EGR and fuel economy

[Mesozoic]

I recently installed a Trickflow 1" phenolic spacer on my '00 Mounty. In the process, I had to modify the EGR tube from the exhaust manifold to the EGR valve, so I ran the truck with the holes plugged on the manifold for about a week. I had to have a friend weld a 1" extension into the tube, so it took a little while to turn around. In this time, I noticed that my Mounty picked up a solid 1.5 mpg around town, who knows what it would've got on the highway. When I got the tube back in place and the DPFE reconnected I noticed that the fuel economy went back down. So... now I'm looking for an EGR delete, but I don't see any way to do this without shelling out for definition for my EEC-V.

Anyone else have a similar experience with removing the EGR? I always thought that EGR improved fuel economy slightly during cruise, but it certainly is not the case in my truck.

 

[1997XLTRollover]

That doesn't make any sense. EGR is only active during cruise so I can't see how city driving would be effected by it that much unless you have an issue with your EGR system. EGR is all around good for an engine from a wear standpoint and fuel economy. The only downside is a little bit of a dirty intake over time.

 

[Mesozoic]

I don't think EGR is good for fuel economy. It dilutes the combustion mixture with inert gas (exhaust) instead of oxygen, lowering both the combustion temperature and power output in order to avoid generating NOx. With the EGR disabled, what would've been an inert gas will be replaced with fresh oxygen, which in order to maintain the ECU targeted AFR will be accompanied with the appropriate amount of fuel, thus producing more power.

 

[1997XLTRollover]

I don't think EGR is good for fuel economy. It dilutes the combustion mixture with inert gas (exhaust) instead of oxygen, lowering both the combustion temperature and power output in order to avoid generating NOx. With the EGR disabled, what would've been an inert gas will be replaced with fresh oxygen, which in order to maintain the ECU targeted AFR will be accompanied with the appropriate amount of fuel, thus producing more power.

More power = more fuel consumed (there are of course exceptions to this rule however). Remember EGR is only open at cruise and you don't need 500 hp to keep a vehicle moving at cruise. Any light acceleration and it disables it allowing a full cylinder fill. If you're saying city driving went up, I suspect an issue with your EGR system. Most city driving the EGR won't even be active.

 

[Mesozoic]

Well, I figured a CEL would indicate any issue with the EGR since the DPFE system is pretty accurate in measuring flow rates. So, not sure what is going on here, but my truck is bone stock with the exception of the 1" phenolic spacer and it picks up 1.5 mpg in town with the EGR plugged.

 

[1997XLTRollover]

Well, I figured a CEL would indicate any issue with the EGR since the DPFE system is pretty accurate in measuring flow rates. So, not sure what is going on here, but my truck is bone stock with the exception of the 1" phenolic spacer and it picks up 1.5 mpg in town with the EGR plugged.

Ha. That EGR system doesn't know it's ass from it's elbow. I put my EGR gasket on wrong one time and it BLOCKED my egr flow through my intake and I never got any kind of code. I did have worse fuel economy than I do now though but other than that I had no codes and the truck ran fine.

 

[colintrax]

You changed your driving habits or something is wrong with your egr. When I bought my old ranger, the egr was blocked off. Fixing that improved my gas mileage about 10% like it shouldve