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Tidbart
06-30-2010, 08:59 AM
The factory sender chit the bed. Potentiometer has a large dead spot and stops adjusting from 5/8 to full. Easy to check, just pulled the sender and put an ohmmeter across the terminals. Regular readings are 33-240 ohm and mine were 70,70,70,70,70, - 240, a little screwy.

Anyways, anyone ever use a Centroid Products electronic fuel sender? They make the Livorsi, and others, senders.

Nifty thing about them is they have no moving parts and if you want more accuracy in your readings, they can add electronics to correct for the odd shaped tanks as in the 22C. I am debating whether or not this is really needed in the 22, to justify the uptick in cost.

I did calculate an inch-gallon chart for the newer style RDS tank that I have in mine and can send it along to the factory to have it built.

Any thoughts?

Bob

Dr. David Fleming
06-30-2010, 09:59 AM
Yes the 22ZX has a fuel sender if you call it that - thank God its better than a dip stick. It reads full until the tank is half full and then drops to empty quick and brother when it says empty you better be at the gas dock! I assume this made sense to Donzi when they constructed the boat which has a Mohler plastic 50 gal tank. Basically I always fill up and when its half empty and the gauge shows some movement I fill up again.

I have wondered if the reason for this is because the bow elevation varies with plane and maybe Donzi just couldn't do any better with this situation. Or maybe it is like my old Ford - people think it has great gas milage because they drive so far before the gauge says fill - some kind of psychological crap?

Then there is the new issue of how high does a gasoline float on the sender change when it floats in alcohol - like the specific gravity of fuels can change and this sends the sender on vacation.

Glad to see someone finally discuss this issue.

BUIZILLA
06-30-2010, 10:23 AM
most high end RV coach's use the Centroid sender..

Tidbart
06-30-2010, 02:25 PM
Yes the 22ZX has a fuel sender if you call it that - thank God its better than a dip stick. It reads full until the tank is half full and then drops to empty quick and brother when it says empty you better be at the gas dock! I assume this made sense to Donzi when they constructed the boat which has a Mohler plastic 50 gal tank. Basically I always fill up and when its half empty and the gauge shows some movement I fill up again.

I have wondered if the reason for this is because the bow elevation varies with plane and maybe Donzi just couldn't do any better with this situation. Or maybe it is like my old Ford - people think it has great gas milage because they drive so far before the gauge says fill - some kind of psychological crap?

Then there is the new issue of how high does a gasoline float on the sender change when it floats in alcohol - like the specific gravity of fuels can change and this sends the sender on vacation.

Glad to see someone finally discuss this issue.

D,

Your post is a little off topic, but the question you raise are concerns. I was curious about a particular type of sender by a company called Centroid Products. The Centroid sender has no moving parts, no float. It measures resistance inside concentric tubes as opposed to reading a potentiometer varied by a moving float and arm. It has other features, that I alluded to previously, the electronics, that allow some level of programming and customization. Of course the items come at a cost.

I have a Classic, so I am not sure about your tank. In the classic the tank is not uniform in respect to fuel level and volume, not linear. This is due to the bottom and sides of the tank are tapered. They are probably made this way in order to fit in the space provided in the hull. This is fine, although it doesn't lend itself well to the use of simple float style sender, which is really a linear-type device. Floats work very well in rectangular tanks that have a uniform volume per level of fuel.
I would assume your tank has the same characteristics as mine and others. This has been discussed before, btw, in various other threads, so I won't get into it too much. Yes, running angle of the boat has something to do with it. I assume a level tank and not running for sake of argument. I am not getting an inclinometer and getting that scientific.

The other issue, spec gravity of alcohol-tainted fuel, is minor compared to innaccuracy of the standard float and meter.

The attached graphs show it better. I show a 9.5 inch deep, 55 gallon, 22 Classic (newer RDS) tank.
The graphs say that as you get down in inches from the top of the tank, the gallons per inch drop fast.
The second graph shows the first 1/2" inch at the top of the tank, so it is skewed by a factor of 0.5, so ignore the first segment.

