Fuel Consumption Tips

[stimps]

Ive idled around in 5th gear alot in my R32, never a problem, in fact ive done it in most of my cars. obviously its not the revs that "strip" 5th, its the torque, so when you need to accelerate in 5th at 60km/hr, drop it back to 4th. No brainer really.

I agree you dont need to run your turbo time alot, in fact hardly at all. Only if you have been a nut right up to your front door.

and if you wanna save more fuel? then get a TEN LED mixture meter and put it right in front of your eyes on the steering column. (mine is there, with a dimmer knob under the dash so i can turn the brightness down at night) and you will be suprised how much you can change your driving to save fuel. You can get just the right amount of throttle to drive up to speed, without putting the mixture into rich, "closed loop" zone, keeping it in open loop, which is WAY economical. While cruising down the highway on cruise control, it will of course be in open loop, saving fuel, which is why highway driving is the best.

and yeah give your car a TUNE

im forever fiddling with the settings to find the sweet spot and get the right comprimise between performance and economy.

[Birds]

With R34's instead of turning your air con on you can use free heat just by pushing the mode button or if u need more press the fan speed up and it will pump out heat to the temperature set by the knob. Fuel economy wise when you turn a/c on you can notice the cars being drained of power and it raises your idle rpm.

Using your head lights is another power drainer and so is the car stereo (if aftermarket) as the electronics are part of the engine due to the alternator

Who uses the air con with heater anyway? Unless you're trying to demist windows every car will work its heater without the air con

Just a question. Using your mountain bike theory say you are in the highest gear and yes it is hard to gain speed but to keep that speed its generally not hard at all. Soon as you try gain a bit of speed it's a helluva lot easier to drop down a few gears obviously. Thought this would be similar with the car if it's basically only rolling or have the smallest bit of throttle to keep it going their shouldn't be high stresses on anything in the vehicle? Also due to the fact that there is next to no engine braking at these speeds the drive train doesn't get that more sudden jolt if you happen to take your foot off the accelerator quickly (albeit this seems like a very minor unless your in real low gears)

Try taking off in the tallest gear from a dead start though. It'll be very, very difficult at first and the more speed you build up the easier it is for you to maintain that speed. In fact, when you try to take off the metal of the pedal arms will actually flex a little bit (might not be noticeable to you while doing it). The point of the mountain bike theory is just to give you an example of how forces increase and decrease when you introduce gears to the equation - the variable of momentum is also introduced and something has to take up the force (either the gears or the thing driving them, and given engines are usually stronger than gears, gearboxes tend to go first).

When you talk about engine braking I think you are mistaking pressures on the engine for pressure exerted on drivetrain. The faster a vehicle is moving, the more momentum you have assisting the engine to make the gearbox turn from the other side of it (output side). If the vehicle is stationary or going very slow, it has little to no momentum to help the engine turn 5th gear from the output side, therefore all pressure is coming from the input side of the gearbox = 5th gear inclined to blow.

Also note that the taller the gear ratio, the smaller the driven gear inside the gearbox is. 1st seldom blows up (unless you're doing burnouts or thrashing it) because it's a large gear being driven by a small gear, as opposed to 5th which is a small gear being driven by a large gear. 4th rarely ever blows because 4th is usually a 1:1 ratio and therefore no reduction is being made by the gearbox, therefore no extra pressure in the driveline for it to take up.

[mad082]

Just a question. Using your mountain bike theory say you are in the highest gear and yes it is hard to gain speed but to keep that speed its generally not hard at all. Soon as you try gain a bit of speed it's a helluva lot easier to drop down a few gears obviously. Thought this would be similar with the car if it's basically only rolling or have the smallest bit of throttle to keep it going their shouldn't be high stresses on anything in the vehicle? Also due to the fact that there is next to no engine braking at these speeds the drive train doesn't get that more sudden jolt if you happen to take your foot off the accelerator quickly (albeit this seems like a very minor unless your in real low gears)

only if the ground is flat. add in to the mix even the slightest of hills (or even a strong headwind) and it will take more effort to stay at a steady speed in the taller gear than to drop back a gew gears.

