Replacing gearbox bits

[SUBYDAZZ]

Just for reference whenever I get around to doing it:

Can you replace the 5th gear cog or whatever in an early Liberty box with a different one that will make it rev a bit lower? 3000rpm @ 100km/h sucks.

[brumbyrunner]

theretically yes the fifth gear is on it's own.
Yours would probably be .871
You could try .738
It would make 15% difference so drop revs down to 2550.
You'd be changing back to 4th a lot more often.
I'd just run taller tyres

[SUBYDAZZ]

You'd be changing back to 4th a lot more often.

Heck, that's what gears are for. I reckon the reduction in revs would pay for itself in time, Can go tires bigger than about 5% profile due to nifty airbag struts

[Point]

i don't think you'd want to get the revs too low for cruising. You want it to sit in the torque band of the engine or it will labour and use more fuel. I had a big cam and carby on an old car of mine and in 5th it was out of it's torque band. It used less fuel in 4th and was a lot nicer to drive too. tested over 3200km. it would have been better with a lower diff ratio to suit the engine's torque range.

[vincentvega]

i agree

lower revs does not equal lower fuel consumption.

Since changing my diff ratios from 4.11 to 4.44 my fuel consumption has decreased dramatically, simply because the engine is back in its torque band. I only increased revs by about 200RPM but it has made a massive difference in the way the car drives

[AlpineRaven]

I worked out a while ago, I was planning to do that in my Liberty - only would make at least 400rpm difference. If you do a LOT of flat road traveling then it may be worth it, or get bigger diameter tyres like what I did... before had 195/60 15" and now on 205/70 15" close somewhat between 450-500rpm difference, fuel is gaining extra 75 - 100kms to a tank.
Cheers
AP

[Matatak]

so wts the 'tourque band' of the engine that we wuld want to be in?

[SUBYDAZZ]

...lower revs does not equal lower fuel consumption.

So higher revs uses less fuel is what you're saying?

I know one of the main things that uses fuel is the wind drag at speeds, but really, this Liberty has never been able to compete with other vehicles of larger engine size at speeds over 80km/h for fuel consumption and the only real difference is purely what revs are doing - significantly higher than the others.

As I said before, larger diameter tyres are not an option.

Is there any middle ground ratio that will drop it a couple of hundred rpm, that'd be good, don't want to go to low as you say?

Also where is the "torque band" of the EJ22? Don't tell me it starts at 3000rpm?

[discopotato03]

Subydazz what car is this early Lib gearbox in ie Lib or L ?

From the boxes perspective you really have to run a 5th gear pair from either an L or Liberty etc AWD box because the counter gear bore is larger on AWD that PT box gears .
The L series turbo gearset (PT and FT) has a taller 5th gear ratio than the non turbo one , first gear is the same but the gaps between the ratios is slightly wider so 2345 are all a bit higher than the not turbo ratios .
I assume Subaru thought that the extra torque from the turbo would pull the higher gearing - sort of helps the engine load the turbo and make it boost .

As for fuel consumption and usage , its really the air fuel ratio and how efficiently an engine can burn its air and fuel . One thing that does make a difference is running as much ignition advance at part throttle cruise as possible because thats generally where the engine makes its greatest torque in a semi closed throttle low effective CR state .
Where the factory screws everything up in early Subies is the exhaust manifolding , if you can improve those and stop them acting as an EGR pipe first and exhaust manifold second - with extra advance things should improve .

Cheers A .

[vincentvega]

i used to be doing 2500RPM at 100kph

i am now doing about 2700RPM at 100kph

I get bang on 10L/100KM now on the highway.

stock revs for my car is 2750RPM = 100kph

So yes, at higher revs I am using less fuel. The car holds hills way easier than before and i reckon this is largely why it uses so much less fuel

[brumbyrunner]

So higher revs uses less fuel is what you're saying?

I know one of the main things that uses fuel is the wind drag at speeds, but really, this Liberty has never been able to compete with other vehicles of larger engine size at speeds over 80km/h for fuel consumption and the only real difference is purely what revs are doing - significantly higher than the others.

As I said before, larger diameter tyres are not an option.

Is there any middle ground ratio that will drop it a couple of hundred rpm, that'd be good, don't want to go to low as you say?

Also where is the "torque band" of the EJ22? Don't tell me it starts at 3000rpm?

What they are saying is don't confuse RPM with load. It is the load you put on the engine that effects your economy. The easiest way to measure load is with a manifold vacume guage. Some cars made during the last oil crisis had them fiitted as standard so you could monitor the load.

Increasing drag with a lift kit and running larger tyres will generally increase fuel economy as it increases the load. Don't confuse engine size with fuel consumption either. A small engine working harder may use more than a larger engine doing it easy because of the bigger load.

I wouldn't go changing one ratio in your gearbox in your stock standard liberty on the off chance that it might improve the economy. The Suby engineers got it pretty right. I used to have the same Liberty as you and it was the most economical car I had ever owned. Also one of the only vehicles I didn't modify.
If I sat right on 100km/h I could get it down to 6.9l/100km. Didn't happen very often as I used to set the cruise control on 140 most of the time. Even then I would consistently get 11l/100km. Nothing I've owned since will come close to that. If your liberty gets worse than 8.5l/100km sitting on a very steady 100km/h then theres something wrong with it.

And the "torque band" starts about 2700/2800 rpm same as the turbo models.

[PeeJay]

I'm currently building a little contraption to connect to my car that will electronically measure the fuel consumption because I've been pondering the exact same thing for a while now. Will post results hopefully within the month.

[Suby Wan Kenobi]

Even the people running overgeared, because of tyres, Liberty's are looking at ways to increase RPM to get back into the fat of the engine torque at cruise speeds.

So as everyone has said Subaru got it right the first time and dont bother

[chriSTIan]

Might have to look elsewhere for better economy,ie:oxy sensor,checking air cleaner,2psi more in the tyres,free flow exhaust.etc...it all helps.

[SUBYDAZZ]

Hmmm... Other than oxy sensor all the later are taken care of. This hasn't been a recent issue though, not much worse over last 200,000km. I think some of the issue would have to be finding much difficulty sitting on just 100km/h.

[Suby Wan Kenobi]

If you have a knowledge of electronics there are other ways to "lean out" the cruise a bit bowever you have to be very careful as it can result in engine damage of the worst kind

[legacytt]

If you decide to do this the answer is to use the 5th gear from and Aus delivered RS which gives around 2800 at 110kph. It makes a difference in economy behind an RS motor as I used to have a close ratio 4.11 box which saw around 3000 at 110 in fifth and the car used more fuel on a long drive.

[SUBYDAZZ]

That sounds like it's on the money...