Miller-Cycle Bargain

The Mazda/Eunos 800 with its supercharged Miller-cycle engine is one of the most forgotten sporting saloons in Australia. If you’ve got about 15 grand to spend on a good, useable car with more than adequate performance, there’s little else to match the luxurious Mazda.

The Miller-cycle 800 was first seen in Australia under the banner of Eunos – Mazda’s short-lived luxury car division. Two 800 models were released in early 1994 – a conventional 2.5 litre Eunos 800 and the supercharged Miller-cycle 800M.

Things get a little messy from here on...

When the Eunos operation folded in 1999, the conventional 2.5 litre 800 was dropped and an updated version of the 800M was carried over to the Mazda stable. The M suffix was dropped at this stage, even though the car still used the Miller-cycle motor.

Then, in late 2000, the Miller-cycle Mazda 800 received a major update - and was re-badged as the Millenia! Unfortunately, the Millenia didn’t even see out 2002 before it was axed due to poor sales. This model was extensively restyled, the interior was revamped and numerous changes were made to the suspension, steering and brakes. Side airbags are also included as standard and, inevitably, the car put on a bit of weight. Note that engine output remained the same across all models.

Okay - that’s the convoluted history out of the way. Now let’s look at the car.

The 800 is the largest vehicle from the Eunos collection and the supercharged Miller-cycle engine is arguably the showpiece of the entire range. The Miller-cycle engine is unique in that it closes its intake valves much later than in a conventional Otto cycle engine - the inlet valves are kept open for the first 20 percent of the compression stroke. This approach reduces pumping losses when the mixture is being squeezed during the compression stroke. The supercharger is essential in this engine configuration because, without it, the mixture could reverse-flow back out of the inlet valves.

The Miller-cycle engine employs one of the most efficient positive displacement superchargers on Earth – a Lysholm screw-type blower, which pumps in up to 14 psi of boost via twin-air-to-air intercoolers. This is one of the world’s most sophisticated engines – even by today’s standards.

Displacing 2.3 litres, the KJ-series Miller-cycle engine uses an 8.0:1 static compression ratio, DOHC, 24 valves and multi-point injection to help it on its way to 149kW at 5500 rpm and 282Nm at 4000 rpm. To ensure flexible performance, 275Nm of torque is available from 2000 to 5500 rpm.

On the road, the engine is uncannily quiet, vibration-free and offers smooth acceleration. The 1543kg luxury saloon is no rocket with 9.0 second 0 – 100 km/h performance, but it always offers grunt when you want it. The faint whine from the Lysholm supercharger will also put a smile on your face. The Miller-cycle engine also provides impressive fuel economy – better than you’d achieve with a conventional engine making the same power and torque. Unfortunately, this saving is largely offset by the need to run premium unleaded for optimum performance.

The Miller-cycle engine comes mated to a creamy 4-speed auto – a manual gearbox was never fitted. The auto’s ‘hold’ function is handy for performance driving, but the lack of a sequential gear shift is noticeable.

But don’t think for a moment that the Eunos 800’s technology ends under the bonnet.

The 800 employs the same electronically-controlled 4-wheel-steering arrangement that Mazda first released locally in the 1988 626/MX-6. At low speed, the system steers the front and rear wheels in opposite directions to enhance manoeuvrability but, at higher speed (above 47 km/h), the rear wheels are steered in the same direction as the fronts. This improves lane-change stability.

The 800 rides on a sophisticated suspension set-up comprising front MacPherson struts and a multi-link IRS. With 16 inch alloy wheels and 215/55 luxury-grade tyres, it’s only natural that the front-wheel-drive 800 tends to understeer - but the 4WS system helps combat this. The standard traction control system also prevents you applying power too early while the front tyres are still struggling with lateral grip. Unfortunately, the TCS is a bit too heavy-handed for our liking. The ride is supple but firm.

The Mazda/Eunos power-assisted rack and pinion steering offers good weight and feel, while the 4WS system offers a usefully tighter turning circle.

Braking performance is powerful thanks to ventilated front and sold rear discs combined with ABS.

The 800 is a relatively large car – but not as a big as, say, a Falcon or Magna. Inside, it can accommodate four adults with comfort – the only issue being limited rear headroom. Mazda always intended the 800 to take on many of the more expensive European luxury cars and its extensive NVH development is obvious. Gliding along at cruise you can barely hear a thing.

As you’d expect in the top-line Eunos, the interior is covered in soft leather. Appointments include subtle woodgrain panels, dual front airbags, seatbelt pre-tensioners, climate control, an ambient temp display, electric front seats and an electric glass sunroof. Remote central locking, an alarm, cruise control, power windows and mirrors are a given.

One of the most impressive interior features is the 6-stack and single-slot CD Bose sound system – it’s wonderfully clear and powerful.

Compared to the early 800M, the 1999 Mazda 800 update adds some interior trim tweaks, illuminated door switches, wider angle mirrors and ski-port access between the boot and cabin.

Cosmetically, the 800 is nicely proportioned and very smoothly styled. The 0.28 aero Cd is also impressive. All models receive effective projector-style headlights, fog lights, colour-coded everything and 16 inch alloy wheels. The 1999 update brings restyled wheels, a new grille, chrome surround for the number plate carrier and new colours.

Note that the early non Miller-cycle versions can be identified by their 15 inch wheels and lack of 4WS.

As you’d expect, paint and panel fitment - like every other aspect of the 800 - is up luxury car standards.

From 1994 through to the 2000 introduction of the Millenia, a Miller-cycle 800 cost new car buyers between around $75k and $85k. In the second-hand market, however, you can now pick up an 800 for stunningly little money - this really is one of the greatest bargain buys out there. We have seen an early 800M for sale privately at just AUD$10,900 but, typically, most examples fetch 15-20k. A good ’99 Mazda 800 pulls 23 - 30k, while a 2000 - 2002 Millenia can now be bought from about 35k - depending on kilometres.

If you’d like a little more power than stock we can’t see any reason why the supercharged Miller-cycle engine wouldn’t respond to some basic intake and exhaust upgrades. A comfortable 10 percent power gain should be achievable with the right combo. Note that the twin air-to-air intercoolers could also be easily improved – after about 10 seconds at full power we’ve measured a post-intercooler charge-temp of 75 degrees Celsius! It certainly wouldn’t be difficult to improve the intercooling performance...

From what we can gather, the Miller-cycle 800 is a very well reliable vehicle – so long as it has been properly maintained. Make sure the cam belt has been replaced in higher kilometre examples and take the time to check out the 4WS system – repairs have been known to top AUD$5000...

The Miller-cycle 800 will appeal to anyone with an interest in technology and who wants a luxurious and practical vehicle with good all-round performance. Ask yourself – what’s a better car for around 15k?

The Eunos 800 SP? A very limited number of Eunos 800 SPs were built in 1998 by Mazda’s Australian motorsport division. The Eunos 800 SP features 17 inch Antera wheels, 235/45 Pirelli P6000 tyres and its ride height is lowered by one inch. The grille is also colour coded or painted black, depending on the body colour. Stainless steel kick panels and a numbered plaque can be found inside. Engine output is presumably a little bit sunnier than the usual 149kW given a large diameter rear section of exhaust was fitted.