recommend me a recirculating dump valve

[SimonR]

Probably a stupid question ... but would this cure the boost creep .... over boost .... fuel starvation type issues ....

[John_W]

Nope ... sorry.

[simonbuk]

Ok, I don't want to start a new thread just for this so apologises to the OP.

Wheres my dump valve then ?! Mine makes the very loud whooshy noises which I might become tied of after a while ! I have looked but can see no dump valve anywhere...

[Fredjohn]

No. A dump valve is fitted on the inlet side of the engine between the intercooler and the inlet manifold and releases the boost pressure when you lift off. The boost creep is a function of the exhaust gases and (not surprisingly) is on the exhaust side of the engine. The porting of the exhaust outlet of the turbo overcomes boost creep.

This is layman's guide, usual disclaimers!!!

Despite my car having a 2 1/4" exhaust I have to the best of my knowledge never suffered the dreaded creep. But I don't know if it's been ported either. One day I 'll remove the turbo and find out, in the meantime if it ain't broke don't fix it.

[SimonR]

Thanks for the explanation fredjohn

[John_W]

Wheres my dump valve then ?

None that I can see. Are you sure that you're not hearing induction roar from the non-standard filter?

By the way, I haven't seen a clip like you have on the CAS cover before.

John

[simonbuk]

Those KnN's normally make a bit of a throaty suck in noise not a whooshy noise when you lift off ? Mind you this has been on n/a cars before not turbos in my experience.

This KnN filter can't make it sound like a dump valve surely ?

[Fredjohn]

The clip on the CAS appears to be ilo the missing/broken plastic lug on top of the CAS case. I can see the metal lug to screw into, but not the plastic bit or screw. There's a 3rd lug underneath.

It's very clear at the front, but not on top. Mine had broken lugs too.

For further clarification the (after market) dump valve would normally be fitted into that big black hose immediately in front of the header tank. If recirculating it would also be piped into the (missing) air filter box, if not recirculating, then just to atmosphere.

[simonbuk]

The clip on the CAS appears to be ilo the missing/broken plastic lug on top of the CAS case. I can see the metal lug to screw into, but not the plastic bit or screw. .

You mean theres a lug missing directly below the U shaped rubber hose in the picture, and then somebody has put that black clip that is going from left to right to help hold it on ?

Must admit I hadn't even noticed it before. Is it just a plastic cover ? Is it alright left as it is ?!

[maz_r]

Yep - it is just a cover. Could be held on with chewing gum for all the difference it would make

(But it does need to keep the cr@p out of the gubbins)

[John_W]

it does need to keep the cr@p out of the gubbins

But it's probably best to keep the technical lingo to a minimum as Simon's a newbie.

[maz_r]

Sorry - sometimes I get carried away and can't stop myself....

[lotusflasherman]

Been running Bailey's DV30 RDV for years but wondering whether to buy one of these in case it packs up ...



Only £20 ???? www.ebay.co.uk/itm/UNIVERSAL-25MM-TURBO-DIVERTER-RECIRCULATING-DUMP-BLOW-OFF-VALVE-FOR-VW-AUDI-BMW/391387076139

[dapinky]

Phil,

Whilst I like the price, I can't comment on the quality......

....it's basically a knock-off version of the Forge DV007 - and the interweb is full of opinions on how good they are

[HJ2]

Hmmmzzz. Interesting find!

[lotusflasherman]

Phil,

Whilst I like the price, I can't comment on the quality......

....it's basically a knock-off version of the Forge DV007 - and the interweb is full of opinions on how good they are

Dave, seriously tempted to gamble £20 and fit one 'just for research'. If I keep the DV30 and a big screwdriver in the car can swap back in 3 minutes..

Forge & this one have a choice of springs, what spring do you use?

[dapinky]

Phil,

I'm not sure (in fact, I don't have any sort of a clue!) what the spring rates are for the valve you link to....

..... but in the Forge 008 I'm currently using a green spring, but considering swapping to the yellow one to try it.... i sometimes feel that it is dumping too easily, even though the theoretical calculations say the green one should be right.

It's all a bit of trial and error, but easy enough to swap them over with an allen key.

[Scott]

Does Elan really needs a dump/blow off valve? I mean could we avoid it or is a must for our car's safety and longlasting?
Also which one should we get? From trusted sellers only PNM does have a dump valve kit

[tigerdog]

Whether it needs one is up for debate but most modern turbo installations use a variant called a Compressor Bypass Valve. The difference is, instead of venting to atmosphere, the bypass valve recirculates the air released during shifts. On the Elan, that's not critical because the fuel metering system does not measure the amount of air going into the engine; it makes decisions based on throttle position, manifold vacuum/pressure, RPM, etc. It's pretty crude by modern standards. My personal preference is for recirculation; even though it does not make a difference to fuel metering, I don't like my car to sound like some teenager's chavv-mobile.

There seem to be very few scholarly works on compressor bypass and stall/surge, especially in engines. Most of the literature is built around industrial compressors for gas pipelines, etc. I found a great PDF from a Swedish university that goes into the modelling of turbocharged systems. The maths are beyond my ability but the text is meaningful.
https://www.vehicular.isy.liu.se/Publications/MSc/05_EX_3712_CFEW.pdf

I cobbled together a cheap Chinese eBay valve a few years ago but I've never been convinced it's doing the job properly. I'm debating either going back to a TurboXS valve or using one of the Kayser units as installed on Saabs, Volvos, Porsches, Audis, etc.

[Scott]

Whether it needs one is up for debate but most modern turbo installations use a variant called a Compressor Bypass Valve. The difference is, instead of venting to atmosphere, the bypass valve recirculates the air released during shifts. On the Elan, that's not critical because the fuel metering system does not measure the amount of air going into the engine; it makes decisions based on throttle position, manifold vacuum/pressure, RPM, etc. It's pretty crude by modern standards. My personal preference is for recirculation; even though it does not make a difference to fuel metering, I don't like my car to sound like some teenager's chavv-mobile.

There seem to be very few scholarly works on compressor bypass and stall/surge, especially in engines. Most of the literature is built around industrial compressors for gas pipelines, etc. I found a great PDF from a Swedish university that goes into the modelling of turbocharged systems. The maths are beyond my ability but the text is meaningful.
https://www.vehicular.isy.liu.se/Publications/MSc/05_EX_3712_CFEW.pdf

I cobbled together a cheap Chinese eBay valve a few years ago but I've never been convinced it's doing the job properly. I'm debating either going back to a TurboXS valve or using one of the Kayser units as installed on Saabs, Volvos, Porsches, Audis, etc.

how could we possibly use a group VAG item and such a valve for TSI engines?