# KA24DET BOV question **URL:** \ **Category:** SON240sx Automotive\ **Created:** [August 27, 2012, 7:27am UTC](https://forums.speedlife.net/t/ka24det-bov-question/225550 "2012-08-27T07:27:04Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Clutchfire](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/clutchfire/32/5654_2.png) [@Clutchfire](https://forums.speedlife.net/u/Clutchfire)\ **Post date:** [August 27, 2012, 7:27am UTC](https://forums.speedlife.net/t/ka24det-bov-question/225550/1 "2012-08-27T07:27:04Z")
So as this is my first turbo setup for you KAT owners or SR owners. What is the proper opporation of the blow off valve between idle, acceleration, deceleration? I have read somewhere that a BOV should be adjusted as followed. Make sure the bov screw is in just enough that it releases no air at idle, then during deceleration it should pop open the fastest. So I adjusted it as such just enough spring load to keep it closed at idle but when I rev the engine and let it cycle down the BOV only opens a very slight amount. You cant actually see it open but I can feel a little bit of air blow past my fingers. It makes no sound other then the surge from the air filter. So what i can gather is the BOV dose sort of work but my engine does not produce enough vacuum difference between idle and deceleration to open it. Is this the fault of the BOV or do I need to find an other method of opening this BOV that can create a larger pressure difference. Pressures: Idle: -22 PSI Deceleration: -28 PSI Full boost +10 PSI ---
**Author:** ![Nismo240SX](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/nismo240sx/32/5755_2.png) [@Nismo240SX](https://forums.speedlife.net/u/Nismo240SX)\ **Post date:** [August 27, 2012, 7:53am UTC](https://forums.speedlife.net/t/ka24det-bov-question/225550/2 "2012-08-27T07:53:35Z")
The blow off valve will open fully depending on the amount of pressure, or boost that is being released. There has to be boost in order for it to open. At 2 psi just say it would just flutter, at 8psi or 10psi for example it will open fully releasing the pressure. Make sure your vacuum line is hooked up after the throttle body for bov vacuum. Everything else seems normal ---
**Author:** ![Clutchfire](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/clutchfire/32/5654_2.png) [@Clutchfire](https://forums.speedlife.net/u/Clutchfire)\ **Post date:** [August 27, 2012, 8:58am UTC](https://forums.speedlife.net/t/ka24det-bov-question/225550/3 "2012-08-27T08:58:09Z")
Yeah the vacuum is coming from the manifold for sure. It just seems strange that if I drive the car like a women it will run fine. If I build the boost up to 10psi and push the clutch in fully and let it cycle down to an idle wile costing the RPMs will drop all the way to 0 and of course stall. I can start the car right after no problem but yeah you get the point this isn’t suppose to happen. ---
**Author:** ![karkas9](https://avatars.discourse-cdn.com/v4/letter/k/f14d63/32.png) [@karkas9](https://forums.speedlife.net/u/karkas9)\ **Post date:** [August 27, 2012, 9:02am UTC](https://forums.speedlife.net/t/ka24det-bov-question/225550/4 "2012-08-27T09:02:29Z")
it should be open a bit on idle(5-20%). it should open a 65% to 100% open at “decel” (max vac). it should close at atmospheric pressure onward (0 PSI). ---
**Author:** ![Clutchfire](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/clutchfire/32/5654_2.png) [@Clutchfire](https://forums.speedlife.net/u/Clutchfire)\ **Post date:** [August 27, 2012, 10:02am UTC](https://forums.speedlife.net/t/ka24det-bov-question/225550/5 "2012-08-27T10:02:34Z")
So whats correct? should it be opened slightly at idle or not? ---
