Airspeed indicator for your car
 

Has anybody tried fitting an airspeed indicator to their car's instrumentation? It would be useful (when comparing its reading to the speedometer reading) for detecting and compensating for headwinds and tailwinds, and would be handy for determining when you were in the proper position while drafting another vehicle.

I priced then on ebay. I am
 

I priced then on ebay. I am not shure how to install one.

I looked into aneometers
 

I looked into aneometers awhile ago. I know someone who has used them for the same purpose. The problem is that they wear out relatively quickly. See the link below for more info and keep reading for infor about adding batteries to Pruis.

https://privatenrg.com/PriusBattery.htm#Storm_Chaser.

The simplest ASI would be
 

The simplest ASI would be the Hall airspeed indicator used on ultralights. It is an 8" vertical tube with an opening at the bottom facing upwind containing a ball which rises higher with increasing airspeed. They read from 0 to 80 MPH, cost about $20, and are readily available on-line. They are normally mounted on a brace or fairing on the ultralight, but could be mounted on your driver's side mirror, or for a more permanent installation, on your dashboard with a tube running forward through the engine compartment to the front of your grill.

How do you hook an air speed
 

How do you hook an air speed indicator up. Do you just hook a hose up to it or what?

https://cgi.ebay.com/ebaymotors/Antique-Luscombe-Airspeed-Indicator-by-Aeromarine_W0QQcmdZViewItemQQcategoryZ26439QQitemZ 4621478864QQrdZ1

https://cgi.ebay.com/ebaymotors/Piper-Cub-Airspeed-Indicator_W0QQcmdZViewItemQQcategoryZ90977QQitemZ4 620970809QQrdZ1

check out the links. Most have threads on the back for srewing in a hose i guess...

Re: The simplest ASI would be
 

Please post a link. For $20, I gotta have one!

Havent you ever heard of
 

Havent you ever heard of google? Anyways...

https://mikes.automated-shops.com/cgi-bin/webc.cgi/st_main.html?p_catid=37

https://mikes.automated-shops.com/cgi-bin/webc.cgi/st_prod.html?p_prodid=349&p_catid=37

Re: Havent you ever heard of
 

I would like to see the business end of the expensive one so I can figure out how it would be mounted. I will try an Google for more info.

It's too bad with something
 

It's too bad with something like this you can't just swerve around until you find the wind you want behind you and somehow get to your destination anyway. :)

Just ordered the 0-80 MPH
 

Just ordered the 0-80 MPH Airspeed Indicator. I went with the pitot tube type instead of the hall style due to mounting issues.

https://mikes.automated-shops.com/cgi-bin/webc.cgi/st_prod.html?p_prodid=340&p_catid=37

It should be an interesting gadget to have.

W00t, you're one crazy fool,
 

W00t, you're one crazy fool, y0. I hope you learn something with it and I might have something else to put on the list of things I wish I had. My vacuum gauge and a pound of swedish coffee are in the mail right now (from sweden), can't wait to get it installed.

Re: W00t, you're one crazy fool,
 

Not so crazy. It is in my tinkering budget, which comes from selling stuff on ebay. Anymore when we buy something I keep the packaging for resale on ebay. If I like it keep it if not it goes on ebay. The latest example is one of those indoor invisible fences for dogs. The first time out the pup got zapped, she has never gone in that room since, about 2 months. So i am about to sell a very slightly used invisible fence. I usually get about 2/3 of what I originally paid. It's amazing how much crap you can find laying around the house to sell.

Anyway, if I decide not to keep it, I know who might want it. Maybe a trade for transmission installation services. Oh yea, and I have a digital fuel gauge that I no longer need (SuperMID instead).

I still need to get that ish
 

I still need to get that ish picked up, if my fuel rail ain't on my doorstep today (or in the mailbox) I'm taking the camry up to visit that guy to get some free stuff, *sigh*

Air Speed Indicator
 

The 0-80 Ait Speed Indicator showed up today. It consists of a gauge, clear tubing and a hollow alimunim rod the size of a pencil. The hose connects to one end of the rod and the other end of the rod is to be mounted on the car with the opening facing forward. The other end of the tube connects to the gauge. When you blow into the end of the rod, voila, the gauge moves. Evidently I am quite a blow hard because it can easily peg it at 80 MPH.

The gauge came with a calibration test report. it was tested in 10 MPH increments from 20 - 80 MPH. The calibration is within +/- 1 MPH at all speeds.