as for the engine breaking bit, if you are very low in the revs, you may have more stress on the drivetrain or engine because the ecu is trying to keep the engine turning over, so it is injecting fuel to try and keep the revs up while the wheels are trying to slow the engine down, so the forces are working against each other in a way.

and to what birds said about 5th gear being the weakest, something else he didn't explain that also applies to why 5th gear blows because of the use of 1 small gear and 1 large yet other gears don't, is that the lower gears have less of a speed change in the gear that they are trying to turn so the overall resistance they are dealing with when trying to accelerate the car is much less. in 5th gear you have the fact that 1 small increase in engine speed is a much bigger increase in car speed, plus the fact that the faster you go the more wind resistance you have.

[Marcus89]

Ah ok i get ya. Didn't realise the gear's actually got smaller as you moved up in gearchanges heard you saying that 4th was 1:1 and what not but still was unsure. Thanks for the explanation

[mad082]

yeah that is how the gears work. it is just like on a bike (but a hell of a lot more complicated)

this is a pic of the inside of a gearbox. i won't go fully into the technical workings of the gearbox, but basically the shaft on the left comes from the engine then goes out to the tailshaft and it is 2 pieces. the shaft on the right is the layshaft and it it doesn't actually exit the gearbox at all.

[Birds]

There really is a ton of physics involved in it and without giving you a years worth of lectures, it's just easier to say stay out of 5th until you are doing atleast 80km/h on a flat ground or going down a hill. If you're going up a decent hill, do it in 4th gear. R33/R34 gearboxes are stronger than your everyday car and less prone to 5th gear failure, but it can and does happen to any gearbox.

As you can see in Marc's gearbox picture above, the driving gear and the driven gear differ in size for each gear but are the same size as each other for 3rd gear (normally 4th but this appears to be a 4 speed gearbox so 4th is is the overdrive gear and 3rd is direct drive 1:1).

The word overdrive itself refers to the ratio being lower than drive (1:1 is direct drive), e.g. 0.75:1. When you get into overdrive gearing, pressures on gearbox are quite large and you really need the road to help you turn the gearbox from the other end or the engine will have alot of weight to be pushing by itself and its hands are gearbox. Common for 6th gear in the T56 gearbox (HSV, FPV V8 gearbox) to blow up because of people using it outside of freeway speeds (mind you the ratio in this gear can be as low as 0.6:1).

[MRSAMO]

Interesting stuff seems to be lurking in here, very nice, i like it!

keep all suggestions comming!

And yes i did say drive like a granny, and yes most cars dont have a standard vaccuum guage, but you can feel when your car is struggling.

Many cars (such like the old mirage *tear*) dont have tachos, and you dont need them, driving is all about the feel, you know when you need to change gears by the sound of the engine, just in the same manner that if you give it a bootful you know you've sucked alot more petrol than you probably wanted.

And i drive timidly during the week because i do go out on the weekends round the mountains and so and have a bit of fun

I just see it as less petrol spent driving my ass to work and more petrol spent boosting my way round a mountain.

And im sure alot of people would want it that way.

Heres another tip, for everybody who has a turbo timer (which about 90% of us would) dont run it. I dont mean dont run it all the time but be mindful of when you run it.

If your own your way home at night and you know its a flat drive of a few 100m's or so to your house, then you dont need to run it. Skylines were built without a turbo timer, and if the cars really needed them they would have came standard with the car. Your turbo timer should only be run if for some reason you've hit boost right before your about to turn the car off.

And most of us run out turbo timers for 30 seconds (1min for mine because thats the smallest time period available on mine due to it being build into my security system) and thats 30 seconds of fuel being wasted while your not even in the car! Even if your paranoid about not running it, most of us dick around in our cars for 10 - 20 seconds before we get out anyway, so just let the car idle for that long and turn her off. Might only be 10 seconds a day but if you work that out for a time frame of a year:

10 seconds a day x 7 days a week = 70 seconds

70 seconds x 52 (weeks in a year) = 3640 seconds a year

3640 seconds (a year) / 60 (second in a minute) = 60.6666 minutes

60.6666 minutes / 60 (minutes in an hour) = 1.0111 hours a year

So for those ten extra secounds a day, your basically letting your car use an hour of fuel a year doing nothing.

