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

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 05-10-2020, 12:14 AM   #81 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 27,562
Thanks: 7,738
Thanked 8,554 Times in 7,041 Posts
Quote:
Separation line marked on outside of aerofoil:
It looks like the next iteration needs an angled or tapered chord.

You're limited by the width of the extrusion. Were it deeper the back edge could be maintained while the leading edge reaches further forward. It would look constant from the front, but catch air moving sideways from the stagnation point. Free air?

__________________
.
.
Without freedom of speech we wouldn't know who all the idiots are. -- anonymous poster

____________________
  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 05-10-2020, 01:17 AM   #82 (permalink)
Master EcoModder
 
Join Date: Dec 2008
Location: Eugene, OR, USA
Posts: 375

Lord Vader - '15 BMW i3 REx
90 day: 35.06 mpg (US)
Thanks: 90
Thanked 167 Times in 123 Posts
Frankly, I had given up on attempting to measure efficiency on my i3 until now. Either the battery thermal management was skewing results, or countless other factors that I could not really control for with how the car manages energy were. In an effort this evening to burn off some charge to verify that my DCFC system actually works (since the only fast charger within 50 miles was just completed last week 2 miles from my house), I decided to do some very informal testing with a throttle stop to that end.

Obviously, pedal travel limiting is the only way to do this, so I used a stack of washers taped under the pedal to limit my top speed to around 70 mph on the flats.

Fortunately the display provides relatively accurate feedback about throttle percentage, so I could see that it would peak and hold at the limit of travel. Doing so, I was able to verify window down drag at about +6% over a distance of just a couple of miles. Frankly, I was surprised to see my top speed drop by 4 mph just from that. Now I can get a little more serious with trying to improve the car instead of attempting to compile annualized data which can swing hugely with varied weather conditions.

I'd thought about doing a throttle stop before, but for whatever reason, just never bothered since nobody else seemed to talk about it.

This is a game changer.
__________________
2015 BMW i3 REx
2011 Ford Flex SEL AWD
  Reply With Quote
The Following 3 Users Say Thank You to Snax For This Useful Post:
bobo333 (05-19-2020), COcyclist (05-19-2020), MeteorGray (05-10-2020)
Old 05-10-2020, 01:18 AM   #83 (permalink)
Banned
 
Join Date: Nov 2017
Location: Australia
Posts: 2,060
Thanks: 107
Thanked 1,605 Times in 1,136 Posts
Quote:
Originally Posted by freebeard View Post
It looks like the next iteration needs an angled or tapered chord.

You're limited by the width of the extrusion. Were it deeper the back edge could be maintained while the leading edge reaches further forward. It would look constant from the front, but catch air moving sideways from the stagnation point. Free air?
Interesting idea. Or maybe a twisted angle of attack, a la propellor blades? Anyway, it will do me as it is. I am happy it is working, and law of diminishing returns applies for ultimate tweaking.

(And it was on a windy day.)
  Reply With Quote
The Following User Says Thank You to JulianEdgar For This Useful Post:
freebeard (05-10-2020)
Old 05-10-2020, 01:40 AM   #84 (permalink)
Banned
 
Join Date: Nov 2017
Location: Australia
Posts: 2,060
Thanks: 107
Thanked 1,605 Times in 1,136 Posts
Quote:
Originally Posted by Snax View Post
Frankly, I had given up on attempting to measure efficiency on my i3 until now. Either the battery thermal management was skewing results, or countless other factors that I could not really control for with how the car manages energy were. In an effort this evening to burn off some charge to verify that my DCFC system actually works (since the only fast charger within 50 miles was just completed last week 2 miles from my house), I decided to do some very informal testing with a throttle stop to that end.

Obviously, pedal travel limiting is the only way to do this, so I used a stack of washers taped under the pedal to limit my top speed to around 70 mph on the flats.

Fortunately the display provides relatively accurate feedback about throttle percentage, so I could see that it would peak and hold at the limit of travel. Doing so, I was able to verify window down drag at about +6% over a distance of just a couple of miles. Frankly, I was surprised to see my top speed drop by 4 mph just from that. Now I can get a little more serious with trying to improve the car instead of attempting to compile annualized data which can swing hugely with varied weather conditions.

I'd thought about doing a throttle stop before, but for whatever reason, just never bothered since nobody else seemed to talk about it.

This is a game changer.
Excellent news. Windows up / windows down I think is a critical evaluative test for anyone trying to quantify drag changes using any technique.
  Reply With Quote
Old 05-10-2020, 01:55 AM   #85 (permalink)
Banned
 
Join Date: Nov 2017
Location: Australia
Posts: 2,060
Thanks: 107
Thanked 1,605 Times in 1,136 Posts
So I tried some rear Edgarwits to see if I could reduce wake size. These were additional to the front ones, and taller. GOE222 true aerofoil profile.



I did some throttle stop testing with the following results (km/h at 30 per cent throttle, low-moderate gusty headwind):
  • No rear Edgarwits: 95
  • 1 finger rear gap: 93
  • 2 finger rear gap: 95
  • 3 finder rear gap (ie about parallel): 96
  • 4 finger rear gap (ie diverging): 96.5

That would make 4 finger vs std about 3 per cent improved in drag.

