Alan MaC

I have a question and, would like some advice please? I have been told that you can change your dump valve and, get a much better response from your Turbo.

Things like, it will kick in quicker help the engine breathe better, and a bit quicker off the mark.

I have a Turbo Technics series 28 Turbo fitted and, it doesn't kick in until about 3,500 revs but, when it does, pulls all the way to 6,000.

Thanks in advance.

Kind regards



Alan MaC

stilover

No idea.

I'm just going to wait and watch you get flamed

Shark Man

False false and false, I'm afraid.

It can have small effect in response between gearchanges, but that is very minor indeed. It has nothing to do with engine breathing. And it won't make your turbo kick in at any lower revs that it already is.

andy.downes

iTrader: (1)

totally agree, doesn't make the turbo kick in any earlier and makes no difference to performance whatsoever - just makes a noise that you soon tire of.
if you do fit one and get any problems like rough running etc, take it off immediately

andythejock01wrx

Had one on the car when I bought it and it's the only thing about the car that my mates consistently take the **** out of !

Don't buy one in order to improve performance etc. Buy one if you enjoy the sound when the number 44 bus opens its doors in front of you !

I've heard that they can cause "bore-wash", but have no idea what that is !

Mangel

Bore wash is over fuelling caused by the fact that the engine management system gets confused as the excess pressure and therfore oxygen is dumped to atmosphere and not back into the manifold.

The only advantage to a dump valve, and it is debatable is that it releases the pressure on the turbo as soon as you lift the throttle reducing strain on the blades and reducing turbo stall.

If you like the sound then buy one but be prepared for abuse on here for it. I have the turbo XS one that can be turned from full venting to full recirc by rotating it. Means if you fancy the bus door noise you can but if you don't you can turn it of.

there is also some debate that you can loose boost pressure by put a vent to atmos dump valve.

Basically, **big brother Voice** You decide!!!!

Brit_in_Japan

Alan, assuming you have a turbo charged car, it will likely already have a dump valve. An Impreza definitely will.

The question is not whether a dump valve is beneficial compared to not having one on a turbo charged engine (it is beneficial, otherwise all the manufacturers wouldn't fit them) but whether changing a dump valve for another will have any performance benefit.

VTA (vent to atmosphere) dump valves will not improve performance one iota and may in fact reduce performance (hesitation, over fuelling etc). The standard OEM recirculating dump valve has been found to be very well matched to the engine, so much so that changing a dump valve on an unmodified engine is unlikely to have any positive benefit at all, and maybe the reverse.

IF you are running higher boost pressures, then upgrading your recirc dump valve is probably advisable as original items have been found to be less reliable at higher boost pressures.

The vast majority of aftermarket dump valves fitted make no performance improvement at all, it's just an aural "enhancement".

Alan MaC

I do run on a higher boost, are you saying that all I can expect is a nice noise to accompany the burble of the exhaust and no gains whatsover?

On some Turbo Advice Pages, it says that, in certain cases, if the Turbo is running on a hgher boost, it can enhance the sharpness of the response of the Turbo.

I have fitted an Sports Back Box only, do you think I would be better off doing the Headers, Down Pipe etc instead?

Thanks.

Alan MaC

Mark_S

If your car is post 98 and performance is your thing then the best bang for your buck will be to decat the down pipe and centre followed by an Ecutek remap.

Alan MaC

Thanks for that Mark.


Any Ball Park Figures on price?

Mark_S

Try and get your hands on some 2nd hand s/s pipes, centres go for £50-60, down pipes will cost fair bit more. The remap will be £600-£700 if the car hasnt been mapped before (one off licence fee is expensive). But, on the up side the performance gains can be amazing depending on your current state of tune.

Just make sure you use a reputable mapper.

Alan MaC

Nice one.

Thanks

Alan MaC

Mark_S

And one good mapper in your area(ish) is Bob Rawle, based in Swindon.
Nice guy and really knows his stuff.

http://www.brdevelopments.com/ his website sucks tho, LOL

andythejock01wrx

What's "turbo stall" ? Does it result in lag ?

Wurzel

iTrader: (1)

I had a VTA DV on my MY00 and it did improve response during gear changes but once I increased the power of the car the DV turned into more of a hindrense than a help, it leaked boost and really screwed up the mapping of my car, plus with it leaking boost it caused serious problems with the car when coming off the throttle after hard acceleration, the whole transmission shook. It also caused the car to pop bang and flames shot out the exhaust.

I changed it for a MY97/98 plastic recirc DV and all my problems immediately dissapeared, plus even though it is 100% recirc it makes a really cool whistle noise, more like air brakes than bus doors. The only problem I have with it is that the pipework is bigger on the 97/98 DV tahn on the 2000 car so you need to get a couple of new pipes.

Now my car is mapped to 360bhp and has no problems anymore.

HTH
Steve

redwrx

I used to have a VTA dump valve on my car ...because i liked the sound. But in performance terms it does sweet F.A. In fact, because of the upsets it causes the ECU, it can lose MPG. As for power gain - None. Gear change smoothness - depends on the driver.

On the other hand, If you want flames out the back, then yeh, you need a VTA dump valve and 'a fully decatted exhaust'...and thats about their use.

And yes, their are more than several claims to them causes piston problems.

But., as our previous Big Brother statement ..... its your car - You decide.


Frank

Alan MaC

Thanks all for your points.

I now have to do the grown up thing and decide.


Alan MaC

nick_wrx

I've got an 02 wrx ppp, if i want to increase performance whats best if ive already had the ecu remapped and an exhaust put on?

Thx Nick

ultraviolate

How do they cause flames to come out of the back?

Mark_S

It gets more expensive after the PPP. But as the PPP still keeps one cat iirc, you could remove it and fit a good panel filter before getting a custom remap which together should give a useful increase. Especially so if you get it mapped for high octane fuel (Shell V-Power springs to mind !).

After that I think you are into a bigger turbo / IC etc...

logiclee

When any rotary compressor has not enough air flow for the blades to cut and cause compression it is termed as being in a stalled condition.
With no dump valve fitted when you close the throttle the pressurised air has nowhere to go and the air stalls across the turbine blades, the turbo keeps spinning as the compressor side is no longer under load (in some applications it can even speed up) this can in extreme cases cause shockloading to the blade tips as well as extra wear on the bearings and shaft as the dynamic balancing goes to pot.
But because you dont have a dump valve all your intake pressure hasn't been dumped so lag coming back on power, such as after a gearchange, should be reduced.

Cheers
Lee

andythejock01wrx

Haven't quite got it. With NO dump valve fitted .... the air stalls across the blades. Is this right ?

Bat-Fink

Hi Andy,

I'll cut to the chase for you.

A normal re-circ DV does not make any noise as you know.

A VTA one does make a ptshhh noise.

Nissan Silvia S13 CA18DET Aftermarket Blow-off Valve (BOV) - Google Video

But if you blank off the dv hole,when you close the throttle what happens is the air hits the now closed throttle plate and travels back towards the compressor wheel on the turbo.

The air gets chopped up by the spinning compressor wheel and thus makes a very cool noise.

This is called comp stall or comp surge.

NOT! wastegate chatter.

A example of comp surge even tho it's called wastegatre chatter.

Nissan 200SX - Google Video

Another good example of running without a DV.

Chatter - Google Video

HTH,

Dan.

andythejock01wrx