Todays question... Torque & BHP

[jambo]

Quite Right Jabba, and now we are onto Thrust!
Thrust is the force exerted at the end of the gearing, so while the engine at 9000 rpm will produce say 64Nm of torque and 70BHp the thrust will be different in 1st to 5th gear as that force is gaered up to be pread over a different number of RPM of the rear wheel!

You can demonstrate this by opening the throttle at 6000 rpm in 2nd and 5th. At both points the engine has the same power, same torque but in a lower gear it has more thrust!

ah explains the cbr at 7-8k rpm in 3rd vs 7-8k rpm in 5th....

the honda certainly has some thrust... probably appropriate I said it launched down the road

and yes Im REALLY REALLY LOVING the HONDA in the snow.... my SV would be carb icing in what I was riding through last night and wouldnt start first time...

Originally Posted by jambo

You can demonstrate this by opening the throttle at 6000 rpm in 2nd and 5th. At both points the engine has the same power, same torque but in a lower gear it has more thrust!

I suspect that, because the engines can rev higher for mechanical reasons, my 600cc IL4 is noticably lower geared than the 650cc V-twin SV. I suspect that this is more than enough to negate the couple of ft.lbs of peak torque that the SV makes.

Simple question for the SV650-ers:

"What is your indicated speed in top gear at 5000rpm?"

Answers for the naked and "S" models would be interesting as, due to different sprockets, they are differently geared.

On my Hornet, 5000rpm in top is an indicated 70-ish mph.

On an S it's 68 mph

being a new uncurvy s model... will look at what it is on the curvy model when I eventually get it back

will look at what the cbr does on way home tonight....

ill check my naked next time i go out on it.

i remember the 5k rpm limit though when i got my s brand new. wishing i could go over that damned 70mph limit!

I suspect that my comment about lower gearing will be more valid for the lower/intermediate gears.

I have a speadsheet somewhere with the Hornet's mph/1000rpm on standard sprockets...... might be interesting to compare with an SV?

I know my bikes overgeared in 6th.......... if it would rev to peak power (12,000rpm) I'd be doing over 160mph

Well, the bike might........there's no way I could hang on at those sorts of speeds

[ophic]

don't think the SV is overgeared at all - i keep trying to find 7th

I've learned alot from reading this, thanks.

I've kinda known what the component 'bits' mean, I just lose it when trying to connect explainations together if you get what I mean! Until now that is.

Main reason why I really rate this site, you guys are helpful and look to educate people first, rather than put then down for lack of knowledge. It's nice.

So... how and why do BHP figures change between the engine and the back wheel?
I've heard people quote figures and then be told by others "aaahhh, but that's not at the wheel is it... blah blah... my figure is, therefore it's better... pose pose!"

I'd just like to understand what they are talking about and be able to recognise b*****ks, rather than actually participate in such ball weighing contests!

Originally Posted by ophic

don't think the SV is overgeared at all - i keep trying to find 7th

You're not alone...........

Right, the figures below gives the Hornet's gearing in mph/1000 rpm with standard sprockets. This assumes a 180/55 rear tyre with a rolling circumference of 1.94m, and 0.62 miles per kilometre.

1st = 4.7mph/1000rpm
2nd = 6.7
3rd = 8.4
4th = 10.1
5th = 11.5
6th =12.7

So at 5000 rpm in 6th, my bike has a road-speed of 5 x 12.7 mph = 63.5mph as oposed to an indicated 70ish.

This ties in with what the copper told me during a motorway trip - he compared it against his police bike's calibrated speedo and told me off for going too slowly

5500rpm would be around 70mph. Worth remembering, as is the 13 Times Table