Hi Folks,
I've been watching and commenting here and there, but but waiting until I had a real question to start a new thread. I've had my Civic II for a couple of weeks now, and thanks to this site, started with a MPG near 50.
I live in a relatively hilly area, not Colorado, but rolling ups and downs, slight inclines as the Appalacians dissipate into Massachusetts. I've experimented with pulse and glide and the general coast/glide down hills and flat areas, but I also wonder about the areas where gravity is not working too your advantage. I've found that I can maintain a pretty steady speed with a light touch and keeping the MPG around 75. Now, I'm not a mathematician. I can wax poetically about fresh air, but I'm trying to wrap my brain around this. When I try and pulse and glide in non-ideal situations, I drop in FE to the 20s or lower as I get up to speed, coast for a bit up at 100, then drop down, etc.
It would seem that keeping steady around 75 would make more sense than bouncing back and forth. I'm not exactly sure how much time the engine needs to kick into its gas FE mode or if it is instantaneous, but it would seem that would make an impact too.
Any thoughts?
Thanks.

 

I think the pulse and glide is used for the Prius owners. You have the right idea for the HCH. Won't mind driving a Prius to give it a try though I don't fit.

 

Fradubio,
I'm having a hard time picturing what you are saying. If you are going up and down in a fairly hilly area, how can you maintain a fairly constant speed, and keep the FCD hanging around 75 mpg? Going up hills, you're either going to have to sacrifice speed or mpg. Going down, it's the opposite.

I can understand being able to do that on a flat stretch of road, but not on hills. Hills are where pulse and glide come in handy, because you can accelerate on the down side and coast up the inclines. What am I missing?

 

Pulse and glide works in theory not only on vehicles such as the Prius, but on standard gasoline-only vehicles as well, if you're obsessive enough to throw them into neutral and go back in gear each time. The method has nothing to do with the electric motors. However, the benefit is more profound on the Prius as that car has the ability to comletely shut off its engine automatically at low speeds.

When driving at steady speeds, the engine must constantly waste power by sucking air across a partially closed throttle plate. This creates a vacuum in the intake manifuld, which leeches a bit of engine power. This loss is most extreme at idle, but very minimal at higher, more efficient RPMs. The technique is done by accelerating for a short period of time at the engine's most efficient RPM, on the case of the Civic, probably around 2600 RPMs, using that surge of extra power to building up extra speed, then coasting for a long distance using that built-up speed.

Having the engine on in a steady level for that time would take about the same amount of power, but would waste energy due to partial throttle losses.

However, pulse and glide technique only works for slower speeds, such as bouncing between 30mph and 45mph. Any faster than that, and you waste power on the pulse phase due to increasing wind resistance, and you also cannoy coast as far on the glide phase due to wind resistance. Finally, since faster speed driving reuqires more power anyway, the throttle will be more open and there will be less of a benefit from reducing throttle loss, anyway.

When driving with hills though, you can do what is called driving with load. Try to keep the engine load steady when climbing, and lose a bit of speed, then, when you go down the backside, if you have a second-gen Civic Hybrid, you can pull the gas pedal almost all the way back, and the engine will actually seal all the valves (no throttle losses, but you still have the pistons sliding around) and kill the injectors. you can then "glide" down the backside of the hill. This woudl be more efficient than keeping a steady speed on the way up, and wasting it by using the engine as a brake on the way down.

 

gang

I am impressed with many on this site who take the time out to find ways to better the use of their hybrids. People on this site are an inspiration to us all with their suggestions . I find it admirable that we never stop trying to better our performance of our vehicle.

But for my time, i am going to drive the vehicle exactly the way it was designed to drive. I find steady and cruise control to work best for us, and we havent put much effort into the pulse and glide. I feel the effort to learn this type of technique may not be wize to driving in general, but again is just my opinion.

I keep my tires at recommended specs, and not try overinflating them. I also always keep the vehicle in gear, not neutral . I did not take the roof rack off my highlander. I like having it on. We use air conditioning when it is over 80 degrees outside.

Its not that the above suggestions are no good. I just want to drive the highlander the way we are instructed by the manufacturer. I am happy with the mileage.

 

Pulse and glide? Don't bother, the benefits are marginal at best, and the shock you put on the drivetrain isn't worth it.

 

Eh?

 

In just about any car but an HSD based car I would agree, as an accidental mishap (say a mis-shift to get back into gear) could cost well more than any gas savings. The reason Pulse and Glide is popular on the Prius however is because the transmission, by design, does not turn the engine over at all with the foot off the gas under 40mph, so no gymnastics are required other than accelerating, then coasting.

 

Well, coasting in gear in the HCH II is almost as good. The engine does turn, but with the valves shut the effort to turn it is so small you could probably do it with your pinky. I'm always surprised at how far the HCH glides if I keep just enough pressure on the pedal to prevent regen.