So now you know what I will be doing this weekend. Anybody have any ideas where to mount the intake tube? It needs to be somewhere that will get the full force of the wind, but without much turbulence. I am thinking that I will mount it in my grille block, sticking out as far forward as possible. Whadda you think?

Awesome. If it works on the
 

Awesome. So it works. I might want to get one.

Re: Air Speed Indicator
 

sounds cool...

methinks that sounds reasonable.

plus, you can use it to poke annoying pedestrians at crosswalks. but be careful: if you hit a bug with it at just the right speed, will it get blown through the tube and pop out inside the gauge?

please report back with the mpg insights you will glean from the wind-o-meter and how it helps refine your technique.

damn for 20 dollars that
 

damn for 20 dollars that can't be beat... actually ill stick with putting a canadian flag up front or something ;) since it requires some installation and I'm the "plug and play" type of guy.

Aircraft Pitot Tube
 

All commerical aircraft have what's called a "Pitot Tube" that measures indicated airspeed. You may have seen it on some aircraft "Do not touch, Hot", it's generally on the Pilot's side by the pax loading door -- looks like a copper tube sticking out the side. That's the secret, it heats up to measure the number of air molecules that pass through at a constant temperature -- as we know the upper atomosphere gets cold -- as does PA, right? An aircraft supply store might be able to provide a used tube and guage. The only thing, it needs to be mounted entirely in the stream of air -- no hiding in the grille. I honestly can't think of a spot to mount it, without it looking like it doesn't belong on a car. Maybe it can be mounted on the roof a-la XM antenna style. At any rate, that will get you the most accurate airspeed without compromise. Sorry, kind of into airplanes as well as gassavers. What, a guy can't have two hobbies?

RH77

*Edit* Maybe I should read the whole thread. One has been bought already. Okay. You need to mount it similarly to what was mentioned - in the stream of air. The outlet on the other end may not work well venting into the grille. It needs to be completely in the flow of air - in and out. I know it won't look fantastic, but maybe under a side-mirror. Better yet, under the car -- air flows under there at nearly the same speed as up front or on top/side. If you bottom out, though, it's toast. Maybe even the rear of the car under the bumper. Unrestricted airflow is the key, or it's bunk.

This one is different than
 

This one is different than the aircraft one because it is really just a diaphragm that deflects with pressure from air flow via a tube from outside the car to the gauge inside. In the back of the gauge is a hole that serves as a static pressure reference. The manufacturer refers to it as a pitot tube but technically it is not.

A true pitot tube (by the way, I used to work for the company that invented the pitot tube, Pitometer Associates was the name)measures the pressure of the air as it is forced into the forward mounted orifice and also measures the negative pressure with a reverse mounted orifice as the air goes by. It then adds the two together to give you a reading.

Anyway this one should work fine as a rod sticking forward out of my grille because I don't need the outlet that you speak of. The outlet is inside of the car and is supposed to measure static pressure so it shouldn't be subject to any airflow.

I do have an XM antenna but had to mount it on the trunklid. My removeable roof is alumunum and the magnetic antenna doesn't stick so well.:)

Phil,
This Airspeed gauge was not the $20 one, it is $134. I will never see a return on investment but at least I will have a lot of fun with it.

OK, its installed. The tube
 

OK, its installed. The tube is on the drivers side just under the air dam extending 3" in fromt of the bumper. There was already a hole in the bottom of the air dam and something to lever the rod against to hold it in place.

The gauge mounting was too easy. I have circular vents in the dash near each front window. I popped out the vent on the drivers side and popped in the gauge. It's a good press fit so no fastening required, I will try to take some pics after a thorough testing. :)

Re: This one is different than
 

Neato - you worked for the company that invented the Pitot Tube. I had a basic understanding of how it works, but didn't know about the 2 measurements - cool (hot I mean). So I assume the heat is used to get a consistant reading at higher altitudes or is it more just overall temperature of the air? To confess, I have a passion for flight as well as FE. I'm a passenger at least 2 times a week (up to 8 or 9) and I still love to fly. I'd like to get my pilot's license, but it's just too expensive of a hobby (the training, plane rental/insurance, CE hours). For now I'm happy flying on the computer. Cheaper and safer.

The product sounds like a good way to measure wind velocity and headwinds (I suppose you subtract your speed from the meter to get a headwind value). Let us know how it works (and if there are limits to the product's range, like if you end up with going 65 with 35 mph gusts, that would be 100 mph wind speed, potentially).

Regarding the XM -- I mounted my antenna on the hood of the TL. It's the little, flat magnetic one that's about 2" L x W with an aerodynamic top. Wiring was simple and hidden. I previously had the big roof-mounted one back when XM was still pretty new. I'm sure that created some drag...

