Why are RPMs shown rather than torque?

[The Pastor]

isnt torque a constant?

at full throttle you make X talks

at half you make 0.5X talks?

[johan]

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

Yes, maybe I'm doing it wrong, them Gixxers always seems to go faster than my trusty old one.

[Deano]

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

You have a different tack to Drew then ?

He simply loads up the gear lever and waits for the limiter to kick in, hey presto !

[White trash]

He simply loads up the gear lever and waits for the limiter to kick in, hey presto !

Fuck that! My yoshi computer had about 1000-1500 rpm of over rev built into it. Wouldn't wanna be repeatedly thrashing it to 15K through every gear.

No mechanical sympathy whatsoever that cunt........

[Maki]

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?

Most lay people, such as myself, look to RPM as an indicator of "fast" (as in higher means "faster" in both terms of acceleration and cruising speed - when gear ratio taken into account). However, 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).

So, if acceleration is best judged by torque, why do bikes/ cars not have a torque read-out (either in addition to, or instead of, RPMs)?

Are bikes and cars just working on old technology instrumentation read-outs? And, if a dyno machine can measure torque at any point, why can't a modern automobile?

Lots of questions but I am genuinely interested in the reason behind why torque is not displayed.

Because there is no point. The more gas you give it, the more torque it puts out. The rpm where your engine puts out max torque should be stated in your owners manual.

Acceleration is not best judged by torque. Horsepower is what you want if you want to accelerate fast. With the right gearing/leverage I can produce more torque with my little finger than a big block V8 can at the crankshaft. The problem is that the torque produced by my little finger is very slow and produces little energy while the big block engine might be spinning at thousands of rpm and thereby putting out a lot of energy/horsepower/kilowatts.

[LBD]

isnt torque a constant?

No!...I I thought you would know that...

[schrodingers cat]

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

If the technology is scaleable in a linear fashion then I'm sure it would. My point is that there are other ways to do it more common for this application

Also note that constants are fairly easy to measure. Transiants not so

[marty]

large turbine engines can have quite rapid torque fluctuations - from zero to 3800ftlbs in say 3 seconds. the torque meter seems to keep up.

[Cloggy]

isnt torque a constant?

Nope,
The formula is horsepower = torque x rpm / 5252
Torque is measured in pound-feet in this equation, not newton-metres
Interesting bit about this is that at 5252 rpm, horsepower and torque figures are equal.

[LBD]

large turbine engines can have quite rapid torque fluctuations - from zero to 3800ftlbs in say 3 seconds. the torque meter seems to keep up.

And a reciprocating steam engine produces maximum torque at.....Zero RPM

[CHR1S]

If the technology is scaleable in a linear fashion then I'm sure it would. My point is that there are other ways to do it more common for this application

Also note that constants are fairly easy to measure. Transiants not so

Not really cutting edge technology, been around for a long time in aircratft! It's relatively straight forward when you have an axial shaft (no idea how you'd set it up on your conventional 4 banger) with a power turbine at one end and a load at the other, a reference shaft, measure the degree of twist and you have an instantanious unit to indicate torque. Sweet set up for $3 million dollar engine..it get's very expensive if you get it wrong

So totally agree wth ya, me tacho can do the job for now!

[IdunBrokdItAgin]

So, apart from the weird KBer random replies telling me that I should be riding a scooter and that I will have a nasty crash because my speed curve is higher than my knowledge curve (WTF? - get over yourselves - the question was about instrumentation readouts), what I am taking from the replies is that some aircraft engines give out this basis already but it would be un-economical to introduce this to automobiles.

This maybe a thing that we see on automobiles of the future though (rather than RPMs as an indication point of when something may occur - to an instrument showing when something actually occurs)?

Also, seems to me that a lot of riders do not fully understand torque at all (not saying that i do though). This thread was intended to answer a late night question I had - seems to have done that, and educated myself and a few other people at the same time.

Thanks for all the replies people - it has been very enlightening.

[onearmedbandit]

Haven't read the thread entirely, so someone may have already stated what I'm about to, and that is marketing. Remember when the R6 came out with it's stratospheric rev limit? Which turned out to be BS anyway. But it worked, as many people made the decision to buy one based partly on how high it could rev. Making a bike that rev's slightly higher than the competition or last years models helps sell your product. We all know torque is improved (generally) year to year, same with power. But we want speedo's that go past 300 and rev counters that sweep through massive arcs.

[imdying]

Would be easy and cheap for the OEM to include. Run a bike up on a dyno, get the torque curves for sufficient throttle positions, build a map from that, stick any type of gauge you like on that displays the torque output for the motor at the given TPS/RPM. It's not likely it actually has to measure the torque for what the OP is talking about. Hell even the figure isn't really relevant, it could even just show a percentage of maximum torque. They only need to dyno a sample of production engines to build the 'map', all of those bikes are likely to be within a few percent at any given TPS/RPM.

[bogan]

Would be easy and cheap for the OEM to include. Run a bike up on a dyno, get the torque curves for sufficient throttle positions, build a map from that, stick any type of gauge you like on that displays the torque output for the motor at the given TPS/RPM. It's not likely it actually has to measure the torque for what the OP is talking about. Hell even the figure isn't really relevant, it could even just show a percentage of maximum torque. They only need to dyno a sample of production engines to build the 'map', all of those bikes are likely to be within a few percent at any given TPS/RPM.

and when you put an aftermarket exhaust system on it? or if you put enough stickers on the fairings? the increased torque would need to be measured and added otherwise the system would be pretty useless.