Go Back   EcoModder Forum > Introductions
Register Now
 Register Now

Reply  Post New Thread
Submit Tools LinkBack Thread Tools
Old 01-25-2020, 12:52 AM   #11 (permalink)
Master EcoModder
Ecky's Avatar
Join Date: Dec 2011
Location: New Zealand
Posts: 4,882

ND Miata - '15 Mazda MX-5 Special Package
90 day: 38.31 mpg (US)

Work Vehicle - '17 Toyota RAV4
90 day: 34.19 mpg (US)
Thanks: 2,799
Thanked 2,423 Times in 1,501 Posts
Subscribed! I love your boat tail.

The Honda Insight could achieve 100mpg (US) from the factory with a little extra air in the tires. You could look for some of the design elements used in that car perhaps? I'm happy to take some pictures or describe those I'm aware of.

I changed the engine in mine from the thrifty 1.0L to a power-oriented 2.4, and the best economy I've seen since then has been around 65mpg cruising, under the same conditions the old engine was showing 100mpg - cruising at no greater than 50mph.

It seems the new engine isn't (much) less efficient at producing power, but that it has larger parasitic losses. For instance, it uses a lossy alternator instead of a highly efficient DC-DC converter, it has a bigger water pump, bigger oil pump, the serpentine belt looks to be a little over twice as large, another cylinder's worth of frictional parts, a second camshaft, etc. Because of these, it doesn't seem to scale down as well - there's a larger fixed amount of fuel consumed just running the engine to do the same amount of work.

Where the old engine could produce (let's say) 20hp, the new one uses around 33% more fuel. However, the new engine can produce ~65hp at close to the same efficiency with my current gearing. Meaning, with pulse and glide (accelerating for periods with 65hp then shutting the engine off and coasting for a bit, rinse and repeat) I expect I could get very near that same 100mpg. It's possible I could get close to 100mpg with the new engine if I had MUCH taller gearing (all of those lossy parts would be spinning proportionally slower) but it simply wasn't possible to fit gears large enough in the gearbox.

All of this is to say, you may be able to squeeze a little more out of your engine with taller gearing and a set of underdrive pulleys, to slow down those lossy accessories. It's not a bad place to look for gains after you've already picked the low hanging fruit from rolling resistance and aerodynamic drag.

  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

Old 03-02-2020, 04:48 AM   #12 (permalink)
EcoModding Lurker
Join Date: Dec 2019
Location: Netherlands
Posts: 16
Thanks: 4
Thanked 65 Times in 9 Posts
Thanks for the help and info!

Small update:

we've completed the front of the car as well, a nice airdam with the front of the undersection closed as well. We've also finalised our camera mirrors, the car looks so much better without those big black mirrors. Tueseday it will get some TLC on the technical side and then we can finally do some proper testing. Keep you updated!

*not visible, but we made the rear panel of the boat tail out of aluminium as well (previously white plastic, see photo on first page) and made the trailer rear lights sunken, so no more blocky structures at the back.
  Reply With Quote
The Following 8 Users Say Thank You to Dizono For This Useful Post:
aerohead (03-18-2020), bobo333 (05-28-2020), Cd (10-08-2020), Ecky (03-02-2020), Flakbadger (03-07-2020), Leinaad (04-12-2020), MetroMPG (03-08-2020), RedDevil (03-02-2020)
Old 03-04-2020, 03:43 PM   #13 (permalink)
EcoModding Lurker
Join Date: Dec 2019
Location: Netherlands
Posts: 16
Thanks: 4
Thanked 65 Times in 9 Posts
There we go, pic of the updated rear as well!

Besides the camera mirrors, all the adjustments seem to be within the limits of the law and re-inspection by local authorities is not needed. That means we can probably get it trough MOT easily =)
  Reply With Quote
The Following 6 Users Say Thank You to Dizono For This Useful Post:
aerohead (03-18-2020), bobo333 (05-28-2020), Cd (10-08-2020), Flakbadger (03-07-2020), Leinaad (04-12-2020), MetroMPG (03-08-2020)
Old 03-05-2020, 01:16 AM   #14 (permalink)
Master procastinator
Join Date: Apr 2017
Location: Panelia, Finland
Posts: 273

Turan turan - '09 Volkswagen Touran Freestyle

Combot - '04 Opel Combo Tour
90 day: 40.37 mpg (US)
Thanks: 103
Thanked 49 Times in 42 Posts
Is that tow loop accessible with the air dam?
Not that i would question 106's reliability but still

