BOV placement
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Ian Turgeon
Cascading Inspiration
Re: BOV placement
can't put a bov behind the throtle body, would be a gool place to put a pop-off valve though.
can't put a bov behind the throtle body, would be a gool place to put a pop-off valve though.
ghettosled
SYTY SUPERSTORE
Re: BOV placement
only problem with using a pop off valve is if you are trying to make it act as a wastegate to control boost.. not good b/c it overspeeds the turbo.
only problem with using a pop off valve is if you are trying to make it act as a wastegate to control boost.. not good b/c it overspeeds the turbo.
moronmechanic
New member
Re: BOV placement
OK, let me clear up something about BOV's POV's, intake bypass valves, whatever you want to call them. Here's what they do:
They dump boost when; A) intake backfire, or overboost. B) throttle plate shuts durring boosted condition, like gear shifts.
The diaphram line is plumbed into the intake manifold after the throttle plate, when the down stream side of the throttle plate goes to vacuum and the up stream side is under boost, the valve opens and dumps boost. This would otherwise overboost the and, no shit here- stop the turbo from spinning and in some cases make it spin backwards- the compressor side acting like the turbine side driving the turbo. When you do a hot gearshift, the BOV opens, the turbo keeps spinning; then you open the throttle again for the next gear and the BOV closes, boosted air suddenly blasts through the throttlebody making the next gear feel real torquey, like a huge flywheel. This is why turbo engines benifit from lightning fast shifts. Or automatic transmissions...
You always want your BOV mounted as close to the throttlebody as possible, NOT close to the turbo. Your boosted air should NEVER change direction in the intake tract. This will cause a noticable hesitation because the boosted air has to stop, turn around, get dumped out of the BOV; when the throttle opens back up, the air has to again change direction and head towards the cylinders. You want to make use of the pressure wave that the BOV causes, not waste it.
Turbo lag is usually looked at as a negative aspect of turbocharging, not in drag racing. Here's why:
It takes a while to spool up the turbo to 100,000 RPM, it takes just as long to slow it down. If you have a manual trans, a BOV and you shift like a crack addict, you don't have to spool the turbo up for every gear shift. It makes my little 1.8L Subaru engine feel like a big block when upshifting.
The BOV is usually vented back to the intake side of the turbo, downstream of the MAF, it is after all, metered air. If you dump it to the air, you will see a brief rich condition. I vent mine to atmosphere in my rally car because it gives me a nice exhaust backfire with a flame. This jolts the turbo up in RPM for a second while I shift- good for power, bad for turbo. Who cares, it's racing right???
-Chuck-
OK, let me clear up something about BOV's POV's, intake bypass valves, whatever you want to call them. Here's what they do:
They dump boost when; A) intake backfire, or overboost. B) throttle plate shuts durring boosted condition, like gear shifts.
The diaphram line is plumbed into the intake manifold after the throttle plate, when the down stream side of the throttle plate goes to vacuum and the up stream side is under boost, the valve opens and dumps boost. This would otherwise overboost the and, no shit here- stop the turbo from spinning and in some cases make it spin backwards- the compressor side acting like the turbine side driving the turbo. When you do a hot gearshift, the BOV opens, the turbo keeps spinning; then you open the throttle again for the next gear and the BOV closes, boosted air suddenly blasts through the throttlebody making the next gear feel real torquey, like a huge flywheel. This is why turbo engines benifit from lightning fast shifts. Or automatic transmissions...
You always want your BOV mounted as close to the throttlebody as possible, NOT close to the turbo. Your boosted air should NEVER change direction in the intake tract. This will cause a noticable hesitation because the boosted air has to stop, turn around, get dumped out of the BOV; when the throttle opens back up, the air has to again change direction and head towards the cylinders. You want to make use of the pressure wave that the BOV causes, not waste it.
