102.3 oct fuel??

[claudeG]

recently 102.3 oct fuel has become available at shell garages, does anybody know if i can use it? (MCS 2003). Should i mix ( 95 and 93 available), Johannesburg is 1700m above sea level..

[The_Bster]

Shouldn't be a problem, your car's internals will be very clean!

[claudeG]

what ratio of mix?

[Aldo]

ClaudeG,
You should always run your car on the highest octane you can find. This is better for the car and will give the most power and drivabilty.

Aldo

[ScienceGuy]

Quote: Originally Posted by Aldo

You should always run your car on the highest octane you can find. This is better for the car and will give the most power and drivabilty.

You should actually NOT do this.

Higher octane fuel burns LESS WELL than lower octane fuel, and using
higher octane than required to keep your engine from pinging will reduce
the power of the engine.

Use only the highest octane you need to keep your engine from pinging
in your driving conditions.

References:
Ref #1
Ref #2
Ref #3
Federal Trades Commission
Exxon

[jdewey]

On this site is a paper by the engineers that designed the MCS engine.

http://www.mini2.com/pdf/mcs_powertrain_us.pdf
Graphs are in the German language version at http://www.mini2.com/pdf/mcs_powertrain_de.pdf

here is what they said about the engine.
The best shape for the combustion
chamber with regard to both efficiency and
knock resistance was obtained with a piston
containing a lenticular combustionchamber
bowl measuring 1.6 cm3.
With the aid of knock control, this makes
it possible to use 91 to 98 RON fuels
throughout the world. However, the basic
design has been optimised for RON 98.

Remember they are quoting EUROPEAN Octane not USA. Add about 3 to a USA pump rating to figure the Euro number.

I ran nothing but 93 (USA) in mine for two years. I even tried a couple of half tanks of ($6.00 per gallon) Unleaded 100 octane. My last two tanks have been Mid grade and Regular at 89 and 87.

I don't notice any difference. Having said that, I will switch back to Premium in the spring a tank or two before I expect to need maximum performance out of the car for a weekend "event".

John

[Aldo]

Thanks Science Guy but I think your references are not wholly correct particularly with regard to a supercharged engine. They only talk about pre-ignition and not detonation. Pre-ignition occurs when there is another ignition source other than the spark plug and this results in unpredictable ignition timing and can cause knock. Detonation is when the fuel air mixture explodes rather than burns. Normal combustion in the cylinder is a controlled burn and this gives a controlled raise in pressure. An explosion gives a large uncontrolled spike in pressure and this is what gives the knock. With regard to fuel octane, detonation occur es when under the temperature, pressure and air fuel mixture condition the fuel becomes unstable and explodes. Higher octane fuel stays stable longer. I am sure there are combustion engineers out there who can explain it better.
My understanding ( and I may be wrong) is that the MCS engine management architecture will advance the engines timing until knock occurs. Thus the engine is running the max advance possible, introducing a higher octane fuel may result in the onset knock being delayed. Thus the engine runs more advance. I suspect that there is probably a limit to how much the advance the system will allow. Some engine management systems will benefit from this some won't.
I have been running 98 RON fuel on my MCS for 2 years and have had no problems and in fact saw an immediate improvement in drivabilty when I converted from 95RON to 98RON. I have also recently installed a 19% pulley under these circumstances there is no way I would run with less than 98RON.

Aldo

[ThumperMCS]

I've always found that the higher the octane used, the smoother the engine revs and it just ensures that the engine is making the most horsepower that it can. There becomes a point where it will just no longer provide additional benefit, and you will just be wasting your money, but it won't hurt anything. If you have custom programming though, you can benefit more from using higher octane, depending on what octane the software is written for.

[wow]

Claude G, where do u get 102oct fuel? I stay in Sandton and would like t get some in my MCS.