So disappointed in my 1st hypermiled tank
 

After my Dashdyno got calibrated, I did 2 weeks nonhypermiled and got 43 and 44 mpg. Then I decided to do a week of aggressive hypermiling. By this I'd do lots of FAS P & G in the city, shutting off at stoplights to prevent idle, and P & G on the hwy from 70 to 60 mph. I had a 53 and 57 mpg drive from work. I avoided a major accident traffic jam to work by going to a side road and then past the jam. Then on Saturday, bad luck - got caught in another traffic jam from a major accident - did 10:20 minutes of idling / slowly moving the car bumper to bumper. This killed my trip mpg down to 39 mpg but with aggressive FAS P & G my total 34 mile 95% city trip went to 46.7 mpg. Then Sunday's shopping - aggressive FAS P & G netted 52 mpg 95% city driving on 35 miles. Driving to work Monday morning, no hypermiling and got only 44.6 mpg.

But my biggest disappointment was I didn't break a 50 mpg tank! After filllup I computed a 45.177 mpg tank! Only 1.177 mpg better than my best nonhypermiled tank! I am so pissed and if my future hypermiling attempts don't break 50 mpg I'm not gonna do aggressive hypermiling!

Has this ever happened to you? - A bad hypermiling tank? Was it the traffic jam that killed me?

If I can break 50+ hypermiled tanks, I'll upgrade either my battery or get a 5 farad capacitor to prevent low electrical surges whenever I crank the starter, - as this usually resets my Dash Dyno trip meter for my hypermiled mpgs. Anyone do this to prevent resets on a Scanguage ? - Or this doesn't happen to a Scanguage?

I drive a 99 Civic HX MT.

well don't give up... FE goes up and down, and some factors you just don't controle... tank to tank results can varry drasticly... the wind, traffic temperature. the way you fueled up, it all affects tank to tank results. what i do is look at my monthly and even yearly results and write down things like temperature and traffic conditions next to every tank. temperature and seasons have a big impact. but when plotted out over a longer period you'll definately see an improvement. i've had disapointing tanks... i've had a few tanks that where unexpected good...but in the end fe was slowly creaping up, and thats what matters!

All it takes is 1 gallon diff in the way you fill up to make it seem "bad". You have to do 5-6 fillups to get true results.

EPA on your car is 30-38 new 35-43 old. Your beating the old highway mileage figure without hypermiling, which indicates your driving style is fairly efficient either way. My 94 VX also doesn't respond very well to hypermiling, so I just stay in the right lane and find a truck to break the wind for me. P&G at 70-60 causes your drag factor to increase from 36 to 49, which probably offsets any advantage. My VX got 65 the last trip when I just went 65 in the right lane a stayed about 100-125 feet behind a truck, on I95 south of DC on Friday night in heavy traffic. My average speed was about the same as yours.

regards
Gary

I found my scangauge mileage to be off by about 1mpg in either direction from the calculated mileage from fill-ups and dash trip meter.I log by the fill-up calculation.
I had good mileage early last November and went down hill from there until the weather started warming up. It's going back up again now.I'm assuming everything I've done to get better mileage was offset by the cold weather and some holiday traffic.I'm expecting the warmer weather to come will increase a couple more mpg. I'm running low on new ideas to improve,but not giving up.

Don't shut off your engine at a stoplight! That wastes gas. You know that cars run between 1:1 and 3:1 air to fuel when cranking, right?

You're not coasting in neutral I hope! Be careful what you assume to be beneficial to mpg.

It took me years to perfect the technique, that is, for each and every car different little tricks apply... So every time I get into another car it's the same old learning experience all over again.

But I still see 10-20% improvement after about a year...

btw don't forget DWB

P&G from 70 to 60 is going to kill your mileage anyway - better off going 65 nice and steady than to get up to 70 then slow down all the time. When P&G is really useful is at 25-30mph.

Yeah I'd think P&G would be a bit useless on anything less slippery than an insight or prius at 60-70. or maybe heavy and moderately slippery cars do better at that, like a lot of buicks.

F'rinstance, bit of an outside example, but take my foot off the gas in my voyager at 60 and it's down to 50 in a few seconds... but coast at 30mph and it just rolls and rolls and rolls. Go down an off ramp and lifting off as I cross the line, it's down to 40mph at half the distance, and the other half will only drop 5mph...

on 65 and 70 mph zones,the P&G I do is to give the car a steady amount of gas so that it gains speed going down hill and slowly loses speed going up hill (down to 55 or 60,depending on traffic). On rural roads I just lightly press the gas and let the car decide how fast or slow it wants to go.

Actually it's better to give it more gas pedal on the uphill part, and let it coast downhill, while trying to maintain a relatively constant speed. Best engine fuel consumption (per unit of horsepower) is at low engine speed and about 70% throttle. It's also more efficient to P&G within the narrowest range of speed, which is much lower (range of speed) when you climb the hill and coast (engine off if you please), because it avoids exponential increases in drag. I think I read that Wayne Gerdes stated that they actually got better mileage on hills than on flat ground, but probably not steep hills, kind of like a roller coaster effect.

