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01 sport - 4.0 SOHC STS turbo charged (Project complete)
- Thread starter Jakee
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2000StreetRod
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vacuum pump
Thanks for the replies Jake. On my Volvo 850 turbo wagon I also can get high boost at mid range engine speeds under heavy engine load. That's what makes the small 2.3L 5 cylinder pull like a much larger engine. The EGR ports were capped and the ECM has a different tune so there are no faults associated with EGR. The cruise control is vacuum actuated and there is a separate vacuum pump for it. Crankcase fumes are vented thru a complex system that includes a filter back to the intake. On my older Volvos there was a flame arrester to prevent fire in the intake from traveling to the crankcase. They had no PCV valve.
I agree that the crankcase fumes should be vented back to the intake prior to the blower. Your catch can reduces the oil vapor condensation in the intake system and keeps it cleaner. Do you have a PCV valve installed?
During normal operation on our SOHC V6s there is no exhaust flow into the DPFE sensor. There is an orifice between the two ports in the EGR tube that connect to the DPFE sensor. The DPFE sensor measures the static pressure difference between the two ports and sends a proportional voltage to the PCM. The PCM uses the voltage to calculate the exhaust flow thru the tube to the intake manifold. The PCM uses pulse width modulation (on/off signal with variable duty cycle) to control the EGR vacuum regulator (EVR) to control the EGR valve. The hoses between the DPFE sensor and the metal tubes attached to the EGR tube are high temperature rated and expensive to purchase. The plastic case DPFE sensor is adequate as long as there is no exhaust flow thru the hoses. If the hose comes loose then exhaust flows and melts the plastic near the hose end.
I have never measured the pressure in the EGR tube but I suspect it is always less than a few psi with a stock exhaust. When the boost pressure equals the EGR pressure the DPFE would register no flow and the PCM should report a fault. When the boost pressure exceeds the EGR pressure there would be oxygen rich air from the intake manifold entering the exhaust system thru the EGR valve when open. The O2 sensor would report excess O2 in the EGR tube connected bank and the PCM (when in closed loop) would adjust the air/fuel mixture. That may be why Volvo eliminated EGR on my turbowagon even though it reduces combustion chamber temperatures reducing detonation.
Thanks for the replies Jake. On my Volvo 850 turbo wagon I also can get high boost at mid range engine speeds under heavy engine load. That's what makes the small 2.3L 5 cylinder pull like a much larger engine. The EGR ports were capped and the ECM has a different tune so there are no faults associated with EGR. The cruise control is vacuum actuated and there is a separate vacuum pump for it. Crankcase fumes are vented thru a complex system that includes a filter back to the intake. On my older Volvos there was a flame arrester to prevent fire in the intake from traveling to the crankcase. They had no PCV valve.
I agree that the crankcase fumes should be vented back to the intake prior to the blower. Your catch can reduces the oil vapor condensation in the intake system and keeps it cleaner. Do you have a PCV valve installed?
During normal operation on our SOHC V6s there is no exhaust flow into the DPFE sensor. There is an orifice between the two ports in the EGR tube that connect to the DPFE sensor. The DPFE sensor measures the static pressure difference between the two ports and sends a proportional voltage to the PCM. The PCM uses the voltage to calculate the exhaust flow thru the tube to the intake manifold. The PCM uses pulse width modulation (on/off signal with variable duty cycle) to control the EGR vacuum regulator (EVR) to control the EGR valve. The hoses between the DPFE sensor and the metal tubes attached to the EGR tube are high temperature rated and expensive to purchase. The plastic case DPFE sensor is adequate as long as there is no exhaust flow thru the hoses. If the hose comes loose then exhaust flows and melts the plastic near the hose end.
I have never measured the pressure in the EGR tube but I suspect it is always less than a few psi with a stock exhaust. When the boost pressure equals the EGR pressure the DPFE would register no flow and the PCM should report a fault. When the boost pressure exceeds the EGR pressure there would be oxygen rich air from the intake manifold entering the exhaust system thru the EGR valve when open. The O2 sensor would report excess O2 in the EGR tube connected bank and the PCM (when in closed loop) would adjust the air/fuel mixture. That may be why Volvo eliminated EGR on my turbowagon even though it reduces combustion chamber temperatures reducing detonation.
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I think a check valve might be the answer for the EGR system used where boost could be more than the normal pressure at part throttle settings when the EGR would be opening. That time period wouldn't be long and surely rare given part throttle use. Check valves are not easy to come by and they usually are very fragile and/or have high resistance to normal direction flow.
The typical PCV valve could be an excellent choice to protect the EGR system(and sensor) from the reverse flow. PCV valves come in various flow rates and generally prevent reverse flow completely. They are made for the environment too.
"Make note to self; include a PCV valve in the boosted EGR system."
