I just want to know if cruising helps hypermiling. I usually do but in the LA - SF trip last night I did not cruise much and was handling the hypermiling myself. I realised when I reached SF that my MPG had dipped from 28 to 23 or so...do you think I should have cruised all the way ?

 

Cruise control is good to use for those not familiar enough with hypermiling to do it effectively. Why?

Cruse control:
a. Keeps your car at constant speed up hill, which is opposite of driving with load (DWL). It is more efficient to allow your speed to sag while climbing hills. (Reducing the negative effect of gravity)
b. Will keep constant speed downhill. This means when you begin the next uphill segment, you will need to burn extra fuel starting at the base of the hill. It is more efficient to slowly increase speed going downhill (Taking advantage of gravity) so you don't burn so much fuel on the way back up the next hill.

Think of yourself riding a bicycle going up and down hills. You want to keep your effort as light as possible. Do you want to keep the same speed going downhill, and face the next uphill already going at your minimum speed?
Or do you want your downhill speed to increase, helping you up the next hill?

c. Cruise control is boring, compared to planning how to be more efficient for a current segment.
d. It is many, many times more efficient to drive at a slower highway speed. If you set CC for the slower speed you will likely create traffic bottlenecks behind you. Instead you can regulate your speed to slower with light/no traffic behind you, and increase to closer match the group of cars which are approaching you from behind, thus eliminating problems associated with slow drivers.

With that said I've never driven in California and don't know the terrain. If it is a completely flat, level road DWL isn't as effective except for humps such as overpasses.

-Steve

 

For about 200 miles the I-5 is pretty flat in the central CA region. From LA to Grapevine its mostly uphill and downhill and same near Gilroy .

 

I hit a situation where I think the cruise control can help --

First some intro: I'm driving a Lexus RX (actually, wif lets me drive it once in a while, 'specially if it needs gas,) which has a 'power-required' gauge, which shows margins for regen-braking saturated, regen vs. battery discharge, and when the batteries are about to be supplemented with engine power. Do other models have a gauge like that? I'm not talking about the engine/motor/battery/wheel schematic, but a gauge with different markings as the needle swings around. I can anticipate when the engine will re-light by watching this gauge.

Also, I thought I read in another thread that the Highlander runs the engine whenever the vehicle is rolling faster than 42 miles per hour, is that true? If so, that's different than the Lexus and changes my cruise-ctrl story. Anyway...

On I-5 North, coming into the Portland area, there's a straight, level to slight downgrade, with the speed limit dropping from 65 to 55. I find that if I hit that segment with the cruise control locked in at 68-70 (same speed as everyone else) I can start using the 'bump-down' function to reduce my set speed by 1-2 MPH. Maybe give it two bumps initially. The engine kicks off and I'm motoring along on batteries.

Watching the power-required gauge creep up as I approach my set speed, I can see when it's about to relight the engine. Give the cruise-ctrl another bump down, and the power-required gauge drops back. As I approach the new speed, the gauge creeps back up and I give it another bump.

What I'm doing is maximizing the draw from the batteries to keep up as much speed as I can and using the gauge to cleanly avoid engine relights, while slowly decelerating since the motors can't maintain 65-68 on this grade. On this segment of I-5 I can maintain highway speed, decelerating from 68 down to 58 over a span of 4-5 miles, all-electric. I don't think it's a generally applicable technique, but it seemed to work in this set of circumstances. Yes, I could do it with my foot, too, but this felt like it was easier to be smooth at.

* With the gauge, it's easy to see the amount of braking actually available due to the motor regenerative braking. I don't know if it's limited by what the motors-***-generators can put out or what the battery can accept, but it's not as much as you might think. To maximize power stored, especially from highway speed, anticipate your slowing, and get on the brakes lightly, early. Maximize the time you're stuffing power back into the battery.

* Another thing that caught my attention how well the RX coasts. On another segment of I-5 with a mild downgrade, maybe 2-3%, I was going 70 with foot off the gas (mild regen) and was still gaining speed. That car really likes to roll...

Benton 6may08

 

If I understand what you are describing, all models (Toyota & Lexus) have it. I use the same way, find its not always correct. There are situation where the engine kicks in earlier, but usually that is due to cold weather driving and wouldn't usually have much effect on a long highway cruise.

The 42mph rule must not be completely true, as I definaly have been electric only as speeds as high as 60 to 65, but only when coasting downhill without any power applied. If I touch the throttle at all, the engine does spring back to life.

The technique you are describing could just as easily be done with your foot, and might actually be more effective as you can keep pumping in just enough power to maximize the run times with ICE (internal combustion engine). Howeve I have to say using the cruise control is often easier, especially if you are going to be doing it over a period of hours.

The actual technique you are describing is usually called P&G or Pulse and Gluide. If you like that sort of thing, you might want to check out http://www.cleanmpg.com; They are a hypermiling site not specific to hybrid vehicles, but the information can be applied and they do have a lot of hybrid users. You can find me there under the same id. The primary guy there is Wayne and he gets some very impressive mileage and does a lot to promote hypermiling techniques which can range from the simple "accelerate slowly and don't speed", to mechanical, "inflate tires to max sidewall pressure" to advanced techniques which may involve manually shutting off ICE when not needed and long distance coasting. I only do a few things from there, but it really helped my mileage.

And I agree, these cars love to roll. I think the Lexas has an advantage. I think it comes with some preety good low-rolling resistance tires.

Have fun,
Jonathan