As above really. Do they reduce or increase the turbo's life for example, etc...

 

From what I know about it:

1. dumpvalves only have one goal: to protect your turbo
2. driving without one does not "stall" your turbo, but will put a shockload to the bearing
3. you need a 360° sleave bearing to drive safely without one
4. no WRC car has a dumpvalve: does not work with anti lag
5. lot's of GrpN evo drivers get rid of the dumpvalve when running with higher boost
6. dumpvalves on <MY98 are known to leak sometimes under boost
7. MY99 and beyond items are fine, even with bigger turbo and upped boost
8. standard system is recirc: the air has been measured by the MAF, so to not confuse the ECU, the vented air is recirculated before the turbo/behind the MAF
9. vent to atmo may temporarily enrichen the fuel mixture, but opinions vary on whether that is bad for your car or not
10. it might be well possible that the recirculated air (with oil mist) might reverse past the MAF to atmosphere anyway, thereby polluting the hot wire/film on the MAF
11. they will NOT increase power or whatever: that is a myth
12. you could gain power by removing them (pressure stays "on tap" after gearchange or liftoff), but a TD04 or VF series turbo might not survive (long)
13. no, the WRC cars don't get the sound from a BOV, but from the wastegate button fluttering with closed throttle (you need hight boost for that)
14. they must be the n°1 topic in Drivetrain, which is strange for an aftermarket item that does absolutely zero for your car (unless your present one is leaking)
15. some of them use special grease as a lubricant. This grease can be diluted from oil in the intake system, effectively making the BOV work "jerky".

That's about it

Theo


[Edited by EvilBevel - 2/28/2002 11:27:04 AM]

 

Bloomin' heck Theo! Great list, can I use it as a reference on my web site?

Harry

 

Harry, sure, be my guest, but mind you, the above is 90 % from learning on this site and 10 % personal experience. And I have been wrong before

 

Isn't a little extra thingy that, whilst not doing anything for power, etc., they allow other components to work better (if better than the standard BOV) by taking a step towards the effects of not having a BOV at all? Seems to be the case in some situations looking back over the past few months. Tidies up those 'intangables' ibles? abels? Odd word, that one.
Although the main 'improvement' is that it seems to makes people happy.
Which is the main thing

 

When you say 'aftermarket dump valve' i assume you mean VTA (vent to atmosphere) dv's and not a custom recirculating (what standard cars have) dv.

if so then the only advantages I know are, noise, for that Fast and Furious sound and possibility of pops and bangs from exhaust as more fuel gets put in due to VTA, though not had this yet (full decat system)

I went for one because I'm sad, plus after some kit vandalised my car I needed some cheering up

 

Erm, Regarding the list..

WRC's don't run dump.. how sure are you? I can see no reason why a dv would be incompatible with anti-lag, in fact aiui it would help.
I'm pretty sure I've heard plenty of whooosh in the forests too..

A good part of the point of DV's is to stop the turbo spinning down as much mid change/off throttle, by allowing the boost pressure to go somehwere (atmos/recirc)

I have been wrong though

- Mark.

 

>>WRC's don't run dump.. how sure are you?

100 %

Theo

 

sure, they have the "Bang Bang" , which holds the turbo pressure in order to avoid turbo lag. Therefore it's a close circuit whereas the dump is not.

C.

 

Advantage - Flames

Disadvantage - 120 miles range

DaveW

 

I've removed the dump valve on my MY95 WRX (TD05) and plugged the hole.
With an induction kit I still get all the right noises and less lag, the risk is that my turbo dies as I'm also running 20 psi but that will be just the excuse I'll need to go buy a bigger one !

 

While there are no power gains I think that the hesitation felt momentarily after a quick high rev gear change say 4th to 5th is reduced. Any comments or observations?

 

Harvey ... that would only be possible if the BOV does not dump the air fast enough - which would mean it is not doing its primary job: protecting your turbo.

When I had my "uprated" dumpvalve (I had it on for a full 2 weeks), I felt the same ... but it turned out it was not fully opening at liftoff (sometimes not at all), effectively giving me a "no dumpvalve" situation. Good for (fast) gearchanges, bad for turbo. Off it went.

Oh, one of the other "advantages" of my standard dumpvalve is that it starts to "leak" under half throttle/heavy load (say in 5th gear). This means there is no pressure buildup pre-manifold, with less risk of the turbo cavitating. With a VTA this would mean bad news (way to rich). The BOV reacts on a pressure difference pre & post throttle, and you need to make sure it works as designed in anything other than WOT situations or liftoff. Half throttle is enough sometimes to open the dumpvalve, depending on what pressure difference it needs to see.

The popular VF series turbos for the Impreza (VF22/23/24/28/29)have this great roller bearing design which means fast spool up, but it also makes them vulnerable for shock loading. They have been known to shed a few impellor blades ... now the VF30 is - AFAIK - a sleeve bearing design, and might "work" without dumpvalve. Try at your own risk though

Theo

 

Thanks for your help guys.