Hey, if seen alot of turbo setups and for the most part the blow off valve is on the cold side/ intake side…why do i see alot of SRs with the BOV on the hot side ?
Does it make a difference?
As close to the throttle is the way I like it.
Purges right away as there will be less pressure decrease compared to the hotside
I believe the reason why most people put it onto the hot side is because you don’t waste the cold air that has gone through the intercooler…
But on the otherhand, if its on the cold side your getting rid of the pressure immediately after the throttle closes…I’ve seen both done, both will work. Mine is on the cold side a foot or 2 from the throttle like most people will say to do it, however I never put it there, it was there when I bought it, personally choice I guess…However cold is probably your best bet…
Agreed. Cold side is the way to go in my opinion.
Cold side is the best option, if you have a choice, but hotside will work just fine. Mine is on my hotpipe, because that’s how it came, and I haven’t had the chance to change it. Never had an issue.
one benefit to the hotside is easier ability to recirculate
If your going to recirc then defiantly go for the hot site… unless you want another 4 foot hose in your engine bay.
Another big plus to the hot side is you loose less pressure between shifts. My thoughts anyways.
Ultimately on a street car it doesn’t really matter. Its really a personal preference thing.
Another reason its on the hotside is to clear the pressure near the turbo so it doesnt come back and load it up. Which is one reason alot of people recommend it being placed as close to the turbo as possible.
And technically, I’m pretty sure the BOV must be recirculated from a legal/emissions stand point?
FWIW, I’ve seen a lot of D1 cars recirc’d with their BOV on the coldpipe.
And yes, from an emissions/legal standpoint, the BOV is supposed to be recirc’d.
Another reason its on the hotside is to clear the pressure near the turbo so it doesnt come back and load it up. Which is one reason alot of people recommend it being placed as close to the turbo as possible.
And technically, I’m pretty sure the BOV must be recirculated from a legal/emissions stand point?
this is what i think aswell… if u let off the throttle it blows off the excess air that was generated for that split second you let off the throttle… in return, taking pressure off your turbo and allowing you to boost right away and not have excess pressure go back to your turbo, spinning it the other way…
the way i see it is… when u let off the throttle your throttle body is pretty much closed, and that air wants to go somwhere so its gonna go back to your turbo… so if you let off the pressure as close to the turbo as possible you pretty much eliminate this from happing …
this is just what i think,
i thought there was a thread where someone was gonna dyno with bov on hot side, and bov on the cold side and see if there was a difference…
The logic doesn’t follow though…
Air is a fluid. It’s flowing in the direction of your TB. When the throttle plate closes, it’s going to seek the closest exit. If your BOV is on the hot-side, it has to flow against itself to get back to the BOV. Yes the boost pressure coming immediately off the turbo will get out quickly, but the rest is flowing against itself to get out.
If the BOV is on the cold side, then the air will have a shorter path to the exit, and will not have to flow against itself to get there.
So really, coldside does stand to be the best option, from a fluid dynamics and physics standpoint.
Maybe I’m confused but when the TB closes it technically reverses the flow (hence it going back at the turbo). There for, it would not flow against itself in order to get back.
Even without a BOV, when the TB closes the flow will be reversed back to the turbo unless the pressure is so goddamn strong that it forces the TB open.
Another thing I’d be interested in knowing is how much of the pressure actually gets dumped because I have a feeling not all of it gets out (think of how big the IC is and how much piping there is) for all of that to discharge every so briefly when the BOV opens seems unlikely to me considering most BOV’s have what a 1’’ opening ?
I see what you’re saying, but if the BOV opens the second the TB closes, there’s going to be less turbulance in the pipes because the air doesn’t have to go backwards, it just exits out the BOV instead of the TB… Basically, the air goes backwards because it doesn’t have anywhere to go… if it has an option to exit right beside the TB, it’s going to head that way… If it has to go all the way backwards out the BOV by the turbo, then it will, but I would think from a flow/turbulance standpoint, having it close to the TB will keep things flowing in the right direction… I believe I remember hearing that having the BOV on the coldpipe gives better response, and I would think that follows with my logic… But I might be right out to lunch.
That’s my story and I’m stickin’ to it, anyway :P…
Speaking from working at a tire shop for a good while, you’d be amazed at how quickly air under pressure will evacuate out of a small hole… I bet most of the air gets out the BOV… That’s why guys who run huge boost will frequently run 2, bigger space for the air to get out… Think of how quick your tire inflated to 35psi, with tons of volume, drains out a nail hole…
Ahh my brain hurts!
Dudes, simply put its better on the coldside for the turbo. If you dont have that option then hotside works too.
Thanks guys!
fyi the main reason alot of bov’s are on the hot side with an sr is the stock cold pipe is plastic, can’t really weld the flange to that…
I dont think thats really the case since all it takes it a plastic mold with a protrusion for a rubber tube to connect to it. Many german cars are like that and I think the stock S14 SR has a plastic pipe where a rubber tube connects to for the BOV.
COLDSIDE FTW 