Influencing Busy Four-Lane Highway/Freeway Speeds to Increase FE

[dwtaylorpdx]

Originally Posted by Christ

Lots of guys on some of the Minivan forums I'm on are claiming better FE at 62-65 than 55 as well, and it's understandable, because they're geared to hold in the most efficient RPM range at those speeds, since many of the highways have 65 and 70MPH speed limits. Many of those same people are using scan gauges, as well.

This isn't to say that they wouldn't be getting better mileage at 45 than 65, with the transmission locked, but FE curves don't specifically follow speed, either.

Of course, another part of it is that most of the people "trying" to get better mileage by going slower, may just be very squirrely at that speed, since they're used to driving faster, and perceive that they're doing something that could be potentially dangerous.

Of course, I have to add that re: slow people causing traffic jams, that's all well and good, but why did the slow people cause the traffic jam? Because they created a bottle neck when others tried to pass them? Yeah, that's what I thought... therefore, it's not the fault of the slow drivers entirely. Your study, thus, was flawed. From the data gathered, I have to wonder if there wasn't some agenda behind it, as well. Something irks me about it, not sure what.

The FE kinda makes sense to me, first, the car has the hands down best cruise control I've ever driven, it actually feathers the throttle instead of shutting it off on long down hills. The speed stays dead on up or down hill as well.. Second, I think the hatch tail hits a aero rollover at the right speed.

Google a image of the 318Ti and you'll see what I mean.

It also has a dual path intake manifold, it has a set of low RPM long runners and a set of short High rpm runners, so in cruise it really pulls the torque.

I'm also only noticing a 2 to 4 MPG rating which I find easy to accept because it peaks fairly sharply which would imply a tuned spot in the engine management.(On purpose or accidentally who knows.

As far as the slow drivers causing accidents, if the speed limit is 65, and your not going at least 55, what happens when a car driving legally, comes around a corner and a car with no brake lights is moving slow? He may not hit it but he has to check up which causes a chain reaction of reflex checking down the lane.

The goal of the study was to identify the moments that cause the traffic jam, and they identified lots of reasons. But by far rigs more than 10 under the limit consistently generated a traffic bottleneck. My logic is, if you don't want to drive the limit, drive to the right. Whats the deal with people trying to "enforce" the speed limit on others to save fuel.? Its dangerous, as dangerous as road rage. And you might meet the guy out there driving 5 tons of steel clad utility truck who is quite willing to Nerf you into the guard rail, not that I know anyone like that or anything.......

The study was used to develop the traffic software that updates all the GPS systems and emergency vehicles with safer faster routes around ongoing or even future traffic events. (It can actually predict a traffic event by up to a minute.

Wow sorry I spewed on so long....
Dave

[Christ]

I don't advocate long trips on the highway at less than 55 MPH. I will not go under 45 on the highway, unless I'm speeding up or slowing down.

Part of your mileage effect at higher speeds can also be derived from a "corridor" effect, if you're keeping with traffic at that time.

I've seen trucks that would run you off the road if they were so inclined. I've also followed them for less than legal reasons, after a couple of them tried.

Also, one of the only two accidents I've been involved in on the road was a matter of some moron driving like a moron. I eventually ran him off the road because of the potential for a head-on collision. The cop arrested him. Details would include that I was driving the speed limit, he was on the side of the road "coasting" (I guess) with his hazard lights on, so I leaned left and passed him about halfway over the double yellow line in a passing zone at 35-40 MPH. I was just pulling off a side road, so I wasn't going 55 yet, and he decided while I was passing him, he was going to basically floor it, force me all the way into the other lane, then attempt to keep speed with me so that I couldn't get back over. I saw what appeared to be headlights in front of me (night time), so I slammed my Mazda B2200 into his rear door as "gently" as I could, to "push" him over some so we'd fit three wide on the rural road. Turns out I saw a four wheeler's spot light, and there was no real reason to push him over, but the officer understood the situation and made the arrest anyway.

That's the only situation I've been in like that, and hopefully, I never have to make the choice again like that. I try to drive safely first, economically second. There is a point where safety is relative, though. The driver can't always control the situation, I agree to a point, but many of us could do so much more to at least prepare for a situation.

BTW - I know what the 318Ti looks like. I'd like to get an older 3 series or a newer 1 series.

[dwtaylorpdx]

I just wanted to make sure I said what I meant

And I am a big fan of the 318ti, its a really amazing little car, simple, fuel efficient, fun to drive comfortable, just wish the Diesel version was available in the US!

And YES a 135 is a cool ride. No throttle all valves....

Dave

[cfg83]

dwtaylorpdx -

Originally Posted by dwtaylorpdx

...

And the 55 magic number is pulled out of thin air. There is nothing magic about 55.
My BMW gets peak mileage at 65 not 55. (34MPG to 36 MPG depending on the terrain.)
Drops to a consistent 30 to 32 mpg at 55. I still get 30 MPG at 75, My state the limit is 65 and I don't save significant time by going to 75 for a < 300 Mile trip so 65 it is...

...

This is the picture I always cite when it comes to higher speeds and MPG :

Fuel Consumption at Higher Speeds - May 2006
Green Car Congress: Fuel Consumption at Higher Speeds


I don't doubt your experience, but I think it falls outside the norm. Your BMW is probably like the Mercedes C 180 K.

I think that getting "better" MPG at higher speeds can sometimes mean "getting almost the same" MPG at higher speeds. It's like a rising fastball, it doesn't actually rise, it just looks like it rises in comparison to other fastballs.

CarloSW2