[Gadzooks]

Does anyone know what would be the optimum speed to do in 1L Stockman on a flat 100kmh road which is what I have mostly here, to use the least fuel?
Lately I have been doing about 60kmh and the car will cruise at 80kmh but I feel that this is pushing the engine quite a lot and therefore may not be very fuel efficient. With the price of fuel going up and already a premium price here, I would like to find out the optimum speed to drive at as I hear that slower speeds use less fuel.
thanks

[hutch]

Gadzooks wrote:

Does anyone know what would be the optimum speed to do in 1L Stockman on a flat 100kmh road which is what I have mostly here, to use the least fuel?
Lately I have been doing about 60kmh and the car will cruise at 80kmh but I feel that this is pushing the engine quite a lot and therefore may not be very fuel efficient. With the price of fuel going up and already a premium price here, I would like to find out the optimum speed to drive at as I hear that slower speeds use less fuel.
thanks

Optimum speed for maximum fuel efficiency would be 0.00 km/hr

[Gadzooks]

hutch wrote:

Optimum speed for maximum fuel efficiency would be 0.00 km/hr

I tried that and its a bit limiting.

[royce]

Faster you go the more you use, the tradeoff is what your time is worth

more important is to keep a steady speed and avoid accelerating, that chews it

[laurie]

go to servo fill up until first click (in fuel nozzle)
drive normal route return at X speed.
return to servo use same pump.
fill to first click. record litres used.
repeat trip at X+10kph.
back to servo repeat fill. record. go again.\ switch to 5kph increments
soon you will know your most economical road speed for your engine, gearing, tyres ect.

[Gadzooks]

royce wrote:

Faster you go the more you use, the tradeoff is what your time is worth

more important is to keep a steady speed and avoid accelerating, that chews it

Thanks.
I think what I am asking is, if there is a speed below which no better fuel consumption can be had, so that there is no point in going that slow.
I imagine this figure would vary depending on which engine is fitted and which model of car.

[royce]

I dont think there would be as the higher your speed the more power you need to push through the air, so slower will always need less power (hence why a person can push a car but you need many horsepower to do 100km/hr) likewise I imagine the more you rev an engine the more drag it has so wastes energy that wastes fuel.

Certainly there are times where you start to lose efficiency due to over or under revving but not speed, you will have an engine speed that the engine is within its peak torque band so is humming along so may be more efficient than a lower speed and revs but I don think it would be much, I barely see a difference between a tank full of accel to 60, stop again compared to a few hundred km on the highway

[Ben_Sierra]

Air resistance is proportional to speed squared, so adding 10% to your speed adds 21% to your air resistance. Adding 50% more than double the air resistance, and double speed means 4 times the air resistance. Obviously other factors count including gear and revs and where the engine is most efficient, but at high speeds the air resistance becomes the biggest factor.

[TZAR]

most cars are designed to be the most fuel efficient at 90kph

but as Royce said get it to its point were the engine is producing the most torque (remember Torque is a measurement of turning force and turning force is what is required to move a car.) and it will use the least amount of fuel.

most 1 litres make the best torque around 3200-3500 rpm. so this is where the engine is most fuel efficient

[SuziBlu]

TZAR wrote:

most cars are designed to be the most fuel efficient at 90kph

but as Royce said get it to its point were the engine is producing the most torque (remember Torque is a measurement of turning force and turning force is what is required to move a car.) and it will use the least amount of fuel.

most 1 litres make the best torque around 3200-3500 rpm. so this is where the engine is most fuel efficient

I disagree on the 90k bit, as this has too many variables, my statesman got 9.5 liters per hundred at 130k, but dropped a bit (9.7) at 100k, open road car, poor fuel milage at 60k, but very good at 80k. (8.6) this is going via the computer.

Like Tzar says, its less about speed as revs, gearing, tyres, size and pressure all play a bit part, but, at the optimum revs, thats the ticket.

My 1.3l is best at 3500, my 1.6l is best at probably 3200.

[Gadzooks]

TZAR wrote:

most 1 litres make the best torque around 3200-3500 rpm. so this is where the engine is most fuel efficient

How could I find out when it is doing that?

[abclarke]

Gadzooks wrote:

TZAR wrote:

most 1 litres make the best torque around 3200-3500 rpm. so this is where the engine is most fuel efficient

How could I find out when it is doing that?

Look on the dash?

[royce]

abclarke wrote:

Gadzooks wrote:

TZAR wrote:

most 1 litres make the best torque around 3200-3500 rpm. so this is where the engine is most fuel efficient

How could I find out when it is doing that?

Look on the dash?

1 litre dont have a tacho

so having said that, youll need to fit a tacho to know

[Gadzooks]

abclarke wrote:

Gadzooks wrote:

TZAR wrote:

most 1 litres make the best torque around 3200-3500 rpm. so this is where the engine is most fuel efficient

How could I find out when it is doing that?

Look on the dash?

