Accelerating for good fuel consumption.
 

I am struggling with trying to get the best out of my little engine under acceleration. I seems that no matter what I do I find that the instantaneous figure drops down into the low 20's (or lower) as soon as I open the throttle.
I have tried monitoring the Throttle Position Sensor, but the values the ScanGauge show seem to jump all over the place. It varies between 12 and 85 but trying to keep it up near 85 without reaching 85 is almost impossible.
My question is, can I use the loop sensor? If I keep the system running in Closed Loop, with the throttle as wide open as I can to keep it in Closed Loop, is this the best acceleration for fuel economy?
I do not allow the revs to exceed 3000, trying to keep them around the 2500 mark. Should I rev a bit higher, so that when I change gear the revs drop to nearer the point of best Brake Specific Fuel Consumption, instead of below it?

Let her rip- harder acceleration means less acceleration.

The sooner you're up to cruising speed, the sooner you're out of the bad instantaneous mpg. Even if you can mitigate it somewhat, it doesn't beat cruising mpg. Get into the throttle more sou you can get out of it sooner.

Your short trip mpg will thank you long before you get where you're going.

Charlie that doesn't work for my Cruze. I feel for NA cars that's a good fit but anything with a turbo seems your best bet is to accelerate just out of boost. I have tested my acceleration many times and my little turbo eats gas.

As you are an experience Hypermiler, driving the same make and model as myself, I will certainly give that a try. My Jazz is the base model, difference is it has the 1.2 litre i-DSi engine. But being naturally aspirated I will certainly try that.

http://ecomodder.com/forum/attachmen...1&d=1502111938

Yes.

Furthermore, you should try to obtain a torque/HP dyno graph of your car's engine. Barring that, try to find the RPM point where your engine torque starts to drop - that's where you want to upshift.

I have the Power/Torque curve here.

http://ecomodder.com/forum/attachmen...1&d=1502115532

So, looking at that graph, I'd probably try to keep my engine speed between 2500 and 4500 RPMs while accelerating.

I've never ever rev'd it past 4000, but I'll give it a try.

Lmfao punch it grandpa eco gotta get the carbon out of there at some point.

I am not against revving a car. Even my Volvo was red lined on a regular basis. Just the Jazz has a gearbox whine (model trait - input shaft bearing), and revving makes it sound like the cogs are coming through the floor to meet you. Not worth fixing though.

Yeah can't blame you there. I don't know the last time I had my car past 4k rpm. My Jeep I redlined constantly because it liked it lol burnt less oil and idled better after being beat on.

BSFC always happens below peak torque, so I don't think you should be revving past 2500ish.

2500 is my normal driving change up point. Even before I tried driving for fuel efficiency changing there just felt right. Starting on a really steep hill I'll take it up to 3500 or thereabouts.

I'd stay between 2000 and 3500 while accelerating.

Well, if we truly want to save as much gasoline as is humanly possible, we should probably rpm match while upshifting. The below chart was made for this Honda Jazz 1.4L:

http://ecomodder.com/forum/attachmen...chmentid=22371

That's just a software generated curve extrapolated from the car stats. Not entirely useful.

You want an actual dyno.

Have one here for the 1.3 iDSi... slightly bigger than your 1.2 (AFAIK, they sold the iDSi in sizes up to 1.5), but should be similar enough:

http://www.speedlab.com.ph/images/po..._dynochart.jpg

Great curves. The 1.2 litre does develop its torque at lower revs than the 1.3 and above. Seemingly it was developed that way. It is a wonderfully smooth and flexible little engine.

As far as I can see, the 1.2 Jazz has the same gearing.

Second gear can take me up to 50mph, good enough for everything but a highway. Yes, the upper end of the tach is less efficient, but I'm out of it and into fourth or fifth immediately.

There's a lot of overall efficiency to be gained from one hard pulse versus a few less hard pulses.

