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Meticulous MX5

A road/race turbo MX-5 (Miata) with show car level attention to detail.
Words by Michael Knowling, Pix by Julian Edgar

1990 MX5 Brillance

Head to any Australian club sprint day and you’ll find a collection of MX-5s (Miatas). These generally fall into two categories – near stock road cars that get lapped by just about everything else on the circuit or race-prep’d examples that’ve seen more than a bit of biff-barge action.

Well, Chris Romano’s 1990 MX-5 is a brilliant mix of both – it’s more than capable of taking on Westfields, TVRs and other track machines yet it is road registered and presents like a show car.

Chris – son of Bob of Bob Romano Performance – purchased this Mazda MX-5 about 3 years ago in what is described as ‘fair’ condition.

“The previous lady owner had three different tyres on the thing,” says Chris.

“She basically had no idea,” he says with a laugh.

The first move was to get the car up to roadworthy standard, which meant replacing the bushes and brakes; but rather than put on OE replacements, Chris upgraded to DBA discs designed for the 1.8 litre version and went with firmer aftermarket suspension bushes. Oh, yeah, and a matching set of tyres went on…

After gaining road reg, it was only a matter of weeks until Chris sourced a low kilometre BP 1.8 litre engine and ‘box. This replaced the gutless and aging 1.6 litre driveline.

Chris had a pretty clear idea of where he wanted to take the MX-5 so the 1.8 engine was fitted in conjunction with a host of aftermarket goodies. Most important is the AVO 1.8 litre Stage 2 turbo kit, which we’re told took some custom modification to suit the 1.8-equipped early MX-5 body. Apparently the supplied air-to-air intercooler (designed for the 1.8 model) won’t fit because of the placement of the 1.6’s air-conditioner receiver/dryer.

The AVO exhaust manifold attaches a Garrett-based turbocharger that is the subject of ongoing development – and Chris isn’t keen to give away the details! The turbine breathes through an Extrude Honed AVO dump pipe and 3 inch stainless exhaust that was fabricated in-house. The system uses a cat converter, a centre resonator and a quiet rear muffler – remember, this car is driven on the street.

The intake to the turbo comprises a JR air filter that’s kept away from under-bonnet heat thanks to a laser cut alloy airbox. Boosted air then travels through a 1.6 litre-spec AVO bar-and-plate air-to-air intercooler with an AVO plumb-back blow-off valve fitted on the return to the engine.

A double thickness PWR aluminium radiator replaces the standard unit, which was way overdue for replacement. The standard thermo fan is mounted to the rear of the new core alongside a downsized Davies Craig fan for the air conditioning core. A compact AC fan was necessary to make space for the cast intercooler pipe that leads into the throttle.

Fuelling the turbocharged 1.8 are undisclosed drop-in replacement injectors working with the standard fuel pressure regulator. The fuel pump is a replacement job that, surprisingly, hasn’t yet required installation of a surge tank; no starvation issues have yet been encountered on the track.

Closed-loop fuel delivery, ignition timing and boost control are left to a MoTeC M4 programmable system.

The 1.8 litre engine remains standard internally, which means boost pressure must be kept conservative to avoid detonation. Accordingly, boost pressure is limited to just 10 psi by the MoTeC ECU – but even in this mild state, Chris’s MX-5 has pushed out more than 200hp at the wheels on the in-house Dyno Dynamics chassis dyno. Not bad for a sub-1000kg vehicle!

Interestingly, the MX-5 1.8 litre engine uses a flywheel and pressure plate assembly very similar to the Mazda Familia GTX – which is, in turn, similar to that used on the Mitsubishi Lancer GSR. Chris uses a Mitsubishi-based flywheel and pressure plate combo modified to suit. A sprung centre ‘streetable’ clutch is also installed – Chris doesn’t believe in going for a pure competition clutch unless it’s absolutely essential. The gearbox is the stock 1.8 litre job. No problems with it so far.

On the other hand, Chris has seen some tailshaft problems in race MX-5s so he’s upgraded to a 3 inch tailshaft as a precaution. The diff is the standard 1600 unit fitted with a KAAZ limited-slip centre – and believe us, it’s a very limited slip centre! Chris makes the point that he should have swapped to a 1.8 litre MX-5 rear-end – this would have opened up a greater variety of diff ratios.

The RWD Mazda MX-5 is famous for its handling – and Chris seems to think that reputation is well-founded. His racecar is equipped with Koni ‘Yellow’ dampers which are converted into adjustable height coil-overs. Custom springs are used. Chris is also playing around with some custom swaybars and the fully adjustable factory alignment set for optimum handling. A Whiteline tower bar improves front-end rigidity.

The Speedy 16 x 7 alloys fitted at the time of our photo shoot are the ‘road spec’ wheels clad in Falken rubber. For track use, Chris switches to lighter 16 inch wheels wearing DOT-legal Toyo Proxes semi-slicks. Full slicks will be tried soon.

Once the turbo engine and suspension had been sorted, Chris ran the car at a local racetrack and ran some competitive times – but there was one obvious weak link. After only one fast lap, the 1.8-spec brakes disappeared…

Chris searched for a brake upgrade that could be contained behind 15 inch wheels but apparently it couldn’t be done – 16s were the minimum wheel size. Accepting this, Chris fitted MY99/00 Subaru WRX 4 pot calipers and associated DBA slotted rotors using custom hats and adaptors. It was a pain of a job. ADR-approved braided brake lines and EBC pads are also installed. Along with the master cylinder, the rear brakes remain untouched – though Chris says he might need to fit a bias adjuster.

And what about that beautiful body?

Well, it wasn’t planned to turn out quite so attractive! Chris says it became almost too good to take to the track after it returned from his friend who did the paint work. The colour is the original Marina Blue. But what’s really striking is the quality of paint application and the shine – Chris obviously uses some pretty trick car cleaning products! The MX-5 has a nicely integrated shape so there are no body add-ons except for an aftermarket front bumper section, which will be used to feed cooling air to the front brakes.

Another body addition that can’t be seen is a removable brace that’s fitted to the front-end to further improve body rigidity. This combines with a half roll cage that is attached to the seatbelt mounting section and a structural area near the hardtop fittings. Track use also necessitates a fire extinguisher and harnesses which hold you into Sparco Junior seats. A Momo wheel and AutoMeter boost gauge complete the interior upgrade; Chris plans to fit a MoTeC mini-dash soon.

Chris hasn’t hit the track as often as he’d like to but says the MX-5 comes together very well without any specific problems; its lightweight certainly helps.

“It’s really nice to drive on the track,” says Chris.

“It’s not difficult at all – it’s very progressive and fast through the corners,” he says.

Although competitive, an obvious avenue for improvement is more power – the engine is still untouched internally, remember? At the time of writing, Chris has another 1.8 litre engine in the build with H-beam rods, low compression JE pistons, nitrided crank and the basic ingredients of a durable high-boost engine.

“I want it to run 15 psi boost all day every day and with about 250 – 270hp at the wheels – I’d be happy with that,” says Chris.

Well, uh, yeah – that kind of power in a beautiful MX-5 should make him happy!

Contact:

Bob Romano Performance
+61 7 3395 8255

www.bobromano.com.au

 

 

At a glance…

  • Road/race 1990 MX-5 (Miata)
  • Converted to 1.8 litre with a turbo kit
  • WRX 4-pot front brakes
  • Aftermarket LSD
  • Show presentation in a competition car
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