I have heard that having no egr or a failing egr can hurt your gas mileage. So how bad is the damage again?

 

Damage as in what? The damage to your wallet?

 

I noticed no loss of mileage when I ditched mine. To bad I bought a new one, now for sell, when I didn't know any better. I bought It for emission purposes.

 

Ive been told that removing the EGR on S4s will have basically no effect. When I rebuild I am using a S5 center housing, so I was concerned about emissions since my S4 has a EGR and the S5 do not. From what I gathered the EGR is basically useless and does nothing at all, and will not effect the car if removed.

 

Oh..Remove that EGR and try to pass emissions...You are gonna be in for quite a shock!

But as we all know, you can get ANYTHING through emissions with enough vacuum leaks and a full tank of alcohol!!!

Jarrett

 

Why do you say this?? Im seriously interested, as like I said, I am using a S5 center housing when I rebuild, so Id like to know what to expect. I know on any other car the EGR is an important part of the emissions sytem, but Ive been told by many people that on a S4 it was basically worthless, and did little if anything.

 

I don't see how taking off your EGR could affect your gass mileage. Considering that all it does is recirculate small amounts of exhuast to be burned up even more. If anything taking off your EGR should improve gas mileage cause no more wasted gases being burnt up again, just pure fresh 02 and gas.

 

Well, the EGR seemed to be part of my troubles when I went to pass emissions. I suppose it depends on the type of emissions done. We have idle and dyno testing. Thats going to take things into different ranges where the EGR would help lower the HCs.

Jarrett

 

A broken or removed EGR valve shouldn't affect fuel consumption at all. It's only used as low loads (cruising), so the ECU will probably be in closed-loop mode to keep mixtures lean and economical.
I'm curious to know why the S4 needs an EGR valve to pass emissions, but the S5 doesn't. I know most of the S5 ECU's increased processing power went into emissions control and self-diagnostics, but I'm amazed it made that much difference.

 

The S5 actually has a sort of EGR system, where the exhaust is rerouted back into the intake system.

 

Where's that?

 

I dont have an S4 and S5 intake manifold handy to show you, but if you were to look at the buisness side (the engine side), there are ports on the S5 that arent there on the S4 intake. That port reroutes exhaust back into the intake stream.

Jarrett

 

Are you sure that's not where secondary air is pumped into the exhaust from the ACV?
You can't just pump ehaust into the intake all the time, as it seriously affects performance. That's why EGR valves are controlled by solenoids. The ECU only operates them at low load so that engine performance isn't noticable reduced.

 

This is why Im thinking not having it will not really adversely affect emissions, since it is only really operating at low load situations, and not at idle or 2500rpm while not in gear....