BoV Location?

[sirtef9]

Always hear it goes before the throttle body, but recently read this..

"The vast majority of people will tell you that you are supposed to place your blow off valve within a couple feet of your throttle body. I am here to tell you that this is not the best location for your blow off valve.

The best location for your blow off valve is going to be in between your turbo and intercooler, on the hot side.

Think about it. If you put the blow off valve on the cold side (after the intercooler), you are pushing hot air through your intercooler for nothing. This increases the speed at which your intercooler and motor become heat soaked.

By putting the blow off valve before, or even on the intercooler itself - you allow all of the hot compressed air to escape to atmosphere prior to passing through the intercooler. A blow off valve does the same thing no matter where you place it on the charge piping. Knowing this - it's only logical to put it in a place where it relieves hot air rather than cold air."



Any truth to this or is it fine before the throttle body?

[doogie06]

This is why I run multiple bov's.

[sirtef9]

one before the throttle and 1 between turbo and intercooler? I guess I wanna know the best place , since im gettin my intercooling piping on that side redone.

[blinx9900]

i would say you want the pressure release point to be further away from the turbo.

[Martian]

21 BOV salute

There are a whole bunch of different theories regarding this. I have mine closer to the TB so that the air doesn't stop moving. IMO, having the BOV in the middle of the charge line you'll have a section of air that stops movement as soon as the TB closes. This can allow heat to dissapate into your charge piping causing it to get heat soaked. I don't think any are wrong, but each affects things in a different way.

[Evil_SpeedRacer]

That sounds highly logical. I am wondering what Tobi will have to say about this. I would be willing to set my car up this way if it is going to make a difference.

[myshtern]

It doesnt matter, it's been discussed 1345098 times on every car forum.
It especially doesnt matter if you're going to be running something like 7psi like everyone else

[sirtef9]

Well thanks I didnt see the 1232423432432432432432 posts, im not on the pc that much like you, just was curious but thanks really

[Evil_SpeedRacer]

Yeah:rolleyes: We all run 7psi......

[M@]

Put it in your anus. Max pressure relief.

[Evil_SpeedRacer]

Bwaaahahahahaha ^ +10 thats the best way, just like gramps does when he goes heavy on the gin and prune juice!

[myshtern]

Yeah:rolleyes: We all run 7psi......
Are you joking?
Yeah, most people are running 5-10psi, any more and parts break.

It's been proven that turbos have been run for years without a bov and without any problems. If you're running a low amount of boost, it really doesnt matter where it is, it gets the job done. I guess if you're running 30psi and really worried for your turbo you can run two blow off valves.

[Evil_SpeedRacer]

I've never been that low in the Laser. As many DSMs do, I run around on 19psi+ I just thought it was funny...7 psi like everyone else....even with the boost controler off I don't think it would dip that low in my car. Must be a turbocharged Honda with stock internals problem...

[sirtef9]

True Indeed;-)

[M@]

Are you joking?
Yeah, most people are running 5-10psi, any more and parts break.

It's been proven that turbos have been run for years without a bov and without any problems. If you're running a low amount of boost, it really doesnt matter where it is, it gets the job done. I guess if you're running 30psi and really worried for your turbo you can run two blow off valves.

Oh, is that why stock boost on a DSM is 13-14 psi? Why did I run 9-15 psi on my stock B16 for 2 years without any problems? Why are stock LS motors able to take as much as 20 psi (with proper tuning), but easily 17 psi, bone stock...? Just curious how your theory is obviously correct with these factual statements of mine.

[M@]

sirtef9 - by the way, it shouldn't really matter where you put it, in my opinion. The air in the pipes is pressurized, and the blow-off valve is there to serve as an escape route for that air to get out of the system, rather than go in a backwards route to where it came from - the turbo. When you close the throttle body, the air would rush to the first open source (should be the blow-off valve), but if for arguments sake it's non-existant (or you have so much pressure your BOV can't allow all the pressure to escape quickly enough), you get compressor surge. That's when the air rushes back through the compressor wheel, quickly stopping it in the direction it's going, and spinning it backwards and out of the inlet. Very rough on turbos.

[Jackrabbit]

Mine is between the turbo and intercooler. Not because of the reason above, just because that was really the only place to put it.
I think location isn't nearly as important as just having one somewhere.
Before I put mine in I was having wicked compressor surge at 15 PSI.

[wazzelby]

There has also been the argument that having it on the "hot" side of the pipe can cause damage to the BOV due to the pipe and the air in the pipe being hot. It's been argued that this could cause damage to the rubber seals in the BOV.
***disclaimer****
This is not my argument, just another opinion that's been brought up in the past.
That being said, I would recomend putting it close to the throttle body since that's where the change in pressure is occuring.

[dreadlocks]

mine is pre-intercooler right after the turbo.. Really the only option for me since I uses a MAF, need to re-circulate it pre-turbine and post-maf which limits your options.

someone said an ineffective BOV causes the turbine to spin backwards, this is not true as it would also spin the exhaust side backwards and cause your motor to choke badly as it would basically cork the exhaust.... what does happen is the turbine basically hits a wall and cant compress any more air because pressure post-turbine exceeds the compressing capability of the turbo.. this causes air to leak back the opposite way as the turbine is spinning and this creates a fluttering noise... This is very hard on the bearings and seals as it exerts alot of stress when the turbine is working against the flow..

If you have a good BOV/DV then the heat before your IC should not damage it plain and simple..

[stu]

The quoted statement in the first post doesn't even make sense to me. How does the placement make it any less efficient?

It doesn't matter what temperature the air that is being blown off is at, the only thing that matters is what temperature the air is that reaches the motor.