Most of the hills around here are not that large and you dont have to worry about too much speed downhill. If you end up going too fast downhill (due to slope) use high gear and release all pressure on the pedal to utilize fuel shutoff, which uses no gas.

65 MPG at 65 MPH on hills between Richmond and DC using that exact procedure with a little aero help from the truckers going 65-67 to conserve fuel.

I dont know why they used to think constant high engine vacuum was an indication of good economy. In reality the more air you get in each cylinder for every combustion pulse the more efficient the engine produces power. In reality your P&G should be in the highest practical gear at 75% of max throttle, ideally between 1200 and 2500 RPM. On a vacuum guage that reading should be as close to zero as possible with the least throttle opening that produces the lowest vacuum reading.

Anytime you are not filling the cylinders completely you are reducing the effective compression when the explosion occurs, which can only reduce the energy extracted from your fuel consumed.

Cars with better aerodynamics can P&G at higher speeds. Consider when I am travelling at 45 MPH with the engine idling, which cosumes .2 gal per hour, I ma getting 180 MPG even with the engine idling, whcih will offset the increased fuel consumed in the pulse, because you are using only half as much more fuel to apply the 50% greater power you use in the pulse phase.

regards
gary

Isn't this a very simplistic explanation?

Could one make the (similarly simplistic) argument that if more air is going to the engine that more fuel is being consumed by virtue of the fuel-air ratio?

By all means, DO shut off the engine at stoplights. Anything more than about 10 seconds is worth it.

Pulse & Glide works wonders on the highway, especially if your steady-state rpm is above 2,000. That's 45mph in my case, and maybe Jesse's as well. I've done 75mpg on the highway using 45-60mph P&G, and 60mpg using 55-70 P&G.

And I do pulse the uphills and glide the downhills. Higher load = more efficient engine operation.

Well, my 2nd week of hypermiling was dissapointing too - 44.314 mpg tank, when I had several 50+ mpg drives but one bad 30 mpg drive with heavy A/C no hypermiling.

Hey Pale - I'm 99HXCivic on Cleanmpg too!

dosco:

Simplistic is the easiest to understand, sorry if I erred in that direction.

The effective compression is the potential compression minus the restriction. If you have 18 inches of vacuum you are only allowing about 1/3 of the air the engine is capable of ingesting.

The result is lower compression which makes the engine less efficient, the difference being you can get 50 hp using only 50% more fuel than 20 hp, by adding only 50% more fuel with the throttle open 70-80%. Your manifold vacuum reading would be close to 0.

Pulse and glide means you are using the vehicles own mass as storage by adding the extra 30 hp into acceleration and then allowing that stored energy to replace the sustained low efficiency demand of continuous operation. The extra 30 hp costs you only half as much as the first 20. You are using fewer total revolutions while increasing the air for each revolution at the same rpm.

Of course cylinder filling combustion events use more fuel than restricted events.

regards
gary

It's not a problem, and sorry if I was being a prick (I was born with that innate talent).

I'm grappling with the trade-off between reduced mass flow through the engine (e.g. at idle RPM) versus operating at "most efficient RPM."

I'm interested in a study (like a bunch of calculations using the governing equations) between the two to determine where and when it would be optimal to let the engine idle versus driving with the engine at max efficiency RPM.

It seems to me that there is some difference of opinion regarding whether it is more better to let the engine idle (i.e. P-G) or run it at load.

I understand the concept of P-G. As I indicated above, where I'm going wrong is the theoretical understanding when to idle versus when to maintain constant load. For example, why is it more efficient to P-G than to operate the car at a steady state at the "most efficient" RPM?

Another thing that comes to mind about P-G....In a perfect frictionless world, using P-G wouldn't get me much because the amount of work I'm applying to the car during the pulse would be the same as I would get out during the coast.

Of course, the real world has losses due to friction, so I have losses during the pulse and losses during the glide. Theoretically speaking, won't the losses be greater during the pulse due to higher speed (thus higher aero drag), windage losses in the engine at higher RPM, and more fuel mass flow during higher RPMs?

I've only begun experimenting with real-world P-G driving. Palemelanesian indicated the "best" P-G is using a wide speed range ... wider than I've yet tried. So I'll soon see what the deal is with my own data/own car.

The deal with P&G vs steady state at the same rpm is load. There's an ideal rpm/load combination. Often it's something like 2000 rpm and 75% load, but it varies with the engine. If you try to maintain the load, pretty soon you're going 120mph. So you use the high-load for a pulse, then glide down on the energy you built up.

See this article: https://www.autospeed.com/cms/A_110216/article.html especially the 5th color-coded chart. You want to be in the red zone. The fuel consumption per power output (unsure what the units are) is 0.42. If you keep that same rpm, but go to steady-state at maybe 20% load, you're in the purple zone at .6 or .7 or even higher. See how quickly it builds up closer to no-throttle.

OK, exactly the info I was interested in!

Thanks for the link.