Gave rpm matching a try this afternoon, and it seemed to work well. I had a great Hypermiling run, along my favourite coasting road. It is like a roller coaster, for mile after mile, with some tight bends which need a bit DFCO. I was in the car myself, so I could throw it round the corners in a manner that would alarm my usual "navigator". The last section is brilliant. You crest a rise at about 20 mph, use a bit of DFCO into the first two bends then stick it in neutral. You are soon doing 60 and it carries you right into town. It finishes with an ascent to the 30 mph zone and the speed bleeds of perfectly. As you pass the signs the road resumes level, and it is just a case of 5th gear and that's you. I love that road. It is about 3 miles longer, but as well as the coasting it drops me almost at my flat, with virtually no town traffic.
A great day out!

It would seem to me that the most important thing while accelerating is not instant fuel mileage, but rather best efficiency.

Internal combustion engines get better fuel efficiencies as you lay your foot into it, at least up until the engine starts to run rich. And lower than max torque is best for best fuel mileage.

In my diesel I just floor it and keep RPMs as low as possible, 1,000RPMs and up. Max injection is still lean of stoichiometric so I don't have worry about that.

I must say getting in it in my ex seems to help. The built in av guage seems to be thrown off drastically by it though got 27.5 mpg and dash readout was 24.4. was shocked when I hand calculated it. It had dropped a bit from 25.4 since I started running up rpm a bit to get to tc lockup faster. My Cruze on the other hand seems to respond decently to the same treatment when it's a bit cold yet. Speeds warm up time vs slow acceleration and helps for efficiency at cruising speed earlier. Yet the route I'm taking currently is a bit windy I call it my hypermiler route. Have to go this way due to road work. Have been coming out with near the same numbers as prior to testing your hammer down theory. I feel my earlier assumption that na would respond better than turbo vehicles was correct.

Came here to say this. Find your engine's torque peak, or if you can find one, look for a Brake Specific Fuel Consumption map which will also show you how much fuel you're consuming at engine loads. Look for the island of efficiency (google those terms in the search window at the top left of the page) and try to put your acceleration regime right in that area for greatest effect. Get up to cruising velocity and there you are.

If you choose to pulse and glide, shoot for the island of efficiency, from its lower to upper rev limits, for all your pulses.

I haven't been able to find a Brake Specific Fuel Consumption map for the 1.2i-DSi engine but using this torque curve
http://i.imgur.com/fkSR1Gx.jpg
I tend to try an accelerate from about 2200 to 3000 rpm

I'd suggest trying going only up to 2,700RPM. Or 2,500RPM max and see how that does. Do you have a vacuum gauge installed?

In city/town driving I try to stick to the figures you suggest, but on hills the small engine needs a bit more, otherwise as soon as you change up you need to change back down.
Also for brisk acceleration such as joining traffic on an on ramp. Or sneaking in behind a fast moving coach, or the like, for draughting.

I have a ScanGauge E fitted.

Without having the BSFC map in hand, that's the rev range I would shoot for, too. Note, too, that that torque curve is for wide open throttle. If you do manage to find the BSFC you may be able to tweak how far you mash the pedal down for better results.

Maybe you could drive like me!

In my Nissan Leaf it won't make it from the next town back to home at highway speeds since it's uphill and there aren't any charging stations on that 70 mile stretch and because my battery has lost over 15% of it's original capacity. So I just drive at 35mph along the shoulder with my flashers on and make it back home ok. I've been doing this once a week for several months.
:turtle:

That is fine when needs must. I did the same when my exhaust broke off and was dangling below the car, but to save a couple of miles per gallon I would just be selfish. I do drive at these sort of speeds, if there is no traffic behind me, but as soon as traffic comes up behind I speed up to what would be considered acceptable for the road.
We don't have a shoulder on our roads like you do in the States, except on Motorways, where you can only pull over and stop in an emergency. You cannot drive on them.
This is typical of the roads around here.
http://res.cloudinary.com/jpress/ima...mage/image.jpg

Couid one not tweak the mpguino or other gizmos software to show fuel used for acceleration?

http://ecomodder.com/forum/showthrea...oad-19594.html

Yes you can.

Some years ago I had a little 1980 Fiat 127 with quite poor fuel efficiency and a worn out engine. Eventually a conrod bearing seized and as a quickfix I simply ripped out two pistons, disconnected the valves and put it all together again re-using the same gaskets. It then worked hard for another year until I sold it.

