Rpm at 120 km

peasant

@ Del2005

In principal a car gearbox is no different to that on a bicycle...a fixed amount of pedal revolutions per minutes gives you a different speed in different gears...but always the same speed in the same gears.

How many bananas you need to consume to achieve those pedal revolutions is a different story altogether

kerten

I'll throw this here.

What rev's your PETROL car doing at 120 kmph?

CiniO

Del2005 wrote: »

If you do a journey of 100km at 100km/h in an empty vehicle you'll use less fuel than doing the same journey in a fully loaded vehicle. The only way to use more fuel is to go bang more often, so if the journey is the same but you use more fuel in one you have to rev higher.

You might need to rev higher because you'll be using lower gears.
But if car does 3000rpm at 120km/h in 5th gear, then it will always do the same, no matter if car is empty, or loaded 500kg + towing 2 tonne trailer.

Yes, with big load fuel consumption will increase, but that's not due to risen revs, but risen engine load.

F.e. car can be revved to 3000rpm when stationary in neutral and be using x amount of fuel every minute.
But the same car doing 3000rpm at 120km/h on motorway up the hill with full load, will use 10 times x amount of fuel every minute of driving in such conditions.

CiniO

V8 Interceptor wrote: »

You must've near killed that poor car. I told you to hire out a TDI for the job!

Car is fine. Engine just got run in during that trip

Del2005

Henry Ford III wrote: »

Again no. The revs will be the same at any given speed. You'll need to press the accelerator down a bit more if the car is heavy - that's where the mpg suffers.

There's no correlation between rpm and speed of a vehicle. Have you never looked at the results of a dyno run? Because I've never seen a dyno output which says that at x rpm you are doing y speed, every dyno output I've seen says that at x rpm you're getting y power\torque.

Now this is obviously the complex bit. If you need to move a mass you need power, if the mass increases you'll need more power to move it. Go back to the dyno output and tell me what gives you more power in a car.

hi_im_fil

Del2005 wrote: »

There's no correlation between rpm and speed of a vehicle. Have you never looked at the results of a dyno run? Because I've never seen a dyno output which says that at x rpm you are doing y speed, every dyno output I've seen says that at x rpm you're getting y power\torque.

Now this is obviously the complex bit. If you need to move a mass you need power, if the mass increases you'll need more power to move it. Go back to the dyno output and tell me what gives you more power in a car.

Honestly I’m not sure if you’re just trolling...
In a manual gearbox it is a direct correlation between engine rpm and wheel speed (for a given gear). That’s just how manual gearbox works. It is not some infinitely variable gear. It’s a few fixed ratio gear sets.

It’s not just rpm that gives you more power. You have throttle position too. Open the throttle a little bit and you’ll get less power than if it was fully pressed. That’s what happens when you have a car more loaded, you press the accelerator pedal a bit more. This means the engine produces a bit more power at the same rpm. There are other factors such as air/fuel ratio, ignition timing, boost pressure etc that can effect engine power also, but that’s irrelevant for the case we’re talking about here

Kenny Logins

Del2005 wrote: »

There's no correlation between rpm and speed of a vehicle. Have you never looked at the results of a dyno run? Because I've never seen a dyno output which says that at x rpm you are doing y speed, every dyno output I've seen says that at x rpm you're getting y power\torque.

Now this is obviously the complex bit. If you need to move a mass you need power, if the mass increases you'll need more power to move it. Go back to the dyno output and tell me what gives you more power in a car.

Where exactly is the link broken - A slipping clutch? Wheels losing traction??

Tacitus Kilgore

Del2005 wrote: »

There's no correlation between rpm and speed of a vehicle. Have you never looked at the results of a dyno run? Because I've never seen a dyno output which says that at x rpm you are doing y speed, every dyno output I've seen says that at x rpm you're getting y power\torque.

Now this is obviously the complex bit. If you need to move a mass you need power, if the mass increases you'll need more power to move it. Go back to the dyno output and tell me what gives you more power in a car.

