Race Engine Forum UK

Hi Guy

Im going to the UK to race this weekend, and as we cannot get higher than 95 ron fuel at the pumps this side of the pond our engines are mapped to run on same. My questions are,
1.Could I use a higher octane rating say 98 or 100 ron fuel that is easly available in the UK with out doing any damage to my engine
2. Also an I right in saying that you can go up in rating without doing any damage and not down.
3. Would I have to adjust the ing timing.

Gary

The octane rating of fuel is, simply put, the resistance of the fuel to detonation (pinking) as such putting 98 or higher octane (RON in the UK, MON or combined in some other countries) will not cause any damage to your engine. If the engine was built to the limit to run on 95 RON fuel then putting 98 RON fuel in will provide a degree of safeguard since it is less likely to detonate, advancing the engine timing will allow you to utilise any remaining potential in the engine that is being wasted but the gains would be marginal. What the higher octane fuel does allow is the engine builder to utilise a higher compression ratio and that is where the real gains are to be made - going down the octane scale from here would be damaging to the engine and should always be avoided.

There are some race fuels that go beyond a higher octane rating to include extra free oxygen in the fuel which does increase delivered torque especially at the upper limits of the rev range but again the engine needs to be built and tuned to take advantage. The downside is that the MSA has pretty much banned the use of such fuels in the UK except where explicitly stated in the SRs and getting such regulations past the MSA is a seriously tall order at the moment. The best pump fuel you can hope for then is the 100 RON super-super-unleaded as sold by a handful of stations (almost entirely in the south of the UK).

So to summise (and answer the questions directly):
1. Yes
2. Yes
3. No (but you may find marginal gains if you do)

Hi Julian

Thank you for your reply very informative.

Gary