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Has anyone looked into plugging one side of the paths leading to the hole leading to the bottom side of the diaphragm. I think these passages allow the delayed opening of the DV to give us the midrange surge. I'm going to get tuned for E85 soon and think I can plug one side to get a higher spike and a slower bleedoff to the normal 22-24 psi. Thoughts?
The chambers on the bottom of DV probably takes time to fill and slowly bleed into the diaphragm to allow the boost spike and taper. Any ideas on how the increase boost holding capacity other than shrinking the hole?
The stock BOVs open at a preset boost level. They're an "over pressure safety valve".
They don't and never have "leaks"as such.
When kids say they leak, they actually mean that it's opening at the preset pressure.
A plastic Evo BOV will start to open at about 1 bar boost , the more boost you give it, the more it opens.
By doing the mod, you modify the BOV so that it acts like an aftermarket one, as in no leaks and no more opening at that preset pressure.
Surging is a function of the turbo. Too much boost for the volume of air that's flowing.
A slightly open BOV increases the airflow through the turbo, reduces surge.
It would be nice to modify the DV to have a higher boost mode for E85 and be able to switch back to stock for 91 octane. I'll have a 3-port upgrade to control boost, so maybe buy a second 3-port to control the diaphragm pressure with a switch? The default "off" mode is plumbed as stock and "on" mode plumbs the diaphragm pressure to the 3-port wastegate actuator side of the 3-port? This way, if WGA is in bypass mode, it is in slight vacuum until WGA opens, at this point, the diaphragm hits higher pressure than default setting and opens DV in sync with wastegate. Thoughts?
It would be nice to modify the DV to have a higher boost mode for E85 and be able to switch back to stock for 91 octane. I'll have a 3-port upgrade to control boost, so maybe buy a second 3-port to control the diaphragm pressure with a switch? The default "off" mode is plumbed as stock and "on" mode plumbs the diaphragm pressure to the 3-port wastegate actuator side of the 3-port? This way, if WGA is in bypass mode, it is in slight vacuum until WGA opens, at this point, the diaphragm hits higher pressure than default setting and opens DV in sync with wastegate. Thoughts?
Hey 2006EvoIXer,
First off don't listen to Rightsaid_fred, he has a rep for trolling the forums and steering people wrong.
Second, I like that you are getting into the technical way to modify the stock diverter valve, but have you thought about simply crushing it in a vice? If done right, it will act just like the stock BOV which is great for drivability and part throttle cornering. I've done this with an evo IX and X bov. Just make sure you follow the instructions carefully and you will be able to hold your boost with E85 and 91.
Thanks, I saw that but crushing is permanent and I can't go back to stock pressures for 91 octane. Or can I? My car will hit 26psi and taper on 91. I don't know if we can go higher without detentions.
First off don't listen to Rightsaid_fred, he has a rep for trolling the forums and steering people wrong.
Second, I like that you are getting into the technical way to modify the stock diverter valve, but have you thought about simply crushing it in a vice? If done right, it will act just like the stock BOV which is great for drivability and part throttle cornering. I've done this with an evo IX and X bov. Just make sure you follow the instructions carefully and you will be able to hold your boost with E85 and 91.
I recall that crushing all the way down will hold 30-31 psi. This is too much for 91 octane. So the car will depend on the 3-port to never over boost since the crushed DV won't open early enough as safety. Maybe I can get away with partial crush to bring it to 28psi.
I recall that crushing all the way down will hold 30-31 psi. This is too much for 91 octane. So the car will depend on the 3-port to never over boost since the crushed DV won't open early enough as safety. Maybe I can get away with partial crush to bring it to 28psi.
The purpose of the bov/diverter is to hold as much boost possible and open properly to vent all turbo pressure when you let off the gas. It's the turbo's wastegate that determines your minimum boost possible.
You don't want the bov/dv valve controlling your level of boost. That would just be a giant, accidental boost leak.
By the way, I'm installing HTA 71 with my own porting of: 10.5 housing, exhaust manifold, and MAP O2 housing (more of cleanup). I'll also have 1200cc and 320 lph fuel pump installed before tuning. I just want to make sure I don't kill the new turbo with the DV holding too much back pressure on the compressor side.
+1 on crushing, its a tried and true method from way back in the DSM days. Just to elaborate on what Pal was saying: You want your DV to hold as much, even more, than the max boost you want to make. Trying to control your boost via boost leak is actually really bad for your turbo. Yah your boost level is lower, but your turbo is still spinning its @ss off trying to pump out as much pressure as the BCS is trying to make. You really want your BCS (boost control system) to be the thing that is dictating how much boost you are running at any given rpm/gear. Its going to control it by controlling the shaft speed via the wastegate and keep your turbo in a nice happy operating range.
May 30, 2017, 10:10 AM
