The AUSubaru.com.au Forums

I was wondering if my motor gets remarkably better economy running hot,
can I retain this economy after I fix the radiator, perhaps with a new distributor?
that's one part I haven't replaced.

My motor is running up to 5-10 mm closer to the "Hot" side of the gauge.
Haven't the foggiest what the actual temperature is.

My economy is so much better,
it's like I can go 15-25% farther for any given point on the fuel gauge.
I'm easily getting another 50+kms per tank.

An engineer once told me IC engines get better and better efficiency at higher temperatures, up to a certain point of course. Maybe with the slightly higher temp your engine has hit a sort of sweet spot?

Probably best to put this in the engine section of the forum...

What you'll find is that a hot engine may be running leaner. A lean engine is ok in small bursts but in the long term you'll end up with a dead engine. Running lean makes the engine run hotter and thus your piston head is hotter and ends up fatiguing that can result in a hole in the piston or piston slap - common on EJ20 turbos in a particular cylinder due to the fuel delivery system's line up of the injectors.

What a lot of people don't realise is that the engine uses the fuel as a cooling method - by not burning all of it in the cylinder. The majority of the burn occurs in the cylinder, but there's a little bit of un-burnt fuel that's pushed into the exhaust where it's finished off. Ever taken the exhaust manifold off and revved an engine - you'll get these little blue flames dancing out the exhaust ports and dead hearing if you're not wearing ear muffs.

By leaning out the fuel you'll burn all of the mixture in the cylinder instead of some in the exhaust, this will result in a hotter operation temperature.

There was a case a number of years ago where a charter airline company had a plane go down and it was found that the bean counters had put the hard word on the pilots to run the engines leaner to save on fuel. This lead to maintenance issues and some plane's engine's failing mid-flight due to holes in the pistons. One went down killing all on board for the sake of a few dollars here and there. Not worth the pain!

Yes better fuel economy is good, but you want to make sure it's because you're doing it properly

Cheers

Bennie

Also - I'm currently looking into swapping my L series 4wd 5th gear with that from the 2wd gearbox - they had a taller ratio, not my much but it will make a difference for the better I reckon.

Cheers

Bennie

El_Freddo wrote:Also - I'm currently looking into swapping my L series 4wd 5th gear with that from the 2wd gearbox - they had a taller ratio, not my much but it will make a difference for the better I reckon.

Cheers

Bennie

I like the sound of that.
What good is 5th while driving offroad anyways?

On second thought, my EA82 is a pig in 5th, so a deeper gear might overwhelm it.

El_Freddo wrote:Probably best to put this in the engine section of the forum...

What you'll find is that a hot engine may be running leaner. A lean engine is ok in small bursts but in the long term you'll end up with a dead engine. Running lean makes the engine run hotter and thus your piston head is hotter and ends up fatiguing that can result in a hole in the piston or piston slap - common on EJ20 turbos in a particular cylinder due to the fuel delivery system's line up of the injectors.

What a lot of people don't realise is that the engine uses the fuel as a cooling method - by not burning all of it in the cylinder. The majority of the burn occurs in the cylinder, but there's a little bit of un-burnt fuel that's pushed into the exhaust where it's finished off. Ever taken the exhaust manifold off and revved an engine - you'll get these little blue flames dancing out the exhaust ports and dead hearing if you're not wearing ear muffs.

By leaning out the fuel you'll burn all of the mixture in the cylinder instead of some in the exhaust, this will result in a hotter operation temperature.

There was a case a number of years ago where a charter airline company had a plane go down and it was found that the bean counters had put the hard word on the pilots to run the engines leaner to save on fuel. This lead to maintenance issues and some plane's engine's failing mid-flight due to holes in the pistons. One went down killing all on board for the sake of a few dollars here and there. Not worth the pain!

