Anyone surging on their FPgreen setup?? High gear low RPM surging on spool up?
Jul 9, 2008, 03:17 PM
#32
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i've got a green,fp actuator,forge bov with the stiffest spring, blitz dual solenoid ebc, boost source tapped at the compressor outlet pipe, and i experience major bov flutter, not surge, at partial throttle especially in high gears.
Would a dual stage bov like the WORKS or APS unit help in this scenario. My other consideration is just to eliminate the BOV completely.
I've got a good friend that ran Evo6 turbo that way for many years at 1.7bar with no damage. Yes you would hear the compressor wheel flutter when the throttle body closed, but that had no ill-effect on performance or durability.
Would a dual stage bov like the WORKS or APS unit help in this scenario. My other consideration is just to eliminate the BOV completely.
I've got a good friend that ran Evo6 turbo that way for many years at 1.7bar with no damage. Yes you would hear the compressor wheel flutter when the throttle body closed, but that had no ill-effect on performance or durability.
Jul 9, 2008, 08:52 PM
#33
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+1
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.
Jul 9, 2008, 10:01 PM
#34
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.
Thanks for posting those graphs btw! Some of us do appreciate them.
Jul 9, 2008, 11:08 PM
#37
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I have the same problem on the stocker, part throttle is a *****. It seems like the DV is confused whether to open close/stutters. Only happens high gear/low rpm, you hear it also especially with an intake.
Jul 10, 2008, 02:53 AM
#38
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It matters very much when your intake manifold pressure is 18 PSI and the pressure at the BOV is 30. It would take a 13 PSI spring setup to keep it closed. 13 PSI BOV is rather tight.
Just because a solenoid can be commanded from 0% to 100% DC doesn't mean it has that wide of a control range. Most don't achieve a 60% pressure drop at 90% DC, and don't do anything extra at 100% DC. The actual DC range where there is control is somewhere between 20% and 90% for most.
Making an internal gate work with a solenoid is more difficult than an external gate, you need to really reduce the pressure to the WG port to get it to close at high RPM, and the common solenoids I tested don't even have a 55% pressure drop at full DC. The only one I found that works well is the Greddy solenoid, it was able to reduce a 35 PSI inlet to 1.5PSI, which was outstanding. The rest were in the 13-16 PSI range, not much better than the factory solenoid, but the factory solenoid locks up and won't operate at all above ~25 PSI inlet pressure. I don't think that was an accident, that gives overboost protection the way they plumbed the system from the factory.
With the Greddy solenoid I can get 22 PSI at redline with 70% DC, and it keeps working to 96% DC. It has the proper control range for internal gates. But it doesn't start doing anything until 30% DC. But between 30% DC and 96% DC it has a nearly linear pressure drop, so each 1% of DC actually does something. None of the others were linear response, some had very odd curves that make boost control very difficult.
Just because a solenoid can be commanded from 0% to 100% DC doesn't mean it has that wide of a control range. Most don't achieve a 60% pressure drop at 90% DC, and don't do anything extra at 100% DC. The actual DC range where there is control is somewhere between 20% and 90% for most.
Making an internal gate work with a solenoid is more difficult than an external gate, you need to really reduce the pressure to the WG port to get it to close at high RPM, and the common solenoids I tested don't even have a 55% pressure drop at full DC. The only one I found that works well is the Greddy solenoid, it was able to reduce a 35 PSI inlet to 1.5PSI, which was outstanding. The rest were in the 13-16 PSI range, not much better than the factory solenoid, but the factory solenoid locks up and won't operate at all above ~25 PSI inlet pressure. I don't think that was an accident, that gives overboost protection the way they plumbed the system from the factory.
With the Greddy solenoid I can get 22 PSI at redline with 70% DC, and it keeps working to 96% DC. It has the proper control range for internal gates. But it doesn't start doing anything until 30% DC. But between 30% DC and 96% DC it has a nearly linear pressure drop, so each 1% of DC actually does something. None of the others were linear response, some had very odd curves that make boost control very difficult.
What about the 3 port solenoids? They can just stop the flow of pressure towards WG canister if you tell them to (at 100% or 0% duty, depending on how they are hooked up), so it shouldn't matter where the source the boost signal is, right? (It would still matter if the duty is anything but 0% or 100% obviously)
Thanks for posting those graphs btw! Some of us do appreciate them.
Thanks for posting those graphs btw! Some of us do appreciate them.
Last edited by GrocMax; Jul 10, 2008 at 03:00 AM.
