BOV vs Recirculating
- Thread starter ryan_v
- Start date
GTti
Member +
The theory with a re-circulation valve is that pressure is maintained in the intake, so there should be more response in a closed then open throttle situation. Air that is re-circulated is also re-intercooled in most situations, so heat has nothing to do with it. However as dac69er said emission and noise control are the main features to take into account.
A atmospheric valve (Vacuum based) releases compressed air pre throttle body into the atmosphere as soon as you are off the throttle. You loose all intake pressure so this has to be replaced when the throttle is open, which is less responsive.
Why waste compressed and cooled air that is ready to be force fed into the engine. These types of valves are useless.
On the other hand, an atmospheric item that works based on a resistance is different. The spring will determine at what pressure air is released from the intake when the butterfly is closed. In this scenario pressure is maintained at a reasonable limit.
I don't run any valve on my race car, but instead I have a rubber flexible intake hose, which swells to accomodate for the increased pressure in the intake.
Obviously this doesn't happen with 'bling bling' intake hoses.
A atmospheric valve (Vacuum based) releases compressed air pre throttle body into the atmosphere as soon as you are off the throttle. You loose all intake pressure so this has to be replaced when the throttle is open, which is less responsive.
Why waste compressed and cooled air that is ready to be force fed into the engine. These types of valves are useless.
On the other hand, an atmospheric item that works based on a resistance is different. The spring will determine at what pressure air is released from the intake when the butterfly is closed. In this scenario pressure is maintained at a reasonable limit.
I don't run any valve on my race car, but instead I have a rubber flexible intake hose, which swells to accomodate for the increased pressure in the intake.
Obviously this doesn't happen with 'bling bling' intake hoses.
Last edited:
Adam_Glanza
Member +
i mainly have a bov for show off perposes i.e i just like the noise and headturning effect and always thought it sounds nuts.
im sure theres lot of theory behind "performance" but i would amagine the difference is minimal
im sure theres lot of theory behind "performance" but i would amagine the difference is minimal
weeJohn
Lifer
I thought that was the whole idea, to reduce pressure pre throttle so as the air being pressurised by the compressor does not dead head against the throttle butterfly, causing the compressor wheel to "stall" and possibly damage the blades??
I know you state you use a rubber pipe that expands to prevent this, but does that pipe expanding not affect your throttle response? I thought that was the idea of hard pipes, no expansion.
Not dissing your views, just asking your thoughts and experiences on these theories mate.
GlanzaV1.3
Member +
Luckily i live in an area where people dont seem to drive turbo's!!
and if they do they dont have BOV's
Head turning factor i will benefit from!
Adam_Glanza
Member +
same here lol
shauntgtt
Member +
Luckily i live in an area where people dont seem to drive turbo's!!
and if they do they dont have BOV's
Head turning factor i will benefit from!
2nd that
Toddi
Member +
Luckily i live in an area where people dont seem to drive turbo's!!
and if they do they dont have BOV's
Head turning factor i will benefit from!
Theres a couple but still turns the head aswell.
GTti
Member +
In racing scenario when you change gear at full boost, your foot is only off the throttle for a split second. At this point compressor surge is minimal, but the pressure of the intake will be increased - so when the throttle is open you have more compressed air mass ready to fill the combustion chambers.
More air and more fuel will give a better combustion, in turn this should give better response.
The expansion of a flexible intake hose means that the energy from the compressed air is being absorbed and stored. As soon as there is a condition where this energy can be forced away then it is. This would be when the throttle is open again.
A solid pipe will not do this, this will force air from back the way it came, back over the compressor turbine. The compressor will never stall, just slow down slightly. My old turbo done 87,000 miles with no re-circulation or atmospheric valve installed. I'm confident that at most boost pressures this will not damage a well prepared turbo.
Suspected_Psycho
Member +
What does it matter if people turn there heads when your proberbly caneing it through a town center!!??
I actually turned my recirc upside down so it vents the air to the bonnect, creates a his but not alot to get people looking, but I did find that haveing it not recurculateing did make it feel a little faster.. .BUT.. This maybe just becuase it "sounds" faster.. if you get my drift.. i dont think it made any diffrence what so ever personally..
I actually turned my recirc upside down so it vents the air to the bonnect, creates a his but not alot to get people looking, but I did find that haveing it not recurculateing did make it feel a little faster.. .BUT.. This maybe just becuase it "sounds" faster.. if you get my drift.. i dont think it made any diffrence what so ever personally..
A properly set up atmospheric dump valve will give the better response. A re-circ valve is used on cars that measure intake with a maf sensor as with a atmospheric valve the ecu overfuels slightly when you come off the throttle as the fuelin' for the amount of air taken in is already accounted for, very common with the Nissan turbo cars.
The stock re-circ valve does blow hot air back into the intake because it's positioned on the intercooler inlet pipe, but it's only good for stock boost level anyway. You can also get different response dependin' on where you position the valve; intercooler inlet = slow response, on the intercooler itself or intercooler outlet to throttle body pipe = quicker relief.
The stock re-circ valve does blow hot air back into the intake because it's positioned on the intercooler inlet pipe, but it's only good for stock boost level anyway. You can also get different response dependin' on where you position the valve; intercooler inlet = slow response, on the intercooler itself or intercooler outlet to throttle body pipe = quicker relief.
