Compression Ratio and Fuel Octane grade

[Papercup]

Hi guys,

 

I came across this passage when was reading an article about improving car performance:

 

"Higher compression ratios produce more power, up to a point. The more you compress the air/fuel mixture, however, the more likely it is to spontaneously burst into flame (prior to the spark plug igniting it). Higher octane gasolines prevent this sort of early combustion. That is why high-performance cars generally need high octane gasoline - their engines are using higher compression ratios to get more power."

 

Is it true? Does it mean that those car with high compression ratio need to use high grade fuel e.g. v-power?

[Octopus]

Yap, that's should be true. The higher octane the fuel have, it can undergo higher compression before self-ignition.

[Papercup]

So those SC and TC got to use those high grade oil right? Hmmm... so those high grade oil really got some advantages.

[Turbonetics]

yah....higher CR vehicle need higher octane rating fuel...

some race cars use fuel moree then 100 ron....

the higher Ron also give racing cars more power...

[Octopus]

[reply]

Hmmm... so those high grade oil really got some advantages.

Of course must have advantage, otherwise how to justify the higher pricing.

[themagi]

Old thread but want more views,

 

I've been asking around Honda owners and according to the owner manuals, City and Oddy at least can run on RON92 but the compression ratio of City is 10:4 and Oddy is 9:7. I thought any CR above 10 must run on at least RON95? Then I checked out Chevy Cruze and its CR is 9:5 and when I checked with a Chevy SA, he said that all the Chevys run on minimum RON95. So like different cars are telling different stories on what CR can accept what RON grade?

 

http://www.------.com/pdb/cd.php?pid=1804 - City

http://www.------.com/pdb/cd.php?pid=527 - Oddy

http://www.------.com/pdb/cd.php?pid=2366 - Cruze

Edited July 11, 2010 by themagi

[Yeobh]

The other factors affecting the fuel octance to be used are piston crown design, position of spark plug, used of pre-combustion chamber and direction of incoming air etc.

[Zyrofillica]

and also whether it is DI or MPI. DI reduces cyclinder temperatures allowing a lower octane petrol to be used even though its at higher compression.

[Good-Carbuyer]

and also whether it is DI or MPI. DI reduces cyclinder temperatures allowing a lower octane petrol to be used even though its at higher compression.

Switched to Diesel engine?