This tank uses about 59% of its fuel in the first 47% of the tank height and 70% of the fuel in 58% of the tank.

Long story short, the electronic senders can compensate for these odd shaped tanks by adjusting the programming. You can't do that with a float.

Bob

OK, OK, I was bored.:bonk:

Tidbart
06-30-2010, 06:49 PM
George,

Your post disappeared. :wink: I guess you found the answer to your question in my long-winded post, only a 1/2" segment.

And, yes, I used the tank drawing that you previously posted. Couldn't of done it without the drawing.

Bob

Tidbart
06-30-2010, 06:55 PM
Here is picture of a sender. They come in a 2 and 3 terminal setup. The 3 term needs a 12v supply line. If I remember correctly Ranman might have put a 3 term in his boat but needed to run an extra wire.

I plan on using a 2 wire one as that is what is existing. Just haven't decided whether to have it programmed with the tank compensation.

Bob

gcarter
06-30-2010, 07:33 PM
George,

Your post disappeared. :wink: I guess you found the answer to your question in my long-winded post, only a 1/2" segment.

And, yes, I used the tank drawing that you previously posted. Couldn't of done it without the drawing.

Bob


Yep, you nailed it.

deejay
06-30-2010, 08:27 PM
From when is the "newer RDS" tank used? Thanks, Deejay

Tidbart
06-30-2010, 08:32 PM
From when is the "newer RDS" tank used? Thanks, Deejay

94 and later.
See this post for pdf's of tanks.
http://www.donzi.net/forums/showthread.php?t=61544&highlight=gas+tank

Bob

deejay
06-30-2010, 08:37 PM
Thanks Tidbart. What a valuable list this is!

Ranman
07-06-2010, 01:59 PM
Here is picture of a sender. They come in a 2 and 3 terminal setup. The 3 term needs a 12v supply line. If I remember correctly Ranman might have put a 3 term in his boat but needed to run an extra wire.

I plan on using a 2 wire one as that is what is existing. Just haven't decided whether to have it programmed with the tank compensation.

Bob


Partially correct. I initially bought a 3 wire unit since they were only available at the time. By the time I got around to installing it a year later, I realized I had ordered the wrong tube length and so I contacted Livorsi for a return/replacement. They exchanged it for a 2 wire version with the correct tube length which is what I am running today. There are high and low limit pot screws and I recommend adjusting the low limit to way beliw "E". I set my empty level right on "E" and ran out of fuel 100' from the fuel docks. The dang thing is accurate.

Tidbart
07-06-2010, 02:50 PM
Partially correct. I initially bought a 3 wire unit since they were only available at the time. By the time I got around to installing it a year later, I realized I had ordered the wrong tube length and so I contacted Livorsi for a return/replacement. They exchanged it for a 2 wire version with the correct tube length which is what I am running today. There are high and low limit pot screws and I recommend adjusting the low limit to way beliw "E". I set my empty level right on "E" and ran out of fuel 100' from the fuel docks. The dang thing is accurate.

Hey Randy, Long time.

The newest version has no adjustments to it. These are self adjusting. I believe the programmable and non-programmable now adjust themselves by remembering the fullest settings for the full reading. I am oversimplifying, of course.

The programmables are really cool in that they can program in adjustments for odd-shaped tanks at the factory. Should be really accurate.

I am glad to hear you think they are accurate. Does not sound as if many have replaced their floats with this type. I am not getting much feedback or interest. I thought there would be more. Also, the programmables should be even more accurate as far as throughout the range of the gauge.

Bob

Ranman
07-07-2010, 10:21 AM
I was happy to hear they went to 2 wires and no +12V. I Was a little concerned with running "power" to the top of the fuel tank.

It sounds like they have progressed with even better technology since I replaced my sender a few years back.

Tidbart
07-07-2010, 02:24 PM
I am consolidating these threads so go here for future posts. http://www.donzi.net/forums/showthread.php?t=62513

Thanks, Bob