The typical PCV valve could be an excellent choice to protect the EGR system(and sensor) from the reverse flow. PCV valves come in various flow rates and generally prevent reverse flow completely. They are made for the environment too.
"Make note to self; include a PCV valve in the boosted EGR system."
2000StreetRod
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high temp check valve
I doubt that the typical PCV valve could endure the flow of high temperature recirculated exhaust. I suspect even a high temperature check valve would soon malfunction due to crud accumulation.
I thought a little more about vacuum in an induction system. I think the throttle plate restricts air flow so the vacuum is much stronger after the plate than before it. It might be best to place a supercharger between the throttle plate and the intake manifold. Then the vacuum tree would be located between the throttle plate and the supercharger. That should solve everything except the EGR.
I doubt that the typical PCV valve could endure the flow of high temperature recirculated exhaust. I suspect even a high temperature check valve would soon malfunction due to crud accumulation.
I thought a little more about vacuum in an induction system. I think the throttle plate restricts air flow so the vacuum is much stronger after the plate than before it. It might be best to place a supercharger between the throttle plate and the intake manifold. Then the vacuum tree would be located between the throttle plate and the supercharger. That should solve everything except the EGR.
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I thought the problem was the reverse flow through the rubber DPFE hoses? That isn't hot EGR gases really, which is why those are still rubber. I'd put the PCV valve in the rubber hose path, then it will never see pressure, and hopefully keep the DPFE from generating a fault code.
Where is the EGR valve located in most boost applications? That would be a bigger deal if boost would get out through the EGR. Isn't the EGR going to always be located just past the TB, like where you suggest placing the vacuum tree?
Where is the EGR valve located in most boost applications? That would be a bigger deal if boost would get out through the EGR. Isn't the EGR going to always be located just past the TB, like where you suggest placing the vacuum tree?
Jakee
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Yes, I'm still running the PCV valve. I've tried with and without and chose to leave it in there.
If my memory is correct, the EGR valves default position is fully opened, meaning open to the exhaust when the engine is off. When on, and like you stated above, the PCM controls some things (have seen it in the tune while tuning (flow rates and such)) but I was under the impression that once vacuum is gone, the valve shuts, preventing any flow. (I've forgot a lot of things I once had figured out)
Does the valve closed mean it will block the boost from going down the exhaust? Not 100% sure. But I'm assuming it doesn't do the best job at blocking, as I've experience the hose blow off in the past.
I think a good vacuum pump on the PCV side is a good idea. That is what I was going for when going back into the intake. I've been checking and there is no "junk" going back into the tract so it seems to be working. The only thing I wasn't successful with was achieving vacuum with a venturi effect.
If my memory is correct, the EGR valves default position is fully opened, meaning open to the exhaust when the engine is off. When on, and like you stated above, the PCM controls some things (have seen it in the tune while tuning (flow rates and such)) but I was under the impression that once vacuum is gone, the valve shuts, preventing any flow. (I've forgot a lot of things I once had figured out)
Does the valve closed mean it will block the boost from going down the exhaust? Not 100% sure. But I'm assuming it doesn't do the best job at blocking, as I've experience the hose blow off in the past.
I think a good vacuum pump on the PCV side is a good idea. That is what I was going for when going back into the intake. I've been checking and there is no "junk" going back into the tract so it seems to be working. The only thing I wasn't successful with was achieving vacuum with a venturi effect.
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The EGR is separate from the DPFE hoses, so it's good that way. I think the EGR should be a good seal against boost if it sees any, but the location is more important.
Have you read anything about installing a vacuum pump to apply to the crankcase? That is very beneficial if you can manage to reliably generate 10-15 in of vacuum. Any exhaust venturi vacuum devices are a waste of time for a street vehicle, they don't make any usable vacuum. The best way to make vacuum is with some kind of pump. There are many choices, but the most reliable stuff is expensive like the oil pump for a remote turbo.
Have you read anything about installing a vacuum pump to apply to the crankcase? That is very beneficial if you can manage to reliably generate 10-15 in of vacuum. Any exhaust venturi vacuum devices are a waste of time for a street vehicle, they don't make any usable vacuum. The best way to make vacuum is with some kind of pump. There are many choices, but the most reliable stuff is expensive like the oil pump for a remote turbo.
2000StreetRod
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vacuum & EGR valve
The EGR valve is closed when no vacuum is present. Vacuum pulls the diaphragm that is attached to the valve. I've tested my EGR valve with a hand vacuum pump while the engine is idling. As the vacuum increases the valve opens and when open far enough the engine dies from the exhaust flow into the manifold.
The EGR valve is closed when no vacuum is present. Vacuum pulls the diaphragm that is attached to the valve. I've tested my EGR valve with a hand vacuum pump while the engine is idling. As the vacuum increases the valve opens and when open far enough the engine dies from the exhaust flow into the manifold.
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