Have to say, very clean&smooth execution on those ecomods

  Reply With Quote
Old 03-05-2020, 10:06 PM   #15 (permalink)
Aero Wannabe
COcyclist's Avatar
Join Date: Dec 2007
Location: NW Colo
Posts: 718

TDi - '04 VW Golf
90 day: 50.21 mpg (US)
Thanks: 690
Thanked 209 Times in 162 Posts
Nice. Subscribed.
60 mpg hwy highest, 50+mpg lifetime
TDi=fast frugal fun

Originally Posted by freebeard View Post
The power needed to push an object through a fluid increases as the cube of the velocity. Mechanical friction increases as the square, so increasing speed requires progressively more power.
  Reply With Quote
Old 03-08-2020, 12:55 PM   #16 (permalink)
Batman Junior
MetroMPG's Avatar
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 22,461

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 55.97 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 70.75 mpg (US)

Appliance car - '14 Mitsubishi Mirage ES (base)
90 day: 67.41 mpg (US)
Thanks: 4,000
Thanked 6,893 Times in 3,577 Posts
Very fun project, and nice workmanship!

How will you be measuring fuel use to determine the difference?

Have you already done a "before" test to get the baseline? Be sure to note weather conditions - ambient temperature has a significant effect on efficiency on its own.
Project MPGiata! Mods for getting 50+ MPG from a 1990 Miata
Honda mods: Ecomodding my $800 Honda Fit 5-speed beater
Mitsu mods: 70 MPG in my ecomodded, dirt cheap, 3-cylinder Mirage.
Ecodriving test: Manual vs. automatic transmission MPG showdown

has launched a forum for the efficient new Mitsubishi Mirage
www.MetroMPG.com - fuel efficiency info for Geo Metro owners
www.ForkenSwift.com - electric car conversion on a beer budget
  Reply With Quote
Old 03-08-2020, 01:52 PM   #17 (permalink)
Master EcoModder
teoman's Avatar
Join Date: Jan 2017
Location: Istanbul
Posts: 1,245

A3 - '12 Audi A3
Thanks: 65
Thanked 225 Times in 186 Posts
Paint them red and put something like a 107 or 108 sticker on the back. People will think it is a different model
  Reply With Quote
Old 03-18-2020, 04:36 PM   #18 (permalink)
Master EcoModder
aerohead's Avatar
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 15,402
Thanks: 23,491
Thanked 6,976 Times in 4,455 Posts
further extension

Originally Posted by Dizono View Post
We've thought about that, but a computional fluid dynamics model suggests that a further extension has only minimal gains. So Wunibald Kamm was right

It also shows that further improvements mainly come from the front and the transistion from windscreen to roof. That last one might be a tricky one, but the right shape of 'wind screen wiper shield' might help to shape the flow in such a way that it creates a more efficient flow over the car.
Kamm's best car,the K-5,at Cd 0.23,had an aft-body length equal to 1.63-X the actual body height (no ground clearance included).He did recommend an inflatable boat-tail stinger which would extend the aft-body out to 2.03- X,chopped off like all 'K' forms,which would deliver Cd 0.1909.Extending the tail all the way to its termination point,at 2.72-X yielded Cd 0.1742.
Sure do like what you're doing.
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
Old 03-28-2020, 07:09 AM   #19 (permalink)
Master EcoModder
kach22i's Avatar
Join Date: Jul 2011
Location: Ann Arbor, Michigan
Posts: 4,121
Thanks: 105
Thanked 2,767 Times in 1,942 Posts
I'm currently having computer issues and have resorted to using my cell phone.

1. The underside of the boatail does NOT look finished and closed off, is this correct?

2. Any plans for a belly pan?

3. I would also like to see the underside of the front chin spoiler, is there a partial pan there?

Overall a fantastic project, rivets and all.
Architect, Artist and Designer of Objects

1977 Porsche 911s Targa
1998 Chevy S-10 Pick-Up truck
1989 Scat II HP Hovercraft

Chin Spoiler:

Rear Spoiler Pick Up Truck

Roof Wing
  Reply With Quote
Old 03-30-2020, 08:17 AM   #20 (permalink)
EcoModding Lurker
Join Date: Dec 2019
Location: Netherlands
Posts: 16
Thanks: 4
Thanked 65 Times in 9 Posts
Thanks, the entire underside of the boattail is closed, it's just a bit recessed to ensure a proper connection to the underside of the car. The front bumper is closed at the underside as well, but there is not (yet) an entire belly pan.

The car is in storage at the moment due to corona... :/

  Reply With Quote
The Following User Says Thank You to Dizono For This Useful Post:
aerohead (04-01-2020)
Reply  Post New Thread

Thread Tools

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2023, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com