2.0 vs 2.5 Duratec/MZR

As the third generation MX-5 continues to age, we’re seeing more and more customers who are in the need for a refresher under the hood. Generally the 2.0 is quite expensive, and the 2.5l duratec, being a Mazda/Ford global platform motor, is a better choice.

Recently we’ve had the chance to tear down both a 2.0 and a 2.5, and we’ve taken the time to measure the rods/pistons to see exactly what the differences are. The conclusion? Basically the 2.5 is the 09+ 2.0 but on steroids. More displacement, bigger and beefier rods, and overall more stout. Lower CR making it ideal for boost, this motor is a much better starting point for Forced Induction. On with the show!

So you can see the stock 2.5 hardware is quite superior to the 2.0 for boost. Stouter rods, dished pistons, fully floating wrist pins…the only thing that is the same is the thickness of the piston rings. While we’ve put down over 350 torque on the 2.0 components, you can expect to best that with the stock 2.5 internals, with even more margin of safety due to the lower compression ratio. Though not up to the levels of fully forged internals, they certainly should do well enough for most. Not to mention be a far superior replacement for even a naturally aspirated MX-5. Some of the Grand-Am/World Challenge teams we work with have hit 200 WHP even on the stock internals. No small feat given how restrictive the MX-5 intake plenum becomes at higher HP levels.