Inline fuel meter

[Bill Perkins]

Is there a fuel meter available that I can cut into my fuel line ? I want to run a measured pint or quart of fuel through my new engine at various rpm , in various conditions , checking the distance covered in each case with the GPS .

[George Ray]

'T' into the line so you can draw off a tall narrow tank that is graduated. Easy Cheap, Accurate.

or

http://www.floscan.com/html/blue/index.php
Welcome to the Website of FloScan Instrument Company, Inc., the world's leading manufacturer of fuel flow instrumentation for permanent installation on diesel and gasoline engines.

[Don Z.]

Do you mean this?http://www.floscan.com/html/blue/itemimages/big/4891.gif

seehttp://www.floscan.com/html/blue/seriesdetail.php?sid=11

Navman makes one as well: http://www.starmarinedepot.com/smd/images/prodimages/navman/NM1150-10_L.jpg

http://www.navman.com/Navman/Templates/productinformation____39340.aspx

[Tom Lathrop]

I'm fairly sure that these flow meters only work on single line carbureted systems. That is, no fuel injection since the back flow would ruin the flow measurement..

[bugeye]

Hi
I installed one of these on a schooner that had twin diesels. For a diesel, you had to have one paddlewheel in the intake line and one in the return. The gauge did the subtraction. It was very fussy and complicated, and extremely sensitive to even the slightest amount of air in the fuel system. What made me laugh my ass off was that in the setup instructions, it said to always check the readings against a graduated sounding stick stuck in the filler neck of the tank, which is what we had always done before we had the stupid meter. I wouldn't waste your money, unless instantaneous fuel consumption readings are for some reason neccessary.

[Ron Carter]

Agree with George Ray. I worked in a business where very accurate flow measurement of petrolium products was required. As long as you have only one meter you will think you have the answer. Don't buy a second and compare the readings or you'll never believe either of them again. Among other things the readings are highly temperature sensative.

[Tonyr]

A reading of the manufacturers' literature seems to indicate that noone offers meters (standard ones, at a reasonable price, anyway) to measure in real time the use of fuel by smaller outboards, say those that use between a third and two thirds of a gallon an hour at modest cruising speeds. I have a 50 HP Yamaha high thrust unit, and would love to have rpm Vs fuel consumption curves. I can't get them.

I think the best idea I have received from this discussion is to build or acquire an upright tube-like tank, and measure fuel used against distance gone (via GPS). I suppose a simpler method might be to weigh the tank before and after a measured run of several miles on a calm day, at a constant rpm.

Comments anyone?

Tony.

[Hughman]

I think the best idea I have received from this discussion is to build or acquire an upright tube-like tank, and measure fuel used against distance gone (via GPS). I suppose a simpler method might be to weigh the tank before and after a measured run of several miles on a calm day, at a constant rpm.

Comments anyone?

Tony.

Once the fuel ran out in the small tank, you'd have to bleed the system. Or live with an inaccurate result.

[George Ray]

Turn the T-valve to the graduated tank and run. Mark level/time on a piece of masking tape on the tank (assumes you can see level thru the tank wall). You can go back and measure/calculate later.

As long as you switch the T-valve back the main tank before the graduated tank is empty you won't get any air in the system.

[Tom Lathrop]

Tony & George,

I also have a Yamaha T50 and would like very much to get RPM and speed vs fuel use data. I did lay out a system like George suggests. Even found a small transfer valve that would do the job of switching from graduated cylinder to normal tank and back. Other stuff has pushed actually doing the job off the front burner. I anticipate laying out a measured course in our creek and making several runs at selected speeds. Both speed and distance would be set with a GPS which I consider acccurate enough for the job.

Biggest hitch I see is the need to run the fuel line to and from the steering station in order to coordinate the functions of setting speed, marking start and end and valve switching. I anticipate a second gravity feed fuel source with a second on/off valve to refill the cylinder after each run. I looked at likely distances and graduated cylinder size and it sooks doable. If I remember correctly, it looks like the distance required for decent accuracy is not very great, hundreds of yards instead of miles.

It's a bit complicated and having two people for the task would be best but so is everything associated with getting good data on boats.

Tony, If you are interested, I will try to find the work I did a few years ago and we can talk by email.

[Tonyr]

Tom, yes, I am certainly interested, and I suspect that others on this thread might be too. My engine is a 2005 fuel injected one., by the way. Much earlier ones were (I think) carburetted.

I will commit to go ahead with an attempt to use the weight difference method I proposed, and will post results as soon as they are available. The only drawback seems to me to be that I can generate only a few discrete points on the rpm/gph graph, with interpreted lines between, but that's probably perfectly OK for my purposes.

