Ignition timing change with 95 Octane

[PeterH]

I've seen an ignition timing change recommended (14 degrees as opposed to 10) for better performance and economy when running with 95 octane.

Any views on that, and how it would do with 91? Or 98?

[Okibi]

It depends on the ambient temperature, engine condition, quality of the fuel etc.

If you're going to run 14" then i'd stick with only 98 fuel and keep a bottle of "Octane Booster" in your boot incase you get stuck having to fill up with lower grade fuel.

[zorruno]

I've seen an ignition timing change recommended (14 degrees as opposed to 10) for better performance and economy when running with 95 octane. Any views on that, and how it would do with 91? Or 98?

It also seems to randomly depend on the engine. I have about 16 degrees BTDC advance, and I can get away with running 91, in summer, with minimal engine load. But I don't - I always run 96 or 98 if I pass a BP station.

Timing advance of 14 degrees is the most commonly recommended performance mod for MX5 owners, and many that I've talked to seem to get away with being able to use 91 Octane without problems.

The only way is to try it - don't fill up with 91 though in case you get knock. If you get knock on 91, then you'll either have to fork out for higher grade fuel, or back off you timing.

cheers

[GEEMCB]

I've been running at 14 degrees BTDC for over 12 months now. For Fuel Card reasons I always use Mobil. When I changed the timing I moved to a diet of Mobil5000 with the occassional fill of Mobil8000 depending on what the station has on offer. I don't really notice any difference between the two & I've certianly not had any knock issues regardless of load, conditions etc. The car has about 156k on it.

Regards,

[Fletch]

Back before I got more modified....

I had no problems running 14 degrees on 91 and 18 degrees on 96.

14 degrees was a little better at the top of the RPM range, but 18 degrees gave a bigger kick down low where you use it commuting in Auckland...



As others have said, what each engine can cope with varies from one car to the next.... suck it and see.

Fletch.