, the physical volume of air between the turbo and the throttle body remains the same(ish), but the volume of air entering the system is larger, therefore simple Physics dictates that the pressure (and temperature, but that is irrelevant to todays lesson) of that air must increase in that fixed volume (if it didn't there would be no point in having a turbo!)......

.... and it is this increased pressure of air being forced into the engine which allows more fuel to be burned and gives us more power.

Depending on the levels of boost produced (0.65 Bar for a 'standard' SE/S2, and up to 0.92 Bar for a 'chipped' car), the ECU will allow the injectors to supply the right quantity of fuel to burn efficiently, and thus produce maximum power.

But when you lift off the throttle, the pressure in the enclosed part of the system remains higher than atmospheric levels, and it has to go somewhere - hopefully into the engine, but not instantly, so it will start to push back against the turbo impellor (fluttering sound can be heard as the pressure causes the blade to slow down and back-pressure escapes the wrong way) - or a pipe /clip bursts.

If this is only for a short time (gear change), it soon goes the right way again, but there is a momentary 'lag' until it is flowing fully - if the turbo isn't used again straight away (lift-off after an overtake??), it settles down to atmospheric pressure and away we (less vigourously) go.

Now, the DV works at this point - the vacuum vs spring equals out, and the valve opens (theoretically, it will open fully once the vacuum exceeds the spring values, but in reality it is probably a 'partial' opening).

With the valve the 'right' way round, the levels of boost will have no effect on it's operation, but when it opens, the excess pressure releases to the engine bay (or back into the air filter box in a recirculating system), This means that the pressure just before the throttle body stays at 0.65 (or 0.92) Bar, and is instantly available again when you hit the throttle - the turbo blades are still rotating freely and there is no 'catch-up' required, no fluttering sound from the fan blades, and less stress on the entire turbocharger unit - which has to be a good thing for the longevity of the parts.

If the valve is the 'wrong' way round, the pressure at the DV will still be 0.65 Bar, but it is also pushing against the piston/spring....

....this is where boost pressures DO matter to the spring selection.

If the spring is too weak, the spring value (5 units) remains the same, the vacuum (4 units?) tries to open it, but the boost pressure *may* add a couple of units of 'push' to the piston from the other side, and it now overcomes the strength of the spring, and opens the valve. This allows precious boost to escape without getting to the engine. If it only ocurrs at lift-off conditions, no problems at all - that's what the valve is for

BUT - if the boost/vacuum overcomes the spring BEFORE the saturation point (lets say the turbo adds 1 unit of 'push' for every 0.3 Bar of pressure), you will never maintain full boost, no matter how much pressure the turbo is developing.

In this example, you will have 5 units of spring holding it shut, 4 units of vacuum trying to open it, and with the turbo doing nowt, all is well. Once the turbo develops 0.3 Bar (1 unit of 'push'), the valve will reach equilibrium. If the Turbo develops 0.65 bar of boost, the valve will open as it now has a '1 unit' negative against the spring, and so all excess pressure now developed will just escape to atmosphere, and not get into the engine... hence anything over that is 'wasted' boost.

So in that case, you will need to fit a stronger spring to maintain maximum boost (a yellow spring with a value of 7 units would be okay in this case, as the 4 units of vacuum, and 2 units of boost would still keep the valve shut...... but if you have chipped the car to 0.92, then we will have 3 units of boost added to the 4 units of vacuum, and it will be marginal, so you may need the blue spring).

Are you still awake at the back?

Bottom line - if the valve is the right way round, once you have the right spring fitted, it doesn't matter what you do to the boost pressure, it will work exactly the same.

If it is fitted the wrong way round, you may need to play with spring rates to get it right, but then it will continue to work the same unless you 'up' the boost.....

..... but every time you run the engine on boost, the valve will be pushing against the spring unecessarily, and will (eventually) start to wear the spring - so for maximum life from the unit, fit it right and leave it alone

Class dismissed

[epipete]

Wow, just Wow!

Thanks, I'll give due consideration to this.

Actually, this can go on the back burner for a while, unless it impacts on any of my other ongoing issues? Emissions - it doesn't does it, its at the wrong end surely?