My interests are in gph at revs between 1800 and (say) 2500, which give me a cruising speed between 5 and 7+ statute mph. Perhaps you could investigate higher revs/speeds with your boat? I would be uncomfortable at relying on runs of less than about an hour (given the crude nature of my measurements) but if I am at least consistent in my methods, we should be able to generate some useful information.

Regards, Tony.

[Tom Lathrop]

Tony,

My Yamaha is a 2000 model and uses 4 carbs. Love to have the injected system but can't afford to change.

As has been mentioned, I'm sure my method will not work on fuel injection systems. They use a dual line system as in most cars which delivers a surplus of fuel to the injection pump so there is always plenty available and the injector is not starved. The surplus which may be more than the engine is using at the moment, is fed back to the fuel tank. I am weak in this knowlege but think I probably have the essence of the situation. In any case, the flow in both lines would have to be measured and my system can't do that.

Your weigh method will work and you could use a small auxilliary tank so that the quantity and time/distance might not have to be as great as you said.

[Tonyr]

Tom, we are going out this week for a couple of days, and will take the bathroom scales with us. (!)

Tony.

[Bill Perkins]

Thanks for the replies , I've been away from a computer. I've got fuel injection . I'll be curious to hear how weighing the fuel works . Maybe a calibrated stick is just as good ? I'll read all the links when I get home .I'm still hoping for an inline solution ,but I don't want to go as far as a computerized system.

[Bruce Hooke]

For anyone doing this sort of thing via scales or a tall, thin tank it would be good to have a clear understanding of significant figures. There is a good, brief tutorial on them here: http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch1/sigfigs.html

Understanding significant figures will allow you to make sound decisions about things like how far you need to go on a trial run to get useful data and how accurate you need to be about measure fuel consumption. Start at the end with how many significant figures you need in your data (is it enough to know that you use 5 GPH rather than 6 GPH or do you want to distinguish between 5.2 and 5.3 GPH?) and then work backwards and figure out what this means in terms of your methods for measuring distance travelled, fuel consumption, and speed. Since speed depends on time, which is pretty easy to measure quite accurately (especially if you let your GPS do it as part of its computations), the next factor is distance. How precise is your GPS at determining your position? However, I'd guess that measuring fuel consumption will be the determining factor...

[Tonyr]

For Tom Lathrop and others interested. Just back from a very pleasant 3 night cruise on New Brunswick's wonderful Saint John River system (forgive the propaganda, but it happens to be true, and we just love the place).

Here are initial results of our measurements, obtained by weighing a 3.5 Imperial gallon tank at the start, and then at one hourly intervals, while running at a constant RPM in pretty calm conditions. Air temperature was between 50 and 75 Farenheit, water at between 65 to 67.

My boat is a 22' Glen-L Eagle derivative, with 2.5 feet added to bring the length to 24.5 feet. Amongst many minor modifications to the design, I raised the last four feet of the run to a total of 2.5" at the stern, resulting in rocker such that the transom has barely 1.5" immersion. Essentially, I now have a conventional inshore lobster boat semi-displacement warped plane hull as would have been built in the 1950s or so, before fishermen began to add serious power. I don't think that this affects the engine results significantly, but these details are included to let people make their own judgements.

The boat was fully loaded with water, fuel, 500 lbs ballast (for pitch trim), stores and two people. My guess at the displacement would place it at around 4000 pounds. I will find out more accurately at haulout this fall. (Amongst the planned winter work is a re-location of the 26 gallon water tank some 5 feet forward, to correct the trim and let me get rid of most of the ballast.)

Run one, three hours at 2200 rpm. Fuel consumption consistent at 5 lbs/hour, equals a nominal .67 Imperial gallons/hour, speed 6.3 statute mph, giving some 9.4 mpg. (1 Imperial gallon = 1.2 US gallon).

Run two, four hours at 2000 rpm. Fuel consumption 4 pounds/hour, equals .53 Imperial gallons/hour, speed 6 mph, giving 11.32 mpg.

Run three, three hours at 1800 rpm. Fuel consumption 3.5 pounds/hour, equals .469 imperial gals/hr, speed 5.4 mph, giving 11.51 mpg.

Avoiding the fallacy of pretending over accuracy, it seems reasonable to conclude that by keeping below theoretical maximum displacement speed, the T50 on my particular semi-displacement hull will give me a safe 10+ mpg or so in most conditions, when running in the 6 mph range.

While the boat will semi-plane up to 13 mph at WOT, I would only run at this speed in an emergency, and am sure that fuel consumption would drop sharply.

Tony.