Projektblogg - Fiat 127 engine downsizing
(try using Google Translate, the webpage is mainly in swedish)

Those experiments gave me the first important lessons about successful ecodriving. The downsizing gave 10-15% improvement and I soon learned about the fuel enrichment that appears at full throttle and noticed quite an improvement by keeping the throttle at 70-80% of maximum opening. (carburetted engine) I also experimented with staying in 3:rd gear all time instead of continously shifting up and down between 3:rd and 4:th (as you have to do with such a weak engine (about 20 hp maximum I guess). Keeping revs down was definitely a winner! I never tried "Burn & Glide" (pulse & glide, burn & coast) with the little Fiat, mainly because I didn't know about that by then, but with that tiny engine I also needed the engine active all the time to get a decent average speed...

If you run an ICE at a realy low rpm I guess more of the combustion energy will get time to get lost as heat in the cylinder walls and head. At higher revs the losses increase due to pumping and friction, and if you close the throttle to match the actual need for power to keep a steady speed, things will get even worse.

It's all about finding the BSFC sweet-spot and keep the engine there. When that is not possible, turn it off completely! If that's not possible (power steering, power brakes and sensitive engine control computers that go crazy), keep it in idle, out of gear.

I once got a 15-20% improvement in a good friend's cool 400hp BMW coupe, a quite modern car with dual turbos and automatic transmission, using the Burn & Glide method. A nice secondary benefit was to enjoy the acceleration again and again. :-) Since it was an automatic, I put it in neutral after every acceleration cycle, and kept the engine running. After 15-20 minutes the ECU got crazy and started flashing strange error codes on the dashboard. We stopped and let the car rest for a while and everything was back to normal.

Ecodriving worth it's name can be difficult with modern cars, so you can definitely ask if all the electronics are realy a development. I feel we are in some sort of crazy limbo between old simple cars and a true change of paradigm, where everybody rides with hyper efficient automated taxis instead of owning their own cars.

I lean toward the philosophy of "low rpm first, then anything else". I rarely go above 2500 rpm at the top of my pulses, usually running 1500-2200 rpm. Of course, I have the 1.5L engine, so as you said there will be places where you NEED more rpm for more power. That's a good thing, it means your engine is actually the right size for efficiency rather than for power.

You might look at MAP on the gauge for accelerating instead of TPS if your TPS is jumping around.

Thanks. I'll check MAP out. What am I aiming for?

Back in carburetted DOHC engine days people would say: enjoy your coked bearings and valves :)

The only logical way to keep a better mileage is to hold most of the time a high, but constant speed. Unless the cops and speed cameras are around.

It takes only about 60 hp or so to keep a Veyron running 60 mph. It takes over 1000 hp to get there in 2.5 seconds. Even getting the best efficiency in the realm of road vehicles, given by electric motors, it still takes 500-600 hp for the same feat, as in Tesla P100D.

In my car (1.8T, gasoline, turbocharged, 234 peak hp, a lot of minor aero tweaks) I can get up to 34-35 mpg (in US gallons) running with constant speed. From 30-31 mpg when bodywork was in stock form. With some acceleration, in the 1.0-1.4 bar on the boost gauge, but only where needed. Sporty road driving may drop to 29-30 mpg.

This is not modding of the car itself, it's modding of the driver - one adapts himself or herself. It takes training.

I've been told accelerate briskly with the throttle well open, accelerate gently, keep the speed up, keep the speed down. I have more or less decided just to accelerate as I have done for the past 50 years (neither one thing or the other) and make my gains when coming back down the speed range (DWB, coasting, anticipation, avoiding stopping if possible and conserving momentum).

And they're all the right thing to do, depending on conditions. :)

An SG or UG will let you see which is right where and when.

According to my ScanGauge there is very little to choose between the options, at least on my 1200cc engine.

Charlie is right, it depends on the conditions. If the road is wide open I would accelerate briskly, if there is plenty of traffic or unpredictable stoplights then accelerating gently is the better option. I need to work on that to get better city mileage.

Today I monitored MAP and it is a nice steady reading. Varies from about 4.2, on a closed throttle, up to 14.5 on a wide open throttle. Short of keeping it below 14.5, what more should I be aiming for?