Dump Valves : Re-circulating v Atmospheric

Bjorn · Post by **Bjorn** » Thu Apr 10, 2003 6:27 pm

Pro's and Con's - Atmospheric is said to be better for the turbo,...your views?

Quiche81 · Post by **Quiche81** » Thu Apr 10, 2003 7:40 pm

I have noticed no difference in performance whichever
one i run with. I think the issues on performance may a
little subjective, one vents off just behind the compressor
wheel and then sent through again so in theory would be
a fair bit hotter than the air infront of it, but would in reality
its sucked through the engine within a couple of strokes
so is of no real significance..
At the end of the day its more about 'do you like being loud ?'

Personally, I like being loud (Most of the time

)

Leif

MGTurbo · Post by **MGTurbo** » Thu Apr 10, 2003 9:59 pm

Can't tell the difference in my experience. Has to be ATMO for me! Except my ones broke

Ti-Andy · Post by **Ti-Andy** » Thu Apr 10, 2003 10:11 pm

Having had both I prefer re-circ .......all that loud shushing is just so "Look at me" ............alright for a while but quite embarassing after a bit. :oops:

(though not had a piston version just Diaphram which sounded very Loud )

Re-circs are also suposed to help reduce Lag are'nt they ?

Steve220 · Post by **Steve220** » Thu Apr 10, 2003 10:11 pm

A lot of people say its "Boy Racer" to have an atmospheric dump valve fitted, yet i like the sound. But it doesn't necessarily make me a boy racer. You could class under bonnet shiny bits and samco as boy racer too, they all serve a purpose, but not to everyone's taste

Ste

Steve220 · Post by **Steve220** » Thu Apr 10, 2003 10:13 pm

Ti-Andy wrote:Re-circs are also suposed to help reduce Lag are'nt they ?

Thats the point of a dump valve, to prevent lag by keeping the turbo spinning.
Ste

Mark · Post by **Mark** » Thu Apr 10, 2003 10:34 pm

Recirc every time for me

I like stealth - though you can still hear the recirc through the HKS filter !

Mark

Jonny 5 · Post by **Jonny 5** » Thu Apr 10, 2003 11:10 pm

Mark wrote:
I like stealth - though you can still hear the recirc through the HKS filter !

I like to think of that noise as pure turbo noise. Atmo are when your trying to hard and its quite embarrassing as a passenger with such DV's (Steve

)

Re-circs also wont leak boost when cruising which aswell as anoying means the turbo is spinning faster than it has too.

Personally i dont like them, and they are indeed boy racer... on cars with a OE re-circ. that is.

Regards
Jonny

Grant620 · Post by **Grant620** » Sun Apr 13, 2003 9:59 pm

For sure, atmos valves are loud, but recirc valves ain't quiet are they?
Especially when you have a decent induction kit.
I'd have the recirc all day long though personally. Keep it as stealthy as possible.
It is a case of whatever floats yer boat, but recirc is the performance choice IMO.

Ross9 · Post by **Ross9** » Mon Apr 14, 2003 9:56 am

I was always under the impression the main function of the Dump Valve was to prevent the turbo from stalling and therefore putting strain on the shaft between the exhaust and compressor wheels, not to prevent lag?

Though obviously if it's not stalling then the turbo will spin rather than be forced back the other way when you let off the throttle which would aid in reducing lag when the throttle is applied again.

Feel free to correct/mock if I'm adopting the "half knowledge" approach again, lol.

As for the Atmospheric vs recirc, I'm afraid I'm going to go for the atmospheric option myself, an unpopular choice by the look of it but as Grant says, each to their own.

Also heard somewhere that it is better to have the dump valve as close to the Throttle Body as possible, ie an atmospheric one in the intercooler pipe to the thropttle body? For the life of me I can't remember why this was reckoned to be a slightly better position though, any thoughts, info on this?

Ross

Post by **TomcatDan** » Thu May 08, 2003 8:40 pm

Atmos for me, I just love the sound.... Ste wondered from the path and fitted a "cupboard door handle" type DV, but I see now he has returned to the light

Steve220 · Post by **Steve220** » Thu May 08, 2003 8:52 pm

LMAO. that was a fantastic little mod. i was waiting for it to fly out through my wing at full boost, yet it got us around CC alright without coming out didn't it Dan?

