pulse up or pulse down a hill, higher or lower gear

[perris]

so there's the question

on a dynamic highway with constant ups and downs are you gonna get better mileage pusling up or down the hill?

I might think up the hill since you're gonna have to go way over the speak limit to get enough momentum to get a return for the down the hill hardly increases mph and you're gonna get to too low a speed limit if you don't pulse on the way up the hill and I think the fewer times you pulse the better

that's the first question, now the second

I can be in 5th gear or 4th gear...wot in 5th is a little bit of labor on the engine but being in forth is obviously "more revolutions per mile"

so what's the best strategy?

[MnFocus]

Hi perris ! Welcome to GasSavers !
I've been doing the pulse uphill > neutral coast down -hopefully up pat of the next >repeat . It's been working for me to hold the throttle @ 1/3 to 1/2 on the pulse . ymmv of course.
It may help us here to know what you drive and the type of terrain you deal with .Add a vehicle to the Garage as well as start a gaslog .

[Bill in Houston]

my vote, based on the bsfc ovals, is...
up hill
5th gear

[brucepick]

I am also interested in whatever people can write on this.
I'm especially interested in any information from people with ScanGauge who can see live data.

As mine is auto tranny and I know there some slippage (no lockup on this old car), I've been limiting myself on uphills to 2000-2100 rpm which is about 50-55 mph. After clearing the top of the hill I might give it some gas and get it up to 5-10 mph over the speed limit. Then neutral coast till it gets down to 50 mph, pulse again.

I'm just not sure if this is the best way to go.

I've been wanting to do some testing but the car has been having some "issues" lately and I don't want too many things changing at the same time.

[MnFocus]

Ah! The Solstice GXP ! Uphill pulse in 5th ,coast down (duh) . Try to keep the rpms as low as you can . Not familiar with the gearing of the GXP .

[perris]

Originally Posted by MnFocus

Ah! The Solstice GXP ! Uphill pulse in 5th ,coast down (duh) . Try to keep the rpms as low as you can . Not familiar with the gearing of the GXP .

ya, it's a gxp and it's really an incredible car...tons of power when in forced induction, 260 horses, 260 pounds of torque at very low rpm) and tiny for fuel efficiency when not in forced induction (2.0 litres)

it's only supposed to do 30 mpg highway but without even hypermiling, lefit in cruise control at between 62 and 64 mph I do 39 mpg once the car gets into closed loop

I think that's the reason the epa mpg is so low, they spend most of the time logging mpg when the car isn't in closed loop and by the time they get to closed loop the mpg average is already killed

anyway, 300 mile trip today, pulsing, plenty of eoc, and pulsing on the way up I did 42 mpg

I think everyone is gonna get a kick out of this;

I get best gas mileage with the top down not up...this is counter intuitive cuz I would think there is more wind buffering top down

best mileage, top down, windows up

worst mileage, top down windows down

btw

I can use the air conditioner and still be in the 38-39 mpg range

[s2man]

perris, like others have commented, I pulse going uphill and coast going down. And I too use 1/3 to 1/2 throttle for pulses. 1/2 throttle or 1/2 engine load are usually recommended for most efficient combustion, but I've not tested it yet.

In light traffic, I like to coast down to about 45mph, pulse up the next hill until I reach 5 or 10 over the limit, then start the next coast. 45 is the speed at which my lockup torque converter will stay engaged with 1/2 throttle. I hate to unlock the TC, or even worse, downshift. So I guess that means I recommend keeping your trannie in the highest gear possible without overloading your engine (which is a point entirely subject to your feelings and opinions).

But on the highway during rush hour, I can't vary my speed that much, so I end up driving a sort of hybrid, Pulse / Drive-With-Load thingamajigee, to keep up with traffic. Which reminds me of a funny story; Two days last week, during my commute, I had an old lady on my tail, angry about my speed variations. They were yelling and waving their hands and pointing at me. Road rage grannies! And when the second one finally decided to pass me, she had NASCAR stickers in her window! Oh, that killed me, I was really cracking up. And remember, my 'irritating' behavior was to do speed limit +5 going downhill and on the level, then slow to exactly the speed limit going back uphill, kind of like a tractor-trailer would do.

[skewbe]

Originally Posted by s2man

perris, like others have commented, I pulse going uphill and coast going down. And I too use 1/3 to 1/2 throttle for pulses. 1/2 throttle or 1/2 engine load are usually recommended for most efficient combustion, but I've not tested it yet.

That is not correct, you want about 2/3 throttle or 3/4 throttle but keep the rpm's low in my experience and that jives with expected results,
http://www.gassavers.org/showthread.php?t=37&page=2#39

[s2man]

Yeah, 3/4 throttle on mine gets me about 50% load. That's where I'd like the engine to be during acceleration, but that's nearing the down-shift threshold on my AT, and open loop on the ECU. :-(

I'm thinking of adding a TC lockup switch, so I can open the throttle further and at lower speeds.

[jcp123]

I had some good results holding a constant TPS value in my Focus on the rolling hills of East Texas and Southwest Arkansas. It was about 1.5mpg better than pulsing up and coasting down, mostly because the hills here are a little too gentle to coast down, yet psychologically seem too long to power down. But the numbers proved me wrong.