Fuel consumption and Navman 3200.

Whitelighter

Whitelighter

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I know a few bods on here have been interested in my success or lack of it with the 3200 diesel kit from Navman. Well, the good news is after a fair degree of mucking around a new part arrived in the post from Plastimo and hey presto - system worko.

Turns out I has the wrong T connector for the twin installation. But hey ho, all sorted and I have even managed to get the NMEA wired properly so the Navman unit sees the speed out put from my Raymarine C70 - result!

After an extensive weekend of testing, I have some interesting results.

Firstly, with the speed input (taken over the ground as this is the most relevent) it seems that in terms of efficiency, the boat is level from when first planing (about 19 knts and 2400 rpm) right up to 3100 rpm which is about 28 knts in a neutral sea - fuel used is always around 1.85 mpg. Running with a 2 knot tide down the solent increased this to 2.1 mpg, and running against the same tide in the opposite direction reduced efficiency to 1.6 mpg.

Punch the boat up past 3100 rpm, all the way to 3700 and 36 knts and the consumption increased, with mpg dropping considerably to 1.4 mpg with the tide and 1.0 mpg against.

I was quite suprised to find running at a slower planing speed didn't really change the efficiency. Also, a 0.5 mpg swing will mean that I pay a lot more attention to tides on longer runs, and will definitley try to go with the flow /forums/images/graemlins/grin.gif

Other than that, quite pleased with close to 2 mpg at 30 knts!
 
Yep Jez - thats about what I find as well.
Once on the plane, it doesnt seem to make much difference going slower - unless you are hammering it of course.
So reducing from say 24kn to say 18kn in a flat sea doesnt make a huge difference to the mpg - burns more of course but you get there quicker.
Now dropping to displacement speed - thats a different matter.

Mike
 
Hmmm, so (assuming similar sort of thing with my engine) does that mean I could actually have an argument for going faster?? i.e. if MPG is the same from say 2400rpm up to around 3000rpm (max revs being 3500) then by going faster we get where we're going quicker and therefore put less hours on the engine and don't have to service it as often /forums/images/graemlins/smile.gif

Can you get a simple fuel flow monitor? would be interested to do the same experiment but don't really want to try and find somewhere for a permenant installation!
 
Thats pretty much what you would expect with most planing boats with the fuel consumption curve flattening out after the hump and then rising again as the boat speed approaches maximum
Have you got any pics of your installation? Was it easy to fit and how is the fuel flow measured? Are they available for twin engined set ups?
Congrats. Seems like a useful bit of kit
 
Hi Mike,

Yep, mine is a twin engine set-up. The kit is actually very advanced, and uses two sets of two volumetric senders (i.e. measuring volume rather than flow as this is more accurate) and a small control unti on the dash (same size as a ST60 tridata etc etc).

Easy enough to fit, as all the cables are plug and play (once you have the right bits) but you will need to cut your fuel lines and have them threaded to fit the senders.
 
I'm in the process of installing the same kit.

Mine will feed into the Navman 8120 unit and with this you can display a fuel curve so you should be able to find the most economical cruising speeds. there a fair bit of calibration to do but when it's all done, I'll post the results.
 
Nah... It's not the calibration of the actual devices, it's the calibration of the graph that generates the fuel curve.

Recordings of the fuel consumption are made at different revolutions, up to the max revs (configurable) and a curve is plotted to give you the fuel consumption throughout the speed range, measured with the true speed, true fuel flow and the true engine revolutions measured from the flywheel sensor that comes with the 3200 system.
 
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