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Old 08-03-2011, 08:40 PM   #1 (permalink)
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fast vs slow acceleration

I know the traditional hypermiling technique is to slowly accelerate up to speed.

I was wondering if it would be more efficient to accelerate faster to get into a more efficient gear quicker. This would probably be more effective on a manual transmission, but I'm not sure.

Has anyone tested this? I'm sure it has been tested before but I can't seem to find any data.

I'd go out and test it myself, but I'm only 15 and I can't "legally" drive yet

off topic: yes I'm new to the forum. I've been implementing fuel efficiency modifications onto my parent's cars for a few years and will soon be getting a car. I'm looking forward to post my build log as soon as I find the right car.

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Old 08-03-2011, 09:02 PM   #2 (permalink)
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Quote:
Originally Posted by HydroJim View Post
I know the traditional hypermiling technique is to slowly accelerate up to speed.

I was wondering if it would be more efficient to accelerate faster to get into a more efficient gear quicker. This would probably be more effective on a manual transmission, but I'm not sure.
Do a search for BFSC. You will find that it's generally a good idea to accelerate briskly to speed.
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Old 08-03-2011, 09:13 PM   #3 (permalink)
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Sounds like you know a lot more about the right way to drive than I did when I was 15. You want to get into a high gear and let off the gas to get good mileage. If you accelerate very very slow, often times you will need to slow down and turn before you ever get up to speed. That will bring down your average. Obviously, testing out your shortest 0 to 60 time will not do your average any good eather. You want a happy medium. Personally, I accelerate about the same speed as the average driver.

The advice I got from here that has helped my MPG more than anything is that getting good MPG is about how you stop rather than how you start. You are not going to get great mileage under acceleration no matter how you do it. You need to make good on the gas investment you made by not wasting the energy by using the breaks. Look ahead and plan ahead to you can controll your speed by letting OFF the gas rather than putting ON the brakes. That often means long following distances in town which is a safe way to drive anyway.
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Old 08-03-2011, 11:33 PM   #4 (permalink)
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Hello Jim!

I'm new here too, and have done some informal testing with the technique you are discussing - it does help IMO. You are minimizing your time spent accelerating, which is your worst MPG.

Getting into top gear ASAP is generally a good idea. Moderate acceleration instead of gentle acceleration gets you there quicker. If you have an auto trans, lifting off the gas to coast when you get to your target speed gets the trans to shift up immediately. You also have added momentum that you can use for more coasting.

You're on your way to being an excellent ecomodder! Hope you are considering becoming an engineer - it sounds like you'd be great at it!


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Old 08-04-2011, 12:00 AM   #5 (permalink)
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Old 08-04-2011, 03:25 AM   #6 (permalink)
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Hi Jim, glad to see you here.
Have you read the 100+ Hypermiling tips? They're a great basis for you to build on.

I find many things, like this fast vs slow acceleration question, vary so much with driving conditions, that there is no "right" answer for every situation.
In general, getting up to cruising speed quickly works well, if you can maintain that speed.
If there's another red light 100 yards away, heavy traffic, sharp corner, road works, etc, etc, there's no point.

My commute covers so many different road and traffic conditions (105km), I tackle each start, stop, corner, hill, etc, on it's own merits, at that time.

Anyway, when you get your own car, I'm sure you'll work out what works well for your situation.

Pete.
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Old 08-04-2011, 11:03 AM   #7 (permalink)
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thanks for all the replies! I'll definitely be integrating these driving techniques into my driving style.

Any ideas what kind of car I should get?
  • I'm looking at $3000 and under
  • 4 cylinder for sure(or 3 if I can find one)
  • the transmission doesn't matter but manual would be nice.
  • I definitely want cruise control because I'm going to be testing different fuel delivery modifications and the cruise control will allow for consistent testing without human input. I wish I had a dyno in my garage
  • the car has to be 96 or newer due to OBD-II. I'm looking to play around with the ECM so OBD-II is a must.

I've looked at the chevy/geo metros/suzuki swifts, but here in cleveland, they're covered in rust. Plus people have seemed to catch on that they get great fuel economy so they are pretty pricey. I don't really want to pay $3000 for a go-kart if you know what i mean.

I've also looked at the Saturn S-series. Probably my number 1 choice at the moment. Good fuel economy, cheap, the body is generally rust free(plastic body panels ) and my dad used to be a mechanic for Saturn so he knows everything about them.

The third car I looked at was the Chevy Prizm. They're basically Toyota Corolla's without the price tag. Same engine and everything! Unfortunately, there are not a whole lot of them around.

I also have looked at Honda Civics or a Toyota Corollas. But, they somehow manage to hold their value forever so I've had a hard time finding one for $3000 that doesn't have 300,000 miles on it

I know I basically covered my choices, but does anyone have any other ideas? Or maybe they know someone who knows someone who is just looking to hook me up with a deal
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Old 08-04-2011, 11:09 AM   #8 (permalink)
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Old 08-04-2011, 01:17 PM   #9 (permalink)
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Quote:
Originally Posted by graydonengineering View Post
The advice I got from here that has helped my MPG more than anything is that getting good MPG is about how you stop rather than how you start. You are not going to get great mileage under acceleration no matter how you do it. You need to make good on the gas investment you made by not wasting the energy by using the breaks. Look ahead and plan ahead to you can controll your speed by letting OFF the gas rather than putting ON the brakes. That often means long following distances in town which is a safe way to drive anyway.
Right on!

It's been debated back and forth as fas as what rate of acceleration is best. Personaly, I've found it hard to notice a difference either way. What really kills your mileage is unecessary acceleration. Hard acceleration is generally thought of as bad becuase, in many cases, people accelerate hard only to have to brake hard at the stop that's right up ahead. It's really the braking that is wasting all the energy.
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Old 08-04-2011, 01:22 PM   #10 (permalink)
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Also, when you're in town, fast acceleration generally means you're going to be going faster. That will mean higher aero drag as well as less time to react to other drivers, changing red lights, etc. that will mean you may have to brake (and waste energy). If you're going slower, you have more time to react.

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My version of energy storage is called "momentum".
My version of regenerative braking is called "bump starting".

1 Year Avg (Every Mile Traveled) = 47.8 mpg

BEST TANK: 2,009.6 mi on 35 gal (57.42 mpg): http://ecomodder.com/forum/showthrea...5-a-26259.html


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