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Old 05-02-2011, 11:51 PM   #11 (permalink)
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when you are running there will be a most efficient indicated speed. Some speed up or down from that depending on what the current is doing will yield the best MPG so some GPS information would be useful but a close enough approximation can be made just by knowing the current speed which can be learned by looking at it. Drifting down stream will be 999999999mpg but that is not useful information.

The OP already has a speed sensor. That will give a good deal of information if the signal is compatible, if not *shrug* the speedometer with knowing the GPH is nearly as good.

Increasing speed over that needed to be on plane is not likely to increase MPG. Yes there is less hull in the water but the force needed to lift the weight of the boat up on step is the same at 25 as at 50mph. The smaller contact area is doing the same lifting by hitting a smaller number of water molecules faster so the drag is about the same. Increasing speed will increase the amount of drag from the lower unit.

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Old 05-03-2011, 12:13 AM   #12 (permalink)
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the second example, coasting back with the engine off, highlights a key point though. It is not instantaneous mpg that is important, but average. If you use a gallon of gas to go 5 miles up river and float back, the trip mpg with the whizwheel will be something between 5mpg and ??? (because it did not accurately detect the return trip and you spent time in different currents, maybe you were anchored for a while and it kept spinning), but with a gps the Actual mpg will be 10mpg. The drifting downstream at 999999 is terribly important for your trip averages.
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Old 05-03-2011, 02:19 AM   #13 (permalink)
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If you drifted back down do you count it as a 10 mile trip or a 0 mile trip
If you are counting it as a 10 mile trip why could you not put 10 miles into the Whiz wheel and find the average for the whole trip? If you derived your distance from a map, you would have an accurate distance.


A GPS will continue to output speed when anchored. Due to how it calculates speed and the error every time it recalculates position, as well as when swinging on the rode.

I once averaged 3 knots while tied to a pier for a couple hours, some of that was stretching of the lines, most of it was position error.

A GPS coupled MPGuino would be very fine for tuning speed and knowing how much to increase speed to compensate for running against the current but with the equipment the OP already has a close approximation can be done from the speed of the boat through the water.

I would love to have a fuel totalizator coupled to a GPS in the plane it would let me know how much to increase airspeed to compensate for headwind. But a whiz wheel and fuel consumption information would do just as well.
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Old 05-03-2011, 05:17 AM   #14 (permalink)
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Originally Posted by bestclimb View Post
If you drifted back down do you count it as a 10 mile trip or a 0 mile trip
Only boaters struggle with the concept I guess But if you go 5 miles, then you go another 5 miles, that would be 10 miles. Pretend you went to the convenient store 5 miles up river or something. You would NEVER say your commute is zero miles just because you wind up at home again. Just sell your vehicle and forget all this tracking business then

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If you are counting it as a 10 mile trip why could you not put 10 miles into the Whiz wheel and find the average for the whole trip?
My mistake, when I heard the term whizwheel, I envisioned a paddlewheel or impellor type speed sensor. I didn't realize an antiquated navigation device was being brought into the discussion.
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While I encourage everyone to be able to use maps, I think a more automated solution is preferrable here.


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A GPS will continue to output speed when anchored.
Good to know. It also puts out grid coordinates too so that it *might* be compensated for (i.e. computer says your x or y haven't changed by more than .0002 for 7 minutes, I will just pretend you are sitting still then), as opposed to manually entering in current river speed or something. I don't know what a good absolute threshold is without experimenting.

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but with the equipment the OP already has a close approximation can be done from the speed of the boat through the water.
Absolutely, I don't know anything about the onboard speed signal though (well I can guess).

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Originally Posted by bestclimb View Post
But a whiz wheel and fuel consumption information would do just as well.
If the gps were sorted then it would just be more convenient and perhaps accurate, and provide a basis to compare with land vehicles. Car miles are already made good


edit: more fun with gps inaccuracies (I never really looked before):
http://www.arduino.cc/cgi-bin/yabb2/...m=1295491451/3
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Old 05-03-2011, 05:03 PM   #15 (permalink)
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This has been a great discussion, Thanks!

