Why no fast acceleration? - Page 2 - Fuel Economy, Hypermiling, EcoModding News and Forum

H-Man · 10-13-2015, 02:26 AM

Then there is my car, you can hoon it up as long as you don't need to waste energy to slow down afterwards without severely impacting fuel economy.

Ecky · 10-13-2015, 07:29 AM

Here's a BSFC chart for a Toyota Corolla:
.

The circles with numbers show the amount of fuel needed to produce a certain amount of power. Note how you get less from your fuel as RPM increases and load decreases. On this particular engine, you want to stay between maybe 1750 and 3000RPM.

prr · 10-13-2015, 10:39 AM

Quote:

Originally Posted by Ecky

Look up "BSFC charts".....
That said, so long as you aren't revving it up, the biggest gains are too be found in the art of slowing down.

Didn't see any for a 1998 Honda Civic, even without searching for the year.

OK I can keep it simple: accelerate but not too fast (I think I've trained myself to do that already), & learn how to coast, and approach intersections.

Fat Charlie · 10-13-2015, 11:31 AM

Yep. Brakes waste gas. Avoid needing them.

PaleMelanesian · 10-14-2015, 09:53 AM

Quote:

Originally Posted by prr

Didn't see any for a 1998 Honda Civic, even without searching for the year.

OK I can keep it simple: accelerate but not too fast (I think I've trained myself to do that already), & learn how to coast, and approach intersections.

I haven't seen one either, but if you look at a bunch of different engines' charts, you start seeing strong similarities. Take that general knowledge and apply it and you WILL get results.

The differences between your engine and the general "other" engine is only a few percent this way or that, and only matters for a portion of your driving time. You've got the right idea - keep it simple and keep working to do better.

prr · 10-14-2015, 10:18 AM

Wait a sec. Just remembered that my 98 civic doesn't have an indicator for RPMs. Some do, just not mine. Oh well at least I can continue accelerating slowly, to avoid breaking as much.

UFO · 10-14-2015, 11:50 AM

Quote:

Originally Posted by prr

Wait a sec. Just remembered that my 98 civic doesn't have an indicator for RPMs. Some do, just not mine. Oh well at least I can continue accelerating slowly, to avoid breaking as much.

Get a Scangauge. It is the best tool for monitoring your engine and ECU. It will give instant feedback on mileage and it can display all sorts of engine fucntions including RPM.

PaleMelanesian · 10-15-2015, 10:15 AM

Quote:

Originally Posted by UFO

Get a Scangauge. It is the best tool for monitoring your engine and ECU. It will give instant feedback on mileage and it can display all sorts of engine fucntions including RPM.

This. So many times. I got my old Civic up to 42 mpg without a gauge. The first tank with a gauge was 46 mpg, and that was my new low - every one after that was even higher.

But you can roughly work out the rpm by calculating speed in each gear. For my 1996 Civic DX, it worked out like this:
1500 rpm - 2300 rpm (my road-tested ideal rpm range for the Civic)
2nd gear: 13 mph - 20 mph
3rd: 20 mph - 30 mph
4th: 26 mph - 40 mph
5th: 33 mph - 50 mph

Or to keep it simple, when you reach (gear x 10) mph, shift. When you're in 3rd gear, shift when you get to 30 mph and don't take 3rd gear beyond that speed.

It gets troublesome with 5th gear. What are you going to do? You don't have a 6th gear to shift into, and you can't limit yourself to 50 mph always. You just grit your teeth and deal with the high rpm cruising and grumble at the engineers who built it this way.

Remember that neutral is an option as well. It takes a good amount of energy just to keep the engine spinning at 2000 rpm at a steady speed. If you shift to neutral it takes a lot less fuel to spin it at idle rpm instead.