And if you dont run the turbo timer, so for example we will use 30 seconds:

30 seconds a day x 7 days a week = 210 seconds

210 seconds x 52 (weeks in a year) = 10920 seconds a year

10920 seconds (a year) / 60 (seconds in a minute) = 182 minutes

182 minutes / 60 (minutes in an hour) = 3.033 hours a year

So for those 30 seconds a day, your car is using 3.033 hours worth of petrol idling over a year.

Doesnt seem like much now but in the long run it makes a difference.

Sorry about such a long post, just trying to provide some helpful info for you fellow SAU'ers

This is interesting, but while 3 hours sounds like a lot, the rate of usage at the lowest idle isn't going to be very much either.

My TT is set to 30 seconds and I think my car is thankful for it.

[MRSAMO]

I just did the Melb to Sydney trip and got 615kms to a tank. I think the key is to :

- not use boost obviously

- stick to a consistent speed if possible (therefore consistent rpm)

- carry light (I had over 100kgs of luggage)

My tire pressure was probably towards the lower end.

[pipster11]

i cant believe no ones has mentioned changing the o2 sensor as part of a fuel saving tip

its probably the sensor that wears out the first in most cars and its the most responsible for the amount of fuel used at cruising/steady speeds

you can get them for $80 and 99% of the time they are lazy and not operating properly

everyone should also note that the o2 sensor is only used under about 3500rpm and is ignored completely at 100% throttle

[mad082]

There really is a ton of physics involved in it and without giving you a years worth of lectures, it's just easier to say stay out of 5th until you are doing atleast 80km/h on a flat ground or going down a hill. If you're going up a decent hill, do it in 4th gear. R33/R34 gearboxes are stronger than your everyday car and less prone to 5th gear failure, but it can and does happen to any gearbox.

As you can see in Marc's gearbox picture above, the driving gear and the driven gear differ in size for each gear but are the same size as each other for 3rd gear (normally 4th but this appears to be a 4 speed gearbox so 4th is is the overdrive gear and 3rd is direct drive 1:1).

The word overdrive itself refers to the ratio being lower than drive (1:1 is direct drive), e.g. 0.75:1. When you get into overdrive gearing, pressures on gearbox are quite large and you really need the road to help you turn the gearbox from the other end or the engine will have alot of weight to be pushing by itself and its hands are gearbox. Common for 6th gear in the T56 gearbox (HSV, FPV V8 gearbox) to blow up because of people using it outside of freeway speeds (mind you the ratio in this gear can be as low as 0.6:1).

actually it is a 5 speed, 1st and reverse are missing though. however i think some 5 speed ones don't have 5 gears (only 4) as they simply lock the input and output shafts togerther to get the 1:1 ratio. not 100% sure about that though

[mad082]

i cant believe no ones has mentioned changing the o2 sensor as part of a fuel saving tip

its probably the sensor that wears out the first in most cars and its the most responsible for the amount of fuel used at cruising/steady speeds

you can get them for $80 and 99% of the time they are lazy and not operating properly

everyone should also note that the o2 sensor is only used under about 3500rpm and is ignored completely at 100% throttle

obviously a new o2 sensor will give you better fuel eceonmy if the old one is shit, and if you do lots of light throttle driving. if you floor it everywhere it won't help at all

[Birds]

actually it is a 5 speed, 1st and reverse are missing though. however i think some 5 speed ones don't have 5 gears (only 4) as they simply lock the input and output shafts togerther to get the 1:1 ratio. not 100% sure about that though

Ah yes, fair enough.

[buckets]

i cant believe no ones has mentioned changing the o2 sensor as part of a fuel saving tip

its probably the sensor that wears out the first in most cars and its the most responsible for the amount of fuel used at cruising/steady speeds

you can get them for $80 and 99% of the time they are lazy and not operating properly

everyone should also note that the o2 sensor is only used under about 3500rpm and is ignored completely at 100% throttle

i didnt wanna say anything about the o2 sensor as it has its own sticky thread about it