4 finger gap:



For people interested, but having other cars, don't forget Insight boat-tails a lot with its narrower rear track.

Interesting to see the better performance at the rear with the diverging duct - opposite to what occurred at the front.

I'll do some more testing on a still day, but to me this result is borderline. I'd need to see a big jump in drag reduction on a still day to go in this direction.
  Reply With Quote
The Following User Says Thank You to JulianEdgar For This Useful Post:
freebeard (05-10-2020)
Old 05-17-2020, 09:46 PM   #86 (permalink)
マット
 
M_a_t_t's Avatar
 
Join Date: Nov 2015
Location: Indiana
Posts: 718

The Van - '95 Chevy Astro Cl V8 Swapped
Team Chevy
90 day: 7.84 mpg (US)

The new bike - '17 Kawasaki Versys X 300 abs
Motorcycle
90 day: 71.94 mpg (US)

The Mercury - '95 Mercury Tracer Trio
Team Ford
90 day: 34.35 mpg (US)

Toyota - '22 Toyota Corolla Hatchback
90 day: 40.11 mpg (US)
Thanks: 131
Thanked 258 Times in 188 Posts
One of the points you make is to have a tps readout. How import would you say that is? My car is a 95 and so it has OBD1, so no obd reader. I installed an old racheting hand brake lever as a hand throttle so I don't believe it will vary any if at all. I feel like it would be fine, but I would like a second opinion.
__________________
1973 Fiat 124 Special
1975 Honda Civic CVCC 4spd
1981 Kawasaki KZ750E
1981 Kawasaki KZ650 CSR
1983 Kawasaki KZ1100-A3
1986 Nissan 300zx Turbo 5 spd
1995 Chevy Astro RWD (current project)
1995 Mercury Tracer
2017 Kawasaki VersysX 300
2022 Corolla Hatchback 6MT

https://www.youtube.com/channel/UC6s...LulDUQ8HMj5VKA
  Reply With Quote
Old 05-17-2020, 10:00 PM   #87 (permalink)
Banned
 
Join Date: Nov 2017
Location: Australia
Posts: 2,060
Thanks: 107
Thanked 1,605 Times in 1,136 Posts
Quote:
Originally Posted by M_a_t_t View Post
One of the points you make is to have a tps readout. How import would you say that is? My car is a 95 and so it has OBD1, so no obd reader. I installed an old racheting hand brake lever as a hand throttle so I don't believe it will vary any if at all. I feel like it would be fine, but I would like a second opinion.
That would probably be fine. Or you could just use a multimeter to monitor TPS output.
  Reply With Quote
Old 05-18-2020, 01:28 AM   #88 (permalink)
Master EcoModder
 
aardvarcus's Avatar
 
Join Date: Apr 2012
Location: Evensville, TN
Posts: 676

Deep Blue - '94 GMC Suburban K2500 SLE
90 day: 23.75 mpg (US)

Griffin (T4R) - '99 Toyota 4Runner SR5
90 day: 25.43 mpg (US)
Thanks: 237
Thanked 580 Times in 322 Posts
I don't actually think the throttle position sensors are varying their output, rather the ecu/ computer is reinterpriting what that output means. Some of the newer chevy sensors have multiple potentiometers built in for redundancy, so the ecu is comparing those results and "deciding" the result.

Thus you would want to monitor the ecu output if possible. Not exactly sure on 95, my experience is with TBI (approx 94 back) and gmt800 (approx 99+).
  Reply With Quote
Old 05-18-2020, 01:32 AM   #89 (permalink)
Banned
 
Join Date: Nov 2017
Location: Australia
Posts: 2,060
Thanks: 107
Thanked 1,605 Times in 1,136 Posts
Quote:
Originally Posted by aardvarcus View Post
I don't actually think the throttle position sensors are varying their output, rather the ecu/ computer is reinterpriting what that output means. Some of the newer chevy sensors have multiple potentiometers built in for redundancy, so the ecu is comparing those results and "deciding" the result.

Thus you would want to monitor the ecu output if possible. Not exactly sure on 95, my experience is with TBI (approx 94 back) and gmt800 (approx 99+).
At this stage, this technique is not endorsed for those cars with electronic throttle control or CVTs. So I am referring to mechanical throttle cars, where I found using a throttle stop, and then monitoring throttle blade position, best for consistency.
  Reply With Quote
Old 05-18-2020, 02:01 AM   #90 (permalink)
Master EcoModder
 
aardvarcus's Avatar
 
Join Date: Apr 2012
Location: Evensville, TN
Posts: 676

Deep Blue - '94 GMC Suburban K2500 SLE
90 day: 23.75 mpg (US)

Griffin (T4R) - '99 Toyota 4Runner SR5
90 day: 25.43 mpg (US)
Thanks: 237
Thanked 580 Times in 322 Posts
Yes, i was thinking his 95 was a vortec but it looks like they were likely still tbi. ( 1995 was a Frankenstein year for some components, splitting from 94 down and 96 up). Thus nevermind.

  Reply With Quote
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com