**Author:** ![rhdcrx](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/rhdcrx/32/5781_2.png) [@rhdcrx](https://forums.speedlife.net/u/rhdcrx)\ **Post date:** [August 27, 2012, 10:27am UTC](https://forums.speedlife.net/t/ka24det-bov-question/225550/6 "2012-08-27T10:27:53Z")
do you have something to control decel air? Since the MAF has all ready registerd the amount of air coming into the engine. It has matched fuel accordingly. Now with a blow off valve you are releasing metered air which is know for causing stalling. Now SAFCs have decel air settings to fix this issue and quote on quote trick the MAF. ---
**Author:** ![Clutchfire](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/clutchfire/32/5654_2.png) [@Clutchfire](https://forums.speedlife.net/u/Clutchfire)\ **Post date:** [August 27, 2012, 10:40am UTC](https://forums.speedlife.net/t/ka24det-bov-question/225550/7 "2012-08-27T10:40:32Z")
The ECU is tuned I would assume its designed to handle this. ---
**Author:** ![danbikes](https://avatars.discourse-cdn.com/v4/letter/d/f9ae1b/32.png) [@danbikes](https://forums.speedlife.net/u/danbikes)\ **Post date:** [August 27, 2012, 10:46am UTC](https://forums.speedlife.net/t/ka24det-bov-question/225550/8 "2012-08-27T10:46:17Z")
> [@Nismo240SX](#): > > The blow off valve will open fully depending on the amount of pressure, or boost that is being released. There has to be boost in order for it to open. > At 2 psi just say it would just flutter, at 8psi or 10psi for example it will open fully releasing the pressure. > Make sure your vacuum line is hooked up after the throttle body for bov vacuum. Everything else seems normal ^ this. Also, a BOV should NOT be open on idle. A recirc is a different story since theres no metered air being lost that way. About the stalling issue, its most likely due to your tune. If you’re running a stock ecu, it doesnt know to compensate for the metered air being released from the BOV, assuming you’re running a MAF. ---
**Author:** ![Nismo240SX](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/nismo240sx/32/5755_2.png) [@Nismo240SX](https://forums.speedlife.net/u/Nismo240SX)\ **Post date:** [August 27, 2012, 10:54am UTC](https://forums.speedlife.net/t/ka24det-bov-question/225550/9 "2012-08-27T10:54:29Z")
Most of these tunes require recirculated bovs. ---
**Author:** ![Clutchfire](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/clutchfire/32/5654_2.png) [@Clutchfire](https://forums.speedlife.net/u/Clutchfire)\ **Post date:** [August 27, 2012, 2:12pm UTC](https://forums.speedlife.net/t/ka24det-bov-question/225550/10 "2012-08-27T14:12:09Z")
I hear the opposite that KA tunes need atmospheric BOV. Not sure witch is right or wrong. What I can tell you is once you push boost and let off holly hell you can hear that BOV and or flutter. Its a chipped ECU. Check out this video its not mine but the sound is almost dead on to what mine sounds like. ---
**Author:** ![nate10](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/nate10/32/5723_2.png) [@nate10](https://forums.speedlife.net/u/nate10)\ **Post date:** [August 27, 2012, 2:25pm UTC](https://forums.speedlife.net/t/ka24det-bov-question/225550/11 "2012-08-27T14:25:39Z")
If it has a mafs then it should be recirculated, if you are running a map setup then u can run it vented to atmosphere. ---
**Author:** ![Nismo240SX](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/nismo240sx/32/5755_2.png) [@Nismo240SX](https://forums.speedlife.net/u/Nismo240SX)\ **Post date:** [August 27, 2012, 2:45pm UTC](https://forums.speedlife.net/t/ka24det-bov-question/225550/12 "2012-08-27T14:45:09Z")
Like I said. A bov needs pressure to open. The less the pressure, the minimal it will(low psi) open (fluttering) the more pressure (more psi) the more it will open (pppssssssshhhhhhh) ---
**Author:** ![Clutchfire](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/clutchfire/32/5654_2.png) [@Clutchfire](https://forums.speedlife.net/u/Clutchfire)\ **Post date:** [September 8, 2012, 5:36am UTC](https://forums.speedlife.net/t/ka24det-bov-question/225550/13 "2012-09-08T05:36:33Z")
yeah you made a good point Nismo. After I did some testing I found what you said you be almost dead on. I had to get that turbo spooled right up before the BOV really opened up. It still stalls so I will give a rs BOV a try. ---