Yes better fuel economy is good, but you want to make sure it's because you're doing it properly

Cheers

Bennie

Yep this makes more sense, ignore what I said

Once read ( and retained) that 95C operating temp is the most fuel efficient temp. Was from an automotive cooling system parts manufacturer article in a trade magazine so until proven otherwise will sort of believe it.

No need to try another distributor, just a hotter thermostat or cardboard in fronmt of the radiator, but don't come back to me if you cook your engine trying to get ultimate economy

steptoe wrote:Once read ( and retained) that 95C operating temp is the most fuel efficient temp. Was from an automotive cooling system parts manufacturer article in a trade magazine so until proven otherwise will sort of believe it.

No need to try another distributor, just a hotter thermostat or cardboard in fronmt of the radiator, but don't come back to me if you cok your engine trying to get ultimate economy

Both 'Cook and 'Cok' [cock] work here!

I really dont think a new distributor is gonna do anything unless its crapped out. It certainly wont affect the temp. I'd be checking the thermostat.

As Scott said, be wary of running the engine too lean...its an engine killer. I've seen pistons with massive holes in the crown from leaning out...not good!

El_Freddo wrote:Also - I'm currently looking into swapping my L series 4wd 5th gear with that from the 2wd gearbox - they had a taller ratio, not my much but it will make a difference for the better I reckon.

Cheers

Bennie

I'd love to get a taller 5th AND shorter 1st & 2nd...

All Ls used the same 1st gear ratio . There is basically an EA82 carby gearset and a turbo set with the carby ratios closer together . The EFI turbo engines made more torque and from low revs so they could pull the wider spaced taller gearing .
Generally the manufacturers set the gearing so it matches the engines torque characteristics , the carby 82 not being a mountain of torque needed short close gearing to keep the engine revs in a narrower band higher up than te turbo EFI one needs to be .
If you want to crunch the numbers for overall gearing I believe the carby 5th was 0.87 and the final drive 3.9 . The turbos if I remember correctly were 0.78 5th and 3.7 final drive . In each case multiply the two to get the overall figure .
I also seem to remember gen 2 Libs having the close set 1-4 and the taller 5th gears .

So many things affect fuel consumption . For example if you ran a heavy grade engine oil in cool climates and jacked the water temp up the less oil sheer drag could show up as better fuel consumption .
The manufactures also get more brag mileage out of their products having good mpg figures so their settings are generally a good yardstick .

A .

Disco, the pre 87 L's were 3.9 diff ratio, the post 87 L's were 3.7 diff ratio.

And the 2wd 5th gear ratio was slightly taller than the 4wd version, probably due to more moving parts in the system I think.

Now if I could only find the chart I'm after to show it!

Cheers

Bennie

Out in the Central West ATM but check the trusty Subie WSM later .

Really the only extras are a set of riser gears to drive the "third motion" shaft and the tailshaft .
In Zoob gearboxes , notably PT ones , the countershaft is the front diffs pinion shaft so there is only one pair of gears per ratio except reverse .

A .

discopotato03 wrote:Out in the Central West ATM but check the trusty Subie WSM later

Looking forward to it Adrian!

Cheers

Bennie

Through Coota , only 415 to go .

Okay , well my L WSMs are for 87+ so doesn't show 85/86 models .
Its 3.7 final drives as Turbo/MPFI and all models for Australia .

It mentions the close ratio gearset 1-5 (3.545/2.111/1.448/1.088/0.871) as "Carb models for Australia and catalyst equipt for Swiss/Austria/Sweden" .
I suppose Sube thought the taller diff with the close ratios was what the polluted 82 carbs could pull . BTW close and wide gearsets have the same 1st ratio . Wide or turbo 1-5 (3.545/1.947/1.366/0.972/0.780) .
These are 4/AWD ratios BTW .

The FrWD only carb 1-5 (3.636/1.950/1.344/0.971/0.783) .
The same MPFI ..... 1-5 (3.636/2.105/1.428/1.093/0.885) .
These are basically wide and close 2WD sets with very minor variations .
That 3.636 would be interesting to those with tractor wheels .

A .