B.O.V's....

[GTMike]

Simple question........" Do you need one ? "

I know what they do etc , but going back to the days of my old cosworths that i used to run (most were 400+ bhp ) most of the well known tuners i used said they were not needed until you were running really high boost and the BOV's were used on the RS500's as they were pushing high boost levels to get the 560bhp they got on the touring cars.
Because of this i never had one on in the 9 years i owned my cossies and never had any problems at all , plus the screaming noise you got was alot better sounding than the feeble "pishhh" sound.

Back to my 34 , i'm after having a big overhaul under the bonnet and was after removing the HKS BOV i've got on now and re-fabricating some better flowing pipes , so can i remove it ?

any help or ideas please.........


mike

[ivor]

it was covered last year some people had theres blanked and were running okay but the general consensus was your better off with one as they can prevent the turbo from stalling giving up a quicker on boost time. Why not go for recirc valve as it would be quieter and still do the same job

[Deggers]

DIYMike

[GTMike]

I've been today to watch Andy Kain get his car mapped at a Skyline specialist and i put this question to the tuner and got the responce that i thought i'd get "you dont need on at all ". After about 20 - 30mins of explaining in depth about how thing work etc ( so he did'nt just say you dont need it , he went into depth why ) he said there not somthing you have to have and said if i did'nt have one already there he would never recommend you to buy one. He also said none of his time attack cars etc run with them either. So job sorted , it's getting binned.

[GTMike]

Originally Posted by Deggers

DIYMike

[Tom]

howdy should the stock bov on a r33 gtst be making a noise or is it a silent one

[spaxy]

the standard one is a recirc one,ive got an apexi power intake filter and you can hear it when lifting off.i was experimenting the other day and clamped off the vac hose to the standard b.o.v and you get that superb flutter noise,but the car didnt feel as sharp on boost and when changing up through the gears.

[Tom]

ok thanks,

is there any serjestions on what i will needs to get i want one that i can almost to replace the orignal one with,

just one that makes a nice sound and hopefully not to steep on the pocket lol

[Richf]

Having had a bov not work properly for a while and then fix it i think there are lots of benefits of having one as i have tried both ways

When you close the throttle on a turbo'ed engine it causes the boost pressure to try and go back towards the turbo this pressure wave normally simply vents out of the bov without one (or a working one) that pressure backs up and stalls the turbo blades and carries on out of the air filter, this will make the car fall on its face power wise between gear changes and confuses the maf (they are only designed to read the airflow over them they dont care which way the airflow is) and will even damage the maf over time

Plus the same pressure wave will also go up any crankcase vent pipes you have attached and pressurise the engine forcing oil mist into the plenum this will increase detonation as oil mist rich vapours ignite easier than just air


I really cant see any reason not to run one

[mule]

Originally Posted by Tom

ok thanks,

is there any serjestions on what i will needs to get i want one that i can almost to replace the orignal one with,

just one that makes a nice sound and hopefully not to steep on the pocket lol

ive got a hks ssqv bov on my gtst r33 sounds nice, easy to fit cost over £200..... there is one here in the for sale section going cheap.

[Little Kez]

im sure gtmike will have 1 for sale too

[ISJ]

Lets just get one thing clear here. The turbo does not "Stall" !

Compressor stall ,if someone mentions it, is not the compressor wheel stopping or drastically slowing down, it is the airflow around the compressor vanes stalling. The airflow stops being laminar as it "detaches" itself from the compressor vanes and becomes turbulent, thus creating a whole load of pressurised air with no definitive direction of movement.
This pressurised air will then take the path of least resistance to a lower pressure area - generally out your air-filter.

The airflow within an intercooler pipe can momentarily slow to a negligible speed due to this compressor stall, but think how long it takes for you to change gear and the butterfly valve to open again - not long.

BOVs purely vent excess pressure which will build up behind the butterfly valve when you close the throttle and in doing so maintain a clear route for pressurised air to continue flowing towards the engine.
BOVs are good, they do help maintain the flow of air into the engine and do provide some sort of protection to engine and turbo - but at the sort of relatively low boost pressures most cars here run, then the effects are negligible.

Personally, I wouldn't take off my BOV. I'll keep my re-circulation BOV, that's all I need.

[Richf]

If boost pushes back against a compressor wheel it will slow or stop or STALL ie bring to a standstill which is the correct use of the word stall

stall definition |Dictionary.com

[Little Kez]

stalling is for gays

[ISJ]

Originally Posted by Richf

If boost pushes back against a compressor wheel it will slow or stop or STALL ie bring to a standstill which is the correct use of the word stall

stall definition |Dictionary.com

So you think a turbo compressor wheel - still spinning from the exhaust gases that drives it - will stop?

Remind me again, roughly, how fast does a tubine spin again? Especially one which has just come off full boost....