RR8 Fuel Consumption Indicator

My understanding is that the RR8 doesn't have a fuel level sensor - it measures fuel consumption and illuminates a warning light when reaching the end of tank capacity.

Can anyone tell me if that warning feature can be re-set to accommodate a much larger tank (bike engine car). I.e. can the ECU be flashed to assume a new starting level of, say 40 litres of fuel, so it flashes it's warning much later than it would with the OE bike tank?

Cheers folks.

Scott

 

Ah, right! Thanks.

So there IS a fuel gauge sensor. I'd had a flick through the service notes, and couldn't see reference to one. I'd imagine it will be somewhere inside the fuel pump assy? Does anyone have a pic - I'd just like to see if it could be moved onto a mount on the internal wall of a 'car-shaped' tank.

 

There must be a fuel level sensor (not necessarily a gauge) activated at 0.7 gal fuel level.
Since there is countdown reading of fuel level, this sensor must be calibrated.
If you change the tank, then where you fit the sensor will determine the amount of fuel left in the tank.
I have no pics but the sensor must be inside the tank. But if you want to use it in a car, why not get one for a car?

 

Cheers. I wanted to use as much of the functionality of the OE bike clocks as possible (and not have to fit a standalone fuel gauge).

 

Right - I physically have a fuel pump to hand, so things are a bit clearer in my head. The low fuel warning sensor is on the pump!

So, I will likely fabricate a rectangular ali tank with a baffled centrally-placed / cylinder-shaped sump on the bottom side which incorporates the fuel tank as orientated on the bike.

I just need to understand at what point the sensor is activated - the obvious assumption is that it'll be the 'tip' marked between the yellow and red lines in the pic. I've added 2 other coloured lines to give folks reference points if it turns out my assumption is wrong.

I'll make the height of the sump such that the sensor activation point stands just above the baffle. So when the light comes on, I'll know I only have sump-capacity left.

I understand that once the low fuel warning sensor has been activated, then there's a 0.7 gallon countdown feature on the clocks??? If that's correct, then I suppose that 0.7 gallons of motion-lotion ain't going to get me all that far when the engine is pushing more than twice the weight of the bike it was designed for. 10 miles if driven sensibly - maybe? I guess that's probably warning enough, so what the hell - I'll make the diameter of the sump such that it holds the same 0.7 gallons at activation point as the bike. If nothing else it will be cool to keep as much of the bikes intended functionality in the project as I can.

Anyone have any views? Is my thinking straight?

 

... Forgive me if I'm wrong but instead of tripling the reserve does it not increase by more? For example if the reserve volume (length x width x height) is originally 10 x10 x10 = 1000cc. If you triple the sizes... 30 x30 x30 it actually becomes 9000cc?

 

I can easily increase the size of the baffled sump portion of the tank to give me a much larger reserve if I want.

The point of making it 0.7 was simply to make use of the 'countdown system' on the bike ECU.

 

Sorry guys - I'm making assumptions that folks know about car tanks.

They can obviously be much bigger than a bikes and can come in different shapes and sizes. On an bike (particularly more modern injected eyes), the tank tapers down to where the fuel pump lives. This is because that's where gravity is pretty much always going to pull the contents down towards on a bike (unless you're riding upside down... or have flipped the thing!). This means there is always fuel at the ready for the pump.

But the gravitational effects of a car going forwards, back wards, stopping and going round corners acts very differently than it does on a bike. The fuel wants to travel with the greatest gravitational pull (left hander - it rushes to the left, right hander - the right, hard stop - forward, accelerate - back, etc.).

This is not a problem for a fuel pump on most 'normal' cars. If driven the way the manufacturer intended, it will always have fuel near the pump feed.

But put sticky tyres and top suspension on your car and track it, and you will eventually lose fuelling on a long bend as fuel level goes down (despite there still being plenty go-juice in the tank - its just out of reach of the pump).

Some performance car builders compartmentalise their tanks with barriers to avoid the slosh. Some put special foam inside. Others run 2 tanks - a big one with a low pressure pump feeding a smaller cylindrical one which in turn feeds the injectors via a high pressure pump.

I'm just just making a hybrid. It will have the normal tank dimensions for volume, but I will be using the cylindrical 'sump' and attaching it in the middle on the underside to achieve a halfway house surge protector.

I could make this surge-protector sump bigger, but the point is - I will be using the bikes clocks and I want it's count-down system to be accurate.

e.g. if I change the size of the sump, then I will always have to do some maths in my head as the bike clock count-down begins. Would be easy if. doubled it, but I don't have the room to double it. Hence, why I will try and make this surge-sump 0.7 gallon sized.

 

Yup - I agree SPS... the low-fuel warning-light and count-down indicator are not going to be the most useful of tools. But as I've said a few times before - I just want the pump / ECU / clocks to operate as they would at the same fuel level as they would on the bike.

My fuel-tank / anti-surge sump shape will always have to be broadly as I've described it.

I could keep things super easy and just use the OE Lotus tank, OE Lotus pump, find a suitable fuel pressure regulator, tap the fuel rail for a return line, and fit a standalone fuel gauge. I don't want to do that though - I want to use the fuel-pump that the Honda engineers commissioned to work with their ECU and clocks.

The only thing I really want to be sure of from the CBR1000RR experts are that, a) I have identified the correct point where the low-warning sensor is activated when dry, and b) the clocks do indeed have a countdown facility from 0.7 gallons once that sensor has activated.

 

I think there are a couple of points to consider:
a- low fuel level trigger (either a float sensor or something other sensor inside your fuel pump ass'y)
b- the countdown calibration.
My assumption is that the fuel delivered by the pump must be metered (this also privides the mpg info).
My next assumption is the ECU countdown is activated by condition a and it has already been programmed to use 0.7 gal as starting point. As metered fuel info is sent to it, it does the substraction from 0.7 and changes the display in turn
You could set the low fuel trigger happen at any level in the tank (depending on where you position the pump) but the countdown can only work over a range of 0.7 gal. ONce you have passed that the display would just show "0"!. Unless you can re calibrate the ECU to a new starting value.
I know the problem you have referred to in cars: fuel moving around and causing fuel starvation. I experienced that (in my youth!) with my sporty car in the days of carburators afte I put wider & stickier tyres on. In my case fuel moving in the float chamber causes momentary fuel starvation. The same principle in tanks (as you mentioned); so baffles were put inside them (or changed to foam filled ones). None of my FI cars suffered from this since and I do like taking my corners at high speed
So you could position your pump/ sensor in the tank so that the low lever trigger happens at 5,10,... ltrs and just keep a mental note of your range to empty but make sure the pump is man enough for the job in terms of adequate pressure & flow for the car engine

 

Thanks Bonjo