Want to know more about Driving with Load (DWL)?

[desdemona]

Hi,

We have lots of hills-- and a lot of times there isn't all that much traffic. This concept makes a lot of sense here. I want to learn more about doing this. I know the basic concept, I think. You keep a steady acceleration and don't accelerate up the hill (unless necessary I guess) and basically you could NICE-on coast if you wanted down (if the hill goes down enough).

Any thing else for a newbie hypermiler.


--des

[Right Lane Cruiser]

Yes, don't think of it as a steady acceleration up the hill. Think of it instead as trying to keep the engine using the same amount of gas on the way up and letting gravity assist you on the way down so you use less gas. The best approximation to get you going is it keep a steady pressure on the gas pedal. Sort of like the poor man's cruise control in the old VW Bus where you would wedge a pine board against the pedal to maintain speed. All that really did was maintain a pedal position. The result? You would go slower up a hill and faster down the other side.

Try that as a start. If there really isn't anyone around, the most efficient way to crest a hill is with just barely enough momentum to get you over it. If the car can FAS this is ideal. If not, just let it get down to the speed that is still more efficient than idle consumption and coast over in neutral (if possible).

I generally will ease off the pedal a bit with moderate hills so I use less gas going up, then coast as much as possible on the other side. Sometimes that means I have to give it a quick acceleration at the top and then coast as far as I can down. Approaching a hill you want to accelerate on the flatter land as then you aren't spending even more gas fighting gravity on your way up the hill.

[hobbit]

Sometimes pushing just a little harder helps keep speed more
even over hills, but I consider that there's probably a range
that staying inside of will roughly equate to "pure" DWL and
still return better MPG than blasting up hills. The Prius
certainly exhibits such a range, up to maybe 2400 rpm and
the Prius control strategy always keeps the engine in a high
torque scenario so it's sort of automatically DWLing in high
gear all the time anyways. I think it would help to clarify
exactly what is meant by "with load" in the spirit of the
original definition, since several discussions seem to
advocate very *light* loads [low torque?] as part of this and
yet we know that higher torque tends to keep an engine
higher on the BSFC map. In other words, which is it??
.
_H*

[tbaleno]

That might have to do with the CVT and motor being able to compensate, but for a normal engine I would think keeping throttle position the same while going over the hill would be best.

[desdemona]

Thanks-- can the Scan Gauge help you do this or no? Does the rpms tell you anything?

I am not doing FAS, I wouldn't do NICE-on because if I don't do something right I hear a nasty noise. This sounds suspiciously like stripping gears and is about as pleasant as chalk on a chalk board?

RL Drifter: I didn't mean steady acceleration but you got my drift anyway. :-) Of course, it is clearly *not* steady acceleration or you would go gradually faster. Of course, I am thinking you will end up going slower and slower. So Hobbit it isn't really gradual acceleration even if that is what I actually said. Sorry to confuse. :-)

I didn't know about the VW bus thing. I never had one. (Surprise given my age and so on I suppose.)

--des

[firenurse4]

I watch the throttle position (TP) with the scan gauge for taking hills.

[desdemona]

I think we are online at the same time now. I don't see a chat thing here, but can you tell me a little bit more about how you do this. I am new to SG (1st day really) and hypermiling.

--des

Originally Posted by firenurse4

I watch the throttle position (TP) with the scan gauge for taking hills.

[Right Lane Cruiser]

Desdemona, the "gauge" setting on your SGII has configurable readouts -- 4 in fact. If you press the button next to one of the readouts you will cycle through the different gauges available. One of them is TPS -- Throttle Position Sensor. That uses a range of numbers which differs from car to car. Mine reads 5 with no pressure at all up to something over 20 for wide open throttle (pedal to the metal!! ). If you have that readout up you can pick a number and make sure it does not change to be sure that the pedal is always in the same position.

I find that with most hills (unless they are very slight indeed) I have to add at least a little pressure to keep from dropping below a safe speed for the traffic. If you are all alone, just make sure you can get over the hill.

[desdemona]

This is very understandable (unlike my initial post :-)). I even printed it out and am going to look at my SG for it.


BTW, I know a certain teenager that uses 20 to back up out of the driveway!


--des

Originally Posted by Right Lane Cruiser

Desdemona, the "gauge" setting on your SGII has configurable readouts -- 4 in fact. If you press the button next to one of the readouts you will cycle through the different gauges available. One of them is TPS -- Throttle Position Sensor. That uses a range of numbers which differs from car to car. Mine reads 5 with no pressure at all up to something over 20 for wide open throttle (pedal to the metal!! ). If you have that readout up you can pick a number and make sure it does not change to be sure that the pedal is always in the same position.

I find that with most hills (unless they are very slight indeed) I have to add at least a little pressure to keep from dropping below a safe speed for the traffic. If you are all alone, just make sure you can get over the hill.

[Right Lane Cruiser]

Glad to help!!

Just to be sure we are on the same page, this is the screen I was referring to:


(Pulled from http://scangauge.com)

I don't remember what mine defaulted to but you can change the readouts to whatever you like.

Keep asking questions if you get confused!