Jul 10, 2008, 03:08 AM
#39
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Try connecting a hose to the comp outlet, teeing it with the intake, then running it to the boost controller. Experiment with restrictors (or a needle valve) inside the comp outlet hose. It will average the pressures between the two but bias towards the intake unless there is a large difference between them. It will help at part throttle and still reduce high RPM boost taper a bit.
The restrictor diameters most likely to work will be between .050" and .020", once you get below .030" things start changing fast.
There is a bleed orifice in the MBC, so a restrictor diameter larger than this won't do much unless the hoses are very long.
The restrictor diameters most likely to work will be between .050" and .020", once you get below .030" things start changing fast.
There is a bleed orifice in the MBC, so a restrictor diameter larger than this won't do much unless the hoses are very long.
Last edited by GrocMax; Jul 10, 2008 at 03:12 AM.
Jul 10, 2008, 07:08 AM
#40
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not true
With a diaphragm type diverter valve like the stock ones or the GReddy the area of the diaphragm is much bigger than the area of the piston that holds back boost pressure. For example a diaphragm with a diameter of 2" has an area of 9.86 square inches the area of a 1" piston is 2.46. The valve will stay closed with 3 times the pressure acting on the bottom than on the top.
Jul 10, 2008, 07:17 AM
#41
It matters very much when your intake manifold pressure is 18 PSI and the pressure at the BOV is 30. It would take a 13 PSI spring setup to keep it closed. 13 PSI BOV is rather tight.
Just because a solenoid can be commanded from 0% to 100% DC doesn't mean it has that wide of a control range. Most don't achieve a 60% pressure drop at 90% DC, and don't do anything extra at 100% DC. The actual DC range where there is control is somewhere between 20% and 90% for most.
Making an internal gate work with a solenoid is more difficult than an external gate, you need to really reduce the pressure to the WG port to get it to close at high RPM, and the common solenoids I tested don't even have a 55% pressure drop at full DC. The only one I found that works well is the Greddy solenoid, it was able to reduce a 35 PSI inlet to 1.5PSI, which was outstanding. The rest were in the 13-16 PSI range, not much better than the factory solenoid, but the factory solenoid locks up and won't operate at all above ~25 PSI inlet pressure. I don't think that was an accident, that gives overboost protection the way they plumbed the system from the factory.
With the Greddy solenoid I can get 22 PSI at redline with 70% DC, and it keeps working to 96% DC. It has the proper control range for internal gates. But it doesn't start doing anything until 30% DC. But between 30% DC and 96% DC it has a nearly linear pressure drop, so each 1% of DC actually does something. None of the others were linear response, some had very odd curves that make boost control very difficult.
Just because a solenoid can be commanded from 0% to 100% DC doesn't mean it has that wide of a control range. Most don't achieve a 60% pressure drop at 90% DC, and don't do anything extra at 100% DC. The actual DC range where there is control is somewhere between 20% and 90% for most.
Making an internal gate work with a solenoid is more difficult than an external gate, you need to really reduce the pressure to the WG port to get it to close at high RPM, and the common solenoids I tested don't even have a 55% pressure drop at full DC. The only one I found that works well is the Greddy solenoid, it was able to reduce a 35 PSI inlet to 1.5PSI, which was outstanding. The rest were in the 13-16 PSI range, not much better than the factory solenoid, but the factory solenoid locks up and won't operate at all above ~25 PSI inlet pressure. I don't think that was an accident, that gives overboost protection the way they plumbed the system from the factory.
With the Greddy solenoid I can get 22 PSI at redline with 70% DC, and it keeps working to 96% DC. It has the proper control range for internal gates. But it doesn't start doing anything until 30% DC. But between 30% DC and 96% DC it has a nearly linear pressure drop, so each 1% of DC actually does something. None of the others were linear response, some had very odd curves that make boost control very difficult.
And if most of the EBC solenoids can't really block the boost pressure, then do they result in laggier spool-up vs an MBC?
Jul 10, 2008, 07:19 AM
#42
That's what I use (well I actually have a DSM 1G) and it works well, except at part throttle, high RPM -- like what you encounter on a high speed autocross course. A winter project that I never get to is substituting an electric solenoid that uses TPS to determine the switchover point rather than boost.
Jul 10, 2008, 09:39 AM
#45
Yes I am. Basically any good amount of boost in 4th 5th and 6th causes this shuddering and when it happens I back off. I have never taken it all the way up the power band with the shuddering in fear it will break or hurt the turbo.
As I stated I have been "driving around" this issue for a while now and I thought the Tomei valve, which has a stiffer spring would help, but it has not. It's a little quieter of a noise, but it still shudders.
As I stated I have been "driving around" this issue for a while now and I thought the Tomei valve, which has a stiffer spring would help, but it has not. It's a little quieter of a noise, but it still shudders.