Questions from beginner car enthusiasts on where to get blow off valves for normally aspirated cars are not uncommon as they don’t know what blow off valves are for, and how they work. It is not possible for you to install a blow off valve onto a normally aspirated car, they are for forced inducted engines. No matter how much you like the sound. Hehe.
Normal engine operation.
Let’s ignore how turbochargers work and just assume it works since this post is not about turbochargers. The engine receives the turbocharged air through the intake. That’s assuming the throttle is open. Now what happens when you lift your foot off the pedal? The compressed turbocharged air has no where to go. It hits the closed throttle plate and goes back up the intake manifold the opposite direction. Back into the turbine. This high pressure air hitting the turbine blades from the wrong side of the turbo slows down the spinning turbine, thus reducing boost. When you press the accelerator pedal again, the turbo has to slowly spin up again to gain maximum boost. This is bad. Very bad. The reverse surge of turbocharged air could also damage the turbine. This is also bad. Very bad.
Air is released. Pardon the noobness of the diagram!
This is why blow off valves exist. It releases turbocharged air coming down the wrong direction of the intake manifold out to the atmosphere. You get longer turbocharger life, quicker spool, and better transient response. Of course, there is the issue of the stock standard ECU expecting air but not getting air, and pumping too much fuel in, but that’s a different issue. For cars with that problem (usually because of the usage of Mass Airflow Sensors) there is a different type of blow off valve that recirculates turbocharged air back into the intake instead of releasing it into the atmosphere. Sounds a lot less cooler though heheh.
Recirculating blow-off valves send air back into the intake
You can’t put a blow off valve on a naturally aspirated car because induction (the sucking of air into the engine) is done using vacuum. The engine itself sucks air in, instead of the turbine pushing compressed air in. When the throttle is closed, no air is being sucked in, and there is no boost bouncing back into a non-existent turbocharger turbine. There is nothing to “blow offâ€.
So that’s what blow off valves are for, and that is why you only put them on turbocharged cars. So if you want that cool sound that turbocharged cars have whenever they shift gears, you need a turbocharged car. Like a Perdana V6 Twin Turbo.
After dabbling for years in the IT industry, Paul Tan initially began this site as a general blog covering various topics of personal interest. With an increasing number of readers paying rapt attention to the motoring stories, one thing led to another and the rest, as they say, is history. An avid electronic gadget aficionado as well as big-time coffee lover, he's also the executive producer of the Driven motoring TV programme.
Biggest Turbo fan here but cant afford any car with Turbo. Any recommendation for cheapest high pressure turbo cars? I seriously mean cheap! Hehe.
hi,jason,i have a problem here.i have hks ssqv BOV.how can i install my BOV at my engine?my engine is standard 1.6 injection 4g92.no turbo.can i install at intake piping?is it work?
Hi Paul…great website!i stil remember frst time i heard the sound of B.O.V, it was from an RX7 FD and Starlet GT.
wow,u just bought a perdana,sell already your satria ?
Perdana twin turbo. Eterna engine ey? I understand got a bit of problems this one and not too powerful for the displacement. Nevertheless, hope you got a good one in your hands.
Jason: Cheap turbo? Go to the half cut shop and ask. every shop holds a different price. Cheap = high maintenence. Remember that.
Paul. I am curious of one thing. There are some variations of turbochargers which do not need blow off valves, eg, Ford's Lynx RS does not include a BOV. So how come they don't need it? Won't it reduce the lifespan of the turbocharger? I think it's a Garrett T93 (not too sure of the model number).
Twin turbo? Is it Eterna?
Yup. 6A12TT from the Eterna. Not bad lah, 220hp from a 2.0 V6 with quite low boost. Too much power is ridiculous anyway.
Woohoo! 6A12TT! Can't wait for ya AWD conversion!
Anyway, BOV is for Turbo or Supercharger ONLY.
Anyone asking whether it can be used on NA is PLAIN STUPID or simple IGNORANT!
Putting those NA BOV Sound Device is just asking for trouble n probably lose face after being chased by a real turbo car.
Get real. Get the real deal. Nothing beats a force-induction car. Drive one to feel it.
I did n although the fuel consumption is a little high… I don't mind because I'm addicted to POWER!
Wahlaueh…
had attended a valueble class.
Paul, do you have any info regard the boosting bar like the higher boost better or lower better??
karheng: simply because the manufacturer did not decide to include one. hehe.
paul, as far as i know la, sometime cars like volvo, saab or even stock cars got turbo but no bov because they got low or light pressure turbo. Other than that they wanna cut cost la i think.
anyway paul, the pic was really cool man, especially the one got pssshhhh.. hehehe simple but easy to understand.. but for the newbies, better go to howstuffworks first la.. hehehe
Nothing surprise la kawan our firebrigade also have turbo what? But still didn't heard the kepishh one lei! lol…
hahha.. really?? fire engines are forced induced engines? hahaha.. new fact everyday i suppose..
congrats on your buy paul. don't break the speed limit yeah?
So guys…. can a BOV installed in a diesel turbocharged engine?
can, but i think it's a BOV if a different kind ler.. anyone care to share some light on this?
I wanted to know about By Pass Valve !! hehehe just bought an Audi A4 1.8T … very reliable car ! (Except the fact that people who doesn't own one dont know anything about it and talk crap bout it….. ) hehe Paul ~~ what do you think? i remembered you thought of getting one right? Go Ahead ! great car !
hi, i’m a complete novice and i’ve just bought a peugeot 306 xrdt. was wondering if i could fit a blow off valve onto it and how would i do it? help appreciated!! ta
can i install my HKS blow off valve without turbo?
can i install my blow off valve without a turbo kit?
how to kill a porsche with turbocharger,Greddy SSQV,and a special intake manifold…?
can i install a blow off valve on my non turbo holden astra
u can put a bov on a na car and make it work if u know what ur doing
make it work lol? are you kidding, even if you did install one on NA, your not even going to get any sound other than a slight hiss like you hear on a turbocharged engine when reving at idle, thats common sense, you wont hear anything like you do when you are under boost then let off the throttle and get the REAL deal sound of the bov you installed is capable of lol, besides a bov is for a function not just sound!!! there is reasons bov are used in turbo/supercharged engines such as keeping pressure from returning back into the charger and vent to atmosphere saving its lifespan, etc..
a question about your diagram, isnt the turbine supposed to be located on the exhaust side?
the diagram is only the flow of intake air, not exhaust. this way the same diagram can be applied for other forced induction devices such as superchargers too.
I have a Cadillac cts 3.2 V6 n I was wondering if I can install a BOV in it..n if its gonna be bad or good if I do..please let me know what u ppl think