Technique on Hills
 

I'm interested in finding out the best way to handle hills while still keeping a good mpg average. Driving a steady speed seems pretty bad overall since the gas is flowing and the mpg are low. I originally thought that trying to only accelerate on the less steep sections would help, which I think it did compared to my driving before. But is it even better to rev high for best power for a few seconds or to try to stay slower the whole time?

In high rpm, gas is used faster, but less time is needed. I guess what I really need to do is try different techniques on a hill nearby. Has anyone done a test about this?

How do you drive up hills?

Thanks

what i do and some outher people do is hold your foot at the same level the whoal time keeping the rpm's about the same but letting the mph fall. once on top i throw it in N and coast down the outher side.

Whatever you do, make sure that you end up with a speed at the top that will not cause you to have to hit your brakes on the way down. If possible, anyway.

Hockey, that's what I did last time. But reading more into WOT and Burn and Glide, I wonder which is better.

Pretty much how I do it, except I turn the engine off and coast down. I typically let my speed drop to 60 km/h before bump starting in 4th to continue up the next hill. If I continue to slow in 4th, I'll downshift to 3rd until I can climb to 1750 RPM, then I upshift.

I don't know if this is correct or not but it seems to work for me. Like anywhere else, I drive in the hills in as high a gear as possible that will let me keep the speed I want. I use full throttle in a higher gear rather than less throttle and higher RPM in a lower gear. I don't do anything special on down hill runs. My Swift still seems to get about 50 mpg in the hills, and we have a lot of hills in my area.

Q

My preferences, depending on the size of the hill & traffic:

1) Pulse up the hill (if it's the right size for a pulse), glide down the back - probably best FE, 2nd slowest avg MPH

2) DWL up & glide down - probably 2nd best FE, slowest avg MPH. I'll do this if the hill is extra long (too long for a 2nd and/or 3rd gear pulse).

3) DWL up & DWL down - 3rd best FE, probably 2nd fastest avg mph. I'll do this if it's a long hill and I don't have the patience to coast down the other side (or if the other side's not steep enough for a coast).

4) Frozen throttle up & down - 4th best FE, fastest avg. mph. Usually I do something like this if there's traffic - trying not to vary speed so much that I hold people up.

(True DWL would actually have your speed falling AND you backing off the throttle on the ascent, potentially also downshifting as well. That's the only way you can actually achieve a constant load / maintain a target MPG. Remember if you hold a constant throttle as speed changes, load also changes.)

Metro, by 1) do you mean speed up before the hill, and roll up to the top in N/EOC? That's what I'm picturing which would be good on smaller hills if there's no traffic behind me.

No, he means follow the target BSFC up the hill in one big pulse, kill it before the top so you will slow down before going down the other side.

Yup, what skewbe said.

Sometimes the hill grade/length or both just isn't optimal for a pulse for the whole incline (or I don't feel like doing P&G). That's when I'll look to another option.

Sometimes I'll even combine methods, like DWL most of the way up and then pulse the last bit up to the crest, if the hill profile is good for it.

Pretty much what I do, although I dispense with the gliding. On the way to Peoria a few weeks ago, the power-up-and-glide-down method got me 31mpg on our rolling hills. On the way back, I held it at a constand 33 TPS, bleeding speed up hills and thundering down them, and was rewarded with a 33.41mpg fillup, over 2mpg better...

Some of that, though, is because the hills here don't really support gliding that well, and I scrub a lot of speed going down hills that I need to make it up the next. Swinging myself into some kinetic energy for the next hill seems to make all the difference.

I was looking for a flat spot to test my car a little bit for optimal acceleration speed and I realized that I couldn't find one in my area, EVERYTHING is a hill.