RH77

Re: This one is different than
 

The pitot tube was invented in 1896 IIRC. I used them to measure water velocity in large munucipal water mains, up to 60" in diameter. The tube is inserted into the pipe and oriented such that one end points toward the flow and the other end away from the flow. Flexible hose was connected to each pitot orifice and connected to a glass U tube that is filled with a substance that has a higher specific gravity than water. The higher the velocity, the heavier the fluid you would use. The flow would cause the fluid to deflect and the measurement of deflection would translate to a velocity for each different fluid used. Typically I would use carbon tetra chloride (SG 1.60), benzene (SG 2.90) or Mercury (SG 13.58). All are seriously carcenogenic.

Anyway once you got the velocity in the center of the pipe you would take readings at different maybe 1" increments to get the flow profile within the pipe. Armed with all of that data, you can calculate the flow rate within +/- 1.5%. You would then compare the flow rate to the metered flow rate and then calibrate the meter to match the pitot reading.


For airplanes, it sounds like the measurement is electronic from what you have said so the heating probably has to do with stabilizing the reading. I can't be sure though.

Back to the airspeed indicator..... Well it works great! The readings are about what I had expected, jumpy but still useful. I headed out for a test drive starting against the wind. At 55, the gauge showed 62. In the other direction at 55, the gauge read 50. So there was a 5-7 MPH wind.

The readings are fairly smooth except during wind gusts or when cars go by. As expected, cars passing in the opposite direction cause a spike in airspeed, 5-10 MPH. But what is surprising is that the increase lasts long after the car passes. When cars pass in the same direction you get a nice drop, again 5-10 MPH. It was fun drafting a tractor trailer. At 45 MPH, the air speed dropped to zero. Since the gauge does not register below 20 Im not sure what the actual number was. At 65, following at one car length, the gauge bounced between 20-30MPH. At a safer distance, maybe 4 car lengths, the gauge bounced between 35-45. Even at 10-15 car lengths there was still some benefit, about 55.

So this gauge will be fun to have and I will be recording relative wind speeds with my daily commute data. It should help to quantify the effect of wind speed on my FE. I will try to get some pics posted today.

Here are some pictures
 

Here are some pictures:
https://img223.imageshack.us/img223/4733/dcp59983tw.jpg
Front view above: Yes, it does need a wash.

https://img223.imageshack.us/img223/8730/dcp59999wz.jpg
Tube mounting. Prius in the background.
https://img223.imageshack.us/img223/2310/dcp60014ue.jpg

Gauge Mounting. It is starting to look like a cockpit in there.

Dremel down the mounting
 

Dremel down the mounting area so it looks more snug, :p

It seems angry to be squar pegged into a round hole.

Re: This one is different than
 

That's a lot of water! Was there a lot of pressure on the main?

Yikes, exactly. Did they provide you with personal protective equipment? Were you nervous to have these chemicals very near to the public water supply?

This is very useful information. A few questions, as usual. I assume you were directly behind the truck. Did you feel wind buffeting the car at 4 car lengths? I can usually feel it at that distance, and figured that it was detrimental to FE. Did you draft at all from the back corner of the trailer in another lane (safer in case of emergency stops, but unknown if useful). A while back MetroMPG noticed an increase in FE on his ScanGauge when cars passed him on the highway, or cruising in a heavy flow of traffic (the econ dropped when exiting the highway). The theory asked whether it was better to take the 2-lane road, or the "Interstate" (or Canadian equivalent). I can't recall the thread, but there was discussion that heavy traffic provides an airflow beneficial to FE vs. a desolate road, and if a continuous pocket of air existed to cruise in. Since the oppositely passing car effected you for longer than expected, there may be some weight to the theory. Good work!

RH77

There is also the theory of
 

There is also the theory of surfing that I would like tested: driving next to a semi so that it's wake is sorta behind you which somehow pushes you forward? I forget for sure the idea.

Re: There is also the theory of
 

Unfortunately, truckers hate that. I was told by one that if he sees a vehicle in his mirror and expects it to pass, but instead hangs out there, it's risky becuase of emergency lane change possibilities, or if the trailer brakes lock-up it might fishtail into you. It's kinda like driving in someone's blind spot. If you piss them off enough, then they simply get on the CB and another truck can do the squeeze-play from ahead to get you out of there. If it continues, the piss-off potential increases, and with road rage these days, I'd recommend another form of FE increase.