My course forward is to use the Paddle Wheel transducer since it is existing equipment. From there I can calibrate the MPGuino's speed against the existing Speedo & GPS in a lake. That leaves me with figuring out uS/Gallon.

With the MPGuino, is there a way to reveal the total injector micro-seconds for the most recent trip? If there is, then I can calibrate the uS/Gallon.
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Old 05-03-2011, 05:37 PM   #16 (permalink)
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you just refill your tank (in a repeatable manner), reset the tank trip, drive a lot, then refill the tank again (in precisely the same manner) and see what percentage the guino is off on tank gallons and adjust accordingly

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Old 05-03-2011, 09:27 PM   #17 (permalink)
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Only boaters struggle with the concept I guess But if you go 5 miles, then you go another 5 miles, that would be 10 miles. Pretend you went to the convenient store 5 miles up river or something. You would NEVER say your commute is zero miles just because you wind up at home again. Just sell your vehicle and forget all this tracking business then

I wish.
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Old 05-13-2011, 11:17 AM   #18 (permalink)
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Quote:
Originally Posted by dcb View Post
I think this is one case where I would seriously consider a gps, perhaps connected to a duino to simulate a speed signal just for "simplicities sake". On a car it is a non-issue (unless you spin the tires constantly), but a boat is of course another matter.

There might be some other methods, i.e. I assume boat speed is largely a function of engine rpm plus some fudge for weight/acceleration. If you have a duino monitoring rpm, and you map out the slippage at different rpms and the slippage under various acceleration points, you could get a pretty accurate distance perhaps, and wish you spent the $60 on a gps module
Hi, I'm new here (occasional past lurker) and I'm interested in this GPS/MPGuino concept. I've got a converted 1.0L Geo Metro engine powering an Experimental Light Sport Aircraft (ELSA). It's a 1990 model engine with factory ECU and throttle body fuel injection, so I think the injector feed should be easy to identify and connect, but in the ELSA application, I don't have speed data.

Would one of you knowledgeable folks know if a 'gps module' - like what's referenced here - is straightforward enough to use for 'speed' that an electronics novice (with decent soldering skills and aptitude) could make it work?

As a little additional background on this ELSA, I made some significant aerodynamic improvements to it a few years back with streamlined strut fairings, gap seals, vortex generators, and a few other subtle, but additive, improvements. I learned a lot in the process and increased the flight envelope by around 20 mph; approx 10 mph lower stall speed, and approx 10 mph faster straight and level flight.

Now I'd like to be able to collect some fuel efficiency data, as well as potentially increase awareness of fuel consumed and in reserve.

In anticipation of the question, I'm quite alright with the speed data being 'ground reference' rather than airspeed.

Thanks in advance for any advice. If I hear that GPS/MPGuino should be relatively straightforward, my next Internet stop will be to buy an MPGuino and other necessary parts.

Best Regards,
Dan Felix
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Old 05-18-2011, 02:32 PM   #19 (permalink)
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current is everything in a boat.

how will you KNOW what your efficiency IS if you don't value the current into the equation? did you get better efficiency because you balanced it right? trimmed it right? or because you had a 3mph current pushing you along faster.

Remember in a car a head wind or tail wind will "move" you but with a boat the "ROAD" can move WITH OR AGAINST YOU since its "fluid"

you would need a way to factor in "ground and air" speed or in this case water speed and "actual" speed

I am not even sure how to do that? would paddle wheel be the equiv of air speed and GPS be your ground speed?

how would you calc that into a guino?

I have a feeling its going to be a VERY tough nut to crack and your going to go with Gallons per Hour for your fuel economy.

IE use time not distance to gauge your efficiency since water speed like air speed is a value NOT under your control.
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Old 05-18-2011, 03:56 PM   #20 (permalink)
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current is everything in a boat...
Really it is only part of the picture. I think it is a legacy measurement (because they didn't have a better way to measure miles made good) that only complicates efficiency measurements.

It would be like saying headwinds and tailwinds are everything to a car, when measuring actual ground distance traveled is still the critical metric along with fuel used. Measuring windspeed might be a nice addition when rationalizing the currently displayed mpg number, but it is a tertiary bit of information when it comes to fuel used and distance traveled.

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