Premium or Standard fuel

[Paul552]

What's best in the old air cooled 2 strokes?
What do you use?

I have read that premium is not the best  for a stock 2stroke and that it will actually make less power.

High octane is designed to stop detonation in high comp engines and burns cooler.


I always use premium just can't go the e10 !! Even though I understand the logic?

Does this make sence?

Will std fuel make more bottom end

[Noel]

I use
 BP ultimate or Caltex 98

[oldyzman]

BP98
Can someone tell me if there is any difference between pinging and detonation. is detonation a really abd ping?
Brett

[Lozza]

BP98
Can someone tell me if there is any difference between pinging and detonation. is detonation a really abd ping?
Brett

Pinging or pre-ignition is defined as occuring before the spark even detonation occurs after the spark event. You will not be able to hear the difference except that with pre-ignition your piston will last a matter of seconds.

What's best in the old air cooled 2 strokes?
What do you use?

I have read that premium is not the best  for a stock 2stroke and that it will actually make less power.

High octane is designed to stop detonation in high comp engines and burns cooler.


I always use premium just can't go the e10 !! Even though I understand the logic?

Does this make sence?

Will std fuel make more bottom end

Standard fuel won't make more low end power, your engine won't run any worse on premium fuels. What makes the power is tuning the engine to the fuel your using.

[Nathan S]

The basic rule is to run the lowest octane fuel that does not detonate.
It will give you the best throttle response (and cost the least).

I got sucked into the "use high octane fuel" nonsense - since dropping back to 95/96 octane, all of my bikes have become easier to ride and feel like they have more midrange.
In reality, they should all be running more compression and demanding 98+ octane fuel - they'd make more more thank to the higher BMEP.

I wouldn't bet money on it, but I suspect that a stock 125D would be happy on 91. But if you're not confident with your jetting skills and/or unfamiliar with what detonation sounds like, I'd stay with 95/96.

E10 is risky on a 2T. There's a big question mark over its comparability with most 2T oils (castor is OK). There's also a fair bit of evidence that it eats things like the needle and seat.

[oldyzman]

Good information Lozza and Nathan...
Cheers Brett

[Paul552]

The basic rule is to run the lowest octane fuel that does not detonate.
It will give you the best throttle response (and cost the least).

I got sucked into the "use high octane fuel" nonsense - since dropping back to 95/96 octane, all of my bikes have become easier to ride and feel like they have more midrange.
In reality, they should all be running more compression and demanding 98+ octane fuel - they'd make more more thank to the higher BMEP.

I wouldn't bet money on it, but I suspect that a stock 125D would be happy on 91. But if you're not confident with your jetting skills and/or unfamiliar with what detonation sounds like, I'd stay with 95/96.



E10 is risky on a 2T. There's a big question mark over its comparability with most 2T oils (castor is OK). There's also a fair bit of evidence that it eats things like the needle and seat.

This is what I also read and also makes sence to me.

Runs ok on 98 but I also thought that a lower octane fuel ie far better on a low comp engine like a 2t

Thanks for the input.

[Zakk]

it would depend on your engine but even with the head relieved my YZ490J engine needs 98 to stop the pinging, i think it was designed to run on 105+ AVGAS.

ethanol is not good for most plastics and rubber, so i'd be carefull using E10-E85 if you have a plastic fuel tank.

[Tim754]

Lozzas key factual statement "What makes the power is tuning the engine to the fuel your using." nothing else really needs to be said.

[micks]

was talking to a mates old man who was (golden handshake last month) a shell refinery worker sydney.as there is no more production at clyde they are shipping it in from singapore now. i would question the quaulity of the import fuels as he said there has been some "out of spec" fuels delivered.this is not sold to the public direct but is blended in with "in spec" fuels.shell`s got to make a dollar somehow.
 

[lukeb1961]

You should really go read
 http://www.faqs.org/faqs/autos/gasoline-faq
which I found most informative.

A fascinating read from the very early days of fuel development is "I Kept No Diary"
To answer your questions truly/fully, we need someone who works in the petroleum industry.


What's best in the old air cooled 2 strokes?
   define best? define old? Are you referring specifically to pump fuel?
   What was the factory recommended fuel?

What do you use?
   Caltex 98  - I don't have to pay for it, so it is my generic fuel. Something to keep in mind is that various countries change the makeup of a given fuel due to seasons - winter fuel in Europe is not the same as summer fuel.

I have read that premium is not the best for a stock 2-stroke and that it will actually make less power.
   are you talking about energy density and/or specific weights?  98 vs 91 - no effective difference in energy density, I believe. It is the actual hydrocarbon and oxygenate components you need to consider.  I have not been able to find out what (if any) variations in OZ fuel.

High octane is designed to stop detonation in high comp engines and burns cooler.
  Octane Rating is nothing more than an anti-detonation rating.  If you want to have higher compression without pre-ignition, you will desire a fuel with a higher Octane rating.  Higher temperatures and pressures translates to more power.  When thinking of 'knocking' there are two areas
   - pre-ignition, due to the fuel not being able to cope with the pressure rise and self-igniting too early.
   - detonation, where rather than burn smoothly, the thing explodes and produces destructive shock-waves.
   Burns cooler? INCORRECT. Apparently, for the various grades, there are only slight differences in combustion temperatures - most are around 2000C in isobaric adiabatic combustion.

I always use premium just can't go the e10 !!
   Ethanol content is something I shy away from for old machines that have rubber and seals from 35 years ago. However despite my paranoia, many I know have run E10.

Even though I understand the logic?
Does this make sence?
  Sure, makes sense.

Will std fuel make more bottom end
   The combustion attributes are mainly due to the oxygenates in your fuel.  (ethanol blends spring to mind) As far as I am aware, there is no difference  between our 91 and 95. Try running richer to find that "stoichiometric" ideal.

   Does anybody honestly find a noteable difference with their VMX machines?
   Luke
 

[EML]

well done Luke
 the only think I have been told is the un-leaded fuel is designed for fuel injectors and with that in mind will ignite better if finely atomised, something that carbies don't do well.
therefore octane has not much to do with it so best you run 91 and save the bucks.

[oldfart]

Luke, Ole mate ( shortshift ) that did the 2 smoke oil thread should be able to shed some light on the matter if he's still lurking around.
 

[Mike52]

Look at it a different way.

If there was a chance that your pride and joy , your reasonably rare old bike that you spent heaps doing up , might ping or detonate on lower octane fuels and destroy that impossible to get piston , then why the hell would you take the risk?

If for a few miserable cents a litre you can get some protection against destroying your motor by buying a higher octane fuel that won't cause you any problems in the lower compression engines then why wouldn't you use it?

I am not talking Ethanol here.