You are correct that you will need more power to move more mass, but you do realise you can have variable power/torque levels at variable rpm?

I.e - you could be at 5000rpm with low throttle input and make the exact same power & torque as at 2500rpm with a higher throttle input.

Henry Ford III

Del2005 wrote: »

There's no correlation between rpm and speed of a vehicle. Have you never looked at the results of a dyno run? Because I've never seen a dyno output which says that at x rpm you are doing y speed, every dyno output I've seen says that at x rpm you're getting y power\torque.

Now this is obviously the complex bit. If you need to move a mass you need power, if the mass increases you'll need more power to move it. Go back to the dyno output and tell me what gives you more power in a car.

Again no.

Gearing in a manual car is fixed. Engine transmits power and torque through a gearbox and clutch. Say 2000rpm at 120kph. It makes no difference to the rpm how heavily loaded the car is. It just means that the driver will press a bit harder on the accelerator to maintain that same speed. That will burn extra fuel.

Consider an unloaded car going down a hill in top gear at 120kph. It'll be doing 2000rpm even with minimal/no throttle. Fuel consumption will be very low.

Now consider the same car going up that hill whilst fully loaded. It'll still be in top gear and will still be pulling 2000rpm.

The difference is that to maintain that speed the driver will need to press the accelerator down quite a bit, and this burns quite a bit of fuel.

No simpler way of explaining it.

zilog_jones

Del2005 wrote: »

There's no correlation between rpm and speed of a vehicle. Have you never looked at the results of a dyno run? Because I've never seen a dyno output which says that at x rpm you are doing y speed, every dyno output I've seen says that at x rpm you're getting y power\torque.

On a dyno run you're looking for peak power and torque - road speed is not relevant.

In anything that's not CVT (like your GS), you have fixed ratios which have a direct correspondence to the road speed. If you want to change what engine speed you're doing for a given gear and road speed, you have to change the gearbox.

My Prius usually does somewhere around 1,800 to 2,300 RPM at 120 km/h, but again it's a continuously variable transmission so the engine speed depends on load at the time (e.g. climbing a hill will increase engine speed).

grogi

Del2005 wrote: »

No its not. A fully loaded car with a roof box will need more power to reach motorway speed than an empty one with no roof box.

Sure

So it'll have to rev highrr to reach a given speed, air resistance is the biggest issue when travelling fast.

No. As long as the required power (exp. 30 kW) is smaller than the maximum power the car can deliver with given rpm (exp. 50 kW @ 3000 rpm), the same rpm can be maintained.

The engine can output 1 kW, 10 kW and 50 kW at the same rotation speed.

Wibbs

Only yesterday I was on a motorway and thought of this thread and mine's doing around 4500 at 120Kph.

Tacitus Kilgore

Wibbs wrote: »

Only yesterday I was on a motorway and thought of this thread and mine's doing around 4500 at 120Kph.

Ya but how hard were you pressing the pedal? :pac:

Tazzimus

Wibbs wrote: »

Only yesterday I was on a motorway and thought of this thread and mine's doing around 4500 at 120Kph.

Ah but was it loaded with canoes into a strong headwind or was it an empty car, clearly the RPM will differ due to these fancy manual gearboxes with gear ratios than can change on the fly.

Idbatterim

PaulKK wrote: »

This is interesting, I previously thought my 2.0 diesel was pretty good at about 1900rpm at 120km/hr, but I was driving a Chevy Impala a couple of weeks ago (3.6 v6) and it was doing about 1500rpm at 75mph. Never saw a petrol car with such low rpm at those speeds.

In fairness, the gearbox left a lot to be desired.

Pretty impressive. Mine does 1500rpm at 100 kmph. I can’t stand motorway driving in smaller cars with revs through the roof!

jimgoose

Leonard Hofstadter wrote: »

...As an aside, I find modern diesels to be hopelessly overgeared, I drove my Dad's 2.0 diesel Avensis a couple of weeks ago and it has no power whatsoever in sixth gear below 100 km/h. Even low powered petrols will pull away from as little as 50 km/h in top gear (not quickly admittedly, but they don't have that feeling of no power at all like a diesel does when the turbo is off boost).

