EGR valve forced open at high boost?
Jul 15, 2009, 06:42 PM
#31
When the ported vaccum line blows off the top of the EGR the car will lose 12-15whp and be more knock prone. While I am not directly saying the EGR opens, something definitely happens. IF the solenoid was at 0%DC then it will never have flow so it cant blow open, but what is taking place when it wings off? We ziptie them in place and forget about them.
Jul 15, 2009, 07:02 PM
#32
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There has to be some seat diameter, otherwise there is no flow through. The fact that its a needle valve doesn't change the fact that exhaust gas pressure will create force on the valve. As ace33joe said, it all depends on whether the load produced by exhaust gases can overcome the spring load. At any rate, the best answer is that you've documented that you've never seen it open, presumably under very high boost conditions.
Definitely true about EGR reducing pumping losses, but I don't think it does much on the Evo. I definitely don't see a change of 35 kpa between having it enabled and disabled when cruising.
One other interesting tidbit is that Mitsubishi does not have an EGR system on the Evo 10.
Definitely true about EGR reducing pumping losses, but I don't think it does much on the Evo. I definitely don't see a change of 35 kpa between having it enabled and disabled when cruising.
One other interesting tidbit is that Mitsubishi does not have an EGR system on the Evo 10.
Once the throttle plate is open past the venturi effect range of the port, the top and bottom of the diaphragm see the same pressure, then its a matter of diaphragm area, spring pressure, and seat area. Since the diaphragm to seat area ratio is very high, it takes a very large amount of pressure differential to open it via exhaust pressure.
There ya go John Bradley, thy explanation.
If you can move the exh cam centerline you have EGR without a valve.
Last edited by GrocMax; Jul 15, 2009 at 07:14 PM.
Jul 15, 2009, 07:10 PM
#33
Block off plate from ebay + red rtv and re used some bolts that I took off the car for something, can't remember. Same thread pitch, perfect length. Torqued to oem specs.
WHen I take off the intake mani for porting I'm gonna have the egr port to the head welded.
WHen I take off the intake mani for porting I'm gonna have the egr port to the head welded.
Jul 15, 2009, 07:24 PM
#34
The area ratio between the diaphragm and the valve is probably 500:1 or more. It would take impossibly high exhaust pressures to open it *unless* something silly happened like the top port was disconnected but the bottom was still connected. Even then its not opening because of exhaust pressure, its because the pressure on the bottom of the diaphragm overcomes the spring exactly like an external WG. Both WG's and BOV's have low diaphragm to valve area ratios and get some assist from the size of the valve.
Once the throttle plate is open past the venturi effect range of the port, the top and bottom of the diaphragm see the same pressure, then its a matter of diaphragm area, spring pressure, and seat area. Since the diaphragm to seat area ratio is very high, it takes a very large amount of pressure differential to open it via exhaust pressure.
There ya go John Bradley, thy explanation.
If you can move the exh cam centerline you have EGR without a valve.
Once the throttle plate is open past the venturi effect range of the port, the top and bottom of the diaphragm see the same pressure, then its a matter of diaphragm area, spring pressure, and seat area. Since the diaphragm to seat area ratio is very high, it takes a very large amount of pressure differential to open it via exhaust pressure.
There ya go John Bradley, thy explanation.
If you can move the exh cam centerline you have EGR without a valve.
Very nice, thanks.
Jul 15, 2009, 08:15 PM
#35
I've had an ebay block-off on mine since the hack was first introduced on this forum. Kept my IM cleaner and now I had the head off recently and took it a step further. MAP installed a block-off plug IN THE HEAD so that zero EGR gasses make it to the intake manifold:
This, combined with a magnus phenolic spacer gasket on the IM keep it cool to the touch after hours on the dyno. I'm really happy with it, and deleting the EGR and all the stuff associated with it cleaned up a LOT of crap in my engine bay.
This, combined with a magnus phenolic spacer gasket on the IM keep it cool to the touch after hours on the dyno. I'm really happy with it, and deleting the EGR and all the stuff associated with it cleaned up a LOT of crap in my engine bay.
Jul 15, 2009, 11:49 PM
#37
The area ratio between the diaphragm and the valve is probably 500:1 or more. It would take impossibly high exhaust pressures to open it *unless* something silly happened like the top port was disconnected but the bottom was still connected. Even then its not opening because of exhaust pressure, its because the pressure on the bottom of the diaphragm overcomes the spring exactly like an external WG. Both WG's and BOV's have low diaphragm to valve area ratios and get some assist from the size of the valve.
Once the throttle plate is open past the venturi effect range of the port, the top and bottom of the diaphragm see the same pressure, then its a matter of diaphragm area, spring pressure, and seat area. Since the diaphragm to seat area ratio is very high, it takes a very large amount of pressure differential to open it via exhaust pressure.
There ya go John Bradley, thy explanation.
If you can move the exh cam centerline you have EGR without a valve.
Once the throttle plate is open past the venturi effect range of the port, the top and bottom of the diaphragm see the same pressure, then its a matter of diaphragm area, spring pressure, and seat area. Since the diaphragm to seat area ratio is very high, it takes a very large amount of pressure differential to open it via exhaust pressure.
There ya go John Bradley, thy explanation.
If you can move the exh cam centerline you have EGR without a valve.
https://www.evolutionm.net/forums/ev...ock-turbo.html
Jul 17, 2009, 11:11 AM
#43
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Your temperature data already proved to me that it doesn't open. :-) However, your 500:1 comment seems a bit over the top, so I'll toss in my 2c. I'd bet the hole is at least 1/4" diameter. If the EGR diaphram is 2" diameter, then the area ratio is 64:1. More importantly though is the load that can be generated from exhaust pressure. C6C6CH3vo measured the exhaust pressure at the EGR hotside. He saw as much as 48 psi with 26 psi at the compressor side at 7000 rpm. Figure maybe 40 lbs is more typical. With a 1/4" EGR opening, that would give a load of about 2 lbs from exhaust pressure. Seems like a pretty light load compared to the likely preload on the EGR spring. Anyhow, good entertainment.
https://www.evolutionm.net/forums/ev...ock-turbo.html
https://www.evolutionm.net/forums/ev...ock-turbo.html
The opening size doesn't matter, the actual valve seat area and diaphragm area are what influences the mechanics. The exhaust pressure is somewhat irrelevant, you can put shop air at 150 PSI on the bottom of the needle valve and it WON'T OPEN, the spring on top of the diaphram is around 3-4 PSI. Simple hydraulics/pneumatics.
Now here's what happens when the top hose pops off-
Notice even though full EGR flow is present, 'Intake Port Temp' DOESN'T CHANGE AT ALL. At the flow rate the engine is operating in, there simply isn't enough volume of 500F exhaust gasses passing thru the 3mm hole to effect temp, but it will effect power a little. This is a very small very fast TC probe located deep in the intake port at the head, and 'EGR Temp' is the same style probe on the outlet side of the EGR valve to indicate when EGR flow is present.
It is impossible to open the valve by exhaust pressure alone. However, any time a pressure differential exists between the top and bottom ports of the diaphragm that is strong enough to overcome the spring tension, it can and will open.
Last edited by GrocMax; Jul 17, 2009 at 11:24 AM.