I feel absolutely no difference between the 2. And i've swapped them dozons of times now. I'm sticking with the Atmos now. I like the sound despite what anyone says about them having a bad boy image.
Ste

Chris220SDi · Post by **Chris220SDi** » Thu May 08, 2003 9:21 pm

Mark wrote:Recirc every time for me

I like stealth - though you can still hear the recirc through the HKS filter !

Mark

I agree with Mark on this one. I like stealth, and the great thing about recirc with a good filter such as a HKS is that if you give it some you'll hear it, and your victim will know your driving a turbo, its just a lot more sublte than TSSSSSHHHHH!!! in-your-face.

I like good filter and recirc me

Mark · Post by **Mark** » Thu May 08, 2003 9:41 pm

During a gearchange - the recirc helps to keep the turbo spinning - although how much it does help is still open to debate.

Still - better something than nothing, and if its quieter too - that must help

Nothing personal - but I've always assumed that loud atmospheric dump valves are for the younger turbo driver - and their main use is to let everyone else know they are old enough to drive a turbo!

Mark

Post by **TomcatDan** » Thu May 08, 2003 9:54 pm

Fair comment, I do admit that I like everyone to know I've got a turbo, different strokes for different folks I guess! And Ste, it did get us around castle combe, but its just a shame your bloody naff brakes nearly got us killed instead :lol:

Anyway, I thought you were supposed to be doing coursework?

Steve220 · Post by **Steve220** » Thu May 08, 2003 10:00 pm

Erm

ah s***. caught out :roll:

I'll have slightly better brakes for our next outing

Mark's point is very valid, i know a lot of turbo fezzy's with atmos DV's, and they're all young, so am i. Steve had one on his GSi T, Neill has one on his GTi T. Does point in that direction. But i'm not to the point yet where serious power is concerned, i'm not sure if the gear changes suffer at higher power with an atmospheric DV, but at standard boost, airfilter and de-cat, they seem to be much the same.
Ste

Gary · Post by **Gary** » Thu May 08, 2003 11:29 pm

Hides under the chair;

I quite like the noise the atmospheric dump valve makes and think that would probably be what i would use but then again the noise might grate after a while. Atmospheric dump valves are seen on lots of boy racers cars, but around where i live no one has a turbo car so they would more than likely think the brakes from the old X78 are sounding mighty fine today :d .

Gary · Post by **Gary** » Thu May 08, 2003 11:33 pm

Mark wrote:
Nothing personal - but I've always assumed that loud atmospheric dump valves are for the younger turbo driver - and their main use is to let everyone else know they are old enough to drive a turbo!

Mark

You probably hit the nail on the head there mate. Nothing too wrong with a little bit of that though as long as people dont go over the top

xr4x4 · Post by **xr4x4** » Fri May 09, 2003 1:06 am

To be honest i hardly hear mine when changing gear fast.

If i do a long slow gear change i get a loud long Tsshhhh..

I have a motobuild DV BTW.

Paul,

sharky · Post by **sharky** » Sun Jun 01, 2003 2:33 am

ive not noticed any difference.

can i just say that if u drive your T16 without the turbo hose connected
it has the same deep wiring noise of a P1 scooby (just me then :oops:

)
sounds well good! but u have no boost, obviosly!

Ross9 · Post by **Ross9** » Sun Jun 01, 2003 8:01 am

You mean it sounds rough as a badgers donkey boy? lol.

I don't think it sounds the same, my Turbo hose blew off at a redline change up while caning it round a track day, and I guess it did make a nasty deep brrrrrrrrrrrrrrrrrrrrrrrrrr noise, as it overfuelled to death and didnt go anywhere.

Guy I know has a P1, very loud, HKS exhaust etc, the Rover did not sound like it, same type of noise perhaps, but not the same as the loud rumble the P1 makes.

David220 · Post by **David220** » Wed May 12, 2004 1:43 pm

Atmospheric is my choice.

Handy when saxo boy tries to take you on at the lights. You can pull along side him, let your dump valve do its stuff and he'll soon realise the error of his ways and back off! :twisted:

I suppose that me being young just backs up what everyone's saying about young turbo drivers.

