One very interesting point of discovery from the Japan trip, is the fuel they use is 100 octane,
this is a point of interest as I have read here that it is the same as ours, so this will help some of you with Japanese ECUs
Isn't that why its always best to update the ECU on imports so they are set up for the right fuel?
Correct me if im wrong but i didnt think 100octance was possible on our system of fuel, the Americans get 100 octance plus but they use a different system of measurement to us? Like i say this could well be wrong but its just something i heard somewhere a long time ago.
There is great confusion on this as the japanese don't seem to specify what system they use to measure fuel octane rating. The Americans seem to have the lowest octane ratings as they use the more precise (RON+MON)/2 method or measurement. The UK/Europe RON system is not that accurate as the test conditions for RON are not that demanding, especially when dealing with high performance engines. MON uses a much tougher test (ie high rpm & high inlet temperatures) to come to a more precise octane rating.
I have never seen a petrol station in Japan advertise which method is used to determine the fuel ratings, and not even a distinction is made between "Regular" and "Hi-Oku" at the pumps with octane numbers. All very confusing!
Sounds like a straightforward question but its difficult to find a straightforward answer. On this and other boards people have mentioned that Japanese hi-octane pump gas is 100 octane. When I asked the guys at Top Secret what it was they said 98 octane (RON). I'm more confused than anything else...
Similarly, I know that HKS Drag Gas is 110 octane although I'm not so sure about whether that is measured in RON or MON. Maybe someone else can shed some light on this.
I covered this in full a few years back on the LSOC but it appears that the 'archive' has been lost, which is a shame.
But, put simply, the important thing to remember and what was explained in the OB thread was that Power is not Octane.
Calorific value gives max power output available at 400hp, but due to its Octane rating of 95RON the max you can get from it is 310hp.
CV gives MPO of 370hp, Octane rating is 110RON the max you can get from it is 340hp
Japanese fuel has a high Octane but has a lower CV than the UK SUL.
Yes, please do Mycroft! This has just gotten more confusing. So Japanese fuel is now worst, and UK uses MON testing but advertises RON??????
Shin what do you mean with your MON/RON listing?? They are certified /standardized tests....why should Japan use different RON? If its 100RON in Japan it should be 100RON anywhere around the world. And why is it that Japanese petrol stations are not required by law to actually let customers know exactly what they are putting into their engines?
the 100oct fuel in Japan is 99.4 to 100.3 MON to be called 100oct it has a CV 4.9% lower than our fuel, to better suit local conditions
The overall effect providing some little change are made to the Spark Plugs, you can run 1 grade cooler (but that is borderline) or open the gap slightly, this is the reason why I found my TT ran better with the 0.9mm gap rather than the 0.8mm as they are in Japan.
With those mods on a standard car we are 'down' less than 1% on the Japanese figures, with more mods the gap increases, at a guess 20hp perhaps on figures around 500hp, but that is just a guess, so treat it with some caution.
Mycroft... thanks for providing us with some information.
However, your answer has prompted another question. Where does the 100 octane fuel you are referring to come from? In other words, is 100 octane that you quoted data on identical to the hi octane fuel that comes from the pump at the typical petrol station in Japan or is that simply the data for 100 octane fuel that you could buy in Japan from a speciality place (ie. similar to buying a can of HKS drag gas)?
I dont need to know , I am happy with the information I was given by Junichi Tanaka and this has also been backed up by mycroft so thats good enough for me,
Have a good time in Japan, bring me back a present