22 replies to this topic

[JoeBodge]

alright,
on my mates golf rally (which is supercharged for peeps that dont know) it has a BOV (blow off valve) fitted, which sounds really cool, can you do this to vmax / jonspeed kits? and of so has anyone done it? what are the advantages of it?

thanks

[mini13]

A blow off/ dump valve is fitted when a turbo has a throttle butterfly after it,

as i understandit there are two resons for this,

1) if you are running a lot of boost if the throttle is shut quickly the air comming out of the turbo has nowhere to go and you end up with a lot of pressure which can damage the turbo.

2) when the throttle is shut the prssure build up will make the turbo slow down quickly and even stop ( or all but) with the dump valve the pressure is released so the turbo will continue to spin, when you open the throttle again the turbo will not need to spin up again so throttle response will be better.


With the jonspeed and v max setups the throttle buterfly (Carb or injector) is before the super charger so you will not have the same incrase in pressure when the throttle is shut. Also as the fuel goe in before the blower if you vented boost pressure you would be venting air/ fuel mix.

[miniman andy]

damn! i am thinking about getting a jonspeed supercharger. and would love that blow off valve just to protect the engine and yes ok ok that silly little sound when they do.

and i get what you mean by "venting air fuel mix" and the last think you really want is fuel and air mix getting round the engine bay. especually near wires if you have any.
next thing you know your engine bay is on fire!


eeekkkk!!!!

is there any out there that crams the air in frist and then the fuel mix. or would that have to be injection side (spi / mpi)

Edited by andy taylor, 14 January 2008 - 12:41 AM.

[mighty_mini]

A blow off/ dump valve is fitted when a turbo has a throttle butterfly after it,

as i understandit there are two resons for this,

1) if you are running a lot of boost if the throttle is shut quickly the air comming out of the turbo has nowhere to go and you end up with a lot of pressure which can damage the turbo.

2) when the throttle is shut the prssure build up will make the turbo slow down quickly and even stop ( or all but) with the dump valve the pressure is released so the turbo will continue to spin, when you open the throttle again the turbo will not need to spin up again so throttle response will be better.


With the jonspeed and v max setups the throttle buterfly (Carb or injector) is before the super charger so you will not have the same incrase in pressure when the throttle is shut. Also as the fuel goe in before the blower if you vented boost pressure you would be venting air/ fuel mix.

this is an egg chicken situation unfortunatly. but alot of myths surround dumpvalves and theyre awesome ability.

First off, when the throttle is closed, the air will return back out the turbo into the filter causing compressor surge. This is what makes the noise which is mis-interprited by many people as "wastegate chatter" which is an entirely different thing.. and infact doesnt even chatter..lol.

With injection cars, the use of a dumpvalve can also be problematic, because air which has entered the induction system would have gone past the afm, so its already metered and the ecu has calculated the required fuel for when the oxygen enters the cylinder. The ecu unfortunatly does know that the dump valve has just chucked all the air out so then you get overfuelling. which in turn fouls plugs and also puts nice fresh fuel into your exhaust sysytem, going into a nice 300'c+ turbo. SUPER!

Responsiveness is debateable... once the dumpvalve has chucked all that compressed air, it will only start compressing it again once the throttles opened. So infact your more than likely making things worse. This will be more noticable depending on what intercooler, piping and turbo you have.

I find that my car responds much better without a dumpvalve and to be fair, so did my mini.


Things like dump valves and pop-off valves (much better) arent anything you need to look at touching until your exceeding 1.5bar, even then theyre not normally used.

My 2pence from a DV hater...


P.S - im running 1.1bar and no dumpvalve...... 2 years and counting, nothing wrong yet. Ask Brawlyrox if my cars responsive or not

Edited by mighty_mini, 14 January 2008 - 03:32 AM.

[LOWRIDERHORNET]

If you like that sound you don`t have to have a turbo mini.You can get these kits that works on the clutch so when you push the clutch in it make that sound.Im going to get on for the Hornet so it may make people think twice of give me a race or not.

[redhotmini]

If you like that sound you don`t have to have a turbo mini.You can get these kits that works on the clutch so when you push the clutch in it make that sound.Im going to get on for the Hornet so it may make people think twice of give me a race or not.

[Turbo Nick]

If you like that sound you don`t have to have a turbo mini.You can get these kits that works on the clutch so when you push the clutch in it make that sound.Im going to get on for the Hornet so it may make people think twice of give me a race or not.

oh dear...

[Southy]

If you like that sound you don`t have to have a turbo mini.You can get these kits that works on the clutch so when you push the clutch in it make that sound.Im going to get on for the Hornet so it may make people think twice of give me a race or not.

oh dear...

Oh dear, oh dear.......

[JoeBodge]

If you like that sound you don`t have to have a turbo mini.You can get these kits that works on the clutch so when you push the clutch in it make that sound.Im going to get on for the Hornet so it may make people think twice of give me a race or not.

now those kits are chavy, and all they are is a speaker playing the sound. a load of rubbish

so fitting a BOV is definatly not possible in the jonspeed / vmax supercharger kits then??

[biggav]

If you like that sound you don`t have to have a turbo mini.You can get these kits that works on the clutch so when you push the clutch in it make that sound.Im going to get on for the Hornet so it may make people think twice of give me a race or not.

oh dear...

Oh dear, oh dear.......

DOH!!!!

Oh Dear..... a female deer!!!!!

[lowandslow]

If you like that sound you don`t have to have a turbo mini.You can get these kits that works on the clutch so when you push the clutch in it make that sound.Im going to get on for the Hornet so it may make people think twice of give me a race or not.

now those kits are chavy, and all they are is a speaker playing the sound. a load of rubbish

so fitting a BOV is definatly not possible in the jonspeed / vmax supercharger kits then??

i have seen a mini at the shows that has the charger before a turbo carb so it would be possable if you had it that way round. but how cool would it be to dump mixed air out of a vent with a spark plug in it mmmmmm........flaming dump valve

[Matrix]

[JoeBodge]

is that a BOV matrix ?? is that the same charger as the jonspeed / vmax ??

PS - welcome to TMF low and slow!!

Edited by JoeBodge, 15 January 2008 - 07:55 PM.

[lil dan]

If you like that sound you don`t have to have a turbo mini.You can get these kits that works on the clutch so when you push the clutch in it make that sound.Im going to get on for the Hornet so it may make people think twice of give me a race or not.

never mind

[mighty_mini]

To me that looks like a pop off valve, the same as they used on the old S12's and back when F1 were turbo'd...

all they do it open to stop it overboosting for obvious reasons. Its not an actual dump valve.


although if thats the setup theyre talking about atm, thats pretty damn stupid if its suck through and venting fuel/air onto a wrapped manifold...

Edited by mighty_mini, 16 January 2008 - 02:42 AM.