Most Economical Motorway Speed?

[ophic]

Originally Posted by Quiff Wichard

oooo

thank you Johnny Ball. !!

i once had his chemistry set

Nothing better then a bit of rolling friction...

[Spiderman]

So the 90mph that i usualy cruise at isn't better than the legal 70mph?

Dpes the fact that i get to my destination quicker therefore use the bike for a shorter period of time not negate the small loss of fuel efficiency between the 2 speeds?

[ophic]

Originally Posted by Spiderman

So the 90mph that i usualy cruise at isn't better than the legal 70mph?

Dpes the fact that i get to my destination quicker therefore use the bike for a shorter period of time not negate the small loss of fuel efficiency between the 2 speeds?

No because efficiency doesn't include time - simply work done for given amount of input energy. The work done is the same - the distance travelled. If you travel at any speed other than the most efficient, you will use more fuel.

Originally Posted by wyrdness

I was once told that you get the best fuel economy when the engine is at peak torque. I've no idea if this is correct. Does anybody know?

Yes it does...

Problem is that often in top gear when at max torque the drag is so large it negates the effect. So unless you go around in a lower gear then no.

[Stu]

Originally Posted by wyrdness
I was once told that you get the best fuel economy when the engine is at peak torque. I've no idea if this is correct. Does anybody know?

Originally Posted by ThEGr33k

Yes it does...

Problem is that often in top gear when at max torque the drag is so large it negates the effect. So unless you go around in a lower gear then no.

But what is peak torque?
From these Dyno charts http://forums.sv650.org/showpost.php...72&postcount=8 and http://forums.sv650.org/showpost.php...1&postcount=22 for SV's
In the first diagram the torque curves are so flat that I would imagine peak efficiency would be quite low down to reduce the effect of drag (which is squared as speed rises) Also I can't believe the VTEC engine would be most economical above 7000 revs when the all the VTEC kicks in and yes torque increases, but is that not just a function of more fuel being fed into the engine?

My car is VTEC and I find the most efficient motorway speed for fuel economy is about 500rpm before the Vtec kicks in
i.e 3500rpm = 70+mph = 40+mpg
Vtec 4200rpm = 80+mph = 33mpg

Vtec in 4th gear,max revs 115+mpg and you can watch the fuel gauge dropping and completely illegal so I don't do it

Originally Posted by Dicky Ticker

Vtec in 4th gear,max revs 115+mpg and you can watch the fuel gauge dropping and completely illegal so I don't do it

Optimistic typo!

In my experience, it's the acceleration and braking of stop-starting that burns fuel. I've had better mpg on runs with an average speed nudging 3 figures when the roads are clear, compared to ones where my speed has fluctuated between 35-80 (probably averaging 60mph) due to heavy traffic.

Talking of fuel, had a heartstopping moment, nearly ran out of the stuff today! Had do do 15 minutes of filtering and oh my god traffic on solid light.