Turbo lag is usually looked at as a negative aspect of turbocharging, not in drag racing. Here's why:
It takes a while to spool up the turbo to 100,000 RPM, it takes just as long to slow it down. If you have a manual trans, a BOV and you shift like a crack addict, you don't have to spool the turbo up for every gear shift. It makes my little 1.8L Subaru engine feel like a big block when upshifting.
The BOV is usually vented back to the intake side of the turbo, downstream of the MAF, it is after all, metered air. If you dump it to the air, you will see a brief rich condition. I vent mine to atmosphere in my rally car because it gives me a nice exhaust backfire with a flame. This jolts the turbo up in RPM for a second while I shift- good for power, bad for turbo. Who cares, it's racing right???
-Chuck-
Ian Turgeon
Cascading Inspiration
Re: BOV placement
the above post is made about once per year
the above post is made about once per year
moronmechanic
New member
Re: BOV placement
Are you saying that in the sy/ty the MAF is located between the turbo and intake rather than between the air filter and turbo? That'a a strange setup, most cars (even the GN) have the MAF between the air filter and the turbo. If so, you are right, there won't be a rich condition if you bleed off unmetered air.
You still want the BOV as close to the throttlebody as possible to keep fliuds flowing in the right direction.
-Chuck-
Are you saying that in the sy/ty the MAF is located between the turbo and intake rather than between the air filter and turbo? That'a a strange setup, most cars (even the GN) have the MAF between the air filter and the turbo. If so, you are right, there won't be a rich condition if you bleed off unmetered air.
You still want the BOV as close to the throttlebody as possible to keep fliuds flowing in the right direction.
-Chuck-
schrgds
Turbos > Superchargers
Re: BOV placement
I honestly dont know how the sy/ty is setup but... On my supercharged S10 I had to have the BOV before the MAF or the truck wouldnt idle properly due to the amount of air a blower pushes at idle.
I never experienced any compressor surge with the BOV right after the blower before the intercooler, MAF, TB etc.
So stock Sy/Ty's are draw through using a bypass valve?
Airfilter--->MAF---->Turbo--->I/C--->BPV--->TB
Thats how my truck was non intercooled. Intercooled it had to be setup blow through:
Airfilter--->S/C---->BOV---->I/C--->MAF--->TB
I could set it up draw through with the intercooler using a bypass valve (BPV) but then the MAF wouldnt see the cooler dense air after the intercooler.
I honestly dont know how the sy/ty is setup but... On my supercharged S10 I had to have the BOV before the MAF or the truck wouldnt idle properly due to the amount of air a blower pushes at idle.
I never experienced any compressor surge with the BOV right after the blower before the intercooler, MAF, TB etc.
So stock Sy/Ty's are draw through using a bypass valve?
Airfilter--->MAF---->Turbo--->I/C--->BPV--->TB
Thats how my truck was non intercooled. Intercooled it had to be setup blow through:
Airfilter--->S/C---->BOV---->I/C--->MAF--->TB
I could set it up draw through with the intercooler using a bypass valve (BPV) but then the MAF wouldnt see the cooler dense air after the intercooler.
moronmechanic
New member
Re: BOV placement
That's good news, I prefer the speed density setup. Less extra crap in the engine compartment, plus you get to mount the air filter right on the turbo if you want to. My setup will be MagaSquirt, also a speed density system.
That's good news, I prefer the speed density setup. Less extra crap in the engine compartment, plus you get to mount the air filter right on the turbo if you want to. My setup will be MagaSquirt, also a speed density system.
Ty1642
Member
Re: BOV placement
I'd like to put a pop off valve on to protect against an overboost, but I haven't been able to find one. I've looked in Summits catalog and done a few searches on the web. Does anyone know where to get one, or is it something that can be built out of Home Depot parts?
I'd like to put a pop off valve on to protect against an overboost, but I haven't been able to find one. I've looked in Summits catalog and done a few searches on the web. Does anyone know where to get one, or is it something that can be built out of Home Depot parts?
