Braking versus Shifting?

stargift · #1 06-05-2008, 06:08 PM

I'm new to hypermiling and the forum. I have a question that will probably seem elementary or even stupid to you veterans. I have always driven manual transmissions and have always shifted down when coming to a stop figuring I'm saving the brake pads. Now, that I want to hypermile with my 2006 Scion XB I'm thinking that I need to coast and use the brakes to keep the rpm's down. Is that correct thinking?

Ophbalance · #2 06-05-2008, 07:02 PM

Or, you could use a combination of both

. Try bleeding speed more gradually by slowing earlier, or even not going quite as fast.

Vooch · #3 06-05-2008, 07:30 PM

Great question and welcome - FYI the xB actually has a pretty good CD @ 0.32 - check out http://en.wikipedia.org/wiki/Automob...g_coefficients

You should be going at a moderate enough pace that any load you put on your brakes is going to be tiny slowing down before a light. You should also be timing lights 3-4 blocks ahead of you such that you essentially never have to use the brakes. It takes a while - but eventually it becomes second nature.

Hey, when I'm ready to leave the parking lot at work - I don't start the engine to leave my parking space until I notice the traffic light waaaaaaay down the hill will be green by the time I get there

SlowHands · #4 06-05-2008, 07:54 PM

downshifting to use engine braking rather than the foot brake will save the brakes, and since most modern FI engines have fuel cutoff, no fuel gets burned during that time. I use engine braking quite a bit.

laurieaw · #5 06-05-2008, 08:01 PM

if i am going faster than i am comfortable dropping to a lower gear, i will touch the brakes a little. but i frequently will downshift to a lower gear and use that. it saves the brakes and recharges my hybrid battery if it's a little low.

kwj · #6 06-05-2008, 08:46 PM

Quote:

Originally Posted by stargift

I'm new to hypermiling and the forum. I have a question that will probably seem elementary or even stupid to you veterans. I have always driven manual transmissions and have always shifted down when coming to a stop figuring I'm saving the brake pads. Now, that I want to hypermile with my 2006 Scion XB I'm thinking that I need to coast and use the brakes to keep the rpm's down. Is that correct thinking?

Welcome Stargift. What do you drive? What's your daily commute like. And ask away. There is no such thing as a "stupid question," (just stupid answers).

As to slowing for a stop, I think you've already heard from the best (make it so you don't have to). If your route is the same every day, you will begin to learn the lights and be able to anticipate the need to slow down earlier in order to catch them green.

I notice in my vehicle, that I use more fuel in my lower gears. These days, I just turn off the engine when I know I'm going to get caught at a red light. The longer I Hypermile, the more I notice that I don't have such "abrupt" stops anymore. I've got almost 60,000 on my brakes at this point, and it's probably time to replace the front pads. Usually an easy job, but I've not done it on this vehicle yet. I think Hypermiling is saving me on brakes, because I try not to use them as much. And, since I'm driving slower these days, I don't have as much momentum to wrestle to a stop.

Have you read the introductory Hypermiling article? It's full of good stuff, and will take you awhile to practice and get proficient. Please continue to ask us any questions you have. We enjoy helping people get successful at Hypermiling and saving gasoline.

digidug · #7 06-05-2008, 08:58 PM

Unless you are very good at syncing the engine and transmission speed, you're putting wear on the clutch instead of the brakes. Brake pads are cheap but replacing the clutch will set you back a bit. For that reason I did not down shift (back when I drove a stick). Instead, I would leave it in gear while breaking to help slow the car down.

Anyway, as others have said it's best to minimize breaking in order to save gas AND brake pads.

gershon · #8 06-05-2008, 10:03 PM

Well, I'm just getting into this, so take my opinion with a grain of salt. Hopefully, others will correct me if I'm wrong.

But I find I can use a much higher gear than I used to use when driving. The gear I'd use would not be low enough to provide much engine braking.

Coasting to slow down with the clutch in and no brakes is the ideal. FAS is even better. With the Scan Gauge II set on LOD, I find I'm about 2 gears higher than I used to be fairly quickly. (5th gear at about 30 mph.)

If you find you have to use the brakes, it should be very light and won't give much wear.

stargift · #9 06-06-2008, 05:43 PM

Thank you for all your excellent suggestions. I've been using a few of the ideas on this site for the past 3 weeks. So far I've increased my average mpg from 34 to 44 mpg on my Scion XB. I've ordered the Scanguage 2 and have a March Labs 2-cell hydrogen generator that I'll try to hook up in about a week. I increased my tire pressure from 32 to 40. I'm pushing for a minimum of 50 mpg average. Most of my driving is on streets with signals that aren't sychronized.

rationull · #10 06-06-2008, 05:58 PM

Quote:

Originally Posted by gershon

With the Scan Gauge II set on LOD, I find I'm about 2 gears higher than I used to be fairly quickly. (5th gear at about 30 mph.)

Just curious.. what LOD range do you consider your "safe" range with respect to not shifting up at too low a speed?