Hi All, new to the MX5 scene but basically Im looking for a 2010 -> Mk3.5 for a BBR turbo conversion. Ive been scouring the ads daily and have noticed a number of 125bhp 2.0 litres being advertised. I though the 2.0 litre was nearer 160bhp and the 1.8 was 125bhp. Did Mazda in fact do a lower powered MK3 2.0 as the adverts suggest? If so, after the engine work/turbo conversion Im guessing the results would be in line with the 158bhp tunes and not the 1.8 litre 125bhp results? Many thanks.
NO they didn’t do a lower power version, they could be 1.8 cars
Thats what I kind of assumed but ive seen six such ads now… there were three on pistonheads alone last night… Hmmm. Ok, thanks for the confirmation. 
I have a theory with this…
The 1.8 engines are not as robust as the 2.0 and quite a number have needed replacement over recent years. Prices for used 1.8 engines, if you can find one are prohibitive. I wonder if these owners have had 2.0 engines fitted but are quoting the BHP off vehicle documentation.
Quite surprised at the low BHP of the 1.8 engine as the MX5 MK1 1.8(1993-8) was a much lighter car but had 130bhp and MK2, again lighter than MK3, 140bhp.
In honesty there is actually little difference between the two engines VVT obviously, and slightly different non forged bits for the later 1.8 cars unlike the 2.0. Both suffer with similar oil starvation issues which seems to be a regular theme for the failure of the MZR engines.
The only reason ironically is the price of a 1.8 unit is more than a 2.0, not down to anything more than availability.
My 1.8 engine has been replaced about 5K ago, mostly as a I began to see more and more larger metal bits on the oil dipstick and the odd less than natural sound, oil was kept pretty much on full or just over 3/4’s full for it’s life until replacement…weird…either way the labour for stripdown would have been huge, and replacement was easier. Lucky for my car I saw past the slightly frustrating financial implications and it’s value to keep her on the road. I had the option of a fully specced ND 1.5 litre, but by the time I started doing the maths it was not worth my time (and effort, cost to get to the same stage as my NC)…and we needed a practical car which the ND was and is not.
In regards to engine repair, there are a number of cases where these engines have historically not been as great to rebuild, and instead replacement is easier and cheaper.
Incidentally, in most cases based on new parts prices it is actually cheaper to buy a full engine, to give an idea direct from Mazda a 1.8 long block is £4,722.53 + VAT, 2.0 long block is £3,988.31 + VAT, 2.0 auto engines are £5,506.94 + VAT. Short block 1.8 is £2,177.17 + VAT, 2.0 £1,358.45 + VAT, 2.0 auto £2,671.44 + VAT.
The biggest issue is visually they look identical to many people, to more experienced people there is the immediate thing of no VVT parts on the 1.8 unlike the 2.0.
Over power, I do not think it was the fault of the 1.8 engine, but more of the 2.0’s lack of power as there is such a small difference between the respective outputs 1.8 circa 130, 2.0 160…
Interesting.
Ok, so if I go and view a car, are there any visual clues on the car as to whether its actually a 1.8 or a 2.0 litre?
Thanks.
Note the missing VVT solenoid from the top front next to the engine cover and oil filling point (1.8 just has the non cut out shape for it)
2.0
1.8
