Shell Fuel

almillar

motorguy - I must check what it is that my engine wants, and if needed, get an octane booster. I'd love to run it on Tesco Momentum.

bigjl

Strider590 wrote: »

Placebo effect..........

Fuel octane doesn't equal power.
That's all just marketing rubbish.

Octane is purely about the fuels stability under compression and therefore a high compression engine needs high octane fuel to obtain it's specified output, whilst preventing damage to it's pistons, that would be caused by pre-ignition.

Running a high compression engine on lower octane fuel requires the ignition timing to be !!!!!!, thus reducing power.

Also 95ron fuel does contain bio-ethanol at 5% and bio-ethanol has a lower calorific (energy) value than the petrol is replaces. As such high octane fuels that have no bio-ethanol, will give slightly better mpg when used in a normal car.

How do you explain cars like the WRX needing Super Unleaded?

You can use 95RON but the engine will not give full power?

In other words Octane does indeed mean more power.

I wouldn't consider a WRX to have particular high compression but happy to be wrong as it has never really been something that concerned me.

BeenThroughItAll

bigjl wrote: »

How do you explain cars like the WRX needing Super Unleaded?

You can use 95RON but the engine will not give full power?

In other words Octane does indeed mean more power.

I wouldn't consider a WRX to have particular high compression but happy to be wrong as it has never really been something that concerned me.

No, it's nothing to do with the octane rating equalling more power.

It is simply that the static timing, fuelling, and ignition timing are all optimised and mapped using higher octane fuel, allowing greater knock resistance. With lower octane fuel, you develop less power because the fuelling and ignition timing are running sub-optimally to compensate for increased propensity for pre-ignition; in other words, the vehicle runs in a fallback mode to protect the engine by adjusting parameters whose knock-on effect is a reduction in power output.

Paradigm

BeenThroughItAll wrote: »

No, it's nothing to do with the octane rating equalling more power.

It is simply that the static timing, fuelling, and ignition timing are all optimised and mapped using higher octane fuel, allowing greater knock resistance. With lower octane fuel, you develop less power because the fuelling and ignition timing are running sub-optimally to compensate for increased propensity for pre-ignition; in other words, the vehicle runs in a fallback mode to protect the engine by adjusting parameters whose knock-on effect is a reduction in power output.

Haven't you just posted a total contradiction?


Octane rating is directly linked to engine power! High octane fuel allows for higher compression ratios & far more aggressive, advanced ignition timings which equal more power... in an engine designed to take advantage of it!
It's true to say that sticking Shell Vpower in a standard 1.6 Focus will have little or no effect on power or MPG but to say octane rating has nothing to do with power is just wrong...

BeenThroughItAll

Paradigm wrote: »

Haven't you just posted a total contradiction?


Octane rating is directly linked to engine power! High octane fuel allows for higher compression ratios & far more aggressive, advanced ignition timings which equal more power... in an engine designed to take advantage of it!
It's true to say that sticking Shell Vpower in a standard 1.6 Focus will have little or no effect on power or MPG but to say octane rating has nothing to do with power is just wrong...

No. More octane does NOT mean more power. It means potential to develop more power based on timing changes.

More power is not directly related to the octane rating. If you don't make other changes, you don't get the power, end of chat.

Paradigm

BeenThroughItAll wrote: »

With lower octane fuel, you develop less power because the fuelling and ignition timing are running sub-optimally to compensate for increased propensity for pre-ignition; in other words, the vehicle runs in a fallback mode to protect the engine by adjusting parameters whose knock-on effect is a reduction in power output.

So if there isn't a direct link between octane rating & power what's the above all about?

bigjl

BeenThroughItAll wrote: »

No, it's nothing to do with the octane rating equalling more power.

It is simply that the static timing, fuelling, and ignition timing are all optimised and mapped using higher octane fuel, allowing greater knock resistance. With lower octane fuel, you develop less power because the fuelling and ignition timing are running sub-optimally to compensate for increased propensity for pre-ignition; in other words, the vehicle runs in a fallback mode to protect the engine by adjusting parameters whose knock-on effect is a reduction in power output.

I know that, you need to consider my post in the context of Striders comment that higher octane producing more power is marketing which I was replying directly to.

A WRX with 95 RON does create more power than one running 98 RON. Which clearly shows it isn't marketing.

Does anybody remember the (from memory) 102RON stuff you could buy from BP? They used to padlock the pump on the A13 in Newham.

Consider also Jap Import WRX's from years ago that needed to be remapped for UK fuel otherwise they would go pop.

KingS6

bigjl wrote: »

I know that, you need to consider my post in the context of Striders comment that higher octane producing more power is marketing which I was replying directly to.

A WRX with 95 RON does create more power than one running 98 RON. Which clearly shows it isn't marketing.

Does anybody remember the (from memory) 102RON stuff you could buy from BP? They used to padlock the pump on the A13 in Newham.

Consider also Jap Import WRX's from years ago that needed to be remapped for UK fuel otherwise they would go pop.

Yes! The price of the stuff as well, ouch!

almillar

If you put higher octane fuel into a car, it needs to change its timings to take advantage. So you would need to run a few tanks to make sure there's no normal stuff left and you're only running on super.
THEN you might need to do an ECU reset to force the engine to learn what fuel it's on - anti-knock settings.
BUT it depends on the engine. Some quite lowly engines will learn, whereas, for example, my RX8, was hard wired for 95 RON. Running Super had no effect, no matter what people thought. In the UK, it was quoted with 231 BHP. In Japan, where they have higher RON fuel, it was tuned for that, and quoted with more power. In the US, it was hard wired for 91 RON fuel, and was quoted with less power.
It's specific to your engine. Read your manual for what fuel to put in!

neilmcl

So where's the OP doesn't he want to join in on the discussion?