[allan5oh]

Originally Posted by jonp

This is an interesting thread but could someone answer a stupid question? I havn't seen an explanation as to why unplugging the egr would raise the fuel mileage.

I can answer that. It will take a bit of history though.

In 2003, the OEM engine makers were required to reduce the NOx produced by the engine from 4.0 grams per horsepower-hour to 2.0 grams power horsepower-hour.

Everyone except cat decided to go with EGR. EGR reduces NOx by diluting the oxygen content in the air entering the engine. Exhaust has less oxygen, therefore the nitrogen thins out the oxygen. This reduces "peak" combustion temperatures, which reduces NOx production. The problem is, it also hurts fuel mileage and actually increases PM if you don't do anything else.

So the way they introduced EGR is by increasing the back pressure before the turbo with a variable geometry turbo. The "variable" is NOT to decrease spool lag, but rather to increase back pressure. Attached to the exhaust manifold is an EGR valve and the EGR system.

When they want to increase EGR flow, the EGR valve opens and allows exhaust to enter back into the engine. The problem with this, is it bypasses the turbocharger. So the theory is by "shutting off" the EGR, you are:

1) Increasing exhaust flow to the turbocharger, because there is no bypass

2) Increasing the oxygen content of the air going into the engine

[jonp]

Originally Posted by heavyhaulerss

the pipe I used to haul was plastic. 13 ft tall & the entire top had to be tarped. it felt like I was pulling an open parachute down the highway.

oh yeah. Hauled a ton of that stuff although I just smoke tarped it.

[jonp]

Originally Posted by allan5oh

I can answer that. It will take a bit of history though.

In 2003, the OEM engine makers were required to reduce the NOx produced by the engine from 4.0 grams per horsepower-hour to 2.0 grams power horsepower-hour.

Everyone except cat decided to go with EGR. EGR reduces NOx by diluting the oxygen content in the air entering the engine. Exhaust has less oxygen, therefore the nitrogen thins out the oxygen. This reduces "peak" combustion temperatures, which reduces NOx production. The problem is, it also hurts fuel mileage and actually increases PM if you don't do anything else.

So the way they introduced EGR is by increasing the back pressure before the turbo with a variable geometry turbo. The "variable" is NOT to decrease spool lag, but rather to increase back pressure. Attached to the exhaust manifold is an EGR valve and the EGR system.

When they want to increase EGR flow, the EGR valve opens and allows exhaust to enter back into the engine. The problem with this, is it bypasses the turbocharger. So the theory is by "shutting off" the EGR, you are:

1) Increasing exhaust flow to the turbocharger, because there is no bypass

2) Increasing the oxygen content of the air going into the engine

Ok, so by increasing the O2 you get a better combustion with the fuel and a higher fuel mileage as a result. I remember that whole thing and cat going its own way.

[solo379]

Hey, Tracer, beat this! 1627 miles, 197 gallons, roughly 8.25 MPG! At the pump!

[tracer]

Originally Posted by solo379

Hey, Tracer, beat this! 1627 miles, 197 gallons, roughly 8.25 MPG! At the pump!

How's that possible?

[BanditsCousin]

I think Solo runs dry van in the Ohio area. I can see him hitting that figure through a few ways.

65mph speed limits, relatively flat demographic, truck maintenance.

Other factors woud be load weight, idle habits, and length of hauls.

[solo379]

Originally Posted by BanditsCousin

I think Solo runs dry van in the Ohio area.

Between OH and NY mostly, 45% of my mileage comes to PA, did you see a lot of "flats" there? I also ran a lot of 2 lanes, and should i mention NJ, NYC traffic? But yes, most of the times, i'm pretty light....

[BanditsCousin]

Never seen a hill in PA. And never once got caught in any kind of traffic in NJ. I cruise right up 95N and over the GWB at 4pm all the time

Solo, you've mentioned you specs before, but tell us again. I know my T600 is specc'd a lot differently, and mine not so much in favor of mpgs! I can get close to your mpg empty at around 43,000 (hhg wagons are heavy).