Fast or Slow Acceleration? Test Results - Fuel Economy, Hypermiling, EcoModding News and Forum

nuverde · 06-26-2014, 12:54 PM

As a new aspiring hypermiler, I have been doing a lot of reading online. Every now and then I come across a post where someone refers to a recommendation by BMW suggesting that brisk acceleration up to speed will give better overall fuel efficiency that slow acceleration.

I just wanted to share the results of some informal testing that I did with my new Civic EX. My conclusion: While the numbers may not be extremely precise, I think the trend is fairly clear (and predictable). Slower acceleration over a longer distance will save you more fuel than quick acceleration over a shorter distance. At least it does for my Civic with CVT.

You can see my methods and results at Acceleration Experiments | Civic MPG. Sorry, can't make this a link since I am a newbie.

--Chris

NoD~ · 06-26-2014, 02:17 PM

So w/ the CVT at the slow, med, and high (1.8K, 3.3K, and 5+K RPM), it was held at said RPM the whole time? Because I think that might be what is killing your MPG far more than throttle position itself!

Daox · 06-26-2014, 02:23 PM

The CVT is a different beast than traditional transmissions. It is capable of loading the engine before increasing engine rpm which is a big efficiency benefit. Automatics increase rpm (and load) as throttle is increased. Manuals increase load as throttle is increased.

Still, good testing, thanks for doing it!

It would be interesting to see what load the engine is at at those rpm ranges.

California98Civic · 06-26-2014, 02:46 PM

Quote:

Originally Posted by Daox

The CVT is a different beast than traditional transmissions. It is capable of loading the engine before increasing engine rpm which is a big efficiency benefit. Automatics increase rpm (and load) as throttle is increased. Manuals increase load as throttle is increased.

Still, good testing, thanks for doing it!

It would be interesting to see what load the engine is at at those rpm ranges.

So this means that with a CVT if you throttle it higher, the engine will first increase load at a relatively steady slowly increasing RPM and then depending on power demand indicated by throttle position, increase RPM by shifting gears if necessary? If that's true we really do need a guaged "engine load" reading rather than the butt dyno, no? Maybe a throttle position reading too?

Daox · 06-26-2014, 02:48 PM

I know that is how it works on the Prius with its e-cvt. As soon as you're off idle rpms, your engine is optimally loaded.

I'm not exactly sure how OEMs are programming normal CVTs. But, theoretically, that is how they can work.

nuverde · 06-26-2014, 02:54 PM

Quote:

Originally Posted by California98Civic

If that's true we really do need a guaged "engine load" reading rather than the butt dyno, no? Maybe a throttle position reading too?

I do have a bluetooth ODB2 reader, so I should be able to get throttle position from that I am guessing. I will have to check it out. I also read about vacuum gauges for measuring load. Does anyone know if this would be available through ODB2?

I enjoyed doing this little experiment and am planning to do more as time permits. I will include some load and / or throttle position experiments.

nuverde · 06-26-2014, 02:56 PM

Quote:

Originally Posted by NoD~

So w/ the CVT at the slow, med, and high (1.8K, 3.3K, and 5+K RPM), it was held at said RPM the whole time? Because I think that might be what is killing your MPG far more than throttle position itself!

Yes, I did try my best to keep the RPMs close to those levels. As mentioned, CVTs have a different behavior that is new to me. I can keep the RPMs steady and slowly the speed will increase.

nuverde · 06-26-2014, 02:58 PM

Thanks for putting that link in there Doax!

California98Civic · 06-26-2014, 03:02 PM

Nuverde, you don't have an Ultragauge? This would be a great and cheap way for you to get great data, such as load and a ton of other things, including reading trouble codes.

nuverde · 06-26-2014, 03:06 PM

Quote:

Originally Posted by California98Civic

Nuverde, you don't have an Ultragauge? This would be a great and cheap way for you to get great data, such as load and a ton of other things, including reading trouble codes.

Wouldn't the same data be available through a bluetooth ODB2 reader and a smartphone? I just ask since I already have both of these. I haven't used them on this car though. Just on previous vehicles for error codes.