Was thinking about this today and started playing with it.

Generally, when hypermiling, I'm trying to feather the throttle as lightly as possible to use as little gas as possible. This has always worked pretty well for me, giving me very nearly 50 mpg doing "light-footed" pulse and glide from about 40-55 mph.

What I started thinking about was that internal combustion engines are actually more efficient under higher loads than that. So, I started playing with doing nearly full-throttle (trying to avoid full-throttle because most cars go open-loop and rich at full-throttle) acceleration in top gear for the "pulse" portion of my pulse & glide instead of the "baby the throttle and barely accelerate" method that I've been using. The theory here is that I'm opening the throttle enough to let the engine suck in as much air as it wants and letting the EFI supply whatever fuel is required for that. The result should be more torque from each bit of fuel used. Used properly, this technique "should" yield better economy.

I'm pretty sure this is how Jeff managed to get 41 mpg out of his Spec V Sentra. He's got the torque to crawl out of just about any hole, so he'd coast down to 35-40 mph in 6th, then floor it and accelerate up to 70... then coast back down again. (of course, he was killing the engine and coasting in neutral, too... so his coasts were longer than my DFCO coasts)

Anyway, using this method as I was able to today (driving around between Safety Harbor and Palm Harbor) I managed to pull an average of 45.6 mpg. So, if it's not helping, it's certainly isn't HURTING anything.

Anyone else see the merit in this idea? I can't say that I really came up with the idea myself, I seem to remember reading it somewhere a while back.

So, I'm accelerating gently through first and second, then carrying 2nd or 3rd up to about 30-35, then dumping it to 5th and giving it a heavy throttle to accelerate up to... maybe 10 mph over whatever the speed limit is, then lift and go into DFCO and coast down either to a couple mph below the speed limit (or slower if nobody is behind me), or prep to start decelerating for the next light, whichever is appropriate.

I still find it stunning how many people freakin' RACE to an obviously red light at a major intersection. You can SEE the light is red from 1/4 mile away and the traffic is so backed up there that you KNOW you're going to have to stop even if the light turns green... still, they stay in the throttle going 20 mph over the speed limit and drop anchor at the last second. People just don't get it. I managed to pass several of those people as they were stopped at some of those lights today without ever even slowing below 2nd gear speed myself by simply taking stock of the situation and choosing the correct lane. Pretty funny, really.

Rambling again. Yep, that's me.

 

that's because most people are fucking retarded... accelerate to a stop... and people wonder why they spend so much on gas..

as for your thoughts, yes, the motor is more efficient near its peak power.... so yeah, you should be getting as much mileage

 

I've played with it some more and found that it depends on the situation. If I'm on a low-speed road with no other cars around (speed limit 30-40), doing a hard 5th gear accel up to 45-50 and coasting down to 30 seems to work very well. Still not sure it's better than a mild accel... but since it could possibly net more time coasting, maybe.

In normal driving where you can't coast down as much because you're in traffic, a gentle foot and trying to maintain speed without varying so much works better.

Ironically, I sometimes get my best mileage in stop & go traffic as long as I manage it right and don't actually have to come to a stop for more than a few seconds here and there.

 

yeah, it all depends on the car too...
some engines perform better in real low RPMS and others work better in the mid range...
some ECUs have a good low throttle fuel map, while others are more efficient with more air
some trannys are geared for acceleration with little power, while others are geared for cruising with low rpms..

all of those differences along with other different details make it impossible to come up with a "this is how you get the most mileage out of any car" type of thing... i mean other than the general don't lead foot it off of the line and don't accelerate to a stop and pay attention to bumps so you don't want to bounce your foot on the pedal...

 

For having such a tiny engine, the Yaris has pretty amazing low-RPM smoothness. You can cruise or accelerate from 30 mph in 5th gear. You don't get a lot of acceleration, of course... but it doesn't buck or complain, either. Gotta love modern engine management technology!

 

This is really cool. I have noticed that I get the best mileage in stop and go as well. As long as i dont have to stop and lose momentum. I usually just cruise in the right hand lane. I am to scared to try your new theory as every time I give my jeep gas I feel like I am burning money away. My method is to use as little throttle as possible and inflate my tires to max PSI. Also, I don't think this method would work well, because my jeep is an auto so it will down shift upon a heavy foot. Is it worth a try or no? Oh side note I cleaned my injectors, replaced my fluids, and changed my spark plugs so maybe I can hit 18 this week.

 

With an automatic, I think you'd want to limit your throttle to as much as you can give it without forcing a downshift.

Played with this some more a while ago, I think a major part of the reason that it works is that it allows you to spend more time coasting. MPG sucks when you're accelerating, whether it's a little or a lot. In the Yaris, ANY acceleration dips the MPG down into the 20's... accelerating briskly puts in in the mid-high teens, not a huge difference for the short burst of acceleration. But, if you can make the accel period shorter and the coast (using NO fuel with DFCO) longer, that's where the benefit is.

 

i have heard that the DFCO makes the car slow down a lot faster though. So is it truly worth it to have or do you think it is just Toyota using experimental technology like usual LOL.

 

DFCO is not just a Toyota thing, most modern cars have it.

Those who know (the extreme hypermilers who live in places that actually have hills) say that you're better off to stay in gear and use DFCO in most circumstances. The exception would be a really long hill that's steep enough that you can coast in neutral without losing much momentum. If you can coast in neutral for like half a mile without losing much speed, then it is beneficial to do so.

Keep in mind that if you go to neutral, the engine goes back to using fuel to idle, where in a DFCO coast, it uses NO fuel. Unless you want to be one of those people who kills the ignition while neutral-coasting... but that's getting pretty extreme.

 

much of diesel's economy is found from the lack of a throttle plate. (commonly refered to as pumping losses) while, I don't "floor" the car when hypermiling, I try to keep it in closed loop. yea the sentra is paramount in being able to accelerate from as low as 25mph in 6th but I never used more then 1/2 throttle. the other thing is keeping the fuel trims low. since the sentra can do a short term trim between -15 and +15% and that's on top of it's LONG term trim of +/- 20% which is why the car can run 85% ethanol on stock fuel system.