I'm unsure if my car has a JDM or UK ecu - is there any way of me telling?

I know fundimentally the engines are the same (JDM has higher compression?) but I thought i'd best ask, incase the engine maps are radically different (I can't see there being an issue, but please don't laugh as I thought i'd better be safe than sorry and ask the question!)

With all the talk of JDM engines needing 100+ RON, i'm guessing using any super unleaded is going to be ok?

 

I don't know from experience of any JDM engines on UKDM ECUs, but I do know of UKDM engines on JDM ECUs running fine.

It looks as if your car is UKDM which means it will have a UK ECU.

F20Cs have knock sensors so putting the JDM in shouldn't present too many problems. The reason the JDMs are known to like the higher RON is due to their slightly higher compression ratio (11.7:1 instead of 11:1) The main issue, off the top of my head, is the VTEC oil pressure sensor is absent on JDM meaning you will not be able to activate VTEC without shorting the ECU Pinout to ground.

 

You're right on the VTEC oil pressure sender being missing - (my car is a UK car, it was fitted with s JDM engine which started knocking, I then purchased it and fitted another JDM engine)Instead of where the sensor should be it had a bolt, so I simply swapped the sensor from my previous engine into this new engine in place of the bolt, and plugged it in - the car engages VTEC so I assume thats worked (I assume Adz did the same when he fitted the previous JDM engine in, and swapped the pressure sensor from the original UK engine onto the JDM engine)

I hope that makes sense lol.

So trying to put 2 and 2 together, if my wiring loom has the plug on it for the VTEC pressure sensor, then the loom is still a UK loom rather than a JDM loom - would this mean it should be a UK ecu too, or will the JDM ecu's plug into both UK and JDM looms? (assuming there are differences between them?)

 

You can absolutely make sure by plugging in an diagnostic tool to the OBD port on your car.

UK ECUs are OBD-II compliant whereas JDM ECUs aren't (But they still happily report on OBD-II features). I use an ELM327 and my PC with Easy OBD-II to connect to the car.

JDM ECUs will fit onto a UK loom. The only other dead giveaway is if your car is limited to 112mph (Well, it's more like 120). Since you have a UK Speedo, you wouldn't need to do any KM/h to MPH conversion so there would be no speed sensor trickery to stop the limiter.

If you haven't got a private road big enough to test the speed out, go with method 1! But I do reckon you'll have a UK ECU.

Actually, simple test! Unplug your VTEC Oil pressure sensor from the loom and see if VTEC works (Bearing in mind this will give you a CEL that you'll need to reset with an ECU fuse pull).

I still recommend Method 1 though.

 

I have a jdm ecu available. Could be the safer bet.

 

Conveniently I did a run on the private land at my mate's workshop complex and it climbed to an indicated 126mph before I needed to brake

 

You know the pistons have a different top on the JDM motor, more compression ftmfw yo!

 

Ah so it's the pistons - any other differences mate?

If the jdm ecu's are speed limited, how do you de-limit them? Could mine be a jdm that's been de limited?

Sorry for all the questions, and thank you for the help so far!

 

I delimted mine with an Apexi RSM. Otherwise you can do what I have already mentioned

 

I thought it was a thinner HG that increased the compression on JDMs?

I also used an Apexi RSM...good bits of kit that offer a few more tricks than standard de limiters.