Open air egr?
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Open air egr?
Ok I don't want to open a can of worms here but through circumstances beyond my control (my catalytic converter was stolen) I am taking the AIR or smog pump system off my 1991 F250 with a 460. In doing this I am thinking about doing away with the egr system by either blocking it of or using one of the several egr simulators, or so I thought until I read a first hand account of a guy who broke down in his 460 Ford RV.
It seems he was out camping and the the fitting that plumbs the egr valve to the manifold let go from corrosion and he limped in to a shop. The fix, to weld up the fitting in the exhaust manifold, supposed to be temporary to get him home where a more permanent repair could be made. So with an egr tube open to fresh air he headed out.
He claims driving home the rig had improved throttle response and better acceleration and in the end his ultimate fix was to cap the egr tube with a filter and allow it to introduce fresh air rather than exhaust gas into the system. Without rehashing the merits of 1980s emissions controls can we discuss why this would or would not improve performance and result in improved throttle response?
It seems he was out camping and the the fitting that plumbs the egr valve to the manifold let go from corrosion and he limped in to a shop. The fix, to weld up the fitting in the exhaust manifold, supposed to be temporary to get him home where a more permanent repair could be made. So with an egr tube open to fresh air he headed out.
He claims driving home the rig had improved throttle response and better acceleration and in the end his ultimate fix was to cap the egr tube with a filter and allow it to introduce fresh air rather than exhaust gas into the system. Without rehashing the merits of 1980s emissions controls can we discuss why this would or would not improve performance and result in improved throttle response?
FTE Legend
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From: Ottawa, Ontario
The EGR system cannot be deleted without setting codes and in many cases that results in a check engine light, and those EGR eliminators don't help with that. And you absolutely do not want to create a big vacuum leak by leaving the EGR line open, this would result in an uncontrolled idle at the very least. This system is small and tidy and does not have a negative effect on engine operation when it is working correctly.. it actually helps make the engine less detonation prone, so I'd advise leaving it alone.
But with cats gone you can safely eliminate all of the air injection plumbing and valves, the exhaust needs to be capped where tubes were attached, the control solenoids should remain electrically connected, and any vacuum lines should be removed or capped. Some codes will be generated for this but they will not trigger a check engine light as this system does not impact engine operation even when operating correctly, it's only purpose is to supply fresh air to the factory cats under certain conditions.
But with cats gone you can safely eliminate all of the air injection plumbing and valves, the exhaust needs to be capped where tubes were attached, the control solenoids should remain electrically connected, and any vacuum lines should be removed or capped. Some codes will be generated for this but they will not trigger a check engine light as this system does not impact engine operation even when operating correctly, it's only purpose is to supply fresh air to the factory cats under certain conditions.
Fleet Mechanic
Joined: Aug 2015
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From: Candy Mountain
Assuming the valve is functional, you would have a large vacuum leak when it opens. I can't see how this would help performance in an otherwise healthy set up. If the valve is disabled and never opens the impact to the user would probably be minimal in the driver seat.
My guess would be that the vehicle was leaking exhaust, vacuum, or maybe had exhaust gas entering the intake when it shouldn't and the "fix" cured whatever was leaking where ever. Leaky exhaust can cause a lean code but it would have to be pretty big to impact performance in my experience. A small vacuum leak can cause noticeable performance issues, and EGR gas will make it run like crap or just stall at low rpms.
My guess would be that the vehicle was leaking exhaust, vacuum, or maybe had exhaust gas entering the intake when it shouldn't and the "fix" cured whatever was leaking where ever. Leaky exhaust can cause a lean code but it would have to be pretty big to impact performance in my experience. A small vacuum leak can cause noticeable performance issues, and EGR gas will make it run like crap or just stall at low rpms.
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The egr isn't open at idle. How is introducing fresh air different than introducing exhaust which is nearly non-combustible?
An egr simulator will allow you to remove the valve should one chose to on the obd-1 equipped trucks. I don't particularly want to remove mine
An egr simulator will allow you to remove the valve should one chose to on the obd-1 equipped trucks. I don't particularly want to remove mine
FTE Legend
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From: Ottawa, Ontario
Introducing unmetered fresh air dilutes the A/F ratio, exhaust gas in inert(no combustables) so it doesn't dilute the A/F ratio.. it just displaces a small amount
EGR simulators don't work as advertised, codes are still set because the valve doesn't move when commanded to.