**Author:** ![Nismo240SX](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/nismo240sx/32/5755_2.png) [@Nismo240SX](https://forums.speedlife.net/u/Nismo240SX)\ **Post date:** [September 9, 2012, 12:39pm UTC](https://forums.speedlife.net/t/ka24det-bov-question/225550/14 "2012-09-09T12:39:25Z")
The car most likely stalls because the bov is not recirculated and most KAT tunes require it to be cause the tune is thinking it has that extra air entering from the bov. So when u hit WOT and build boost and then let go, the car is dumping fuel in but it also thinks it is getting the recirculated air from the bov but it’s not. Causing it to run rich and most likely stall and mine used to do that yes. ---
**Author:** ![Clutchfire](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/clutchfire/32/5654_2.png) [@Clutchfire](https://forums.speedlife.net/u/Clutchfire)\ **Post date:** [September 9, 2012, 7:48pm UTC](https://forums.speedlife.net/t/ka24det-bov-question/225550/15 "2012-09-09T19:48:03Z")
I have the RC BOV installed now. Sad to let my fun Sound BOV sound go but what ev. the flutter is almost completely gone and the car has a hell of a dip in RPM but seems to hold on now. No stall so far I’m cautiously optimistic. ---
**Author:** ![Nismo240SX](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/nismo240sx/32/5755_2.png) [@Nismo240SX](https://forums.speedlife.net/u/Nismo240SX)\ **Post date:** [September 9, 2012, 7:50pm UTC](https://forums.speedlife.net/t/ka24det-bov-question/225550/16 "2012-09-09T19:50:00Z")
It could’ve been that. Try also turning up your idle using the Ecu idle screw or the throttle body screw. With the throttle screw, caution only open it up very very very tiny turns. It’s sensitive. ---
**Author:** ![BCHLR240SX](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/bchlr240sx/32/5754_2.png) [@BCHLR240SX](https://forums.speedlife.net/u/BCHLR240SX)\ **Post date:** [September 9, 2012, 7:54pm UTC](https://forums.speedlife.net/t/ka24det-bov-question/225550/17 "2012-09-09T19:54:24Z")
I use to run a recirc on my ka-t and switced to open, I’ve had no stalling issues though. Odd. ---
**Author:** ![Clutchfire](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/clutchfire/32/5654_2.png) [@Clutchfire](https://forums.speedlife.net/u/Clutchfire)\ **Post date:** [September 10, 2012, 8:41am UTC](https://forums.speedlife.net/t/ka24det-bov-question/225550/18 "2012-09-10T08:41:52Z")
I had idle screw all the way in, i set the engine when i was running it NA. I ran about 6-700 RPM at the time. Then added the turbo. the turbo forces some air into the intake at idle with the screw all the way in it allows my idle to stay at about 900 RPM. if i open it anymore the idle will of course go up over 1000. Do KAT owners run that fast of an idle? When I accelerate produce 10PSI of boost then drop the clutch the rpm drops to about 500 then settles at 900 when it comes to a stop. it could be the BOV needs a stiffer spring. I can try that next. ---
**Author:** ![Nismo240SX](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/nismo240sx/32/5755_2.png) [@Nismo240SX](https://forums.speedlife.net/u/Nismo240SX)\ **Post date:** [September 10, 2012, 12:15pm UTC](https://forums.speedlife.net/t/ka24det-bov-question/225550/19 "2012-09-10T12:15:53Z")
Ya. What’s ur vacuum read on the boost gauge at idle ---
**Author:** ![Clutchfire](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/clutchfire/32/5654_2.png) [@Clutchfire](https://forums.speedlife.net/u/Clutchfire)\ **Post date:** [September 10, 2012, 4:25pm UTC](https://forums.speedlife.net/t/ka24det-bov-question/225550/20 "2012-09-10T16:25:21Z")
-22 psi give or take. [Next page](https://forums.speedlife.net/t/ka24det-bov-question/225550.md?page=2)