Replacement Engine Advice/Options

  1. My model of MX-5 is: Mk3
  2. I’m based near: Brighton
  3. I’m looking for technical help or recommendations on: Replacement Engine

My son has a lovely 1.6 Mk2 - and his best friend who has a less well cared for mk3 1.8i has just gone “bang” in a big way and put a piston through the block - ouch ! - Its aa’d home on trailer and hes very sad _

I have swapped a few engines in my time … - (last one was a subaru into my 1981 VW camper !) and I offered to help him out and install a used one for him as his dad isnt very good with the spanners .

Its a 2005 MK3 with a 1798cc Engine - code L8 286356 - any advice or tips on this job would be welcome such as
what engines will fit -
what should I be looking for
(immobillser/ecu issues…

and last but most importantly… pointers on a supplier - mx5 breaker would be very gratefully recieved…

Matt - Brighton

It went bang for a good reason.
Don’t fit a used one, it’s likely it’ll do the same unless it’s been properly rebuilt.

Get a Connaught v10 that will do the job

Prestige Spares on Facebook are in Rutland,. They sell lots of MX5 spares, engines by the dozen and cheap. It’s rare these engines disintegrate big time unless they’ve run out of oil. Buy one and do mild refresh and refit to car. I would also remove crank bearing caps and check for wear.

If it ever comes to fruition.

Thanks for the replies - I will get in touch with the breakers today :blush::+1:

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These engines are weak unfortunately. My 1.8 also went. Got myself a 2.0 in the process for the same price. If you can find/afford it, an NC2 or NC3 engine is still not a great engine but better than NC1 reliability wise. For a 2.0l you will need a different ECU however. ECU’s are coupled to ignition barrel and instruments for the immobiliser. You need to find someone that can couple a 2.0 ECU to your 1.8 barrel and instruments. This would be the easiast for a dealer to do that knows how the process works; a code is needed that has to be retrieved from Mazda software. Or prepare to swap instruments and losing your original mileage in the process and swap your ignition barrel along with the transponders of the keys. If you swap the complete keys you also need to replace all locks. Doors, trunk and the one inside the center cabinet. A third options is a flashed ECU. Not sure if Versatune can disable the immobiliser but if it can it’s probably the cheapest way for applying this third method.

Someone on said he read the ECU map for both the 1.8 and 2.0 and he said it was the same. The difference was in the table for the VVT, which the 1.8 doesn’t have and the 2.0 does. That table was empty in the 1.8 ECU. This means VVT on the 2.0 won’t work with a 1.8 ECU. But since the map is said to be the same, you should be able to run the 2.0 on the 1.8 ECU. I did that for a couple of months without any problems.

Engine is pretty much identical on the outside. So should be a very straight swap. While you’re on it, I would advise replacing the header for an after market one for a few reasons. Sometimes the precat in the stock header breaks down and can clog up the second cat. This happened to me, I need to replace both header and mid pipe. Replacing the header will prevent the second cat also being destroyed if the first falls apart. Second, the OEM header is very restrictive. Replacing the header is a pretty shitty and time consuming job when the engine is in the car. From what I’ve read, depending on experience, availability of help, specific tools and state of the car/rust, people seem to need 6 hours to 2 days. While the engine is out of the car I would not expect the job taking more than 30 - 45 minutes. Depending on the rules of where you live you might need an after market header with cat. IL Motorsport seems to have the most cost-effective header with decent quality. At least my 4-1 catless header looked pretty decent and gains have been proven many times.

Make sure you get the 2.0 with it’s own loom, otherwise there is no VVT. Brakes on the 1.8 are the same as the 2.0 so that isn’t a problem either. It really seems the only difference between the 2.0 and 1.8 are the ECU with VVT and the bore/stroke on the inside and of course VVT.

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Thanks so much

That’s exactly the level of detail and advice I was looking for - your help and guidance are very very much appreciated

I will post here how things process in case it helps anyone else here too


Hello Matt
Roddisons Motorsport Sheffield a fair distance from Brighton is probably a good starting
point 0114 244 5300 ask for Paul.

Spoke to paul at Rodissons and he was amazingly helpful and gave me some good advice and options. Thier recondition engines are £1200 which I thought was a bargain. My sons friend probably can’t stretch to that but I have found a good low mileage mk2.5 1800 engine - I just need to find out if it will be compatible with the ecu on the car it’s going into which has the l8 engine code

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The MK2.5 engine is completely different to the MK3. It’s not just the ECU that it won’t be compatible with.

Thanks Robbie - that’s a shame as it was a low mileage engine at his price range - I will have to keep looking for an L8 engine then - thanks for the reply - disappointing but better to find out now

Appreciate all the help and advice I am getting here from the MX5 community - all replied are very much appreciated



Sadly there currently seem to be no L8 engines from running cars (mot failures) to be found apart from fully reconditioned ones a - :slightly_frowning_face:. His tale of woe is a familiar story. I have phoned all the breakers and MX5 specialist I can find and trawled e bay for a few weeks too.

The cost off a similar mk3 being advertised locally is under £2k and a Mazda MX5 specialist has offered him £500 for his broken one

We can’t get into the complications of fitting a different code /type from another model or. 2.0 - so it looks like the grim reaper will be visiting

Thanks again to everyone who offered replies and advice - it’s much appreciated


Is an exchange-engine deal not possible?

I guess such engines are too expensive.

You mentioned “… less well cared for…” at the start of the thread.

If the guy has been running it on the cheap, and not bothering too much with basic maintenance,
and he wants a cheap replacement engine…

tbh, I’d stand well back from this. You’re on a hiding to nothing.

the reconditioners want a “re-conditionable” engine - and his isnt as its got a hole in the block - so its a £500 surcharge on top of cost


In fairness to the lad ……he has only had it a few months and it was previous owners who hadn’t cared for it I was referring to so I would have liked to help him out - and I was lucky as my dad taught me all about car maintenance and repair-

I will help him find a better replacement and give him some tuition on basic maintenance and care of older cars

Thanks again to everyone for help and advice - it’s much appreciated

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Aha, i can see how a hole in the side could be an issue.


You could put a 2.0 in there and run it on the 1.8 ECU. Still big performance gains and later on when he’s got 100-200 quid to spare he can fix the ECU-thing. But even with the 1.8 ECU it’s a lot faster. But I don’t know how prices are in the UK, here a 1.8 was just as expensive as a 2.0 Also, while searching for that thread with fuel maps comparing the 1.8 to 2.0 I found a thread which shows the timing on the 1.8 to be more advanced compared to the 2.0 so if you do run the 2.0 on the 1.8 ECU then only RON 95 or higher :slight_smile:

Can’t find the thread quickly in which I read someone compared both stock fuel maps and said they were the same :slight_smile: