I was thinking about highway mode today. It seems that highway mode works hand in hand with the egr(indirectly). Using the egr is how you can push lean a/f and high spark. W/O an egr the payoff of gas mileage vs engine life is not worth it...

thoughts?

 

Don't most masks add fuel when the EGR is on?.

EGR doesn't allow for leaner mixtures, just in theory allows for less fuel consumption, since there is inert (well, they call it inert) material displacing actual Air Fuel Mixture. And having inert gases in the chamber drops the combustion chamber temps some.
And in theory there should be some gain from less pumping loses.

 

I love this stuff. EGR seems to effect everything, usually sacrifice power to gain everywhere else. The only other downsides are it's control functions, cost, and how it gunks up your intake the same as PCV.
I'd like to see proof of engine service live decreasing with highway mode. Does the exhaust valve sealing become effected? Is the piston disinagrating? I'm not doubting this, I just haven't seen any papers or scientific proof.
Most of the "better to be 5% rich than 1% lean" has come from people that haven't had tools to actually measure the actual AFR. Who's to know if lean burn engine failures were at 16:1 or 20:1, that's just something I'd like to see because it would answer a lot of questions.
It might even be said that running an AFR for peak torque would wear down your bearings faster because of a higher BMEP! I don't know where I'm going with this .

 

Having been doing a serious amount of reading lately(mostly on vette stuff), even the engineers seem to go with a continuous AFR of more than 15.5 to 1 is detrimental to engine life...

McClellan and Hill both said the same number and commented about combustion chamber heat and the like.......... Now also consider they have to look at the big picture and keep cars together for the duration of the warranty and the emission issues involved.

So realisitically I believe it is possible to run a in the low 16 or 16-1 range and make an engine live a happy life. Would more than likely have to do with vehicle maintenance during the lifespan and how good the overall tune is, from the spark being near dead on to the fule being perfect and all the AE stuff being tweaked to a T so u dont knock when coming off the lean AFR's..

Look at some of the gasoline direct injection stuff people and oem's are playing with and some oif the ludicrous afr they claim..... I have to believe it will happen from the oem's and we will see it become a very common thing in running lean burning engines. Obviously its not reliable enough or not cost effective at this time... lot of work to make it all work right and last a 100k I would have toi imagine :-)

Too many variables so little time
Later
Jeremy

 

It got me thinking.... if my engine at the time cost me $1950 3 years ago... and the price of gas were $2.00 and my milage was 10mpg then in 10,000 miles I'd have spent more on gas than on my engine! If my milage was 20mpg then 20,000 miles.
So let's say I save only 2mpg with highway mode and lean burn tune (4mpg on the highway is actual). Then 150k miles and I'd have saved enough to replace my motor with a grand new longblock!!!! , I think I can get 150,000 miles out of this motor and with the way gas prices are going I'd need less miles to save.
Funny stuff.

 

Best place I've found for information on running piston engines lean is in the aviation world. A little lean from stoich and the cylinder head temperature goes up, even leaner and the cylinder head temperature starts dropping.

An aviation engine is also running at high power levels, much higher then a street car cruising on the highway, all the while running lean.

They do it for the same reason: fuel economy. Can only carry so much fuel between landing strips.

RBob.

 

If you want to get some actual costs for maintance, Hertz, and Avis used to publish all sorts of data.
As far as wear and tear, and long term costs, Yellow Cab of NYC, did some long term testing involving it's fleet of cars for ~150K mile per vehicle. Goggling should get you the numbers you want, by using fleet/ maintance, Yellow Cab, etc..

10% MPG increase.
150,000 miles
7,500 gals
15,000 dollars
10%
1,500 savings.

Your still almost 30% off on the cost of the long block, not including labor, down time, what your time is worth, etc.

You might want to use the 4 MPG, but I doubt you'd see that as an AVERAGE increase.
And as the engine does wear, I'd betcha, the MPG increase, drops.

Not to mention that in some surveys, they compare a well manintained car vs a poorly maintained one, for gathering their data, you have to look at the testing procedures, very closely, if you want accurate info.. Just like the Mobil Economy Runs of years past, they got so creative that they lost being meaningful in the final analysis.

Not to mention the good juju, of a happy engine.

 

It's kind of funny because my 406sbc likes the a/f richer than 14.7(of part throttle). How do I know this? Well it's simple, when I pulled the motor last winter all the exhaust valves was bone white. It was a fresh rebuild when first installed. I pulled it after maybe 30,000miles for upgrades.That is when I noticed the valves....

 

now wot is much different. I have seen engines go lean as free air on the dyno. It didn't hurt it one bit. I'm sure if there was a power adder then it would have melted something. But for n/a it's hard to blow an engine by running lean. Over time running lean is not good. But for short experimental burst it's ok. I ran my formula 13.0 across the boards at the track w/o problems(not like 13.0 is that lean...). As long as you don't get lean misfires then it's ok. Sure that applies to highway mode too.

But the point of this thread is to point out the relationship of the EGR and hwy mode. Can anybody see the connection?