Would increasing the octane value decrease the knocks
Thread Starter
Pro
Joined: Mar 1999
Posts: 678
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From: Oslo, Norway
Would increasing the octane value decrease the knocks
Hi I have an 85 4+3 manual with slightly higher CR and I hear some few knocks when flooring the throttle pedal.
I mus be on the edge with the ignition adjustment but I have 6 degr BTDC.
we have normally 95 octane here but there are 98 also. Will that do the situation better?
I mus be on the edge with the ignition adjustment but I have 6 degr BTDC.
we have normally 95 octane here but there are 98 also. Will that do the situation better?
Race Director
Joined: Oct 2005
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From: Rolla Missouri
2021 C4 of the Year - Unmodified Finalist
St. Jude Donor '10 thru '25
I believe the octane rating in Europe uses a different method than here in the states.
So, on the surface it looks like a higher octane.
So, on the surface it looks like a higher octane.
Generally, octane ratings are higher in Europe than they are in North America and most other parts of the world. This is especially true when comparing the lowest available octane level in each country. In many parts of Europe, 95 RON (90-91 AKI) is the minimum available standard, with 97/98 RON being higher specification (being called Super Unleaded). The higher rating seen in Europe is an artifact of a different underlying measuring procedure. In most countries (including all of Europe and Australia) the "headline" octane that would be shown on the pump is the RON, but in Canada, the United States and some other countries the headline number is the average of the RON and the MON, sometimes called the Anti-Knock Index (AKI), Road Octane Number (RdON), Pump Octane Number (PON), or (R+M)/2. Because of the 8 to 10 point difference noted above, this means that the octane in the United States will be about 4 to 5 points lower than the same fuel elsewhere: 87 octane fuel, the "regular" gasoline in Canada and the US, would be 91-92 in Europe. However most European pumps deliver 95 (RON) as "regular", equivalent to 90–91 US AKI=(R+M)/2, and deliver 98, 99 or 100 (RON) (93-94 AKI) labeled as Super Unleaded - thus regular petrol sold in much of Europe corresponds to premium sold in the United States.
Safety Car
Joined: Dec 2006
Posts: 4,290
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From: St Marys GA
Higher octane will prevent the knocking. However, if you're looking for maximum performance, a little bit of knocking at WOT and low RPMs is a good thing. That means your spark timing is as advanced as it can get, which means more power. And a little bit of light knocking won't hurt your engine.
Safety Car
Joined: Jan 2004
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Not withstanding anything else the knock sensor should be retarding the timing way before you can hear it.
My datalogs will show knock retard and timing being pulled out when I can not hear anything from the engine
My datalogs will show knock retard and timing being pulled out when I can not hear anything from the engine
Melting Slicks
Joined: Mar 2008
Posts: 2,141
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From: Santa Maria, CA
I'm not sure you'll get the same warning with an 85. The computer is much slower (160 Baud). I used to have knocking with my 85. When I installed aluminum heads, the knock went away completely. I think the cast iron heads run hotter and are much more prone to knock.
