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BiKenG

Fuel tank and level

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Much has been talked about the fuel capacity of the VFR1200F, but in order to fully understand how the fuel level sender is operating, I conducted a test with my 2012.

 

Starting with a completely empty tank (i.e. dry, not just unable to pump any more) I measured the sender resistance and then added fuel litre by litre, measuring the sender's resistance at each step. At 19 litres it is completely full, up to the very top and some way above Honda's recommended maximum level, but in my opinion there's no need to take any notice of Honda in this instance. There's at least an extra litre that can be squeezed in after the level has reached the bottom of the anti splash ring around the filler neck. Honda say "no more", but why. What's gonna happen. The worst is that it might drip a bit out the overflow (although never had that myself) and the best is that you gain additional range. Anyway, whatever the rights or wrongs of this, it's what I measured.

 

In fact it's nicely symmetrical then as there are 4 litres at the top and also 4 at the bottom that do not change the sender's output since it is already at the ends of its travel. It is also far more linear than I expected. I added an 'Ideal' straight line to the chart so you can see, but the reality is not as far out as one might expect.

 

I also discovered that the low level warning came on at 180 miles with about 3.5L remaining in the tank, so I was able to squeeze in (i.e. right to the very top) 15.5 L. That represents about 11.5 miles/litre average which is quite acceptable IMO.

 

Hope others will find this of interest.

 

2048486291_eVo4data-Fuel.thumb.png.266b8f5a97bb32f7ca8175a558216532.png

 

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What's frustrating to me is for some reason my level has been inconsistent. It used to be if I could get 50 miles before I lost the first bar, I was good. It used to be 125 miles and it would flash but I'd only fill 3.1-3.4 gallons.

 

The bike was knocked over by a $-+*"$ with a backup camera equiped SUV. Since the repair, it will knock a bar off before 50 miles, but can do 140 miles before it starts getting mad at me. I pushed it to 160 miles and only filled 3.8 gallons. No idea what's happening, but I'm all over the place.

 

 

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Well the range of the sender unit is unlikely to have changed, but I guess it's possible the arm could become bent and shift the whole output, up or down.

 

It's also worth remembering that prior to 2012 there was NO low fuel sensor. They just relied on the main level sender output to decide when to display the low level warning in the dash. But this was rather unreliable so they fitted an independent low level sensor from 2012 onwards. This required a change to the tank and also the dash. If they have become mixed up then you might get unexpected results.

 

The first check would be to measure the full and empty readings of the main sensor. They should be within the specs as stated in the manual, that's 12-14 and 119-121 Ohms respectively. As you can see, mine are slap bang in the middle at both ends. So I know my sender is good.

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2 hours ago, BiKenG said:

Much has been talked about the fuel capacity of the VFR1200F, but in order to fully understand how the fuel level sender is operating, I conducted a test with my 2012.

 

Starting with a completely empty tank (i.e. dry, not just unable to pump any more) I measured the sender resistance and then added fuel litre by litre, measuring the sender's resistance at each step. At 19 litres it is completely full, up to the very top and some way above Honda's recommended maximum level, but in my opinion there's no need to take any notice of Honda in this instance. There's at least an extra litre that can be squeezed in after the level has reached the bottom of the anti splash ring around the filler neck. Honda say "no more", but why. What's gonna happen. The worst is that it might drip a bit out the overflow (although never had that myself) and the best is that you gain additional range. Anyway, whatever the rights or wrongs of this, it's what I measured.

 

In fact it's nicely symmetrical then as there are 4 litres at the top and also 4 at the bottom that do not change the sender's output since it is already at the ends of its travel. It is also far more linear than I expected. I added an 'Ideal' straight line to the chart so you can see, but the reality is not as far out as one might expect.

 

I also discovered that the low level warning came on at 180 miles with about 3.5L remaining in the tank, so I was able to squeeze in (i.e. right to the very top) 15.5 L. That represents about 11.5 miles/litre average which is quite acceptable IMO.

 

Hope others will find this of interest.

 

2048486291_eVo4data-Fuel.thumb.png.266b8f5a97bb32f7ca8175a558216532.png

 

That’s interesting.

 

Over my nearly 300 fill ups I have found the fuel gauge to be very repeatable.  My average tank range is right at 205 miles, so I am used to running my tank low.  The low fuel warning comes on at .8 gallons, or about 3L.  I believe it also states this in the manual and is independent of anything do with range or miles remaining.  The farthest I have gone before getting the low fuel warning was a bit over 206 miles IIRC.  I can confidently run down to .4 or .3 gallons remaining.  I don’t think I have ever put more than about 4.5 gallons in it.  Side stand fill up to the plate thing.  I think I usually get about 80 miles or so before the first bar drops off the gauge.

 

Your resistance measurements suggest I could stretch my range a bit more beyond the .2 or .1 gallons remaining but I don’t think I’ll risk it.

 

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Great work BiKenG, thanks for quantifying it by actual measurements. And, of course thanks to Swimmer too with his relentless collection of fuel mileages.   My puny contribution is I've heuristically determined that with the one bar flashng I can easily go another 47 miles, maybe a few miles further.  I get about 44 MPG on my sea level highway commute, which is about 1.07 gallons, or 4.05 liters.  That jives pretty well with your measurements of 4 liters of residual fuel. 

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I stuck to just quoting miles/litre as that avoids the US/Imp. gallon confusion. I also quite like it and find myself thinking in those units.

 

As I mentioned, it must be kept in mind that pre 2012 bikes relied on the sender output to determine low fuel level. But this is not accurate and so in 2012 they added the low fuel level sensor like (all that I know) other Hondas. This works entirely independently from the main sender and is quite accurate.

 

I have the VFR1200X Crosstourer dash on my bike and the fuel display is not yet matched to the F sender output. The display basically is not getting the full range it expects so drops quicker from full and still shows at least 2 bars when low fuel level is detected. But what is interesting is that as soon as that low fuel level is detected (due to the low fuel level sensor), even though the dash might still be showing 3 bars, the display immediately changes to a single flashing bar. So that low fuel level warning definitely overrides whatever the main level sender was indicating prior to the low level being detected.

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