How could I lose 10 mpg in a week of BETTER driving?!

[razor02097]

Do not use DFCO when you desire to coast. Use DFCO when you desire to slow down. I have a tiny 1.6L engine and DFCO will slow me down as well as mild braking.

Idling while coasting uses a miniscule amount of fuel vs your speed. This can give an instant calculated MPG in the hundreds.

[RedDevil]

Also idling will maintain brake and power steering support. Just like DFCO, but unlike coasting in neutral or declutched with the engine off.

[razor02097]

DFCO has it's uses...such as going down a hill and exiting an expressway. It is better than using the brake but it still means at some point fuel was used to accelerate you to the point you have to use it.

[RedDevil]

Yup, if you have to lose speed anyway it is better to cut off the fuel completely and have the engine do the braking than spend fuel on idling and wear out the brake pads.

Then again, the Insight has the mother of all DFCO's by setting all valves wide open and even give electrical assistance when needed; I can coast down for almost a mile like that
I even have to select Sports mode to get real engine braking like when descending a hill. That's theory so far; up till now I have not yet taken the Insight over 100 ft above sea level. In fact, it spends most of its miles below.

[ciderbarrel]

Crazy Fiat 500 gets a 580-hp Lamborghini V-12 | Motoramic - Yahoo! Autos

580 hp v-12 FIAT

[Atheria]

OMG I need to put a 580 hp Lamborghini engine in Sophia!! That is awesome! Would probably ruin my gas mileage though. ;-) My Fiat got 44.65116 mpg this week with a mix of city and highway driving. I was hoping to average over 45 but didn't make it.

When I coast in neutral I still have power steering. I don't understand that one comment. My instantaneous mpg goes to --- if I coast in neutral without my foot on the clutch and also when I'm coating in gear with my foot off the clutch. But in gear, the car clearly doesn't coast as freely. I can feel the car held back. My mpg sensor seems to show that my mpg goes up more when in neutral. Also, my built in sensor said 46.6 today, so it's about 2 mpg off.

This was on 91 octane gas.

I feel that I'm still doing something wrong. I think Sophia has more potential. I guess I can try more in gear coasting just to test things.

Atheria

[alvaro84]

Originally Posted by Atheria

When I coast in neutral I still have power steering. I don't understand that one comment.

I think it was about coasting in neutral, with the engine off, which really takes power steering/brakes away. Though you should be able to brake a few times before it stops working.

Originally Posted by Atheria

My instantaneous mpg goes to --- if I coast in neutral without my foot on the clutch and also when I'm coating in gear with my foot off the clutch. But in gear, the car clearly doesn't coast as freely. I can feel the car held back.

It seems that the FCD isn't too accurate then. Like in my instructor's car, a Suzuki Swift. That one would never show numbers below 2.0l/100km, no matter what I did - if I tried to coast with the clutch ('soft neutral') or engine brake, it always showed the same 2.0 regardless the speed (=117.6 US mpg), which is impossible.

But my Yaris' FCD clearly shows the difference between coasting and DFCO.

I still owe you an experiment with Teresa, opening the throttle while engine braking with the kill switch off. This is an interesting one.

[razor02097]

The 3 dashes may be on purpose. Otherwise while you are changing gear it would indicate all sort of wacky numbers. It is just a guess though. Either way The computer should still account for the MPG during the coast.

[Atheria]

I think it does. It's just hidden.

[Occasionally6]

If it only displays two digits to the left of the decimal point and you can get over 100mpg coasting in neutral that would explain why the display goes to "---". That makes it harder to tell when/if the fuel is cut off completely. It may not matter much in practice though - either way, "---" is good.

Something else that I think we've overlooked is that this is a Multi Air engine. That is probably going to mean a rethink on some of the driving techniques. Because the pumping losses are reduced I expect it's going to respond more to Diesel appropriate techniques eg. gentle acceleration will probably be no worse than trying to get some load on the engine. Or at least there's less scope for improvement with it.

Lower pumping losses also might mean the DCFCO coast is more usable. The car will still slow of course but you won't have (literally) half the engine acting as vacuum pump and wasting energy.

If this model has the gearshift indicator are you using that? It will be interesting to see what feedback you get from the uploaded data too (if you do that).