proper operation of BOV

[PaulC-turbo5.0]

Been having issues with rich to lean swings when shifting and its making me wonder if i have my BOV operating properly. I have a turbosmart supersonic BOV vented to atmosphere which has an adjustable cap to set spring tension. Stock cam so 18-20 inches of vacuum at idle. I have always had the spring set pretty soft so the valve dumps on every shift and will even dump on a higher rpm free rev. I have recently started wondering if this is correct and havent found a detailed breakdown on exactly how it "should" function for my application on the web. Even the directions for setting it from TS themselves are extremely basic.

So in my application how exactly should this BOV perform? Or what is the proper way to "tune" the spring tension of a BOV? I have increased spring tension a bit 2 times over the last day and its not dumping as easily but still pretty easy and doesnt seem like its lessened the AFR swings.

[decipha]

http://efidynotuning.com/pre.htm#bov

bov should be mounted as close to the turbo as possible well before the IC and the throttle body. MAF should be mounted in the inlet pipe leading to the throttle body.

shouldn't have any reversion going on to affect AFRs

[PaulC-turbo5.0]

cool thanks for the info. I have posted about this a few different times, youve asked for logs and tune files but doesnt seem you have found time to check them out.

I have it setup correctly and just today adjusted so the spring is on full hard and it still seems to blow off relatively easily, not super easily like previously but still blowing on shifts when not in boost. cant for the life of me figure out why its affecting the afr so much

[decipha]

yeah no free time

[PaulC-turbo5.0]

It’s cool man I’m fairly confident there isn’t anything tune related that’s going to help.

Would you recommend I try shimming the spring? Even in the full hard position it seems like it’s popping off to easily.

[dleach1407]

cool thanks for the info. I have posted about this a few different times, youve asked for logs and tune files but doesnt seem you have found time to check them out.

I have it setup correctly and just today adjusted so the spring is on full hard and it still seems to blow off relatively easily, not super easily like previously but still blowing on shifts when not in boost. cant for the life of me figure out why its affecting the afr so much

What you are describing seems to be normal operation for a BOV. Mine also "blows off" when not in boost but this is attributed to the turbo spinning and the throttle plate closing causing a backup of pressure. The turbo isnt spinning fast enough to produce pressure when the throttle is open but it is once the plate is closed which is why you get the blow off sound. I dont think there is anything wrong with your BOV but it appears both of us are still dealing with this.

[PaulC-turbo5.0]

Glad to hear yours operates the same. I haven’t second guessed it’s operation until recently while trying to narrow down the afr swings.

[PaulC-turbo5.0]

interesting results this morning. by the time i pulled out of the driveway the car was in closed loop, i still got the afr swings on the gauge on shifts but didnt hear the big rush of air blowing off and the hesitation was not noticeable. one shift i got the rpm's up a bit higher, heard the pshhhh and sure enough the car stumbled. easier shifts afterward with no stumbling. this makes me think it is related to the BOV spring stiffness and that i need to somehow add more tension still. its something that should be easy enough to experiment with at least.

[dleach1407]

Is your maf in a blowthrough or draw-through configuration. The only way that makes sense is if the BOV is after the maf.

[PaulC-turbo5.0]

blow through. my intact tract is for sure setup correctly so yes it doesnt make sense whats going on. if it wasnt for this issue i wouldnt be second guessing a thing

[decipha]

if its popping off though its building pressure. Even the slightly bit of pressure is going to escape back out so it could cause reversion and skew the maf readings regardless.

[PaulC-turbo5.0]

that does make sense. I am sure i just caught up on this BOV thing in hopes of correcting this issue.

what can be done to help or correct reversion? i guess thats why i am trying to correlate the 2, if the bov stays closed the air cant possibly revert lol.

[decipha]

you only want the bov to pop when there is boost in the inlet. If it pops up and you hadn't built any pressure then the spring is too soft.

[PaulC-turbo5.0]

well i specifically remember paying attention at one point yesterday and my gauge read 12 inches of vacuum and the valve still popped.

its my 8 year wedding anniversary today so its likely i wont be able to mess with it tonight lol but i want to get the valve off to shim the spring and experiment with it further

[dleach1407]

Wouldnt the pressure being released cause reversion any time the bov opens due to excess pressure? Seems like the issue would be present every single time you shift in boost.

[PaulC-turbo5.0]

just wanted to update this the BOV is not the problem, i have it set back close to where it was originally.

car acted up again this morning and the wideband read rich with just a throttle release, no shifting.