Right now I tend to do a combination of Pulse up Glide down and frozen throttle up and down, depending on the grade/length of the hill. I wonder however if I might be able to gain some efficiency by tackling things differently. What about downshifting for example? Right now I don't use any gear but 5th other than in initial acceleration, but maybe it would be more efficient to downshift on certain grades? It also gets a lot more complex when you have stop signs and stop lights at the tops and bottoms of hills, because then you need to treat those situations separately (I plan my routes to avoid stop signs at the bottoms of hills to preserver momentum).

Now that I think about it, hypermiling would be way simpler if you lived in say Kansas and there were no hills. All you'd have to do would be P&G and avoid traffic LOL.

What do you all think of the opposite strategy: accelerate going down in order to coast going up?

Try it out for yourself and see what you think. It means going 90 or 100 mph down a hill, and hoping to coast to the top of the next one without going below, say, 50 mph. It would be fun, but the aero losses (and the tickets) would start to add up...

I have no idea what is "best". But FWIW I have been trying various techniques, and this is the one I seem most comforatable with now (and my gas mileage has been slowing going up, so hopefully I'm on the right track here):

1) Somewhat easy/steady foot going up the hill. However, I do use enough pressure that my speed accelerate slowly going up hill (at least until I reach my "target" speed, which is often somewhere around the posted speed limit).

2) At the top of the hill I often give a brief pulse (a little more throttle for just a momentary boost). This sets me up for a decent downhill coast.

3) I then coast down the hill. Depending upon the hill grade I'll either coast down in neutral or 5th gear (whichever I estimate will let me coast down the majority of the hill without overly slowing down). Neutral lets me coast further (no engine/transmission drag), but I pay the gas for "idle". OTOH 5th gear lets me have fuel injector shutoff (i.e. "free" as far as fuel goes), but at the "cost" of a little more drag slowing down your coast.

At the bottom on the hill, start over at step 1 (for the next hill). If you get too much drag/slowdown (even in neutral) before getting to the bottom of the hill, simply start over at step 1 early.

NOTE:
That extra downhill drag (of being in gear), is actually "a good thing" if you have a steeper hill, as it will not only give you fuel shutoff, but will also help you from speeding up too fast coasting downhill (without having to use any brakes to get that slowdown)!

BTW:
I've found that coasting distance depends a LOT on how good you have the car lubed up (and working on aerodynamics also helped coasting distance)! My coasting distance is now several times what it was when I started, in large part due to good synthetic lubricants (in the engine, in the transmission, and especially good synthetic grease in the wheel barrings). And even duct tape over air gaps on the underside of my car's bumper (thereby helping the aerodynamics of the car) even helped coasting distance some. So if you are going to do a P&G technique (such as my hill based P&G technique, above), doing an extra good job of lubing up your car (as well as working on aerodynamic issues) will pay for itself in increased coasting distance (thereby making the P&G technique that much more effective).

GeekGuyAndy,

My Sven is about same weight as your Subie and is also automatic, similar size engine 2.3 liter. I drive constant rolling hills on my commute, 60 mi. x 2 daily.

My hill technique is nearly exactly the same as DracoFelis but I dunno if his is a standard?

I try to strictly P&G between the targets I set BUT I use throttle lightly going up, with a fixed foot.

I hold a steady foot going up, in top gear. I really avoid letting it downshift. For me about 2000 or 2100 rpm. This gives about 48-58 mph depending on the hill. For a very gentle uphill I'll do a pulse as if it were flat but only up to my upper target speed, and never heavy into the gas pedal.

Once over the top I give it some gas to get speed up to 60-70 mph depending on conditions. Going downhill it doesn't take long to build speed. Then into Neutral and coast till I reach the lower target speed. If it's a good downhill I might make it half way up the next hill before I need to go back into gear. If it's shallow or levels off the speed might reach lower target before the next upgrade.

Wish my car could a ScanGauge, then I'd have some real #s to see. Sorry but I don't want a SuperMID because I don't want to hack into the speedo and injector wiring. Maybe with a Japanese or USA car but if the Euro stuff inside Sven is different from what Yoshi built for then I could make trouble hacking in there.