23 replies to this topic

[floatintoast]

I live next to a very long straight road so am used to hearing the 'ffft' sound of a dump valve but never known what purpose they serve and what it is that makes the noise. got a few ideas in my head and various people tell me different thing, just thought u guys would be best to ask.

cheers

si

[Angeleyes]

Hi there

Don’t know if this will help, but I have been told that the noise is made by Air from the turbo, the dump valve basically lets the air come out and makes the noise.


Hope this helped.

[Brett]

basicaly the turbo builds up 'boost' pressure for the engine to run off to creating more power but when you lift off the gas the engine cant use all the 'boost' that has been created so it would backup through the turbo causing it to slow right down if not stop or even reverse it this can cause damage to the (expensive) turbo, then when your foot is on the gas again the turbo has to spin up from a standstill (takes long time), a dumpvalve is what it says on the tin...a valve that dumps the 'boost' this is so the turbo doesnt slowdown much and this reduces the amount of turbo lag between shifts(on a more practical side it stops a lot of unnesesary wear on parts such as the turbo)

on most(almost all) standard turbo cars the dumpvalve is quiet and it then re-uses the dumped 'boost' (but that is a whole different story) on aftermarket dumpvalves they usualy range from loud to super extremly loud and they dont re-use to dumped 'boost' the sound it makes is all down to the type and the preferance of the driver, on my dads scooby i think his bumpvalve is a little quiet (compaired to the exhaust) but he likes it quiet, where i like it to be on the same level volume as the exhaust (if it has loud exhaust it should have loud dumpvalve)...there is also another problem with dumpvalves, that is all the chavs have super extreemly loud ones and it is giving them a bad name......think of this how far away from the road do you live and you can still hear the dumpvalve sound of the cars that pass, while it might sound nice from where you are (because you got to love the sound) how loud do you think it must be if you are next to the car?

ok i waffled to long over questions you didnt exactly ask so i will stop now and dream of the day my engine is finnished

[Wil_h]

Brett has pretty much summed it up.

They're not strictly necessary when running less than around 10psi, and don't forget that they bypass the air filter at tickover.

[Turbo Phil]

don't forget that they bypass the air filter at tickover.

This is true, but you can get some with a small K+N type element built in to help filter the incoming air.

Phil.

[Wil_h]

I didn't know that Phil, they should all be filtered.

[floatintoast]

thanks alot, brett especially.

cheers guys

[josh_tacon]

good info there!

what ones are quiet and have a k&n element in them then, as i dont want mine to be to loud as i recon it would just be to much with a 2" maniflow stright through with single back box, s/c gears and a realy load d/v!!!! o and the whistle of the t2 (are they load, never heard one...yet lol)!

cheers
josh

[Brett]

quiet dumpvalve = recirculating basicaly it dumps the 'boost' back in front of the turbo after the air filter


i know the type of dumpvalve you mean...the ones with built in filters, dont quite understand why thy have em
anyone want to share their wisdom?


loud type basicaly dumps the 'boost' to air

[josh_tacon]

they say above that dump valves bypass the air filter at tickover

cheers for that mate, do they perform differntly/harder to set up etc?

will the quiet dump valves be silent or just quieter that normal?
i want one thats not going to be too loud as i think there will be enough noise coming from my mini once its done lol
has anyone got any vids/sound clips of what there turbo mini sounds like with a dump valve and s/c gears etc?

cheers
josh

[Brett]

they bypass the airfilter maybe it is only certain types because mine dont do this (but then a gain mine aint on my engine )

the sound depends on which you get (there is sooooo many type's) but the re-circ types can (just) be heard from in the car (maybe not with loud exhaust) but they are realy quiet

[mighty_mini]

thats about right. but i doubt you'd ever stop or reverse a turbo. Dump valves are more of a bling item over performance. If anything, not running one is better. especially on injection.



Dave

[pikey7]

The problem with dump valves that dump to air is that the system is not expecting to lose that air, and consequently as you let off the throttle and the valve opens, the car runs incredibly rich momentarily. A recirc valve is better in that respect as at least it keeps the right volume of air in the system and prevents that from happening.

[Purple Tom]

The problem with dump valves that dump to air is that the system is not expecting to lose that air, and consequently as you let off the throttle and the valve opens, the car runs incredibly rich momentarily. A recirc valve is better in that respect as at least it keeps the right volume of air in the system and prevents that from happening.

Is that why quite a lot of modified turbo cars with loud dump valves often create a flame at the exhaust when changing gear under hard acceleration?

[josh_tacon]

Is that why quite a lot of modified turbo cars with loud dump valves often create a flame at the exhaust when changing gear under hard acceleration?

Do they??.............EXALENT lol