Setting up for higher octane petrol?

[mrflibbles]

I assume my bmw e30 318is is set up to run best on 95 RON, and AFAIK it doesnt have a knock sensor.

Its currently having a top end rebuild, so while its in Im tempted to have the ignition timing changed, so it will run with better performance on 98 RON, i.e. optimax.

Is it difficult to do? Is it worth it? (I only ever run on Shells finest)

Who is this RON bloke anyway?

[Fatboy]

Not difficult to do at all IIRC - since you only run optimax anyway, can't see any reason not to while the head's already being rebuilt...

[mrflibbles]

Hmmmm someone over on E30 Zone told me that the timing is controlled by the ECU..... this isn't the case is it?

I thought the ECU only controlled the mixture?

Hmmmm....

Thoughts?

[Mr2Mike]

Simply advancing the ignition will not take advantage of a higher octane petrol. In fact, as higher octane fuel usualy burns slightly more slowly than straight unleaded, advancing to igntnion may get you back the slight power loss you may otherwise experience using high octane fuel in an engine that dosen't need it.

As you have the head off, consider skimming it to raise the compression ratio which will make use of the higher RON fuel. Provided you don't go silly, a higher CR will give power and economy benefits.