Fast or Slow Acceleration? Test Results

[California98Civic]

Maybe. I don't know what is on the items you refer to. But do they offer calculated engine load? Calculated instant MPG, trip MPG, and tank MPG? Engine load is the great critical calculated reading for access to the best hypermiling strategy "DWL" or "driving with load."

[user removed]

In a CVT when you give it gas the engine will basically pick a certain RPM and it will stay there until you change the throttle position. In my Altima I tested for acceleration consumption, but I stopped measuring at the same point on the road. Faster acceleration got me to speed quicker which allowed just about the same average MPG to the same spot in the road. Of course more rapid acceleration got me to speed faster, while slower acceleration took longer. Bottom line was the MPG was just about the same regardless of the throttle position until you really accelerated quickly which cost MPG, measured to the same point.

Our 2006 Murano would accelerate to 70 MPH without the RPM changing at 1700, with a constant throttle position.

regards
Mech

[PaleMelanesian]

On my old Civic, Scangauge told me that 75 engine LOD was roughly equal to 12.5 MAP vacuum.

On the Fit (and probably the new Civic), it's not so simple as there are electronics in between you and the actual throttle.

[serialk11r]

Everyone is talking about CVTs and whatever but I think you're all missing the elephant in the room. Cruising 0.6 miles at 65mph takes WAY more energy and that's not negligible. Someone on Spyderchat did a test with different shift points and a 2ZZ-GE engine and concluded that the slowest acceleration uses the least fuel as well, but that is hardly an indicator of what engine load is most efficient.

[P-hack]

That is a very good point, it would be interesting to look at fuel used just to reach target speed as well (i.e. merging/p&g), that would have a bias towards faster acceleration, and you can just EOC out the rest of the distance if time doesn't matter anyway (sans CVT).

[nuverde]

Indeed, the point of my little experiment was not to pinpoint the most mpg efficient load/mpg/gear ratio/other. The point was for me to "discover" how I should be accelerating up to (and maintaining) my cruising speed using the least amount of fuel. In the end, isn't that the goal: to use the least amount of fuel to traverse a certain distance?

My finding was that for my car, accelerating slowly up to 65mph and cruising for a short amount of time until I reached the one mile mark used LESS FUEL than accelerating quickly and then spending more time cruising at 65mph (until the one mile mark).

Now I concede that more experimentation could be done to determine the sweet-spot in the low acceleration range... maybe someday.

[P-hack]

I think you are assuming slowly merging onto an empty hiway with a long on-ramp and then maintaining a speed. Around town the best technique is to use your engine efficiently (if the transmission allows it) and avoiding the brakes (don't over-accelerate, coast to stops). You also have options if the hiway is mostly empty, such as drive slower and pulse and glide, drive with load, etc.

Also there appears to be some issues with the accuracy of the imid
What is your Civic SI's best MPG? | 9th Generation Honda Civic Forum
It may not be recording fuel consumption directly, unfortunately (indeed since you are inferring fuel used from displayed mpg...)

Experienced hypermilers understand the compromises involved. I've p&gd a beater 5 speed all over the state to the tune of 55mpg. As well as route selection becomes a factor also, i.e. efficiently pulse and glide on surface streets, or a 65mph burn on the hiway, might only make a 4 minute difference in commute and cut your mileage in half.


It's complicated... My prius (arguably a cvt) loses a lot of efficiency in the transmission if I go over 2400 rpm at lower speeds, but my 5 speed civic doesnt.

[vskid3]

Nice testing.
I have a question about your procedure. When you say 1 mile, is that 1 mile from the 0MPH starting point or 1 mile from where it hit 65MPH?

[nuverde]

Thanks!

That is one mile from the 0mph start. So the distance covered was 1 mile for all test runs, regardless of acceleration rate.

[j12piprius]

It would be interesting to accelerate (1) with different % engine loads to the same average speed, plus (2) coasting back down to 0 mph and comparing the results.

You're going to get better mpg with slower acceleration through the pulse, but a faster acceleration will give a better ratio of pulse to coasting. For example, A accelerates to 60 mph in .25 miles, and coasts for .75 miles, whereas B accelerates to 60 mph in .75 miles, and coasts for .75 miles.

A is accelerating 1/4 of the time, and B accelerates for 1/2 of the time. Thus B gets better mpg for the pulse, but A gets better mpg for each complete cycle, due to a greater percentage of coasting. This doesn't apply to keeping the same speed the whole time.