I just found this very interesting article. I think it somes up a few things that have been said on here in a few random threads.

I thought some of you might like to read it.

http://www.superchargersonline.com/content.asp?id=105

Take note of the paragraph "What's the benefit of higher octane?"

Cheers,
Hymee.

 

Is it true that some engines would continually advance the timing until it senses a knock? That way it will in some sense detect the higher octane and thus utilizes the most efficient timing for that level?

 

That would depend on how the PCM is programmed. From my experience, they retard it from the pre-programmed value when knock is detected as a saftey measure, rather then the other way around for a perfromance measure.

Cheers,
Hymee.

 

Great find... thanks Hymee.

I think fuel additive to increase Octane do nothing for Renesis.

But it does better for VTEC engines - I have knocking in 2nd gear 6500rpm unless I use BP or Optimax and fuel additives.

 

Sorry what the Hell is Knocking? :p

Is it something that sound like knocking on your engine?

I don't quiet understand.

 

Did you read the link? There was a short explanation there, and a link to an more in-depth article.

Your mission, ypwpat, is to read the articles and provide us with a summary

Cheers,
Hymee.

 

ok is this right?
Knock/detonation is the Ignition of air/fuel Mixture before the spark plug ignite it due to high temperature on the engine?

 

You have now discovered what Mazda & all other Wankel license holders found out back in the 60's..........

The compression process within a rotary engine is (obviously) different to a piston engine & as a result the Octane range is far larger than a piston.

I recall an engineering paper from Curtiss Wright (USA license holder) I read some years ago. Back in the early 70's they tested a 160hp 2-rotor NA engine (RC2-60=9.2:1 compression rotors). From a RON range of 85 right through to 103, the engine ran perfectly without any knock & recorded a variance of 4hp.

They noted in the paper that the jets from the carby required altering in the higher RON ranges. A piston engine with the same compression would ping & go bang........

I have mentioned this before, but the only difference you will find between normal ULP & Ultimate/Optimax is in the wallet.

Get a turbo happening & the compression increase changes the story when boost comes close to 1-bar.

 

You got it. Basically it is an explosion (rather than a burn) before iginition is intended, and puts all sorts of undesirable stresses on things.

Cheers,
Hymee.