Where do you draw the line?

[VetteOwner]

some newer ones dont have an egr, i think theyve moved onto somehting else(cant remember what)

[red91sit]

I'm a fan of clean air, but most of my cars either have non-functional cats, or no cats, it's not that I took them off or broke them, I just don't feel like investing in a new one.

[R.I.D.E.]

Just my thoughts;

EGR was originally designed to reduce peak combustion chamber temperatures(high NOX emissions), which should reduce power since its a direct function of the difference in temperatures between the intake charge at the instant before combustion occurs and the peak pressure die to combustion of the same charge. In most cases when you disconnected EGR you created heavy spark knock and had to reduce the timing to compensate.

My VX has EGR and I wont disconnect it, because its illegal (you could be fined $2500 as an individual) and I believe it is an integral part of the lean burn system. Now I could be wrong (wouldn't be the first time).

Air injection was rendered unnecessary when fuel shutoff was utilized with fuel injection, and possible some of the more sophisticated later carburetion setups at the end of the carb era. Without high vacuum fuel delivery there was no necessity in adding air to the unburned fuel in the exhaust. Fuel injection fuel shutoff solved the problem.

I would imagine EGR could also be eliminated by simply working with back pressure and valve, size and valve timing to keep a residual amount of exhaust gas in the combustion chamber. In my opinion there is always a small amount that would remain anyway, without forced induction or other means of purging the last remnants. No way the piston can force all the exhaust gas out of the cylinder, due to non displacement combustion chamber volume.

In 1975 when Nissan introduced fuel injection the system was good enough (in the time period) to allow them to eliminate the air injection, EGR, and cat converter. I always like that year but the fuel injection was fairly primitive compared to modern systems.

The nice thing about no EGR was the fact that the inside of the intake manifold didn't have the tar like residue due to the mixing of PCV vapors with exhaust gases. Later systems had EGR.

The same year California cars had cats and EGR.

regards
gary

[brucepick]

About cats -
I'm old enough to remember what our air smelled like before cat converters. Not just in the cities, but in "the country" too. Standing near an idling car you would smell a noxious disgusting odor. Same smell existed when walking along any street that had cars/trucks moving. And it comes right back to me when I'm near an idling vintage car, which does happen occasionally - just last week I filled up next to a 1921 Rolls, right hand drive - now that was a surprise!

It's one bit of government "intervention" that I'm thankful for.

[Ford Man]

I don't know what effect the EGR has on fuel mileage on the newer cars, but I bought a new Buick Regal in 1977 with a 350 2 barrel and straight off of the lot it was getting about 12 MPG and when you accelerated hard there was a flat spot where it felt like the engine just shut down for about 2-3 seconds. I told someone about the problem and they took the vacuum line off of the EGR and plugged it with an eraser off of a mechanical pencil and told me to try it like that a while. The fuel mileage went to 16-17 MPG and the flat spot disappeared. Needless to say I never removed the eraser.

[VetteOwner]

Originally Posted by brucepick

About cats -
I'm old enough to remember what our air smelled like before cat converters. Not just in the cities, but in "the country" too. Standing near an idling car you would smell a noxious disgusting odor. Same smell existed when walking along any street that had cars/trucks moving. And it comes right back to me when I'm near an idling vintage car, which does happen occasionally - just last week I filled up next to a 1921 Rolls, right hand drive - now that was a surprise!

It's one bit of government "intervention" that I'm thankful for.

hehe smells like my chevette, oddly enough my model A engine exhaust doesnt smell like anything, just smells like hot lol