BOV Placement
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Staging Lane
Joined: Jul 2005
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BOV Placement Ok.....I'm pretty sure I know the answer but I want to double check. I have a 3.8L Camaro that has the MAF integrated INTO the top of the throttle body. I am switching to an LS1 MAF this week.
Does it matter if the BOV goes before or after the MAF on the intake piece? I don't think it does..just want to check...
Does it matter if the BOV goes before or after the MAF on the intake piece? I don't think it does..just want to check...
it does matter, before the maf.
If you put it after the maf, the bov will blow off all the air the maf just read and you would be really rich because you just took away the air the engin thought was going to come in. It would not kill the motor but its not the way it should be done.
If you put it after the maf, the bov will blow off all the air the maf just read and you would be really rich because you just took away the air the engin thought was going to come in. It would not kill the motor but its not the way it should be done.
Thread Starter
Staging Lane
Joined: Jul 2005
Posts: 89
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Well.....crap......
Looks like I am gunna need to do something different than what I thought I was going to with either my intake piece or BOV Placement.....Crap....
Or else I'll need to invest in some more couplers which I really wasn't hoping for.....
Where is it best to put the BOV? Close to the throttle body, correct?? Would it be OK to put it a good bit closer to the intercooler instead???
Looks like I am gunna need to do something different than what I thought I was going to with either my intake piece or BOV Placement.....Crap....
Or else I'll need to invest in some more couplers which I really wasn't hoping for.....
Where is it best to put the BOV? Close to the throttle body, correct?? Would it be OK to put it a good bit closer to the intercooler instead???
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Another vote for pre-MAF ... I started out having my BOV right near the TB (after the MAF), and it would have a bad rich condition/stumble on decel that would take several seconds to clear.
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Staging Lane
Joined: Jul 2005
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Ok. So as long as I put the BOV AFTER the intercooler I am ok?......... And then the MAF after the BOV?
Do you just want the MAF as close to the TB as possible, or also the BOV? As it is looking, the BOV will be about 1.5' of piping behind the TB, and the MAF will be about a foot or so.........
This sound ok?
Do you just want the MAF as close to the TB as possible, or also the BOV? As it is looking, the BOV will be about 1.5' of piping behind the TB, and the MAF will be about a foot or so.........
This sound ok?
Something to consider...
using some of our numbers, say your at full boost of 28psi. At max RPM, that's something like 95 to 100 lb/min of air, or in the neighborhood of 1500 to 1800 CFM give or take.
All of your charge system from intercooler to motor is at 28 psi and flowing that air. Between your turbo and the inlet to the cooler is something reasonibly higher than that. At that flow, probably closer to something like 33 psi. (another thing to keep in mind when considering pressure ratio, but that's another topic
)
Now drop the throttle. You're still flowing all that air until the turbo slows down, but you've just removed the only source of consumption for that 1800 CFM. You've already got things at 33psi on the inlet side of the cooler (hope you've got good beads and thick endtanks) Now shove 1800CFM into a closed system.
Where would you put the valve, right at the source of the feed or after all of your plumbing??
There's a reason you see coolers with extra straps on the joints, and 60mm HKS wastegates as BOV's. Having rewelded a few tanks, and moved a few valves, I put the biggest I can fit BEFORE the cooler
2 ATI race valves are going on my new setup. I don't wanna pop an endtank with it sitting next to me in the car.
using some of our numbers, say your at full boost of 28psi. At max RPM, that's something like 95 to 100 lb/min of air, or in the neighborhood of 1500 to 1800 CFM give or take.
All of your charge system from intercooler to motor is at 28 psi and flowing that air. Between your turbo and the inlet to the cooler is something reasonibly higher than that. At that flow, probably closer to something like 33 psi. (another thing to keep in mind when considering pressure ratio, but that's another topic
)Now drop the throttle. You're still flowing all that air until the turbo slows down, but you've just removed the only source of consumption for that 1800 CFM. You've already got things at 33psi on the inlet side of the cooler (hope you've got good beads and thick endtanks) Now shove 1800CFM into a closed system.
Where would you put the valve, right at the source of the feed or after all of your plumbing??
There's a reason you see coolers with extra straps on the joints, and 60mm HKS wastegates as BOV's. Having rewelded a few tanks, and moved a few valves, I put the biggest I can fit BEFORE the cooler
2 ATI race valves are going on my new setup. I don't wanna pop an endtank with it sitting next to me in the car.
makes perfect sense,i was thinking something along the same lines since there is an obvious pressure drop from the FMIC,it makes sense to release pressure where there is the most amount.
Thread Starter
Staging Lane
Joined: Jul 2005
Posts: 89
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Doing that really isn't an option with my car, and I will be running 18 psi at the max on a T70 turbo........ Built 3.8L Motor. I think putting it right after the IC will be fine in my case.........
TECH Resident
Joined: Oct 2005
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I think y2khawk's explanation was excellent with a real world example of a high airflow system. ATI also shows the valve placed just after the supercharger in its race plumbing diagram. However I personally feel the ideal placement of the bypass valve is between the I/C system and throttle body. Here is why, when the throttle shuts the pressure will dramatically increase in the system and the pressure wave will travel back towards the supercharger through the intercooler which caqn cause distress to the I/C and plumbing. Any working I/C will have a pressure drop across it and threrefore causes a restriction to flow. This will increase the ammount of time it takes for the pressure in the system to drop. By placing the valve near the throttle body the pressure will not spike as the consumption of the engine is replaced by the area presented by the valve as its action is pretty instantaneous if adjusted properly.
Now placing the valve just after the supercharger will completely remove the supply but the system has to bleed down after it opens which includes the entire I/C assembly doing reverse flow.
In practice it might not matter all that much. The important thing is to make sure the valve is sized appropriately to the airflow of the supercharger. Remember its not the "boost" level but the delivered airflow of the supercharger that determines what valve to use.
Make sure that any air measured by the MAF is only measured once and is consumed by the engine. Any recirculation from a bypass valve should enter the plumbing well away from the MAF so that is doesn't introduce false measurements. This especially applies to draw through system plumbing.
Now placing the valve just after the supercharger will completely remove the supply but the system has to bleed down after it opens which includes the entire I/C assembly doing reverse flow.
In practice it might not matter all that much. The important thing is to make sure the valve is sized appropriately to the airflow of the supercharger. Remember its not the "boost" level but the delivered airflow of the supercharger that determines what valve to use.
Make sure that any air measured by the MAF is only measured once and is consumed by the engine. Any recirculation from a bypass valve should enter the plumbing well away from the MAF so that is doesn't introduce false measurements. This especially applies to draw through system plumbing.