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So, how about supercharging?

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Last week we mentioned a hit list of things to do to the Exocet. One of which was, of course, more power.

We don’t actually know how much power our MX5 had when we got it. A nice new 1.8 Mk2, off the shelf, had 140bhp and did 0-60 in around the 7-8 second mark. Not quick, but a weight reduction from 1025kg down to 600 means that in theory, the Exocet has a little more oomph than a stock Mk2. But on our 100,000 mile donor car, with no service history, well lord knows what it has these days.

With 500 miles under our belt, let’s consider options for more power. Because, you know, why not….

First off, new for old. Replacing the slightly tired, high mileage engine with a newer or rebuilt engine, which still has all of its horses, is one option.


A friends Mk2 engine certainly has some er, issues. Cylinder 4 seems to be the most unhappy. This might be because it had no oil in when he brought it, or because cylinder 4 on the MX5 is prone to overheating. Ours might be in much the same state, so a rebuild might restore a few horses. A direct replacement engine might be another option, but ones with less mileage are thin on the ground. VVT Engines from later models with 42,000 on the clock are available, but this isn’t quite the direct swap we might hope for, requiring a new ECU, immobiliser etc.

This might also be a long route to a few bhp, though if we are stripping the engine down, we could have it ported and played with. Blink Mortorport - offers a range of porting, polishing and general head work which can breath new life into the engine. But we cant do that at home and the car will be off the road for 4 weeks.

So, next up is improving the power in what we have (We might also buy a “spare” engine, refurbish it and send the head off to Blink whilst no one is looking….)

For some quick power, we could reverse backwards through a Halfords, install a big air filter and a “Cold air induction kit”, maybe some exhaust tips, and make Ermy sound louder. Sadly Mighty Car Mods sort of debunked this on their youtube channel, suggesting that the power gains from induction kits are negligible. We also already have a big K&N Cone on there, as this was easier than re-installing the original MX5 filter.


Some people argue you need a remap on the ECU to get the changes needed, others suggest it wont matter; natural aspiration, even with a big wide open breathing tube isn’t going to add much.

What is needed is forced induction.

So, that leaves us some options. Turbo or Supercharger. The Mighty Car Mods guys covered this too, in a pretty convincing manner, using MX5’s. Your text to link here… The general theory is that Turbo lag’s no fun and for little windy B roads, the supercharger was going to be more responsive and give more bang for your buck. Especially at the low revs which the MX5 lives in during gear changes. Which it does a lot of. I also have a personal preference for superchargers, for no reason other than the noise they make.

Jackson racing supercharger kits are available as bolt ons, though these are very expensive and seem to be rarer to find these days. We did consider buying the remaining 80% of a crashed Westfield based on the MX5 and stripping it, but a vastly more sensible option seemed to be using an Eaton M45, from a Mini Cooper, with some modifications, custom mounting brackets and pipe-works.

Indeed the following kit: https://bofiracing.co.uk/product/sr1-supercharger-kit-for-mazda-mx-5-na-nb/

Seems immensely comprehensive. Given 1/4 of the cost is in the ECU, and the Eaton M45 runs to about £200 on its own, it seems very well priced.

But, we spotted this after we started our own efforts. So, here is our Eaton M45.

Eaton M45

We just need to weald up a pile of custom manifolds, brackets and flanges, install a second throttle body and find somewhere to hide an intercooler. Given we just built a car though, this feels like an easy task…..

Manifold1 Manifold2 Manifold3 Manifold4 Manifold5 Manifold6

A little bit of CAD, some box section and 6mm plate.

Looks easy right?

Yeah, we aren’t actually that good at fabrication. This burnt out a lot of drill bits, took hours to cut a single hole and the welding is probably a bit sketchy. A lot of investment is needed in kit, time and tools to get this far and we would probably want to remake it all as the second attempt would undoubtedly be better.

Alternatively this bloke sells the kit on eBay - Supercharger Mounts and the design looks very similar to ones we were looking to copy. It looks like he has a laser cutter and a decent sheet metal bender, which we don’t have.

So, long story short, Supercharging is the way to go, and bolt on parts are how we will get there!


Welcome to Twits with Spanner. A blog following two chaps as they attempt to build an Exocet kit car with bits from a donor MX5, spanners and lots of hope. Read more about us