Enlarging my fuel tank

[rocketdoc]

While we are all waiting for more pictures and an update on this project, I will throw my .02 cents worth in on the power /mileage discussion. I understand that reducing the weight of the bike's load by 12 lbs. is like adding one hp. I read this a few years ago. So if you lose 40 lbs. it would be like gaining 3.3 hp. This would not help your gas mileage but sure make it a lot more fun if you can appreciate the difference. Like acceleration mainly.

I know guys who have spent a shitload of money reducing the weight on their sport bike, while their gut just fatter and fatter....go figure!

 

[UselessPickles]

I understand that reducing the weight of the bike's load by 12 lbs. is like adding one hp. I read this a few years ago.

The actual amount depends on the HP of the bike and the weight of the bike + rider. Losing weight is only "like" increasing HP/TQ in terms of acceleration. It won't help your top speed at all because that's determined by actual TQ output at the wheel vs. air resistance.

Example:

FJR weighs 640lbs + I weigh ~160lbs with gear = total weight of ~800lbs.

FJR has about 125 RWHP.

That's 6.4 lbs./RWHP, so losing 6.4 lbs. would be "like" gaining 1 RWHP for acceleration purposes. Note that this is not linear. As you lose weight, your weight/HP ratio lowers and less weight must be lost per perceived HP gain.

 

[Texan]

What are you guys smoking? Of course carrying extra weight costs extra fuel.

 

[meosborn]

What are you guys smoking? Of course carrying extra weight costs extra fuel.

If for no other reason than because of the increased friction between the tires and the road. Not to mention acceleration.

 

[chrisflock]

Well, still waiting on updates, so I'll throw my hat in the ring on the weight/mileage thing.

Increasing weight of your vehicle WILL decrease fuel mileage because of increased energy required to accelerate, an increase in rolling resistance of the tires (this can be partially offset by increasing your tire pressure). The difference that it makes, however, is highly variable, and depends largely on driving situation. If you filling up the bike and hopping right on the interstate and driving straight on to the next gas station, the difference is going to be very small because you only accelerate up to speed once. If you are riding a twisty road where you are speeding up and slowing down for corners, or if you are driving through town stopping for stop signs (I know, some people stop for those!) it will make a much bigger difference.

There are a lot of other variables as well. For example, adding to the bike will cause it to sit lower on the suspension, and that will change the angle of the drive shaft, and the angle that the universal joint (or CV joint when applicable) operates at can have a significant impact on driveline losses.

 

[mcatrophy]

...Here's a question, though, that's always intrigued me: Does an overdrive give better gas mileage? If it takes a certain amount of energy to push a certain mass through a certain resistance (and it does), then it should take the same energy (and thus the same amount of fuel) regardless of whether I'm in a "normal" fifth gear or an overdrive sixth....

Simple answer: Yes, due to pumping losses, the losses caused by the work done to create the vacuum in the inlet manifold.

Pumping losses are caused by the way power output from a petrol "Otto" engine is regulated. It is regulated by controlling, or rather constricting airflow to the engine. This constriction of airflow creates partial vacuum (low pressure) in the inlet manifold. Maintaining this "low pressure" in the inlet manifold wastes energy.

Lower revs means you need a bigger throttle opening to get the same rear wheel torque, which equals lower pumping loss each revolution, and fewer revolutions to the mile, so less work again.

Try the experiment, zero your average MPG readout, hold a steady speed on straight, level road with no traffic in 4th for a few miles, try it again in 5th (same road, same direction, same wind etc), check your computer fuel consumption for each.

One of the reasons that diesel engines are more efficient is that they run at full throttle all the time (we're talking air into the engine, not the driver's right foot), power being regulated by the fuel injected. Can't do that with a petrol engine, the mixture won't ignite with a very weak mixture (even if the resultant NOXs or whatever didn't exceed allowed pollution levels).

 

[Alex]

Sorry for the lack of updates. I was out of commission for 1/2 a week due to the H1N1 flu. I was getting stir crazy sitting at home so much.

I've progressed further on this project, here is an overdure update.

First off I needed to finish welding the sides.

Then cut off the top section.

Heated up the bottom of the tank removing the vent and overflow lines

I then braised in some longer replacement lines.

i spent 30 minutes or better trying to proplerly blend in this top section to the lower area.

The first cuts were to widen the area where the front will join. To do this I just cut back a 1/4" on each side. Next was to drawn new lines that flowed across the uneven bends of the tank. 10 measurements and 2 templates later, I had my new cut lines.

I welded up the rear of the tank and kept the factory curve.

 

[kaitsdad]

Alex, this is sizing up very nicely - I'm really looking forward to seeing how it looks on the bike.

And very nice work. :thumbsup:

 

[charismaticmegafauna]

Pumping losses are caused by the way power output from a petrol "Otto" engine is regulated. It is regulated by controlling, or rather constricting airflow to the engine. This constriction of airflow creates partial vacuum (low pressure) in the inlet manifold. Maintaining this "low pressure" in the inlet manifold wastes energy.

Lower revs means you need a bigger throttle opening to get the same rear wheel torque, which equals lower pumping loss each revolution, and fewer revolutions to the mile, so less work again.

Try the experiment, zero your average MPG readout, hold a steady speed on straight, level road with no traffic in 4th for a few miles, try it again in 5th (same road, same direction, same wind etc), check your computer fuel consumption for each.

I'd like to see the results of that experiment.

With a vacuum gauge used as a gas-mileage indicator, the higher the vacuum reading (more closed throttle) -- for a given speed; the higher the gas-mileage reading. (now the FJR's instant -mileage-readout might not be solely vacuum sourced...?)

Contradictory, wider-open throttle butterflies dictate more fuel to be mixed with the air -- less gas-mileage.

