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evo X BOV hindering boost.
Posted: Sun Oct 31, 2010 11:56 am
by Mixedmotorsportmedia
hi guys.
i had fitting a turbo smart BOV to my evo when i did my AMS intake and front mount and piping. i took it to the dyno to see if i had and power differance.... so i went from stock 168.8 KW to 168.9 KW... but the boost was ramping to 21 ( ish ) psi as normal. then dying to 14psi it made full power at 4000rpm...
so i just thought it needed to be tuned but after a while of reading up on the web about other people doing the same mods and getting up near the area of 50hp atw gains. i started to think somthing was wrong... i went hunting for boost leaks yesturday... to no avail.
then when looking on the internet i found this
http://clubralliart.com/showthread.php?t=641
so i swapped it back out to the standard BOV and it seems to pull WAY harder and faster up past 4000rpm.
Anyone heard of this?
Thanks
Posted: Sun Oct 31, 2010 12:47 pm
by shamrockshirts
50hp at the wheels from a filter and BOV change isn't possible. Unfortunately you just can't bolt on stuff and make good power increases. You need a custom tune to match your aftermarket parts.
Also your AMS intake may be causing you issues. The AFM on our cars is especially sensitive to airbox changes with sometimes the end results actually being worse than the stock setup (double check your AFR's). The stock airbox isn't the restrictive part as many people are getting 250KW+ with the stock intake parts.
Also Sounds like your BOV isn't fitted correctly or has a spring fitted that is too soft and is opening under high boost levels.
Unfortunately the two parts you have bought aren't the best choice for increasing KW's. Your money would be better spent either on a tune and/or exhaust.
Cheers
John
Posted: Sun Oct 31, 2010 1:25 pm
by arutha
shamrockshirts wrote:
Also Sounds like your BOV isn't fitted correctly or has a spring fitted that is too soft and is opening under high boost levels.
that would be my guess. the bov spring is too soft to hold boost under higher loads.
Posted: Sun Oct 31, 2010 3:24 pm
by scraverX
arutha's making 335kw at-the-wheels (or there about). if anyone knows what stuff needs changing he does.
Posted: Sun Oct 31, 2010 4:03 pm
by JaCe
I thought to get decent power gains you'd need to have the car tuned, even moreso to make use of the BOV + intake which you ordered.
Posted: Sun Oct 31, 2010 6:08 pm
by Mixedmotorsportmedia
arutha wrote:shamrockshirts wrote:
Also Sounds like your BOV isn't fitted correctly or has a spring fitted that is too soft and is opening under high boost levels.
that would be my guess. the bov spring is too soft to hold boost under higher loads.
thats pretty much what im saying.. that the spring is to soft and leaking boost... speaking to ams they said i should have had gain of some sorts.
even on its hardest setting its nowhere near as firm as the stock BOV.
thats why i removed it. and seems to be alot better now.. what i was getting at was. is this a common thing.. bov not being aplicable for application. i am also sceptical about the 50hp but it is america and they have dynographs to prove it lol.. but thats not the point.. the loss of boost was lol
seems to be fixed now.
Posted: Sun Oct 31, 2010 6:21 pm
by McCoy
Nope, standard bypass valve is good for holding 25-26psi without any issue, not sure what your problem is, but a tune will fix any issues you are having.
Posted: Sun Oct 31, 2010 6:54 pm
by Mixedmotorsportmedia
lol thats what im saying lol.... that the STOCK one is good. and Turbosmart is trash lol
Posted: Wed Nov 10, 2010 7:33 pm
by mr_evo
yeah im going to get a tune done with no supporting mods and see what I can get... money better spend me thinks
Posted: Wed Nov 10, 2010 9:02 pm
by jimmytim
Last time I put a turbosmart dual port bov in my old car got worse performance, bought a new spring for it and re-lubricated (still got half a bottle of spray in the garage) but made minimal difference.
Put the original one back in the car runs fine....go figure.
(I'm guessing the spring is still not hard enough or something like that)
Posted: Sun Jan 23, 2011 11:58 am
by Nuliaj
Slightly old thread, but after reading through some of the responses I thought it might be good to correct a myth that seems to be going around - here some info from
http://www.frozenboost.com/stpg.php?page_id=bov
The purpose of the spring in a BOV IS NOT to hold your BOV closed under boost pressure! Selecting a spring based on PSI is incredibly confusing/meaningless and it makes us wonder if the people who pioneered aftermarket BOV design in the first place even understood how they work.
All BOVs have a reference line coming into the top of the BOV from your post-throttle body intake manifold. Under high boost, the force holding the BOV closed is BOOST! The pressure coming through the reference line is equal to the pressure under the BOV piston. Therefore a VERY mild spring will hold it shut just fine under these conditions.
Rather, the purpose of the spring in a BOV is to hold the BOV closed when your throttle plate is closed, IE during idle and deceleration conditions. Under these conditions, the vacuum in your intake manifold is much higher than the vacuum in your intake piping (therefore under the BOV piston) so the BOV has a natural tendency to spring open. Being open isn't even a problem if you are recirculating your BOV into your intake, however if you are NOT recirculating, it can allow unfiltered air into your intake which IS a problem.
Therefore, your goal when selecting a BOV spring and adjusting the BOV should NOT be to select a spring based on your boost level; that makes no sense. Your goal is to get the BOV to stay CLOSED during high intake manifold vacuum/closed throttle plate conditions, using the very smallest amount of spring energy possible. Using less spring energy will allow the BOV to snap open as rapidly as possible when pressure release is necessary.