No no no. You lot must have deluxe versions. I just went out and checked and there really is no sign whatsoever of a revcounter. There is:
Speedo, petrol and temp; unless I am missing something........

[SuziBlu]

I tink you will find, unless you do a lt of miles, and do a lot of tests, that there will be very little diff tween say, 70 and 90k.

Do a tank at 70k open speed, one at 80k open speed, and one at 90k open speed, record the kilometers and the fuel to fill it.

Divide the fuel used by the kilometers run and this will give you, lph or liters per hundred kilometers.

Say you do 350 kilometers and use 35 liters of fuel, this will give you 0.10000, multiply that by 100, and you get, 10lph

I suggest to everyone to do this at every fuel fill as it is the first sign of something amiss if the fuel usage is excessive.

The best way, get used to your car, after a few fils you will know that it uses say 10lph, if this becomes 11, that is a 10% rise, and if nothing out of the ordinary, ( driving into a big head wid or something) has occurred, then its time to look at tyre pressure, plugs, leads, timing and tune as something is out of whack.

HTH

[abclarke]

royce wrote:

abclarke wrote:

Gadzooks wrote:

TZAR wrote:

most 1 litres make the best torque around 3200-3500 rpm. so this is where the engine is most fuel efficient

How could I find out when it is doing that?

Look on the dash?

1 litre dont have a tacho

so having said that, youll need to fit a tacho to know

Manual car with no tacho? Just plain strange

[TheOtherLeft]

SuziBlu wrote:

TZAR wrote:

most cars are designed to be the most fuel efficient at 90kph

but as Royce said get it to its point were the engine is producing the most torque (remember Torque is a measurement of turning force and turning force is what is required to move a car.) and it will use the least amount of fuel.

most 1 litres make the best torque around 3200-3500 rpm. so this is where the engine is most fuel efficient

I disagree on the 90k bit, as this has too many variables, my statesman got 9.5 liters per hundred at 130k, but dropped a bit (9.7) at 100k, open road car, poor fuel milage at 60k, but very good at 80k. (8.6) this is going via the computer.

Like Tzar says, its less about speed as revs, gearing, tyres, size and pressure all play a bit part, but, at the optimum revs, thats the ticket.

My 1.3l is best at 3500, my 1.6l is best at probably 3200.

Factory trip computer's are known to be inaccurate. Have you compared your trip computer with calculating your fuel efficiency manually?

[SuziBlu]

Every fuel stop.

I trust my maths skills better than a trip computer, I mentioned the trip computer for instance sake.

when i pull up at the fuel station, I look at the ks I have done, quick mental sum, and calculate my fuel needed, if its varied by much, I use a calculator.

[whincup]

i found my sierra gets the best fuel economy at 80km/h. mind you, i have a 1.3, so its different...

Edit: 215/75r15 tyres, stock engine & gears...

[Gadzooks]

royce wrote:

I dont think there would be as the higher your speed the more power you need to push through the air, so slower will always need less power

When oil hits $200 a barrel, only the rich will be able to speed.

[alien]

my sierra with 215/75r15 highway tyres and 2" lift was most efficient at 80km/hr on the speedo, so roughly 90km/hr real speed.

now i'd say 80km/hr real speed would be its best point (running 31" tyres, 1.6 efi and 5.14tcase).

[SuziBlu]

Gadzooks wrote:

royce wrote:

I dont think there would be as the higher your speed the more power you need to push through the air, so slower will always need less power

When oil hits $200 a barrel, only the rich will be able to speed.

When this happens, I will still be the same, fuel, beer, ciggys, who gives a rats the cost, you want, you pay, dont look at the price.

[JrZook]

TZAR wrote:

most cars are designed to be the most fuel efficient at 90kph

but as Royce said get it to its point were the engine is producing the most torque (remember Torque is a measurement of turning force and turning force is what is required to move a car.) and it will use the least amount of fuel.

most 1 litres make the best torque around 3200-3500 rpm. so this is where the engine is most fuel efficient

Just to clarify a bit. Peak torque of an engine and what ever RPM it is at, generally corresponds to the engine's peak volumetric efficiency.

[BertZook]

yeah you really need a tacho to know exactly..... aint weird to drive a manual car without be abble to see the rpms

but well... Ill say jsut get to your highest gear and drive with the lowest amount of RPMs that you can, or be able to stand.... keeping in mind that when you re getting to your crussing speed try to change gears with the lowest RPMs that you can too to minimize fuel..... of course youll spend a bit more time to get to the cruising speed... so is a matter to find a sweet spot between minimal consumption and how patient you are hahah

[TZAR]

don't need a tacho just some basic math

will do the math later for you to work out speed/gear/tyre/rpm info

[smiffkid]

if u driving on a run at get to a decent hill its better to drop down a gear and either slow down a bit or keep the motor revving when the motors labour / lag they use more fuel,
driving around town taking off a bit slower will also help,
that was i have learnt any way