Hmm. My 2011 1.6 Focus TDCi 110 (five gears) is like a small, zippy artic at around 1,200 RPM. 120k is seen to in fifth at around 2,300 RPM, IIRC.

H3llR4iser

As it's already been said, there isn't a single "rpm value" that should be expected for a given speed, it depends on gear ratios, engine type and a lot of other, built-in, factors. That said, somewhere around 4000 rpm is a very common value for most 4-cylinders, NA petrol cars of "common" displacements (between 1.0 and 2.0 liters, essentially).

The reason is simple - turns out the engineers designing the engine-transmission groups usually know what they're doing and set things up so that in the highest gear at motorway cruising speeds, the engine is turning at close to peak efficiency and torque. This engineering choice has a dual effect: it lowers the fuel consumption and keeps the engine in a reactive state, lessening the need for the driver to change gears; If you're traveling at 120-130kph in a decently powerful petrol engine, suddenly flooring the accelerator will still result in an appreciable "lunge" forward (obviously, more "appreciable" say in a BMW 320i than in a 1.2 Polo ).

Contrary to popular believ, lowering the rpm in such case won't necessarily result in lower fuel consumption - quite the opposite in fact; When the engine is running outside of its peak torque band, it will struggle to generate enough "push" and require more fuel - that's also why consupmtion skyrockets when the engine is actually worked towards the red line.

As an example, think about lifting a heavy barbell during a bench press: the further down you lower it, the more effort it requires for you to push it back up - and there will be a "point of no return" where you simply can't apply enough force to lift the weight. This is due to the geometry of your bones and muscles - in a very similar way the characteristics of an engine will give it an "ideal torque band".

The same concept is valid for diesel and turbocharged engines as well as different displacement ones - and that's why different types of engines will "cruise" at different RPMs in top gear.

sligojoek

2006 Astraa 1.4 petrol. 3700 RPM @ 120 Kmph this morning 3000 = 100

Another thing re. a fully loaded car is that you'll be spending longer in lower gears burning fuel to get up to that speed than you would with an empty car.

Alun

Idbatterim wrote: »

Pretty impressive. Mine does 1500rpm at 100 kmph. I can’t stand motorway driving in smaller cars with revs through the roof!

My " smaller car" is running at just under 2500rpm at 120km/h and around 2000rpm at 100km/h. Nissan 1.2 petrol in 6th gear.

V8 Interceptor

Idbatterim wrote: »

Pretty impressive. Mine does 1500rpm at 100 kmph. I can’t stand motorway driving in smaller cars with revs through the roof!

I was like that for a long time. Went from petrol to diesel and couldn't understand why lads preferred petrol. Got a bit bored after a while and went back to liking a high revving petrol. Its cyclical for me

pm.

1.6x1000 at 120kph Audi A4 3.0 TDI

Esel

pm. wrote: »

1.6x1000 at 120kph Audi A4 3.0 TDI

Why not just say 1600 instead of 1.6x1000?

Edit: It's km/h, not kph.

Noveight

Iirc 3000rpm in 5th gear will get you 120km/h for me. Corolla 1.4D4D.

ShadowHearth

Checked last night.

1.8 petrol turbo

2100rpm when at 100km/h
2600rpm when at 120km/h

Henry Ford III

I checked last night. 6th gear 120kph. 2000rpm on the flat. Ditto uphill, downhill, with the wind and against it, empty and fully loaded.

CiniO

Henry Ford III wrote: »

I checked last night. 6th gear 120kph. 2000rpm on the flat. Ditto uphill, downhill, with the wind and against it, empty and fully loaded.

Impossible.
Didn't you hear more power more rpm no matter the speed ? :D:D:D:D:D

V8 Interceptor

Asking lads on here, do you generally like a low revving torquey diesel or do you mind having a relatively small petrol revving fairly hard at Motorway speeds? Perhaps you prefer the latter?

