Why is 'driving with load' better than constant speed

[bikenfool]

Originally Posted by betasniper

Vacuum gauge can also give you load. And on my bsfc chart I give approximate vacuum readings that correspond to the load for magenta Optimum efficiency line. Useful for acceleration and P&G.

How did you derive your approximate vacuum readings?

[betasniper]

20"hg is 0% load, 0"hg is 100% is an average I found in a report on engine load for a mixture of fuel injected cars. Some were higher some were lower, but trended like that. I can't find that pdf at the moment but the trend was very linear (Unlike throttle position). I then converted the % loads to "hg.

[davelobi]

How do you guys manage to keep saying the same things over and over for 8 pages without the op getting it. He doesn't seem to want to get it.
Let it go. Lets back off on the up-hills and coast down the other side and save our own fuel. Just my thoughts on this long thread.

[bikenfool]

Way to go davelobi, the threads been dead for 6 days and you woke it up

I may think me stupid because I don't get it, but I've tried to understand this technique but no one has been able to explain it using the fundamentals of physics/engineering, or test data, I'll take either. It's mostly faith based, myth and lore. The descriptions of what DWL is are all over the place.

There are cases where it makes sense, but it doesn't make sense as a general rule. It probably makes sense on low grade rolling hills, but that's a special case. My rav4 is geared really high and it wants to shift down at the slightest whim, DWL works sometimes.
Here's what I think makes sense: do what it takes to stay in high gear on the climb and neutral on the downhill. Depending on the hill and the vehicle that may be WOT or DWL.

Perhaps there's a fundamental misunderstanding. Perhaps it works when you allow the speed to drop to something really slow like 30mph instead of reasonable highway speed. I'm not willing to do that so that means I'm not a hard core hypermiler, I'm just trying to get from A to B efficiently. Just as there is an optimum cruising speed somewhere in the range of 45-55 there must be some optimum speed for a climb and I don't know what that is. I think in my intial post I said that I was looking at the trade off between fuel consumption and travel time, if all you want is maximum fuel efficiency and that means going 20 mph up a hill, then perhaps DWL is the way to go.

[davelobi]

Originally Posted by bikenfool

Way to go davelobi, the threads been dead for 6 days and you woke it up

Hi Bike, ha ha, not only did I poke the hibernating bear, I'll now go against what I was teasing the others about and respond again

I know close to nothing compared to a lot of the guys on here but have put up some decent fuel economy numbers with very little modification and mostly driving effort/style. Forget about DWL and just do like they say. Even if their logic or explanation doesn't make sense to you, they do know how to squeeze every possible mile out of a gallon of gas.

Originally Posted by bikenfool

no one has been able to explain it using the fundamentals of physics/engineering, or test data, I'll take either. It's mostly faith based, myth and lore

Again, forget physics and engineering. This is way more than myth and lore. The fuel economy numbers are test data in the best possible form. Look at the fe I've gotten, better yet, others on this site. These are tried and proven ways to save fuel. You simply can't question or say they are faith based theories. The documentation is fanatical, the depth of research is crazy, the proof is simply in the numbers that these guys are achieving.

Don't forget, the absolutely best way to save gas is to never start the car. Keep that bike! Tough to pick up kids on a bike tho huh? That's my problem.

[Arragonis]

I find kids can ride bikes though. Sort of comes naturally by way of falling off a few times

[IamIan]

Originally Posted by bikenfool

I've tried to understand this technique but no one has been able to explain it using the fundamentals of physics/engineering, or test data, I'll take either.

What part of my physics/engineering based approach in Post# 61 would you like clarified? ... Or what part would you like more thoroughly explained (from a physics/engineering perspective) ... Or what part of it , do you not understand?

I'm happy to walk you through all the science/physics/engineering/math/etc ... of it all if you can be more specific about what part already presented you are struggling with.

[Arragonis]

Originally Posted by bikenfool

....There are cases where it makes sense, but it doesn't make sense as a general rule...

No technique makes sense as a general rule, so you did get it really.