Go Back   EcoModder Forum > EcoModding > Instrumentation
Register Now
 Register Now

Reply  Post New Thread
Submit Tools LinkBack Thread Tools
Old 06-14-2013, 05:11 AM   #1 (permalink)
EcoModding Lurker
Join Date: Jul 2010
Location: Hampshire (the old one)
Posts: 29

Merc Estate - '01 Merc W210 E320CDi Estate Elegance
90 day: 37.56 mpg (US)
Thanks: 2
Thanked 1 Time in 1 Post
Thoughts on a new feature

I would like a scangauge but they say it's not compatible with my car (Boooooooooooooooooooo!!!!!)

However I'm an electronics R&D engineer.. and these sort of devices are bread and butter to me.. so I've been thinking about the details of how they work and realised they (to my knowledge) miss a trick.

When doing P&G people are still kind of guessing about the P.. is it 60% throttle, is it 85%.. have a play.. 80% seems better, but it's all 'have a play'.

What occured to me was that the MPG calculation could invlove an intermediate stage that would allow us to see just how efficient we're really being.

The idea is to include an accelerometer. This would be used to calculate the vehicles acceleration or deceleration. Knowing the vehicles weight the gauge can then

A: work out the gain or loss of momentum.

B: work out the energy efficiency of the engine.

C: work out the energy consumption of pushing the car along.. to produce the mpg figure.

So.. during the pulse phase, or going up hill, it notes we're gaining potential or kinetic energy.. it keeps a note of that, and makes its estimate of the engine efficiency.. lets say it's 25%.

When coasting it can see the loss of momentum over time, if you're going slightly downhill, it sees that with the accelerometer and accounts for it.

The bottom line is it ought to be able to work out your rolling resistance and your coefficient of drag.. at least over time.

It would also allow the gauge to put up really really BAD figures when you hit the brakes.. which is more honest I think.

any thoughts?


  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

Old 06-15-2013, 12:44 AM   #2 (permalink)
Lots of Questions
Join Date: Jan 2013
Location: San Jose
Posts: 656

Motor-Rolla - '01 Toyota Corolla LE
Team Toyota
90 day: 28.3 mpg (US)

Gaia - '99 Toyota 4Runner SR5 Highlander
90 day: 19.78 mpg (US)

Gaia - Round 2 - '99 Toyota 4runner SR5 Highlander
90 day: 17.22 mpg (US)
Thanks: 337
Thanked 97 Times in 76 Posts
Don't know if you saw this thread yet, but I was thinking about doing something similar, although a step behind what you are talking about.

On-the-Go Slope Measurement

Once I get it good to go, I might add in what you are talking about as I was wondering the same thing yesterday about P&G efficiency (specifically the fact that I have an automatic, so I have to glide in neutral not EOC, which I assume means that I have to glide for longer than a manual).
Don't forget to like our Facebook page!

Best EM Quotes:
Originally Posted by aerohead View Post
It has been said, that if you peel the duct tape back on Earth's equator, you'll find that the two hemispheres are held together with J B Weld.
Originally Posted by Dan9 View Post
subscribed with a soda.
Originally Posted by aerohead View Post
If you're burning,and someone throws gasoline on you,there will be a localized cooling effect, but you're still on fire.
  Reply With Quote
Old 06-16-2013, 04:52 AM   #3 (permalink)
Master EcoModder
Join Date: Apr 2013
Location: World
Posts: 385
Thanks: 82
Thanked 82 Times in 67 Posts
That is exactly what I am doing ^. Even just PE and KE will be useful. Instantaneous BSFC calc. and coast down drag is icing.

While I know how to do it, both conceptually and technically, it's not part of my day job to do what is required, thus it requires a certain amount of effort to figure it out. Consequently it is progressing as I feel motivated to work on it. Another "brain", perhaps a different approach, would be interesting.

I think a "calibration" neutral coast down (or more than one), in a straight line, on level ground, will allow the (total) drag related to road speed to be calculated. With that, a fuel consumption input (proxy by injector DC as per MPGuino) and the rate of accumulating KE and PE the engine efficiency (BSFC) can be calculated.

The extra drag associated with cornering might be harder to account for. A spread of constant radius corner coast downs and a steering angle input? I'm not sure where that would be possible at road speeds.

  Reply With Quote
Reply  Post New Thread

Thread Tools

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com