(Henry, which Fiat do you have?)

Tazzimus

V8 Interceptor wrote: »

Asking lads on here, do you generally like a low revving torquey diesel or do you mind having a relatively small petrol revving fairly hard at Motorway speeds? Perhaps you prefer the latter?

(Henry, which Fiat do you have?)

I have both, so both

2.2 Mazda 6 Sport
DC2 Type R

Type R sits somewhere around the 5k mark on the motorway with the current gearing.

fancy pigeon

The 607 does 2.5k rpm at 120kmh. Can't remember what it is at 100kmh... 406 was dead handy, 5th gear at 2k rpm was 80kmh, 2.5k rpm was 100 kmh and 3k rpm was 120kmh. 4th gear at 2k rpm was an indicated 40mph

Must try the Z later and see what it does at motorway speeds...

Henry Ford III

V8 Interceptor wrote: »

...(Henry, which Fiat do you have?)

A Fiat Focus

Tazzimus

Henry Ford III wrote: »

A Fiat Focus

Rare enough yoke

V8 Interceptor

Henry Ford III wrote: »

A Fiat Focus

Sorry, misread your post. You said 'on the flat'. I read it as 'in the Fiat!'

Specsavers appointment made...

Wibbs

Tazzimus wrote: »

DC2 Type R

Type R sits somewhere around the 5k mark on the motorway with the current gearing.

96 spec T? They had a shorter final gear IIRC. My 98 is more like 4500. Still buzzy as feck for those not used to it.

I generally prefer high rev engines, as I'd be more a HP than torque kinda chap and prefer working for it as it were, though I do little enough motorway driving.

Tazzimus

Wibbs wrote: »

96 spec T? They had a shorter final gear IIRC. My 98 is more like 4500. Still buzzy as feck for those not used to it.

I generally prefer high rev engines, as I'd be more a HP than torque kinda chap and prefer working for it as it were, though I do little enough motorway driving.

Yup.

They had a longer FD from what I can remember (4.4 I think) but I have a mongrel of a gearbox in mine with a 4.7 FD so it sits higher in the revs at 120 ish

CJhaughey

2.2 I-Dtec 2200 @ 120 in 6th.

cena

I started this thread talking about a petrol car and it went in a different direction talking about diesel.

Tazzimus

cena wrote: »

I started this thread talking about a petrol car and it went in a different direction talking about diesel.

It's a mix actually.

Fuel doesn't matter as it's gearing/revs at a certain speed that we're all discussing anyway.

SweetCaliber

2012 1.2 Polo TDI 2500rpm @ 120km/h. Good little car to go plenty of torque.

Odyssey 2005

1500rpm @120 kph on cruise control

demanufactured

cena wrote: »

I started this thread talking about a petrol car and it went in a different direction talking about diesel.

Well doesn't that bate banagher

route66

Tazzimus wrote: »

It's a mix actually.

Fuel doesn't matter as it's gearing/revs at a certain speed that we're all discussing anyway.

Well it does really. Diesel has natural lubrication and this can lead to slippage - and therefore varying revs in a given gear at a fixed speed. 4-speed drivetrains are the worst.

Likewise with EVs. A complex contra-flux -inherent in motors but not engines - can induce reverberations in the propshaft resulting in a CVT-type experience. Carbon props suffer more than titanium ones - this is why the Alfa Romeo Giulia Quadrifoglio will never have an electric drive option.

Tacitus Kilgore

route66 wrote: »

Well it does really. Diesel has natural lubrication and this can lead to slippage - and therefore varying revs in a given gear at a fixed speed. 4-speed drivetrains are the worst.

Intriguing, can you go into this a little more please?

jochenstacker

Tacitus Kilgore wrote: »

Intriguing, can you go into this a little more please?

I believe it has something to do with the Einsteinian curvature of space time, causing solid metal gears to flux in and out of reality.
This causes them to skip a few teeth every now and then. How many depends on the load on the gearbox, since more load equals more mass equals more gravity, therefore accentuating the space time curve.
It's the equivalent of levering the teeth of the gearbox away from each other with a bloody great crowbar.
That or drugs. Definitely drugs.
Or a seriously knackered gearbox and slipping clutch.

