1999,105Landcruiser,petrol,gearbox ratio change ???

I have a hilux and have increased my RPM and gained economy.

As I had fitted bigger tyres my motor was labouring at 100kmh after changing my ratios I am now 250 rpm higher at 100 and about 1.2 ltr per 100 better off.

Craig

you need to let people know the vehicle set up, like tyre size and mods to the engine if any. Usually car makers have the ratios already worked out for best economy and power on standard vehicles.
cheers Dave.

You can actually modify the gearbox or differential ratios to lower the engine RPM for a given road speed. Don't forget if you choose to change diff ratios you have 2 diffs to do...lol. Also as others have said, you may actually increase your fuel consumption by making the engine work at a lower RPM than it's optimum. Have you looked at a free flowing exhaust and a set of extractors and maybe a so called"chip" fitted to the engine management system. Probably a lot cheaper and more likely to achieve better lt/klm fuel usage and better performance as well.


Cheers
Pop

Wow a petrol 4.5 liked fuel, a supercharged one must really drink it!
Seriously though for best economy you need to have the engine at is optimum RPM which is usually the point on the power versus torque graph where they intersect. There is usually some leeway but most of the time that is the most economical point.
Aggressive tyres, roofracks, trailers and just sheer weight all affect economy to a certain extent, sometimes lifting the foot is the only way to improve it.

G'day Get On
Most petrol vehicles get the best fuel economy with less than the overdrive 5th gearing. So to get fuel economy you would be better to get an overdrive ratio which is 4th and a half.
All fuel efficiency trials all run in 4th, never 5th.
Most people are conditioned from birth to believe 5th gives economy and it aint necessarily so.
Cheaper than two diffs and 5th gear ratio changes etc.

If you are towing then smaller Dia tyres will lessen the load on the engine, let it spin slightly quicker and the resulting less throttle opening may give more economy.
Borrow some wheels from someone else and try it, youmight be pleasanlty surprised.
Bigger tyres, wider tyres will always use more fuel.

By using really good oil in your engine you will also increase the efficiency and any extra revs won't be a worry.
What fuel do you use?
If you use the highest octane fuel you can afford it usually uses less for the same distance.
My use of 98 octane in some engines often means it is actually costing less to go the same distance. Yes, it saves money.
Don't use Shell fuel as it hasn't proved to be the best one around.
BP and Caltex 98 octane do ok.

Ross M

Totally agree with Ross on that , Get On . I fitted 285x75x16s on my FZJ105 partly to drop revs and gain economy. Yes dropped the revs about 300rpm in 5th but economy was worse . Fitted extractors after crushing the std. system in the bush, sounds nice but negligible improvement. I don't think you'll get a big improvement without spending heaps on the motor .

Hi, The 1FZ is most economical at approx 2700 rpm. Try a drive in 4th to bring the revs up and see if it works for you.