BOV swap has me confused.
Apr 23, 2007, 04:11 PM
#18
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Last week I did a little experimenting. I plugged the return line on the greddy s BOV and let the BOV dump to atmosphere. I did this to see what would happen to A/F and power if I temporarily ran BOV to atmosphere while I conduct IC testing. One of the results was you could hear the BOV leak during part throttle spool up. Not a small leak but a very audible one. I couldn't hear any leak at WOT and the A/F seemed to not change at all. Power felt good. Drivabitilty on the other hand was complete crap. Stalling all over the place, very rich during light cruise, etc. I was thinking that at part throttle the pressure in upper IC pipe was greater than in the intake manni. Meaning there was no boost on top of BOV to hold the valve on its seat. This valve has the small inner spring removed, and is set to open only 4-5mm or so. It is very easy to push open with thumb. So I decide to try MR BOV which kills your thumb trying to open it. MR installed recirculating. Instantly I noticed the car felt slower. It also stalled more often and ran a good bit richer. I made this swap right after an alternator change. So I was thinking the ECU has to relearn some fuel trims and I shouldn't jump to conclusions. So I drive it for a few days. Power never seems to return. Today I swap back in the S BOV. Well my butt dyno was not lying. The car is a good bit faster with the S in place. A/F is most of the problem I am sure. A/F with S = 10.8, A/F with MR = 10.3. G-tech g's in 4th gear: MR =.52G, S =.62G. This is with 1.8 bar at redline on both valves. Slight spike to 1.9bar.
Now obviously form the A/F change we can easily deduce one of the valves is leaking under WOT. Question is which one? When you have a boost leak and a MAF it is very easy to see the A/F go rich. This is because metered air in not making to the engine so there is access fuel. But does this same rule apply when recirculating?
Now obviously form the A/F change we can easily deduce one of the valves is leaking under WOT. Question is which one? When you have a boost leak and a MAF it is very easy to see the A/F go rich. This is because metered air in not making to the engine so there is access fuel. But does this same rule apply when recirculating?
But why would you have a leaner AFR with the Greddy valve VTA than the MR valve recirculating? If the Greddy valve is leaking under boost while VTA you should have a richer AFR with that than the MR valve recirculating. I am very confused.
Apr 23, 2007, 05:36 PM
#20
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Ok i got ya. I am anxious to hear what happens on this because I cannot think of any good answer as to why you think the greddy valve that leaks makes the car faster than the MR valve that did not leak. You got me on that. Maybe I should sell my MR and get the leaky greddy...lol
Apr 25, 2007, 02:19 PM
#22
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Wow!
you can't figure out how to hook up a BOV, or reason out the way one works, but you feel justified questioning buschur's little test with a wind speed meter with some questionable math?
hilarious!
you can't figure out how to hook up a BOV, or reason out the way one works, but you feel justified questioning buschur's little test with a wind speed meter with some questionable math?
hilarious!
Apr 26, 2007, 02:31 AM
#23
I dont have a problem hooking up a BOV. Only asked a simple question which I thought was common knowledge but the responses in this thread suggest everyone is clueless as to why I am getting the results I am. The only post attempting to help was TTP post on possible hz disturbance being the cause
I guess you are sore at me because I insulted your lack of intelligence in thermodynamics. So now you have nothing better to do but make useless posts furthur showing us your lack of intelligence. Thanks for you input, or LACK thereof.
Apr 26, 2007, 06:20 AM
#24
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What intake pipe are you running (MAF to turbo)? If not stock, does the recirc port direct air towards the MAF or towards the turbo (the stock pipe directs air towards the turbo)? With a pipe that directs air towards the turbo or perpendicular to flow, it is even more likely that TTP's explanation is possible. Another possiblity is that one of the valves has an atmospheric leak, which is the only way that metered air could escape. By atmospheric leak, I mean a leak out of the BOV that does not follow normal airflow through one of the two ports. The situation does seem very strange.
-Paul
-Paul
Apr 26, 2007, 06:45 AM
#25
the oem style bov's take uicp pressure & apply it to the bottom side of the diaphram. that is 1 reason why you loose boost reponse in part throttle conditons compared to the type s, as you have all this pressure within the uicp/under the bov diaphram & no boost pressure on top it the diaphram holding the bov closed, since your boost source for the top of the bov comes from he plenum, which has no boost.
this pressure source is there to provide a type of damping effect when the bov opens & closes, it should produce less car bucking/jerking when the bov is doing its thing during part throttle.
this is also why there is so much more seat pressure applied to the oem bov valve when you try to push it open with your finger.
i have no idea for the strange afr's....i havent given it any thought.
this pressure source is there to provide a type of damping effect when the bov opens & closes, it should produce less car bucking/jerking when the bov is doing its thing during part throttle.
this is also why there is so much more seat pressure applied to the oem bov valve when you try to push it open with your finger.
i have no idea for the strange afr's....i havent given it any thought.
Apr 26, 2007, 06:46 AM
#26
What intake pipe are you running (MAF to turbo)? If not stock, does the recirc port direct air towards the MAF or towards the turbo (the stock pipe directs air towards the turbo)? With a pipe that directs air towards the turbo or perpendicular to flow, it is even more likely that TTP's explanation is possible. Another possiblity is that one of the valves has an atmospheric leak, which is the only way that metered air could escape. By atmospheric leak, I mean a leak out of the BOV that does not follow normal airflow through one of the two ports. The situation does seem very strange.
-Paul
-Paul
I am tempted to remove my hood and try rubber glove trick to see whats going on. I would have to put a check valve inline to keep vac from sucking valve open. Then I could see how much leakage there is during boost.
Apr 26, 2007, 01:09 PM
#27
94AWDcoupe,
I don't think you have the concept yet.
https://www.evolutionm.net/forums/sh...ad.php?t=24611
I don't think you have the concept yet.
https://www.evolutionm.net/forums/sh...ad.php?t=24611
Apr 26, 2007, 01:12 PM
#28
there is a vaccum at the manifold... this will decrease the pressure observed.
the ic pipe is hwere you're supposed to source your bov pressure source, it is explicitly stated in the dejon tools leak stop kit instructions which should hold universal due to the things i've stated above.
Apr 26, 2007, 01:16 PM
#29
So there is suction at 150psi and suction at 5psi. Anyone want to guess if there is suction at 25psi? I am quite certain the answer is yes.
So while that whole 16 page thread about BOV testing was nice, he completely left out the real world testing. real world testing includes suction on the valve.
So while that whole 16 page thread about BOV testing was nice, he completely left out the real world testing. real world testing includes suction on the valve.
Apr 26, 2007, 01:17 PM
#30
The suction you mention is called the venturi effect. You didn’t mention the other thing that holds the valve closed and that is the differential between the surface area on top and bottom of the valve. Five PSI is equal to ten PSI if the surface area is doubled. Example 1 PSI on top of a thumbtack equals 100 PSI on the bottom.
5 psi on 1 square inch is FIVE POUNDS. 5 psi on 2 inches squared is TEN.