Bruthal

Del2005 wrote: »

If you do a journey of 100km at 100km/h in an empty vehicle you'll use less fuel than doing the same journey in a fully loaded vehicle. The only way to use more fuel is to go bang more often, so if the journey is the same but you use more fuel in one you have to rev higher.

More fuel is used because to maintain the same RPM with a heavier car load, each piston needs more fuel/air per cycle, than the lighter loaded car, to maintain the same RPM

Engine RPM/Wheel RPM is fixed for each gear, therefore if a car does 120kph at 4000rpm in 5th, this is fixed no matter what the car loading is, unless the clutch is slipping.

If what you say is true, then all energy problems are over, as that would mean an engine running a generator at 50hz wont ever need any extra fuel for a heavier electrical load because it doesnt need any if its revs remain the same. The reality is however, that as the loading increases, the rpm will reduce unless more fuel is injected.

jochenstacker

Anyway,back to rpm.
When I drive the Duster (1.6 petrol) it sits at 4000 rpm at 120 km/h. To me that just feels wrong, but seems to be the norm for many petrol cars. But I don't fancy it for long Autobahn cruises.
My Cmax, 2 liter diesel with 6 speed gearbox, 136 hp, sits at 2500 rpm when doing 150 km/h, it's just cruising along at that speed, it's nice and relaxed.
Great mile muncher, not as good as an Audi maybe, but cost me less than €3k to buy.

Odyssey 2005

cena wrote: »

I started this thread talking about a petrol car and it went in a different direction talking about diesel.

Better not mention lekky so. 120kmh 0 rpm

jochenstacker

Odyssey 2005 wrote: »

Better not mention lekky so. 120kmh 0 rpm

Well, i presume the motor will have an rpm, so that would be quite interesting.
Especially since most do not have gears, so you're doing standstill to top speed in the one "gear", for want of a better word.

Odyssey 2005

jochenstacker wrote: »

Well, i presume the motor will have an rpm, so that would be quite interesting.
Especially since most do not have gears, so you're doing standstill to top speed in the one "gear", for want of a better word.

Not burning fossil fuel,how's that.?

jochenstacker

Odyssey 2005 wrote: »

jochenstacker wrote: »

Well, i presume the motor will have an rpm, so that would be quite interesting.
Especially since most do not have gears, so you're doing standstill to top speed in the one "gear", for want of a better word.

Not burning fossil fuel,how's that.?

Well, if I remember my mechanics correctly, there is a spinning shaft in an electro motor.
If you count the revolutions of this shaft over the course of one minute, you get a figure called RPM, or Revolutions Per Minute.
So one wonders how many of these so called "RPM" the shaft contained within the electric motor completes in order to propel the vehicle to a velocity whereby it may travel a distance of 120 of your finest, organic, free-range kilometres over the course of 60 minutes.

Or:
For sumthink to turn, sumthink has to turn, innit?

route66

jochenstacker wrote: »

Well, if I remember my mechanics correctly, there is a spinning shaft in an electro motor.
If you count the revolutions of this shaft over the course of one minute, you get a figure called RPM, or Revolutions Per Minute.
So one wonders how many of these so called "RPM" the shaft contained within the electric motor completes in order to propel the vehicle to a velocity whereby it may travel a distance of 120 of your finest, organic, free-range kilometres over the course of 60 minutes.

Or:
For sumthink to turn, sumthink has to turn, innit?

You're wrong. Everybody knows electric motors don't turn and therefore don't "do" revs. They work on the principle of magnets and they just push the car along - I'm guessing there must be some metal in the road structure that they push against to produce forward momentum.

There are lots of other examples of this - e.g. the motor in the windscreen wipers. When was the last time you saw your wipers clean the screen by rotating? Again, there must be magnets in the mechanism that "push" the blade across the screen and then these reverse to bring it back, and so on and so forth.