EGR simulators don't work as advertised, codes are still set because the valve doesn't move when commanded to.
Hotshot
Joined: Jun 2015
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My guess would be that the vehicle was leaking exhaust, vacuum, or maybe had exhaust gas entering the intake when it shouldn't and the "fix" cured whatever was leaking where ever. Leaky exhaust can cause a lean code but it would have to be pretty big to impact performance in my experience. A small vacuum leak can cause noticeable performance issues, and EGR gas will make it run like crap or just stall at low rpms.
IMO, disabling a functional EGR serves no purpose. It could actually decrease fuel mileage because without adding (inert) exhaust gas into the engine you will have a more oxygen rich charge which will require more fuel.
Fleet Mechanic
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From: Candy Mountain
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5th Wheeling
Joined: Mar 2017
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progress ?
Union_Guy ... I have a similar situation. Since your post is several months old, I'm wondering if you've resolved your system. Did you leave your EGR system in place with open air ?
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I wish I had at least tried it. I went looking for data on how much exhaust gas was recirculating and when and how introducing fresh air in at that point would change the a/f ratio. My hope was the 02 sensors would compensate for the difference but I couldn't find enough to have the confidence that it wasn't going to run excessively lean. I could have put it on a smog dyno and checked the a/f mixture at speed but I decided it wasn't worth the trouble. I removed the egr valve and installed a resistor module that was supposed to make the pcm think the valve was still present. It didn't, the check engine light still comes on. I welded the exhaust manifold bung closed and the truck runs great, more like a pre smog 460. The power still is what it is but it runs better.
Hotshot
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If the 460 uses an EVR solenoid to control the EGR valve then all you had to do was leave it electrically connected. There was no need to purchase a resistor module to do the same thing. You could have also installed a thin piece of metal between the EGR valve and the intake manifold to stop the flow.
FTE Legend
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From: Ottawa, Ontario
I wish I had at least tried it. I went looking for data on how much exhaust gas was recirculating and when and how introducing fresh air in at that point would change the a/f ratio. My hope was the 02 sensors would compensate for the difference but I couldn't find enough to have the confidence that it wasn't going to run excessively lean. I could have put it on a smog dyno and checked the a/f mixture at speed but I decided it wasn't worth the trouble..
5th Wheeling
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The computer could compensate for the relatively small increase in fresh air with feedback from the O2, but that will only happen when the computer is running in closed loop and with the 7.5L in particular that isn't the case most of the time... that comes down to how the PCM is programmed for this motor. The bigger issue is the big vacuum leak leaving the port wide open would create, that leak would be too much for the IAC to compensate for so idle speed would be out of control.
Such a small amount of air to not upset the Air Fuel ratio.
And would the valve itself still continue to respond to commands such that the position sensor feedback would look normal to the PCM ?
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From: Ottawa, Ontario
The way to do this that I have personally used with good luck, is to sandwich a piece of sheet metal between the valve and intake with a couple gaskets to seal it up, remove the tube completely and plug the port in the exhaust manifold. Then connect the EGR valve as it should be with vacuum and the position sensor and let it do it's thing. I ran my 5.8 like this for a few years with no issues, I don't remember if any codes were set but the light didn't come on and the motor ran well.
Hotshot
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Why do you want a second way for fresh air to enter the intake? Metering fresh air is the job of the throttle body. You will still be introducing more oxygen into the system so the computer will try to compensate by adding more fuel until the fuel injectors max out.
5th Wheeling
Joined: Mar 2017
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Thanks for sharing.
The way to do this that I have personally used with good luck, is to sandwich a piece of sheet metal between the valve and intake with a couple gaskets to seal it up, remove the tube completely and plug the port in the exhaust manifold. Then connect the EGR valve as it should be with vacuum and the position sensor and let it do it's thing. I ran my 5.8 like this for a few years with no issues, I don't remember if any codes were set but the light didn't come on and the motor ran well.
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