Which fuel sounds better for my EA82?

[2nd Hand Yank]

EA82, carburated

I tried a full tank of unleaded fuel, no ethanol as an experiment.
I usually run 91 octane with 10% ethanol, just because it's so common.

Unleaded:

I instantly noticed it had a harder time idling,
easily 1/3rd the torque from idle to about 1500 rpm is gone
which corresponds with detonation happening more easily under load
afterwards its torque is about the same to 2000 rpm
from 2000+rpm there is a dramatic increase in torque, but with a slight dip between there and 4000rpm
keeps pulling like a freight train past 4000rpm
You can hear the engine is noticeably smoother beyond 3000rpm
it's like it fires so much better
yet below 2000 rpm it sounds like it might stall, motor hiccups occaisionally
Torque curve feels like an upside-down W

91 Octane + 10% Ethanol:

Resists detonation better below 2000-2500rpm
torque curve is relatively flat after 1500rpm, but slowly drops after 2500-3500rpm?


I cross a bridge at 80 km/h everyday on a steep slope, crossing the Hunter River.
My estimate is it's 100 metres tall and takes 15-20 seconds to reach the top driving at the speed limit.
With 10% ethanol fuel in 4th gear and WOT I always maintain my speed or even lose 1-5 km/h, wind-depending.
With pure unleaded fuel, I never lose speed in the same conditions and could actually gain 3-6 km/h before I reach the top if I wanted
I've also tried going 80 km/h in 5th gear using pure-unleaded and it still seems a bit more powerful up this bridge.

Fuel economy is about the same when I'm not using air-conditioning.
I suspect I'd get better economy on pure unleaded with air-conditioning since there's better "pick up" at cruise speed.

Fuel economy with 95 and 98 octane is actually progressively worse than 91 + E10, respectively.
91 + E10 for some reason gives me the best bottom end torque.
Pure unleaded however seems to have the worst bottom end torque compared with even 95 and 98 octane.

**Which one sounds better? There's only 2 cents a Litre more for pure unleaded.

Thanks

[Davidov]

I'd probably go the option that results in the least detonation. I find it strange that you have detonation issues with any fuel.

With out L series EA82 we would run on just unleaded 91 without an issue, no detonation. And found that it would run better on 95 and 98 respectively. Surprising that yours isn't the same. Perhaps your carby needs a bit of tuning? When we played with the carby and had it wrong we would get some detonation and idling issues but when set right it ran like a dream on all fuels no matter how hard we drove it.

Got the beast to 160 up a slight slope without too much effort. Would have gone more too if the car didn't feel like it was going to shake apart.

[pitrack_1]

Was your EA82 approved for ethanol blended fuels? See this FCAI page
* All Subarus before 1990 are NOT approved to run ethanol blended fuels.
* All Subarus post MY1990 (with some exceptions- Sti, GT, B4) are approved to run ethanol blended fuels E5 and E10

Last year for this engine was 1990 (according to Bantum)? I know some vehicles aren't as they have fuel system components that are damaged by ethanol. My N13 Pulsar is one of them. In particular, I think the plastics(dissolving/reacting) and/or certain rubber parts (softening/swelling) are the problems, but could also be steel parts susceptible to corrosion (as the ethanol will absorb water from the atmosphere).

Two thoughts on the detonation/knocking/pinging:
a) You've got buildup in the combustion chambers
b) Your ignition timing's too advanced, at least for 91RON. If it's manually adjustable, you could retard it a bit. If you have a distributor with centrifugal/vacuum advance (if they exist for your vehicle: I don't know), check it's working properly eg the centrifugal springs haven't broken or weakened.

It may be that your engine is just on the edge of knocking with the other fuels, and it's triggered by the 91RON.

Ethanol suppresses knocking/detonation/pinging. Therefore the E10 (10% ethanol) will help suppress knocking compared to ULP. This also has to do with the octane rating (RON=Research Octane Number).

However ethanol reduces the energy content of petrol, thus worsening fuel economy. You would expect to worsen fuel economy running E10. This can be offset, at least partially, if the ethanol has raised the RON so the ECU can advance the ignition more (not in your carburetted case?) and make it more efficient. The 2cpl for 'normal' ULP should be worth it.

ULP is 91RON
E10 is 100RON from United Petroleum, apparently (see Octane Rating on wikipedia)

Good luck and I'd suggest sticking to the straight ULP with a retune.

[thunder039]

im pretty sure E10 fuel is already 95 octane which is why it would run better then 91.

fuel of higher octane will generally be better, but i do not run ethanol fuel in my cars as i get rubbish fuel economy so another thing to consider. i would try premium 95 fuel with out ethanol and compare fuel economy, could work out cheaper to use as you SHOULD get better fuel economy and it SHOULD run better then regular 91, if not a retune might be needed as you shouldnt experience detonation

[El_Freddo]

If you're testing between different fuels you need to run at least two tanks through of the same fuel and take the results from the second fill up. You also need to re-adjust your timing to get the most potential from the fuel your using - all of those fuel RON/ethanol ratings/content have different flash points, thus your timing needs to be adjusted appropriately.

Cheers

Bennie

[2nd Hand Yank]

I might be getting the fuel names muddled up.
I'm comparing "unleaded" to 91 octane.
91 Octane in almost every service station says it's an "ethanol blend."
The 91 octane in particular I was using was from Shell.

So I might be better using unleaded, but changing the ignition timing

My L Series is from 1993, so it should be safe to use with ethanol blends

[Brumby Kid]

Ok,
You have the following fuels at most service stations.
LPG
Diesel
Unleaded 91
Unleaded 95
Unleaded 98

Now some have ethanol and bio organic crap now too like e85, e10.
Don't know anything about them though.
Hope this clears a few things up.

Cheers Cam

[thunder039]

E10 is 95 octane rating as i said before not 91, unless this is only a victorian thing...
http://www.colesexpress.com.au/shell-fu ... d-e10.aspx

[2nd Hand Yank]

E10 is 95 octane rating as i said before not 91, unless this is only a victorian thing...
http://www.colesexpress.com.au/shell-fu ... d-e10.aspx

Thanks, but what I buy here is Shell 91, which is coincidentally a blend of petrol and ethanol.

I'm comparing it to "regular unleaded" from Caltex. Sorry forgot to mention where I got the pure unleaded from.

[El_Freddo]

Thanks, but what I buy here is Shell 91, which is coincidentally a blend of petrol and ethanol.

I'm comparing it to "regular unleaded" from Caltex. Sorry forgot to mention where I got the pure unleaded from.

I didn't know there was a 91RON ethanol blend out there. Seems a waste to me, even the 95RON with 10% ethanol doesn't go as far as the 91 RON in my EJ22. I'll stick with the 91RON without ethanol, not that we can get that in Victoria...

Cheers

Bennie