Why are RPMs shown rather than torque?

[Shadows]

Fixed that for you. Engineering requires precise language

If that is so, then it should be spelled "approximately".

[LBD]

Fixed that for you. Engineering requires precise language

yes okay, within the tolerances of general public understanding then...but you get the drift

[jonbuoy]

What you say is true and strain gauges would measure the twist very well. However, where are you going to mount it in the drive train so that it doesn't have to go round and round?
The signals that the measuring devices produce are very small so that commutators/slip rings etc screw them up completely.

Its not that hard, send power through the slip ring and you can put some electronics in there, convert it to something you can superimpose on top of the power supply and sniff it off the other end.

[Bass]

Its not that hard, send power through the slip ring and you can put some electronics in there, convert it to something you can superimpose on top of the power supply and sniff it off the other end.

I thought about putting the amplifier into the rotating mass and yes, that would work. It's still a pretty rigorous environment and not one that I'd care to design for.
I never said it was impossible - I've seen it done - my point was that it's not easy.

[marty]

Close but no cigar. .

Works on 5000hp/7000ftlb aircraft engines so I'm sure would be fine on a 50hp bike.

Interestingly, aircraft piston engines are not measured in torque - power is measured in manifold pressure (or vacuum as the case may be depending on the engine) - turbine engines are measured in torque. Some by shaft twist, some by a clever means of helical run gears and pistons that increase an indicator oil pressure as torque comes on. That psi is converted to a torque reading (or just read in psi as is the case in smaller (750hp) engines)

[Swoop]

May sound like a damn silly question on it's own but the real question is why do both cars and bikes show RPMs as a read-out as opposed to torque?

Kiwi drivers' cant work out how to use their fucking indicators, let alone giving them something else to think about.

Sorry, but on a serious note, have you ever seen a deaf person driving a manual without a rev-counter

A deaf mate (some years ago) rode his motorcycle very happily, by feeling when to change gears through his butt. No need for a rev counter.

[CHR1S]

A MAP/Vacuum gauge is handy with the loss in density you get with altitude, dunno why they put one in a sh*tbox Camira I once had..

[marty]

you really won't start to see a reduction in performance until about 4500-5000', or when you are at WOT and still climbing. To see a reduction in MAP in a climb you woud have to lock off the throttle at your starting altitude, then climb, and not touch the throttle - you would see a drop then of about 1"/1000'.

I fly a normally aspirated aircraft regularly to 12000' - WOT height is usually around 5000', at 25". Continuing a climb means at 12k I am only at 18-19" - a pretty serious drop in performance. The same engine with a turbo will hold 30" all the way to 16000' Of course, the turbo engine only has 1/2 the life of the normally aspirated, but it's a heap more fun

[scumdog]

A MAP/Vacuum gauge is handy with the loss in density you get with altitude, dunno why they put one in a sh*tbox Camira I once had..

An excellent tuning/economy indicator.

[BMWST?]

its actually quite simple isnt it?
I know for example that my car develops maximum torque at 4000 rpm......hence if i want max performance i manipulate the gears to get the rev counter at about 3500.....
On the bike i just use the butt o meter..if there doesnt seem to be the required urge i just change down a gear,its so easy on a bike.If i think i will require more urge than i have NOW i just blip down a gear

[BMWST?]

An excellent tuning/economy indicator.

in my car i call it the guzzle o meter its marked in Litres/ per 100 k(from 0 to about 40)

[Paul in NZ]

Look - really shouldnt post this because I'm sure someone will get all upset... and frankly I'm not bothered either way.

RPM's are used because its always been historically availiable on 'sporting' vehicles. You can probably run your GSXR1TRIPLEHORNET thingie at max rpm nearly all day now without it imploding into a heap of molten slag as the engine management system wont let that happen. Just the same way it modifies engine output in 1st gear to stop you killing yourself. This has not always been the case.

If you look at (just as an example) the 1980 Moto Guzzi LeMans in my shed. It has an orange bit on the tacho. That means you can rev here quite often, have fun but dont over do it. After the orange bit is a red bit which means you better not rev to here too often and if you do be prepared to spend big $$ because there IS NO rev limiter or anything else except for physics. ie open the throttle all the way and it will destroy itself happily. The two colours were widely understood and all is happy.

Go back 10 years to my 1970 Triumph twin. It has the tach option fitted. A good old Smiths 0 to 10,000 rpm jobbie. There is no red line or any other mark at all but trust me, even thinking about a number like (say) 8,000 will see you looking at a big hole in the engine and wondering how you will explain that to the wife.. That tach was fitted to heaps of different vehicles so marking it with a red line was not done cos it differed.

As you go back in time the expectation of the maker on the ability and knowledge of the operator has changed. Owners of sporting machinery were expected to have a more advanced knowledge of all this.

Today the makers assume nothing and try to make bloody sure you cant blow it up (at least until the warrenty runs out) so you have leds, lights, dials and whistles and warnings galore.

Seriously - you are on the right track but try to learn this shit faster before your knowledge curve crosses your speed curve and you recieve a nasty accident...

Oh - and just ride the bloody thing - it can go faster than you can calculate shit.

[johan]

This is an interesting topic.

When accelerating, I try to to keep the RPMs between max torque and max power, which would be between ~7500-10,000 on the 998.
(these bikes seems to be tuned to produce most torque close to max power)

The ratio between 5th and 6th gear is very close so I shift earlier between those higher gears.

2nd gear spins up so quickly I sometimes hit the revlimiter, so I try to short shift from second to third.
(the electronic hard revlimiter is at 11.500 which is a really bad place to be for this engine, and it will throw you over the bars)
First gear is useless.
From 3rd to 4th to 5th I have the shift lights set to 9500.

Any reason I should change this habit?

Is there a link to this other site where they were discussing this, I'd like to learn more.

cheers

[The Stranger:Me]

having just read a thread from another forum of optimum places to change up (in RPM terms) it seems to strongly allude that change up points are best selected for the points where torque is strongest (calculated both in the current gear and the next gear).

Do you have a link to the other thread you mention please? I'd be interested to see their proof/conclusions.

I can dig it on say VTwin, but not so sure on an IL4.
Gears convert revs to torque. I would have thought that wringing out in first to drop the bike in second even if after the torque band is probably still a winner as you have more revs to convert to torque through the gearbox.

Either way, that's why I select a bike that develops it's torque high in the rev range, then you get the best of both worlds peak engine torque and peak torque as a result of the gear box too.

[White trash]

This is an interesting topic.

When accelerating, I try to to keep the RPMs between max torque and max power, which would be between ~7500-10,000 on the 998.
(these bikes seems to be tuned to produce most torque close to max power)

The ratio between 5th and 6th gear is very close so I shift earlier between those higher gears.

2nd gear spins up so quickly I sometimes hit the revlimiter, so I try to short shift from second to third.
(the electronic hard revlimiter is at 11.500 which is a really bad place to be for this engine, and it will throw you over the bars)
First gear is useless.
From 3rd to 4th to 5th I have the shift lights set to 9500.

Any reason I should change this habit?

Is there a link to this other site where they were discussing this, I'd like to learn more.

cheers

That seems to be a shitload to remember mate.

Buy a Japper. K7 GSXR thousand for example. Little red bit starts at 13.5, set the shift light to 13. Change gear when it flashes. Simple as