550xp Which Fuels?

[skyhuck]

I'd go with spud on the Aspen, there's loads of stockists all over the country.

If you've got to use pump fuel, stay away from supermarket stuff and use normal unleaded and not super unleaded and a good quality 2 stroke and keep the mix the same every fill.

 

 

What makes you say that?

[NFG]

Aspen 2 or

 

Aspen 4 with Red Line oil

 

N

[GardenKit]

What makes you say that?

 

I agree with that statement from Riggerbear, and this is my take on it.

 

Many people think that Premium (higher octane) petrol has, 1) a higher energy value than Regular and will therefore, 2) produce more power.

 

1) It has not.

2) It can, in the right engine, but will produce less in the wrong one.

 

High octane fuels are in fact just a little 'deader' than regular. This is because higher octane resists detonation for longer and can enable higher compression engine to fully combust their fuel without 'knocking'

 

Use low octane fuel in a high compression engine and it burns very quickly after ignition and develops it max pressure too soon in the cycle resulting in a waste of energy and a 'knocking' or 'pinking' which causes engine damage.

 

A high octane fuel resists the temptation to burn and expand too rapidly, which means the power is released progressively past TDC and downwards on the power stroke giving max efficient energy usage and max power.

 

But high octane fuel in a lower compression engine results in the burn being too slow and energy being wasted towards the end of the power stroke, resulting in loss of power.

 

Standard saws have compression ratios suited to regular fuel, so using premium is counter productive. Only Spuds ported and lowered squish saws may benefit from high octane.

 

Others may, and no doubt will, disagree.

[Mick Dempsey]

Good explanation, always wondered about that.

[skyhuck]

I agree with that statement from Riggerbear, and this is my take on it.

 

Many people think that Premium (higher octane) petrol has, 1) a higher energy value than Regular and will therefore, 2) produce more power.

 

1) It has not.

2) It can, in the right engine, but will produce less in the wrong one.

 

High octane fuels are in fact just a little 'deader' than regular. This is because higher octane resists detonation for longer and can enable higher compression engine to fully combust their fuel without 'knocking'

 

Use low octane fuel in a high compression engine and it burns very quickly after ignition and develops it max pressure too soon in the cycle resulting in a waste of energy and a 'knocking' or 'pinking' which causes engine damage.

 

A high octane fuel resists the temptation to burn and expand too rapidly, which means the power is released progressively past TDC and downwards on the power stroke giving max efficient energy usage and max power.

 

But high octane fuel in a lower compression engine results in the burn being too slow and energy being wasted towards the end of the power stroke, resulting in loss of power.

 

Standard saws have compression ratios suited to regular fuel, so using premium is counter productive. Only Spuds ported and lowered squish saws may benefit from high octane.

 

Others may, and no doubt will, disagree.

 

Cheers

[Peter]

As much as I like the idea of aspen 4 plus redline, I buy aspen in 200l drums. I'd need 8.5 of those little bottles which would cost £110 just for the oil.

 

Does anyone in the U.K. Stock the gallon bottles of oil? In the us those are $85 which is on a par with Husqvarna fully synthetic.

[GardenKit]

As much as I like the idea of aspen 4 plus redline, I buy aspen in 200l drums. I'd need 8.5 of those little bottles which would cost £110 just for the oil.

 

Does anyone in the U.K. Stock the gallon bottles of oil? In the us those are $85 which is on a par with Husqvarna fully synthetic.

Being as Aspen2 is only £10 a barrel more expensive than Aspen4, why not simply buy Aspen2? It save all the hassle of mixing too.

 

The 2 stroke FRT oil was specially developed to meet the needs of all modern 2 stroke machines including Husqvarna and exceeds the specs of most, if not all, oils on the market.

[Stubby]

I agree with that statement from Riggerbear, and this is my take on it.

 

Many people think that Premium (higher octane) petrol has, 1) a higher energy value than Regular and will therefore, 2) produce more power.

 

1) It has not.

2) It can, in the right engine, but will produce less in the wrong one.

 

High octane fuels are in fact just a little 'deader' than regular. This is because higher octane resists detonation for longer and can enable higher compression engine to fully combust their fuel without 'knocking'

 

Use low octane fuel in a high compression engine and it burns very quickly after ignition and develops it max pressure too soon in the cycle resulting in a waste of energy and a 'knocking' or 'pinking' which causes engine damage.

 

A high octane fuel resists the temptation to burn and expand too rapidly, which means the power is released progressively past TDC and downwards on the power stroke giving max efficient energy usage and max power.

 

But high octane fuel in a lower compression engine results in the burn being too slow and energy being wasted towards the end of the power stroke, resulting in loss of power.

 

Standard saws have compression ratios suited to regular fuel, so using premium is counter productive. Only Spuds ported and lowered squish saws may benefit from high octane.

 

Others may, and no doubt will, disagree.

 

Agree entirely and have said the same myself on occasion but not so eloquently

[MattyF]

I'd run it on normal pump fuel and the highest quality husky 2 stroke you can get.

My girlfriend runs her 550 on aspen and it has still needed a rebuild also she has recently ran it on pump fuel because it was impossible to get aspen on that day and had no choice and it made it run very badly not to mention the cost.

I've ran saws/ hedge cutters myself from new on aspen and personally don't think it made a difference to longevity and if any thing they don't like been chopped and changed between alkylate and pump fuel which unless you have a dealer on your door step for it will happen !although it is more pleasant for working in tight spaces or hedges with no breeze but actually found just using a high quality two stroke nearly as beneficial.

[openspaceman]

 

Many people think that Premium (higher octane) petrol has, 1) a higher energy value than Regular and will therefore, 2) produce more power.

 

1) It has not.

 

I agree and it tends to have lighter fractions so on a volume basis it has less energy.

2) It can, in the right engine, but will produce less in the wrong one.

 

Yes because it allows higher compression and expanding from a higher pressure means more power but I'd qualify the second point slightly as I think it will produce the same power if the mixture strength is the same on a mass:air basis

 

High octane fuels are in fact just a little 'deader' than regular. This is because higher octane resists detonation for longer and can enable higher compression engine to fully combust their fuel without 'knocking'

 

That's right

 

Use low octane fuel in a high compression engine and it burns very quickly after ignition and develops it max pressure too soon in the cycle resulting in a waste of energy and a 'knocking' or 'pinking' which causes engine damage.

 

In fact the problem is that the pressure increase of the flame front detonates the unburnt mixture in front of it, the shock from which can damage the engine but I don't think the energy is necessarily wasted.

 

A high octane fuel resists the temptation to burn and expand too rapidly, which means the power is released progressively past TDC and downwards on the power stroke giving max efficient energy usage and max power.

 

Yes the higher octane fuel resists detonation so the flame front passes smoothly through the mixture.

 

But high octane fuel in a lower compression engine results in the burn being too slow and energy being wasted towards the end of the power stroke, resulting in loss of power.

 

I doubt this but it will lead to the mixture being fractionally weaker

 

Only Spuds ported and lowered squish saws may benefit from high octane.

 

I doubt this though am not sure, generally 2 stroke engines are running lower compression ratios than 4 stroke as compression doesn’t start till the transfer ports are closed, so similarly pressures aren't high enough to support detonation.

 

Others may, and no doubt will, disagree.

 

Not disagreeing just my explanation differs slightly