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Old 06-11-2019, 11:39 AM   #1 (permalink)
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Question about braking for turns while hypermiling.

Most every day on my way home, I have a fairly steep down hill S turn followed by a nearly 90 degree right turn up hill.

Hypermiling 101 says stay off the brakes. Brakes eat precious momentum which would largely carry you up that hill.

The problem with this is that following this practice means my tires are howling around that right hand turn. I typically do the downhill in 4th gear in DCO. This provides enough braking that I can negotiate the turn, at the expense of some tire wear. Also, if there is a car sitting at that intersection, the driver may get a bit wide-eyed as some idiot comes barreling straight at him at speed in his Sportwagen.

So the question is do I consume tire or brake pads/diesel? I suspect it probably makes sense to lean towards braking, especially since I have a very efficient engine that absolutely loves to pull hills anyway.

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Old 06-11-2019, 12:31 PM   #2 (permalink)
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Quote:
Originally Posted by pete c View Post
Most every day on my way home, I have a fairly steep down hill S turn followed by a nearly 90 degree right turn up hill.

Hypermiling 101 says stay off the brakes. Brakes eat precious momentum which would largely carry you up that hill.

The problem with this is that following this practice means my tires are howling around that right hand turn. I typically do the downhill in 4th gear in DCO. This provides enough braking that I can negotiate the turn, at the expense of some tire wear. Also, if there is a car sitting at that intersection, the driver may get a bit wide-eyed as some idiot comes barreling straight at him at speed in his Sportwagen.

So the question is do I consume tire or brake pads/diesel? I suspect it probably makes sense to lean towards braking, especially since I have a very efficient engine that absolutely loves to pull hills anyway.
Keep in mind that hypermiling always comes secondary to safety. You may be able to pull that corner at speed when it's sunny, 75, with no wind. But what happens if it rained while you were at work and you don't realize that bit of ground is still wet. Or what if someone drove over that piece of ground and their car leaked some oil there? What if there's a little bit of sand/gravel on that stretch?

I would use the transmission to slow down as much as you can (if you have a manual), but definitely don't take corners at top speed, the little bit of fuel you save doing that won't nearly cover the cost if you wipe out just one time.
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Old 06-11-2019, 12:32 PM   #3 (permalink)
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I hate to use my brakes but sometimes you just have to use them. The road that turns onto the to road I live on if coming from one direction has a hill with a stop sign at the bottom at the intersection going to my house so if I'm coming from that direction I have no choice but to brake and lose the momentum from the hill I just came down. In your case I say brake enough to be safe and save as much momentum as possible.
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Old 06-11-2019, 01:20 PM   #4 (permalink)
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You might be able to start your downhill at a slower initial speed and so therefore save a little fuel on your last pulse before this combination of curves and a turn on a downhill comes. In other words, recontextualize the combination to include adjustments that will save more fuel before and after it. Definitely do not make a practice of screeching through a hairpin turn. You might also, on the downhill, choose a lower gear to spin the engine faster and therefore the alternator for more DFCO ("free") power generation.
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Old 06-11-2019, 03:14 PM   #5 (permalink)
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Safety first, always!

Try starting your descent at a lower speed. On my drive home, I have a steeper hill, then a steep downhill, then a right turn with a slight uphill about 100 or 200 feet right after the bottom of the steeper hill (2 way stop, I don't have to).

I generally downshift from 5th to third, keep engine load at best BSFC (70%-80% load) and allow my speed to bleed off from 35 mph down to 20-25 mph, then just before the crest of the hill I kill my engine, and am down to 15 mph by the top of the hill, then I roll down the hill and by the time I'm at the bottom (there's a small flat after the hill before the turn) I'm usually at around 20 mph by the time I make the turn. I typically am able to make the turn without using brakes (and then it's 2nd gear half throttle to 30 up the hill, then EOC the next half mile into my driveway).

The key is to be at the slowest possible speed at the crest of the hill. The lower the amount of fuel you use to climb the hill, the less kinetic energy you will have at the bottom that must be wasted either in brake heat or tire wear.

Also keep in mind traffic behind you. My drive home is typically past 10 PM at night when there is pretty much no traffic. Going that slow on the other side of a hill is not safe in heavily trafficked areas.
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Old 06-11-2019, 06:50 PM   #6 (permalink)
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Move to Illinois. We don't have hills. Or curves. Problem solved!
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Old 06-11-2019, 10:04 PM   #7 (permalink)
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Move to Illinois. We don't have hills. Or curves. Problem solved!
But then you have the risk of falling asleep on the road from the boring drive! Lol. I-57 going all the way down through Illinois is by far the most boring and sleep-inducing road I've been on. But it is true that there isn't really any downshifting for hills necessary though.
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Old 06-12-2019, 10:46 AM   #8 (permalink)
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Originally Posted by mpg_numbers_guy View Post
But then you have the risk of falling asleep on the road from the boring drive! Lol. I-57 going all the way down through Illinois is by far the most boring and sleep-inducing road I've been on. But it is true that there isn't really any downshifting for hills necessary though.
Illinois isn't nearly as boring as driving I29 through North Dakota. Other than where it goes over one railroad, and one spot it goes over the other highway instead of having a normal overpass, and a couple road crossings in Fargo there is literally not a single hill to be seen for the entire length of the state on that road. The Agassiz basin is FLAT
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Old 06-12-2019, 01:11 PM   #9 (permalink)
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Quote:
Originally Posted by pete c View Post
Most every day on my way home, I have a fairly steep down hill S turn followed by a nearly 90 degree right turn up hill.

Hypermiling 101 says stay off the brakes. Brakes eat precious momentum which would largely carry you up that hill.

The problem with this is that following this practice means my tires are howling around that right hand turn. I typically do the downhill in 4th gear in DCO. This provides enough braking that I can negotiate the turn, at the expense of some tire wear. Also, if there is a car sitting at that intersection, the driver may get a bit wide-eyed as some idiot comes barreling straight at him at speed in his Sportwagen.

So the question is do I consume tire or brake pads/diesel? I suspect it probably makes sense to lean towards braking, especially since I have a very efficient engine that absolutely loves to pull hills anyway.
just fall back to EV mode
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Old 06-12-2019, 03:31 PM   #10 (permalink)
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Quote:
Originally Posted by Shaneajanderson View Post
Illinois isn't nearly as boring as driving I29 through North Dakota. Other than where it goes over one railroad, and one spot it goes over the other highway instead of having a normal overpass, and a couple road crossings in Fargo there is literally not a single hill to be seen for the entire length of the state on that road. The Agassiz basin is FLAT
I drive 57 all the time, and I've driven 29 through ND. I've driven across most of the country, and IMO the most boring stretch of interstate is I-90 across southern Minnesota, hands down.

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