Huge Variations in FE Figures?

[Brian]

So, I started doing some of my trips to Tirunelveli on my Bullet 350. On average the trip comes to about 165 kms (both to and fro). I measure FE by reserve-to-reserve method. The FE during the previous trip was a mind-blowing 42.99 kmpl (no room for errors because R-to-R method is pretty accurate). The next time I measured, I was in for a very rude shock because the FE figure was 29.99 kmpl!
Is this even possible? I'm really, really sure that I did no mistakes while calculating and petrol was filled again only after going into reserve and not before that. I'm worried

 

[pravin1987]

Re: Large variations in FE figures?

So, I started doing some of my trips to Tirunelveli on my Bullet 350. On average the trip comes to about 165 kms (both to and fro). I measure FE by reserve-to-reserve method. The FE during the previous trip was a mind-blowing 42.99 kmpl (no room for errors because R-to-R method is pretty accurate). The next time I measured, I was in for a very rude shock because the FE figure was 29.99 kmpl!
Is this even possible? I'm really, really sure that I did no mistakes while calculating and petrol was filled again only after going into reserve and not before that. I'm worried

can i bullet350 return 42 kmpl? .

 

[macsvin]

Re: Large variations in FE figures?

You need to check this couple of more times since there is a wide possibility of getting cheated on Petrol Pump. One cannot be sure that if you have asked or paid for X amount of Petrol the same is been filled in your vehicle

 

[Brian]

can i bullet350 return 42 kmpl? .

Yes dude. On constant highway runs, It will return 40+ kmpl without breaking a sweat. This is when riding at 70 to 85 kmph speeds.

You need to check this couple of more times since there is a wide possibility of getting cheated on Petrol Pump.

I highly doubt this possibility because it's in the centre of the town. We've been getting fuel from this pump for as long as I can remember (that's more than a decade!). It's a reputed Bharat Petroleum station. I don't think that might be the issue but thanks for laying out this possibility

P.S: Sincerest apologies for the accidental back to back post. For a moment, I typed away absent-mindedly. I tried looking for ways to delete it but couldn't find an option. Mods, please make changes if required.

 

[macsvin]

I will suggest to check mileage one more time and then decide the further line of action

 

[Alpha]

Brian

Either your calculations are wrong or you changed your riding style drastically or your petrol pump guy tricked you or your Bullet is leaking fuel (a possibility since my friend's Thunderbird leaked fuel from the knob which is used to switch between fuel options and he used for cry about mileage).

Also pease elaborate about how this R-to-R method works. According to me, it can be accurate only when you start the trip when the bike hits reserve which is highly impossible. There is a problem in this method if you want to calculate for the exact 165 kms trip. However if you are considering a wider data other than the trip also, then it will be accurate.

Regards,
Alpha

 

[Brian]

Brian

Either your calculations are wrong or you changed your riding style drastically or your petrol pump guy tricked you or your Bullet is leaking fuel

There's a very slim chance of my riding style being the culprit because as much as I'm not trying to brag, I ride and drive very smoothly and restrict my speed chases to my laptop. My calculations might be wrong but then again, they must be right if the odometer was not lying. Again a very slim chance of the petrol man to trick me but there's that possibility. And no, my bull doesn't leak fuel

Also please elaborate about how this R-to-R method works

Well, I base it on the logic that @ reserve, fuel tank = empty. Once reserve falls, note the reading when you fill next time. Ride your bike, and when it falls into reserve again, note the reading. This is the distance covered using the fuel filled at the last station visit. Divide distance by fuel amount and you get the kmpl figure. Yes, I do it with overall distance and not a particular trip distance. We keep a fuel log diary. According to that, from the day we got delivery till now, the average FE is 35.7 kmpl

P.S: Accurate only if you fill within 1 or 2 kms of reaching reserve. Driving more on reserve means more fuel you fill after that will go into reserve and will give you a wrong answer.

 

[Rumbutan]

I too felt some variation in FE, by R_to_R method, for std 350. But my overall fuel and km shows average of 40+ as FE. Don't worry much , try a tankful , anyway petrol price is going to rise soon, so do a tankful and try ;)

 

[Brian]

average of 40+ as FE.

Average of 40+? That would mean pure highway FE of 45+!!! Yeah, it is possible with extreme tweaking but still incredible! Hope your calculations are correct. Hope you get such high figures always

 

[pkprasad]

My two bits:
I had noticed this with my Hero Honda CD100 almost 28 years back. I don't know if this applies to Bullet. What I found was that the fuel tank sits on the frame like a saddle, with the two lower sections, holding almost 1.25L each. The fuel tap is on the left, so the right side remains untouched even after the reserve is used up. I used to flatten out the bike to the left in emergencies. This dead reserve quantity will not be used up at all if refuelled immediately after reaching reserve. Otherwise, especially in rough roads and going up steep gradients, a major part of this dead reserve will spill over to the left and used up. So the observed FE used to vary, especially while filling smaller quantities.
Prasad.

 

[Brian]

My two bits:
So the observed FE used to vary, especially while filling smaller quantities.
Prasad.

I never thought of this possibility. Well, nothing much to do with the gradient but when riding, leaning to the sides is inevitable sometimes. That coupled with the inertia may have forced more fuel to be used from the tank in the first trial. Well, I'll just keep checking the FE on more occasions. In any case, the figure is nothing to worry about for a 350 cc engine

 

[Alpha]

In any case, the figure is nothing to worry about for a 350 cc engine

But REs are generally fuel efficient despite their cubic capacities. My neighbour's 350 Electra used to return 38+ kmpl on most occasions and even go beyond 45 kmpl on long rides. Part credit goes to the tune of the engine as well. Due to torquey nature, engine mostly stays very low in the RPM range which would result in leser consumption.

Your fuel efficiency still remains a mystery Brian.

Regards,
Alpha

 

[Brian]

Your fuel efficiency still remains a mystery Brian.

For now, however, I'm actually expecting a low-ish number because It's been a while since it even glanced at highways. For the past one month, it's been running for only 3 or 4 kms a day and that too at very low speeds on bad and congested roads