Anyone surging on their FPgreen setup?? High gear low RPM surging on spool up?
Jul 9, 2008, 09:56 AM
#18
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I don't seem to be having this problem. Especially in pull department in 5th gear. I really have no problem getting around traffic in 5th. Maybe a slight pause to build up a pound or 2 and then it just gets going. I bought my Green around April from Xtreme PSI if that makes a difference.
Also I have a Hallman and its tapped off the mani from the BOV line.
Also I have a Hallman and its tapped off the mani from the BOV line.
Jul 9, 2008, 09:57 AM
#19
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This log is an extreme case of BOV flutter. Boost control is electronic ECU duty table type sourced from intake- this is important to note; the nature of this type of control is it maintains XX DC to maintain XX intake manifold pressure REGARDLESS of what throttle position is, and this table is made at WOT. Problem is small turbos can and will produce lots of boost with little exhaust energy at part throttle compared to a large turbine. Having the BCS source at the intake helps solve the issue of boost taper at high RPM to a point, but there is a drawback.
Notice the very large difference in pressures pre and post throttle body.
As soon as the pressure differential gets near the 7 PSI spring rating in the BOV, IT GOES FRIGGIN NUTS!
There are two conditions you are experiencing- the above, which is very loud with a vented BOV, very obvious, and annoying, and causes noticeable driveability issues, DOES NOT happen at WOT (pre and post throttle body pressures are then equal), and a condition known as presurge, which is a light flutter heard thru the filter/compressor inlet when there is a small amount of inlet pressure fluctuations, but NO outlet pressure issues, NO driveability issues, and can occur at WOT.
In order to get an internally gated smaller turbo to maintain target boost at higher RPMs when the exhaust pressures and WG flow % go high and start forcing the WG open, we have to start taking more extreme measures to do this, and this tends to compound the problem. MOST of the WG solenoids on the market CANNOT drop the pressure far enough on the port connected to the WG canister at max DC's to allow the WG flapper to start closing again at high RPM. When you source the BCS or manual controller from the intake mani it helps combat the taper because the pressure is lower, but at part throttle another problem exists.
Notice the very large difference in pressures pre and post throttle body.
As soon as the pressure differential gets near the 7 PSI spring rating in the BOV, IT GOES FRIGGIN NUTS!
There are two conditions you are experiencing- the above, which is very loud with a vented BOV, very obvious, and annoying, and causes noticeable driveability issues, DOES NOT happen at WOT (pre and post throttle body pressures are then equal), and a condition known as presurge, which is a light flutter heard thru the filter/compressor inlet when there is a small amount of inlet pressure fluctuations, but NO outlet pressure issues, NO driveability issues, and can occur at WOT.
In order to get an internally gated smaller turbo to maintain target boost at higher RPMs when the exhaust pressures and WG flow % go high and start forcing the WG open, we have to start taking more extreme measures to do this, and this tends to compound the problem. MOST of the WG solenoids on the market CANNOT drop the pressure far enough on the port connected to the WG canister at max DC's to allow the WG flapper to start closing again at high RPM. When you source the BCS or manual controller from the intake mani it helps combat the taper because the pressure is lower, but at part throttle another problem exists.
Last edited by GrocMax; Jul 9, 2008 at 10:19 AM.
Jul 9, 2008, 10:07 AM
#21
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I have yet to have this issue. But dont get me wrong, i have seen this issue on my stock turbo. But for me the FPGreen has been very, very, good. It might be my setup or parts i have currently installed on the car (check my list and look for yourselves), or 93 octane. who knows. but i dont want to be the one people say disproved something. i hate being the one who says otherwise but since Robert has helped me out so much in the past with my car and some other issues i will attempt to help him out any way i can. Keep this thread going so we can all see what the progess/outcome is...
Jul 9, 2008, 10:29 AM
#22
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I'd like to point out also that the stock configuration for the WG vacuum lines is for the boost source to come off the turbo outlet pipe, which happens to be the better way if one is attempting to avoid the BOV flutter with smallish turbos that make good boost at part throttle. Otherwise you dont know it but the turbo is making 30+psi in the intake pipe to give you 15psi in the manifold, and in the process the turbine is doing the work (and making the back pressure) that goes along with the 30psi boost pressure in the UIC pipe.
BOOST ON!
Robert Young
BOOST ON!
Robert Young
Jul 9, 2008, 11:03 AM
#24
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well my forge bov always flutters, its extreeeemely annoying. there is no such thing as part throttle anymore. i pretty much have to just putt around without using any boost to get the car moving. unless i go wot
Jul 9, 2008, 11:11 AM
#26
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Outside the box thinking here.....but what kind of shape is your clutch in? My car did almost the exact same thing when I noticed it was taking a poo on me .the tsststssst sound and inconsistent feel when there was the most load on the car, low rpm, high gear, lots of throttle
Jul 9, 2008, 11:23 AM
#27
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It doesn't matter WHAT turbo, WHO made it, WHAT brand it is, WHERE the phase of the moon is currently. It DOES matter what BOV diaphragm area+ valve area, what the pressure difference pre and post throttle plate is, and how the boost control is set up. Small responsive turbo + part throttle. If you have a flutter and it annoys you look into ways of reducing or eliminating it by understanding what it is and why its happening. It is NOT surge. 99% of you have never experienced surge. Many of you HAVE experienced presurge, and need to understand the differences between induced BOV flutter, presurge, and true surge and why presurge should be considered normal in performance applications.
Last edited by GrocMax; Jul 9, 2008 at 11:30 AM.
