Recently installed a Mugen ECU as the last link in a chain of Mugen mods to my car, these include CAI, Exhaust header, exhaust and cooling mods. What has come up in conversation on several threads about the Mugen ECU is that a LOT of the safety features have been removed as a RACING ONLY ECU. I don

 

Have you seen this: https://www.s2ki.com/forums/index.php?showtopic=72881

 

Yeah thanks, just needed to re-read it again. So the Mugen ECU will run the car leaner at the lower and peak revs and it will advance the timing. The knocking sensor is disabled/ignored so it makes it all the more important that you install the basic cooling mods and run the car on a higher octane fuel to retard any knocking. Not the best news for a car that is primarily to be used on the road, the problem is it feels better, its quicker pickup from a standing start and better torque in the right spots, bugger. Still tempted to keep it just need to reduce the possibility of knocking so, okay talk in the US/Canada is of 91 RON being used, is that the equive of 95 here in the UK?

 

A number of us find the Mugen ECU to be very good. The 98 RON fuel you are using is a safe bet, as is the 93 AKI fuel in the US (I would say that 92 is marginal and 91 can cause problems in some load situations).

US Anti-knock-index is the average of the RON and MON octane ratings and is generally a broader measure. It is said that AKI 93 is generally equivalent to 98 RON but I don't think there is a clear mapping. I would not use lower octane fuel unless left with no choice.

I am careful when I cannot get 93 fuel but find the ECU improves drivability so much I would not consider going back to stock.

 

thats the kind of info I need, I have been having kittens over this.