Maybe, maybe this could be an issue if you were talking about a very efficient air/water intercooler setup that cooled the air to far below ambient temperatures. Otherwise, I really can't see how it would matter at all.

[M@]

Okay, I worded it wrong, that's correct that it doesn't spin backwards, but it more or less does the same thing. The air is forced backwards, like I said, to the first opening the pressure is able to find.

[stu]

I re-read the first post, and understand what it is saying now, as far as reducing total heat from going through the intercooler. I still think the results would be negligible though.

[Evil_SpeedRacer]

I wonder what the hard numbers for the temp would be. I remember back in the day in CODSM I was talking to a guy about FMICs at the road racing courses. He put a temp sensor at the TB and tried a Supra side mount VS. the FMIC and the side mount was cooler. Anyway, couldn't we try that on 2 similar cars that have the 2 different setups? The results would be interesting..but at this point after lots of thought, it seems that it would not be very much of a difference.

[stu]

The more I think about this, the more I see the idea that having the BOV be before the IV, would keep the IC cooler for longer.

[sirtef9]

sirtef9 - by the way, it shouldn't really matter where you put it, in my opinion. The air in the pipes is pressurized, and the blow-off valve is there to serve as an escape route for that air to get out of the system, rather than go in a backwards route to where it came from - the turbo. When you close the throttle body, the air would rush to the first open source (should be the blow-off valve), but if for arguments sake it's non-existant (or you have so much pressure your BOV can't allow all the pressure to escape quickly enough), you get compressor surge. That's when the air rushes back through the compressor wheel, quickly stopping it in the direction it's going, and spinning it backwards and out of the inlet. Very rough on turbos.
Thanks, not trying to break any numbers anytime soon, Just want this one of the last time doing altercations to my piping lol

[M@]

Gotcha. Like I said - my saying the turbine shaft spins backwards was incorrect, I let my fingers type faster than my brain thinks. Read a few posts up for a better explanation of compressor surge.

[myshtern]

Oh, is that why stock boost on a DSM is 13-14 psi? Why did I run 9-15 psi on my stock B16 for 2 years without any problems? Why are stock LS motors able to take as much as 20 psi (with proper tuning), but easily 17 psi, bone stock...? Just curious how your theory is obviously correct with these factual statements of mine.
In theory.... who cares
In reality, most guys on this board who have a turbo setup run 7-10psi.

DSM stock boost is 13-14psi?

[myshtern]

I kept my BOV pretty close to the turbo. I'm not sure how fast the air in there moves back and forth once the throttle body closes but my logic was that if I'm shifting gears fast I want it to maintain as much of the pressure in the piping as possible right up until it comes back to the turbo. As long as the turbo isnt spinning backwards, why not keep as much pressurized air in there as possible?

But maybe the air comes back to the turbo faster than you can shift gears so it wouldnt matter.

[Evil_SpeedRacer]

I'm pretty sure I have seen stock 1G DSMs run anywhere from 10 to 13 psi at least. I always see a variance in that as well as the fuel cut but that is ECU related. The Laser had 12psi stock when I first got a boost guage on it. That was when the car had 72,000 on it, from the original owner. Never been modded, never had any major work done on it besides the timing assembly. The one I almost bought at the begining of the year was at 10psi with all of the stock components. I also know that the listed numbers from place to place in the DSM webring would indicate that the stock boost is anywhere from 10 to 14psi as well. It all depends on who you ask, the car, and possibly the elevation and barometric pressure in a given area on a given day. The stock ECU would control the stock boost controller, and would back off boost and also timing depending on the knock sum because of the grade of fuel used in the car, or increased ambient air temperature. The point is the standard boost pressure in a DSM could vary for a number of reasons due to the nature and combination of parts unlike a Honda or similar platform that started out NA and became turbo.


Okay I'm all finished ranting now:ring:

[myshtern]

I had two dsm turbos, one wastegate actuator was set for 6psi, the other for 8psi.
Thats my extent of knowledge about DSMs

...Except they suck :)

[talice]

I don't see why it would matter with placement of the BOV.


And my dads 81 Vw Truck is running 18psi. So, I wanna know how you say, "most" people on this board are running 7-10psi. I'm pretty suprised that you know what "most" people run around here, the only way thats possible, is if you've talked to each and everyone of them about their motors.

[STIBungy]

Coming from someone like you, that doesnt say much.

I had two dsm turbos, one wastegate actuator was set for 6psi, the other for 8psi.
Thats my extent of knowledge about DSMs

...Except they suck :)

[sbiggi]

It isnt going to make any real difference where to bov is located.

I prefer to keep it as close to the Throttlebody as possible, because the throttlebody is were the pressure change happens, like Wazzelby said.

The only thing the BOV does is give the pressure somewhere to go. So as long as its their and functioning, who really gives a shit where you put it. For most people its where ever is convienent.

Venting before the intercooler.... well whoopidty fucking do about heat. Heat is caused from compressing the air, as soon as the BOV opens, the compressor isnt compressing air any more, so I suspect their wouldnt be much heat at that point.
If your intercooler is getting heat soaked and you think putting the bov before it is going to make any real difference, maybe you should buy a bigger intercooler.

[95eghatch]

i had my before and after teh intercooler and havent noticed a difference

[dreadlocks]

an intercooler will heat soak anywase, the argument is stupid because venting a small fraction of air would not have any measurable effect on how long it takes your IC to go from ambient to its normal operating temps.. once the IC has heatsoaked, the BOV location could not possibly have any effect on reducing temps.

BOV location is moot.. end topic

[dsmrider]

i run mine on the boost side after the turbo before the intercooler is where i place my bov so i can cool off my intercooler to control heat soaking before racing drag race tip