Steve220 · Post by **Steve220** » Wed May 12, 2004 2:26 pm

I found a good web page with some sounds of blow off valves, there's one on there some where of a re-circ HKS one and it sounds quite nice

http://www.935motorsports.com/hksbov.htm

Sheaf · Post by **Sheaf** » Wed May 12, 2004 2:57 pm

I personally think atmo ones sound cool.
The excessively loud ones just sound like a bus is slowing down near you, but most sound cool, especially when changing at high rpm. It kind of finishes off the sound of the engine revving, if you know what I mean.
But then again I'm young....

Alex

Raistlin · Post by **Raistlin** » Wed May 12, 2004 4:20 pm

I suppose that me being young just backs up what everyone's saying about young turbo drivers.

Yeah, that MUST be right cos I have an atmos (SSQV) and I'm a young turbo driver

Steve220 · Post by **Steve220** » Wed May 12, 2004 4:22 pm

you're a bigger kid than me

Tom™ · Post by **Tom™** » Wed May 12, 2004 4:22 pm

Ross9 wrote:Also heard somewhere that it is better to have the dump valve as close to the Throttle Body as possible, ie an atmospheric one in the intercooler pipe to the thropttle body? For the life of me I can't remember why this was reckoned to be a slightly better position though, any thoughts, info on this?

Ross

it is for better throttle response

Tom

Steve220 · Post by **Steve220** » Wed May 12, 2004 4:41 pm

Colin had his Baileys DV just after the turbo. He said it made no difference

Though i can see its probably best to keep the air flowing in the rest of the pipework, and having the DV almost next to the TB will mean the airwill probably be at the velocity to pressurise the pipes as soon as the TB opens again.

My ssqv is about 7" away from the TB, where the baileys was. Hoping that when i get some other piping made, i can locate it a little nearer.

Colin · Post by **Colin** » Wed May 12, 2004 5:10 pm

Steve220 wrote:Colin had his Baileys DV just after the turbo. He said it made no difference

Indeed, and it's still there. Tried it in a few different places and made naff all difference where it was...

Colin

4977 · Post by **4977** » Fri Jul 02, 2004 7:11 pm

I would just leave what is on as standard if i were to upgrade i would put on whatever type the car came with as there is issued with the car stalling if you put a atmos dv on a re-circ system due to the ecu and air sensor. I do prefer re-circ though

Grant620 · Post by **Grant620** » Fri Jul 02, 2004 7:16 pm

4977 wrote:I would just leave what is on as standard if i were to upgrade i would put on whatever type the car came with as there is issued with the car stalling if you put a atmos dv on a re-circ system due to the ecu and air sensor. I do prefer re-circ though

No issue on Rovers mate - they don't use crappy AFM's or MAFS.
They use MAP sensors and air temp sensors.

Post by **MarkCoupe** » Sat Jul 03, 2004 4:29 pm

There is nothing greater in life than noises various engines etc make, v8's, fto V6's at 9k rpm, the ticking from an N2O solenoid and bovs, this is the one on my car :

http://www.935motorsports.com/media/blitzBOV.wav

Blitz bov with trumpet, does the job

talkingcars · Post by **talkingcars** » Fri Jul 09, 2004 8:19 pm

4977 - it is the turbo its self that stalls and needs to start respinning, not the engine.

James

Nom620TI · Post by **Nom620TI** » Fri Jul 09, 2004 8:52 pm

4977 wrote:I would just leave what is on as standard if i were to upgrade i would put on whatever type the car came with as there is issued with the car stalling if you put a atmos dv on a re-circ system due to the ecu and air sensor. I do prefer re-circ though

talkingcars wrote:4977 - it is the turbo its self that stalls and needs to start respinning, not the engine.

In the situation "4977" is talking about, it IS the engine that stalls.

Lots of modern turbo systems, like VAG's setup, are very easily fooled. If you replace the recirc valve with an atmo valve, the ECU can't account for the vanishing air.

This doesn't apply to Rovers though - MEMS doesn't care where the air is dumped to.

rich820coupe · Post by **rich820coupe** » Mon Nov 01, 2004 11:58 pm

atmos for me fitted my bailey dv at the weekend and it is about 3 inch off the throtle body and ive aint noticed any difference in response to be honest

Rovertech 2.0

Dump Valves : Re-circulating v Atmospheric

Dump Valves : Re-circulating v Atmospheric

Which BOV