Opinion on BOV....

[JUDGENINJA]

Right............ I know certain people like them and I know of others who can't see the point of them, but I thought I post a query....

Most People's advice is when fitting a optional BOV (Dump Valve or PSSSSSSHHHHHH thingy you here from some turbo cars as they speed off up the high street) that the recirculating dump valve that is already fitted as standard should be removed for better performance of the new one....

I've just fitted the Baileys BOV that I got from Fraz (Thanks Fraz) and what I've found is that the new BOV starts to dump gas at around 3500 to 4000 rpm even with the original one in place.

To my mind this shows up the following :

The point of the BOV is to function as a turbo protector to get rid of excess gas as and when required and generally lowers the stress on the turbo internals (bearing etc).... Having two Dump valves fitted means that the gas transfer efficiency has been raised and removing the original would place stress on the new one.. I am fully aware of the fact that possibly I won't be getting the full PSSSSSSSHHHHHHHH!!!!!!! sound that some people can get but, the sound produced is the end result of fitting one, which is not really the reason for their invention.....

The only other think I can thing of is possibly the orignal one is knackered....

Anyway I thought I'd give some of the tuning bods something to ponder on over coffee....

[dj_rog]

I've just fitted the Baileys BOV that I got from Fraz (Thanks Fraz) and what I've found is that the new BOV starts to dump gas at around 3500 to 4000 rpm even with the original one in place.



That sounds like a loss of boost to me...

If you want to reduce the stress on your internals, either lower your boost levels of don't use full throttle... but I am sure you don't want to do either of these!!

There are some very good reasons from not running with both the BOV and the recirc valve at the same time but I can't help you on those... Sorry!

[JUDGENINJA]

My issue isn't the fact that I'm loosing boost as I get a peak reading of 0.7-0.8bar on the boost gauge.
My query is : Is there any advantage on removing the original one other than to make the new one louder?

[JUDGENINJA]

As I have got no responses I'll assume that No-one has an opinion on this I'm gonna leave my CBV on for the time being, until someone informs me that there is a functonal reason for removing it.....

p.s. making a louder "pssshhh" is not classed as a functional reason

[fraz13]

Hey mate :wink:

A think its just a case of run one or the other basically for noise, if you keep both surely its not doing any harm, just means its dumping back into the system and into the atmosphere aswell just at a lower pressure than only running one,

That Baileys DV has a strong spring in it so it only dumped above 3k anyway where as ma new one dumps around 2k but in that its no good for long motorway journeys as a found out on ma way home lol although thats just typical haha

[Paullyp]

Fitted a Baileys DV, and an MBC ..(Thanks to Bracer)..and a K&N in addition to xtra cooling, and a boost gauge...all very pretty but no difference at all, I will remove the recirc valve tomorrow. Any advise is well welcome I assume when u fit an mbc all pipe work to the solenoid is not required,Paul.

[Pedro Fandango]

Fitted a Baileys DV, and an MBC ..(Thanks to Bracer)..and a K&N in addition to xtra cooling, and a boost gauge...all very pretty but no difference at all, I will remove the recirc valve tomorrow. Any advise is well welcome I assume when u fit an mbc all pipe work to the solenoid is not required,Paul.
something is very wrong then, i think the only mod you will feel the actual difference with is the MBC but it really will transfrom the whole drive of the car (becomes alot more violent when boost comes in)

[mat562be]

In theory, a dump valve which dumps to atmosphere won't make any difference to performance at all. The benefit of an aftermarket one, is that it is les likely to degrade as there are no parts (in a premium valve) that will be affected by the hot air that is passing through it. The regular type, recirculating valves generally have a rubber diaphragm which degrades and can allow boost to leak, thus degrading performance. Many of the aftermarket valves have a "piston" made from a more resilient composite which provides better sealing, and a longer life.

The only purpose of a dump valve is to allow the boost pressure to be vented when the throttle is released. If this is not done, back-pressure is created which then passes back to the turbocharger and can either stall the turbo - meaning that it takes more time to spool up when the next gear is engaged and the throttle re-opened, causing lag - or in the worst case (when running very high boost) the turbocharger blades or bearing can be damaged due to the volume of air being forced back into the turbo under pressure.

Essentially, it's just a release valve, and it either works or it doesn't. There's no "better" or "worse." Some dump valves e.g. those that dump to atmosphere can dump pressure more quickly, due to the less-restrictive design, but essentially are no better than a recirculating one, since the differences are barely perceptible other that in all-out driving.

One problem with a lot of dump valves is the quality of the vacuum seal - ask any Cosworth driver about this - which can cause some problems if even minute quantities of air are allowed to leak when the valve is shut. At best, this can cause lumpy idle, as the air flw meter gets confused, and at worst it can cause engine damage over the long term due to the unfiltered particles entering the inlet tract.

The moral of the story, in my experience (I did the dump valve thing for a while on a couple of Cosworths and a Subaru) is buy a good 'un. Baileys are excellent, being a piston-type, and give a nice "whoosh."

I haven't got one on my Volly, as I think they only look and sound right on something that is bit of a "rally car..."