Manual Information

[Beemerman59]

There are two things I can't work out from the manual on my 08 GSA. It's probably me being thick but its bugging me:

1. Manual says the fuel tank is 33L with a 4L reserve. I'm not brave enough to run the thing dry so can you tell me if the 33L includes the 4L or is the total actually 37L?

2. The section on the Tyre Pressure Monitors talks about the pressures being adjusted/optimised or something like that (I don't have the manual in front of me) to a 20 degrees air temperature. What does that mean? I have always set pressures when the tyre is cold whatever the ambient temperature - and I will continue to do so but don't understand what the TPM's are doing adjusting to a target 20 degrees. Anyone explain this to me in easy language?

 

[The smudger]

33L INCLUSIVE. I ran mine down to --- on the range for 10 mls, and got 35L in, but dont take my word for it!!!

You might notice the TP's are different when the bike is hot? In our terms the ideal temp to set the tp's in is about 20 degrees. this is a 'middle' figure as it is very different wherever you are/time of year etc..

Basically temperature will alter the tp's slightly, hope this makes sense?

 

[Andy_E]

Don't know for certain about the tank capacity but I've never got more than about 32 litres in, and the range at that point has been down to a couple of miles.

The bit about the TPM means that the readings are compensated as if the tyres were always at 20 degrees, in theory allowing you to ignore the effect of temperature on the pressure - the TPM wont show the pressure drifting up / down as the tyre temperature changes. TBH I'm not a physicist so don't know exactly how much variation in pressure there is over the typical range of temperatures.

IMO this is sensible as the TPM should give you an indication that there might be pressure loss rather than being a pressure gauge. In reality I've noticed the pressure wanders up and down by about 0.1 bar but other than that remains fairly stable regardless of temperature. The only time I noticed a larger drop I did in fact have a puncture and spotted it on the TPM before I noticed any real effect on handling.

In terms of checking actual pressures I use a normal pressure gauge once every couple of weeks when the tyres are cold and go by that.

 

[JJH]

35ltrs 8 miles to go JJH

 

[elefantmanshawn]

they do around 10miles with ----range showing,might do more but i found a garage,had to have the seat removed from my arse though

 

[Andy_E]

Just thought of a more succinct way of phrasing the point about the TPM than my earlier post.

They're compensated because you only want to see the numbers changing when you've got a puncture!

 

[Nice 'n' Fat]

I've done 20 miles with the fuel indicator showing --- and then filled her up with 35 litres

 

[Beemerman59]

The bit about the TPM means that the readings are compensated as if the tyres were always at 20 degrees, in theory allowing you to ignore the effect of temperature on the pressure - the TPM wont show the pressure drifting up / down as the tyre temperature changes. TBH I'm not a physicist so don't know exactly how much variation in pressure there is over the typical range of temperatures.

IMO this is sensible as the TPM should give you an indication that there might be pressure loss rather than being a pressure gauge. In reality I've noticed the pressure wanders up and down by about 0.1 bar but other than that remains fairly stable regardless of temperature. The only time I noticed a larger drop I did in fact have a puncture and spotted it on the TPM before I noticed any real effect on handling.

In terms of checking actual pressures I use a normal pressure gauge once every couple of weeks when the tyres are cold and go by that.

I completely agree that its best to only rely on the TPMs to tell you if there's a problem rather than for any accuracy in pressure. The bit I can't get my head around is how the TPM's compensate and does that mean I have to make any adjustments for the cold tyre pressure. My tyre manufacturer specifies 2.5/2.9 bar pressures - which I set them to manually the old fashioned way at ambient temperature. When I set off on the bike I get these readings but when the tyres heat up after 10 minutes they will have increased pressure by usually 0.2 bar showing 2.7/3.1 typically. This increased pressure is a natural event and would happen irrespective of TPM's or not. So where does any compensation fit in to the equation?

I'm not at all worried about this or in anyway asking about the validity of TPM's or not before anyone jumps on that old bandwagon. I would just like to understand the theory of how the "compensation" works. Or maybe I'm thinking there is something cleverer going on than there actually is.

 

[tommygun]

How accurate is the 'miles to go' on reserve indicator? I recently was down to my last 11miles and gave it a bit of 'ooompf' on a straight. Got a misfire as if it was about to run out of fuel. I know sloshing the fuel around a bit does give you a few more miles if you get stuck.

 

[Andy_E]

I'm not at all worried about this or in anyway asking about the validity of TPM's or not before anyone jumps on that old bandwagon. I would just like to understand the theory of how the "compensation" works. Or maybe I'm thinking there is something cleverer going on than there actually is.

The theory of how the compensation works probably goes like this (I used to write software and firmware that compensated for various factors when measuring sound levels, the principal should be the same). The handbook doesn't give enough detail to work it out completely but at a guess there are two possible options.

Both options need either a compensation formula or table of compensation values. This would let the system 'normalise' the reading to 20 deg. C. by taking the current pressure and temperature and deciding what value to add or take away to the pressure to show what the value would be at 20.

For example (made up numbers) if the temperature is 5 deg. C and the pressure reading is 1.7 bar the system might add on 0.5 bar to compensate for the temperature being lower than 20 deg - telling you that with that much air in the tyre at 20deg the pressure would be 2.2 bar. If you're in the south of France and it's 30 deg. C with a reading of 2.5 bar it might take 0.3 bar off to compensate back to what the pressure would be if the temperature was 20 degrees.

1. The clever option: the TPM measures the pressure inside the tyre AND the temperature. It sends both of these back to the onboard computer and the compensated pressure is worked out. Even cleverer would be to have the TPM itself apply the correction.

2. The simpler (and cheaper) option. The TPM sends back the pressure to the computer. The computer reads the ambient air temperature from the sensor that feeds the temperature display and decides that what temperature the air in the tyres is based on that figure. It then applies the correction.

I'd suspect option 2 is used as it would appeal to the bean counters. It would also explain why the pressure does drift a little as obviously the air temperature isn't going to be exactly the same as the tyre temperature. Simples