Mapping JDM for UK fuel
 

Hi,

Might be a stupid question but can you map a JDM for UK fuel without changing the performance? I.e. not a power chasing map but purely to allow the safe performance from the factory on 99Ron fuel?

Thanks

You can remap the car without increasing the boost (which would normally give you the greatest gains). The more the fuel and ignition is optimized, the more efficiently the engine will run. A byproduct of that optimization will be increased fuel economy and power. Obviously the engine could be remapped with aggressive timing etc to try and eek every last bhp from the engine or you could run a very conservative map will the timings pulled (I don't why you would do this unless you live somewhere with unreliable supplies of decent fuel). Any reputable mapper should be able to advise by I don't see why you wouldn't want a remap to be optimized for the fuel you are using . It will almost certainly increase the efficiency of the engine, so I would worry if the power increases by a few bhp.

The reason for the map maybe wasn't clear but i had put it in the title. It was a question around mapping to ensure it is suitable for UK fuel on an import from Japan. I often read adverts etc. saying 'mapped for UK fuel' and assume (possibly wrongly) that this should be done as a matter of course before running too much on UK fuels following import. There would be no issue with some gains as a by product of the map but i was just getting at the fact it would be for the fuelling and engine safety rather than going for power gains as the main aim.

Thanks

Japan fuel and UK fuel are different or at least were back in the 90s. Even if you don't get a remap its worth checking the stock map.

Running the car on 99RON without a remap will be fine. 95RON, not so much. But then I wouldn't run a UK car on anything less than 98/99RON anyway.

You can have the car mapped to any fuel - 95-99RON. The higher the fuel rating the greater the potential efficiency. If you somewhere for example, where it was hard to get SUL, you can have the car mapped to safely run on 95RON. It will get worse mileage and have less power of course.

I suspect if the car has been "Mapped" by the importer for UK fuel, it will probably be a generic map that pulls timing and increases fuel to make the car "safe" for lower rated fuel. That's not the same as having a custom mapped produced live on a rolling road, where every aspect of the unique set up of the car is optimized (including whatever fuel is in the tank).

Understood, thank you. Guess it would be a full remap then that would make sense to optimise efficiency, performance and safety of the engine.

thanks

From what I've been reading, mapping for UK fuel is a thing of the past (early 2000s) that needed to be done in classics.
Japan's high octane gasolines normally have 98-100 octane rating regardless of brand.
As said previously, if you use 99RON in UK and as long as the car is checked on a RR and runs fine (the ECU doesn't pull timing, it doesn't ping and AFRs are OK) there is no need to map it for UK fuel.
I am aware of plenty JDM Subarus of friends (Imprezas and Forester STis) that have been running the stock JDM map and done over 100k miles without issues.

OK, great. Thank you for that info

many JDM cars have very aggressive ignition maps and we often find they are already totally retarded (regardless of fuel used) to the point of detting when first run........
Gen4 twinscroll Legacy's in particular are notorious for this so its simply wrong to suggest that only "classics" require maps

IMO you need to map check any import as a min. and like all things even if its been 'mapped' the quality varies massively!!

Thank you for this

At bare minimum I would have a map check, because an experienced mapper will be able to provide you with a extensive health check.

You also need to consider that it may have been mapped already in Japan. I think any turbo car with unknown history would benefit from a map check at the least.