Road Rage Incident:
I didn't know if I should post this, but maybe a lesson can be learned out there if you get into a road rage incident. About 2 weeks ago my wife and I were driving along in the city here and this guy cuts us off (no blinker) to the point where I had to really hit the brakes. Instinct had me honk the horn, then he gave us the finger. I just smiled and didn't let it get to me (I used to get all bent out of shape and would've gotten really angry, but with the slower driving, I've mellowed out). Long story short, the guy later tried to run us off the road (at that point my wife called the cops), then when we stopped, he gets out of the car with a 5" knife and knocks it on the driver's-side window at me. Meanwhile the dispatcher is hearing all of this going on and we peel out of there and wait for the Police to intercept. They go and arrest the guy on Felony charges at his house. No priors - the guy just lost it, and after he calmed down, he admitted that he did something wrong. Then he said that he thought we had a gun. The officer was like "Yeah right, so you get out of your car with a knife to attack the people with the gun. Right."

Anymore, I just let it go. It's sad. The Police said they have an average of 4 calls per day on road rage. People get shot anymore with this stuff. Anyways, might have to go to court and all that crap.

Just be careful out there folks...

RH77

Re: There is also the theory of
 

lol wow what a story... makes me wonder if should get that "**** ***" hat if people were to eye me down because my hypermiling didn't let them be first in line at the red light.

Re: This one is different than
 

The water pressure ranged from 40 to 100 PSI. It all depends on the hieght of the local water towers.

I had no protective equipment but I wasn't particularly concerned. I was in my early 20's and stupid. It would be difficult for the chemicals to actually get into the water supply, but even if they did, the concentration would be extremely low. Still, it is scary to think about what someone could do to the water supply if they really wanted to.


I was directly behind the truck and there was buffeting, but not bad enough to hurt FE. Actually FE was noticibly higher while drafting. I cant really follow in another lane because there are only two lanes and I will be blocking the fast lane. I have had discussions on other forums about what you are referencing and in that case it was called the "corridor effect". I believe that there is something to it but you have to drive fast enough to stay up with traffic. It might be worth a try, but due to my short gearing, my rpms will be high. Prolly better results when I get my CX tranny installed. Anyway, it deserves a try, for at least the highway portion of the commute.

I tested this theory today.
 

I tested this theory today. Previously my best trip to work was 60.41 MPG at 30F, Dry roads and a 9MPH tail wind. Ths was pulling out all of the stops and taking the "road less traveled" route which takes 55 minutes. The distance was 40.57 km, 1.580 L, engine on 67% of distance.

Today I took the "road that more traveled" route which includes 6 more miles of highway and three fewer miles of engine off coasting. It took ten fewer minutes that the normal route. I didn't do any drafting, just took advantage of the wake left behind by cars in front of me and cars passing in the left lane. The windspeed / speedometer difference was -10 to -20 mph as a result.

The temp was 44F, wet roads, light and variable winds. The result was 59.59 MPG, 39.60 km, 1.563 L, engine on 81% of distance. So the MPG was slightly less, but the fuel used was also less because of the shorter distance.

One other benefit of the faster drive is that when I get off of the highway, there is less traffic and I made all of the lights. Had I not done that I would have been 2-3 MPG lower.

This deserves further study. More aerodynamic mods could help further now that I might be spending more miles at higher speeds.

Based on the effects on my
 

Based on the effects on my coasting car as a semi-truck slowly passes me, I get a slight reduction in drag when the front of the truck is just behind my car in the adjacent lane, but there is a significant increase in drag as the truck is running alongside me, and then there is a noticable drag reduction as the rear of the truck pulls ahead of the front of my car.

The heat associated with an aircraft's pitot tube is to prevent ice from forming on and clogging the tube while flying in icing conditions. Typically there is a switch in the cockpit that turns on the pitot heat.

krousdb, since the static
 

krousdb, since the static port of your airspeed indicator is inside your car (and inside your ventilation system based on your description of ASI's location on your dashboard), what effect does running the ventilation fan and/or opening the windows have on your indicated airspeed? On aircraft, the static port is typically on the side of the fuselage so that the indicated airspeed would be unaffected by window or air vent activity.

Yes, I was concerned about
 

Yes, I was concerned about that also so I did a test to see if there was an effect. Cruising at 30 MPH on a calm day, the gauge also shows 30 MPH. Turning on the vent fan at full speed had no effect. Nor did opening a window.

Another note.... I tried moving the pitot tube into the bumper further so it became less noticeable, leaving it protruding only by an inch. This caused the ASI to under register by about 1/3. I moved it back to 3" protrusion and it registers fine again.