Hymee

iTrader: (1)

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.

downshift

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?

Hymee

iTrader: (1)

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.

takahashi

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.

ypwpat

Sorry what the Hell is Knocking? :p

Is it something that sound like knocking on your engine?

I don't quiet understand.

Hymee

iTrader: (1)

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.

ypwpat

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?

DMRH

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.

Hymee

iTrader: (1)

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.