Just a curious question regarding engine and transmissions

Hi Folks!

I know some of you here are a lot more techincally inclined then I am regarding engines and stuff, but I am always trying to learn!

I was just curious about something I've noticed between my car and my bike. My Car has a 2.5L i4 in it, and my Rocket has a 2.3L i3 in int. When I drive my car, which weighs a huge amount compared to my bike, why is it able to cruise at a lot lower RPM then my bike?

For example... The car Idles at 500RPM, but my Honda Motorcycle with a V4 has to idle at 1100rpm, and the rocket at 800... why Can't they idle lower? Is it something to do with heat or fuel consumption?

Second example is on my Rocket in 5th gear at 80kph I am doing 2000rpm, but my car does 1400-1500rpm in 5th gear at the same speed. With the car being heavier, wouldnt it require a higher RPM To keep it from being in such a low power band?

I guess the question I Am really asking is why do engines of a similar size (2.3 vs 2.5) and weights between my bikes 750lbs vs my cars 2500+lbs why does the car have a much lower RPM to cruise and idle vs a motorcycle? I know that an Inline 4 can rev higher and faster but in this case, it has the same amount of gears but can cruise at a much, much lower RPM then my bike with the same size motor.

Hope that makes sense

Idle speed is much due to the difference in the rotary mass. Car engines have big heavy flywheels that retain a lot of momentum, allowing it to keep running at lower RPMs.

The difference in RPMs in the same gears in the difference vehicles is due to the different gear ratios in the different gearboxes.

Sorry if I am explaining clumsily, my brain isn't working properly at the moment.

You have hit on one of my gripes about the RIII. It needs a taller top gear so that instead of cruising at 75mph (real speed) at 3,000RPM, it should be doing it at 2,400rpm - or even less. The T'bird, and even HDs, cruise at 3,000RPM at 75MPH, BUT (and it is a big but) they have 33% fewer bangs so the perceived engine speed is much lower (like about 2,000RPM). The RIII would have no problems cruising at the lower revs and it would get better fuel economy, have less wear on the engine, and be a lot more comfortable on long trips.

C'mon Triumph - give us a very tall 6th gear!!!!

idk said:

You have hit on one of my gripes about the RIII. It needs a taller top gear so that instead of cruising at 75mph (real speed) at 3,000RPM, it should be doing it at 2,400rpm - or even less. The T'bird, and even HDs, cruise at 3,000RPM at 75MPH, BUT (and it is a big but) they have 33% fewer bangs so the perceived engine speed is much lower (like about 2,000RPM). The RIII would have no problems cruising at the lower revs and it would get better fuel economy, have less wear on the engine, and be a lot more comfortable on long trips.

C'mon Triumph - give us a very tall 6th gear!!!!

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Yeah agreed. I asked for this on the feedback form but as always, no response from triumph!

they have lower gears because we want the power and don't give a **** about mileage
extra gear = extra weight

On an 800lb bike with an unspecified amount of rider (let's face it, few of us have the build of a racing snake) I doubt the addition of 1 set of gears and linkages would make much difference

idk said:

C'mon Triumph - give us a very tall 6th gear!!!!

Click to expand...

Or (heresy alert) a variable rate torque converter with lock up overdrive. And whilst we're at it - a Diesel.

Bad boy @barbagris

Maybe there's not enough space for a 6th gear. Maybe if they made the other 5 gears a bit smaller, they'd get crushed by the torque, which the T-Bird doesn't have.

A selection of differing rear drive ratios would be great if feasable