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

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 03-17-2018, 11:19 PM   #1 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 11,493
Thanks: 2,639
Thanked 3,709 Times in 2,939 Posts
airspeed indicator

I don't get into the Instrumentation sub-forum much, living in a pre-OBDII world. but I noticed this:


Just A Car Guy: smart way to see if the mass air flow sensor works

Rather than adapting a light-plane pitot tube, couldn't the output from a mass airflow sensor be read via an Arduino input and compared to road speed? The front face of a rear view mirror might be a good monitoring location, with an annular outlet. You could have one on each mirror and DIFF them for crosswinds!

__________________
.
The generation of random numbers is too important to be left to chance.
_________________
  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 03-19-2018, 12:19 PM   #2 (permalink)
Master EcoModder
 
Join Date: Nov 2013
Location: Texas
Posts: 452
Thanks: 14
Thanked 98 Times in 90 Posts
That could be a good tool for adding another variable into your fuel mileage calculations. It would give you true aerodynamic speed. for comparisons when you are evaluating changes to the body or running gear. 60 mph (through air) vs 60 mph (through air) regardless of ground speed.

Last edited by Angel And The Wolf; 03-19-2018 at 03:20 PM..
  Reply With Quote
Old 03-19-2018, 12:28 PM   #3 (permalink)
Master EcoModder
 
Join Date: Nov 2013
Location: Texas
Posts: 452
Thanks: 14
Thanked 98 Times in 90 Posts
Quote:
Originally Posted by freebeard View Post
The front face of a rear view mirror might be a good monitoring location, with an annular outlet. You could have one on each mirror and DIFF them for crosswinds!
I would think you would want them out of the disturbed air near the car, maybe mounted a foot or so in front of the mirrors so they could read ambient wind speed (+ vehicle speed) without the near car squeezing and stretching of the airflow.
  Reply With Quote
Old 03-19-2018, 01:28 PM   #4 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 11,493
Thanks: 2,639
Thanked 3,709 Times in 2,939 Posts
(FYI: Within five minutes of posting you can Edit your post without accruing an edit notation. Just use the button in the lower right.) But hey, three replies.

An aircraft pitot tube is about a foot long to pierce through the laminar flow and best practice is to place it at a stagnation point. On a car that would be the nose.

I don't know the velocities involved in the intake system. A tube smaller than the throat might make measurement difficult, else a bellmouth could gather more air.
__________________
.
The generation of random numbers is too important to be left to chance.
_________________
  Reply With Quote
Old 03-19-2018, 02:08 PM   #5 (permalink)
Master EcoModder
 
Join Date: Nov 2013
Location: Texas
Posts: 452
Thanks: 14
Thanked 98 Times in 90 Posts
Quote:
Originally Posted by freebeard View Post
(FYI: I don't know the velocities involved in the intake system. A tube smaller than the throat might make measurement difficult, else a bellmouth could gather more air.
I would think intake velocity could be calculated By multiplying displacement by RPM, or, aren't Carburetors rated in CFM? Wouldn't that apply to throttle bodies too?

BTW, thanks for the edit tip.

Last edited by Angel And The Wolf; 03-19-2018 at 02:23 PM..
  Reply With Quote
The Following User Says Thank You to Angel And The Wolf For This Useful Post:
freebeard (03-19-2018)
Old 03-19-2018, 08:33 PM   #6 (permalink)
EcoModding Newb
 
redpoint5's Avatar
 
Join Date: Aug 2010
Location: Oregon
Posts: 4,474

Acura TSX - '06 Acura TSX
90 day: 28.24 mpg (US)

Lafawnda - '01 Honda CBR600 F4i
90 day: 47.32 mpg (US)

Big Yeller - '98 Dodge Ram 2500 base
90 day: 21.82 mpg (US)

Prius Plug-in - '12 Toyota Prius Plug-in
90 day: 79.06 mpg (US)

Mazda CX-5 - '17 Mazda CX-5 Touring
90 day: 29.67 mpg (US)
Thanks: 1,674
Thanked 1,454 Times in 1,016 Posts
I just want to see a pitot tube installed on a vehicle, that and a wind vane to get wind direction too.

Of course, a malfunction of the pitot tube would likely cause the driver to stall the vehicle with tragic results.
__________________
Gas and Electric Vehicle Cost of Ownership Calculator







Give me absolute safety, or give me death!
  Reply With Quote
The Following User Says Thank You to redpoint5 For This Useful Post:
Xist (04-04-2018)
Old 03-19-2018, 09:08 PM   #7 (permalink)
Master EcoModder
 
Join Date: Nov 2013
Location: Texas
Posts: 452
Thanks: 14
Thanked 98 Times in 90 Posts
Quote:
Originally Posted by redpoint5 View Post
Surely, you jest!
Ground vehicle "pilots" have a speedometer and other visual clues to determine their speed. The pitot tube is just for research.
  Reply With Quote
The Following User Says Thank You to Angel And The Wolf For This Useful Post:
redpoint5 (03-21-2018)
Old 03-20-2018, 01:08 AM   #8 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 11,493
Thanks: 2,639
Thanked 3,709 Times in 2,939 Posts
One can mouse over the links and see that it is no laughing matter.


Just A Car Guy: Wow. Found in a box in the barn... the UFO hood ornament designed by Alex Tremulis

Sparrow strainers. Dump the plastic housing and wind your own coil.
__________________
.
The generation of random numbers is too important to be left to chance.
_________________
  Reply With Quote
Old 03-21-2018, 09:21 AM   #9 (permalink)
Master EcoModder
 
Piotrsko's Avatar
 
Join Date: Sep 2013
Location: 1826 miles WSW of Normal
Posts: 338
Thanks: 16
Thanked 78 Times in 60 Posts
There used to be charts available for airflow vs throttle position. However if you have obd2 you can read it semi directly, if you have a spare light plane airspeed indicator you could just drill a hole, shove a tube into the duct and read direct
__________________
2000 F250 7.3 CC 20+ MPG @ 10000 #
2013 Golf tdi 50+ mpg
1988 Ranger EV Volt batts>> 15,500 MPG and climbing.
  Reply With Quote
Old 03-21-2018, 01:40 PM   #10 (permalink)
EcoModding Apprentice
 
Join Date: Sep 2012
Location: Motor City
Posts: 220
Thanks: 0
Thanked 149 Times in 97 Posts
Sounds like a great idea to me. I work with MAF sensors at work for their intended purpose, measuring airflow. Some quick numbers from an engine I'm working on now:

Idle airflow - 6 g/s
Peak airflow - 660 g/s

Air is about .0806 pounds per cubic foot. Just math to get to speed...

With a 4" tube this equates to about 1 MPH at idle, and about 140 at peak flow.

Seems like an appropriate measurement range. The ones I work with output a frequency, but there are others that output a voltage. Voltage being a bit simpler to measure easily.

Just need some wind tunnel time to calibrate it.

  Reply With Quote
The Following User Says Thank You to ennored For This Useful Post:
freebeard (03-21-2018)
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2018, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com