The answer is (I think?) that happy-zone where gear ratio and throttle opening are in serendipity -- that only happens with a CVT (continuously variable transmission), always searching for optimum gear ratio....

 

[str8]

Alex, this is sizing up very nicely - I'm really looking forward to seeing how it looks on the bike.
And very nice work. :thumbsup:

+1

 

[meosborn]

Alex, this is sizing up very nicely - I'm really looking forward to seeing how it looks on the bike.
And very nice work. :thumbsup:

+1 You got skills man.

Increasing weight of your vehicle WILL decrease fuel mileage because of increased energy required to accelerate, an increase in rolling resistance of the tires (this can be partially offset by increasing your tire pressure). The difference that it makes, however, is highly variable, and depends largely on driving situation.

Definitely. The biggest variable in mpg for a given vehicle is throttle control.

 

[FJRGuy]

I wonder how much my range would increase if I just lost 40 pounds. :assassin:

It wouldn't affect fuel consumption at all at steady cruising speeds. ...

... if you take a highly simplified approach to calculating it. In the real world it will make a difference over all. Try throwing an extra 40# on the bike and see what it does for you. I'm not saying it will be alot, or even significant for that matter (as significant can be qualitative,) but you'll notice a difference.

I understand that reducing the weight of the bike's load by 12 lbs. is like adding one hp. I read this a few years ago.

It can be EXACTLY like adding 1 HP (if your HP is 1/12 of your weight) when you are talking about Power to Weight Ratio!

Alex,

Nice work! You are an artist!

 

[mcatrophy]

...ith a vacuum gauge used as a gas-mileage indicator, the higher the vacuum reading (more closed throttle) -- for a given speed; the higher the gas-mileage reading. (now the FJR's instant -mileage-readout might not be solely vacuum sourced...?)Contradictory, wider-open throttle butterflies dictate more fuel to be mixed with the air -- less gas-mileage.

The answer is (I think?) that happy-zone where gear ratio and throttle opening are in serendipity -- that only happens with a CVT (continuously variable transmission), always searching for optimum gear ratio....

The answer is that in any given gear, a higher vacuum is caused by a lower demand for fuel, so less fuel used IN THAT GEAR. With a CVT, a lighter fuel demand (don't like saying "throttle", it's ambiguous in this context) will tend to raise the gearing, so again will mean less fuel.

What we are talking about is raising the gearing but keeping the same rear wheel torque, which means higher engine torque but lower rpm. Higher torque requires a greater throttle opening.

The "ideal" for fuel consumption at any given vehicle load would be a gear that required a fully open throttle. Not practical in the real world.

Anyway, we're off topic fftopic: . Using less fuel isn't as much fun as using more, so:

More Range + More Fun = Bigger Fuel Capacity

If I've scraped 300 miles out of my tank, it's usually been a boring ride .

 

[Wolfhound]

Very nice Alex ! I'm also anxious to see the tank mounted.

 

[mattster31]

OK...............so.

You increase the size of the tank to carry more fuel.

More fuel adds more weight.

By the way this conversation is going it sounds to me like Alex is negating his extra fuel with decreased gas mileage. Therefore eliminating the advantage of carrying extra fuel...............right????? Alex therefore needs to lose weight (not that you're fat.....it's the pants). What's the weight of a gallon and a half?? 15lbs approx???? This way he can truly benefit from the added fuel. :dribble: :dribble: :dribble: :dribble:

Nice work though...........I look forward to the results and the photo on the bike!!!!

 

[Bokerfork]

OK...............so.
You increase the size of the tank to carry more fuel.

More fuel adds more weight.

By the way this conversation is going it sounds to me like Alex is negating his extra fuel with decreased gas mileage.

This is why I only put in a cup or two of gas. Without all that extra weight, I can run over 1000 miles or more. B)

 

[charismaticmegafauna]

OK...............so.
You increase the size of the tank to carry more fuel.

More fuel adds more weight.

By the way this conversation is going it sounds to me like Alex is negating his extra fuel with decreased gas mileage

And..., and..., with more weight you need a bigger or more powerful engine to get the same performance; and..., with that you need bigger tires (or car tires...!) to handle it all; and..., that means more weight and more fuel capacity and more power and...

"Less is more" (More is less...?)

 

[palerider]

"Less is more" (More is less...?)

I'd say you've got it, more or less.

:dribble:

 

[user 213]

And..., and..., with more weight you need a bigger or more powerful engine to get the same performance; and..., with that you need bigger tires (or car tires...!) to handle it all; and..., that means more weight and more fuel capacity and more power and... "Less is more" (More is less...?)

That's right........ It will never fly.

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Thanks god its a motorcycle, not a plane!

If I've scraped 300 miles out of my tank, it's usually been a boring ride.

There's more out there than the apex of the corner. Try looking around a bit.

Nice on-going work Alex. I'm sure you'll enjoy it when you have it done. And all the funny looks you get as people try and figure out what's different.

 

[mcatrophy]

QUOTE (OCfjr @ Oct 24 2009, 04:21 AM) <{POST_SNAPBACK}>

...

QUOTE (mcatrophy)

If I've scraped 300 miles out of my tank, it's usually been a boring ride.

There's more out there than the apex of the corner. Try looking around a bit.

...

I agree absolutely. I live near some beautiful countryside (Derbyshire Peak District National Park), and a couple of times a year I go touring in Scotland.

(Click on image for larger view)



However, usually if I'm admiring the scenery I'm not in fifth, and we all know that means lower fuel consumption. I'm really referring to 70 mph motor-way stints where I get good fuel consumption, but I'm concentrating on the wayward cars rather than the views. Unless I'm pretty sure there are no speed cameras around, then I might do 71 (?), which seems to clear the cars but lower the tank range.