HYPO HEAD-SWAPPED MIVEC MIRAGE
It would seem that true pioneers within the car world are few and far between these days. For the most part, what’s being created is not groundbreaking; it’s simply building on what someone before laboured over. It takes a brave soul to actually step off that proven path and forge their own trail — especially when it’s so easy to go the known route and you’ve had a spectacular failure that saw two rods exiting the block at around 10,000rpm on your first attempt. To then come back from that, pick up the pieces, and start all over again — well, that right there must take some serious downstairs hardware to want to risk it all over again.
While at first glance this Mirage might not seem like something out of the norm, popping the bonnet will result in head-scratching, as quadruple Jenvey throttle bodies punch you in the face where you’d expect a big old snail to be. To recap, it’s not the first time that we’ve seen Cameron McElroy’s ’96 MIVEC Mirage before; in fact, we were there the day that the rods ejecto-seato’d out the bottom of the block at the 2010 Honda Mega Meet, as we had just shot it for a feature in Issue No. 171. Hypo naturally aspirated (NA) Mitsis just aren’t the norm, so, as you can imagine, it was grabbing its fair share of attention from the rev-happy Honda crowd that day. It had not been a short road to get to that point for Cam, so it was a big kick in the aforementioned hardware for the first outing to end the way it did.
Featuring a custom 5.1-ratio final drive, the gearbox is a trick unit running a ’98 RS gear set, ’98 RS shifter cables, and a short shifter. The diff is a Cusco 1.5-way limited-slip
Being an RS, the Mirage is devoid of any creature comforts — but who needs those when you’re strapped into a Bride Gardis III, chasing that next apex?
Custom carbon guards were produced to house the 225 Hankook semis come race time, when the 15-inch TE37s are bolted on
“I was pretty anti NA for a while after that,” he says. “It had cost a lot of money to build that engine, and, after only 3000km, it went bang. I contemplated putting an Evo motor in — I had good contacts at Mitsi New Zealand at the time and got offered an Evo X engine — I thought pretty long and hard about it and almost did, but the front-wheel-drive gearbox was going to be an issue, and still, to this day, I believe that not really anyone has done an NA MIVEC properly.”
Spurred on by the believers in support of what he was trying to achieve, Cam refused to quit, and a new plan was hatched for what he calls a “simpler” combination. Forgoing the previous short-stroke hybrid 1600/1800 combo, this new package would utilize a later model 1800cc 4G93 turbo block retaining the factory stroke and bore, with a MIVEC head on top. Simple, right? Well, the fact that the head normally lies in the opposite direction is where the trickery that consumed Cameron for a good number of years lies. “If someone mentions a head flip on a B-Series Honda, you’d instantly think he’s a madman,” says Cam. And while you’d probably also be quick to class Cam as one too, he had an ace up his sleeve, given that, in ’96, Mitsi swapped all its engines, excluding the V6s, from the left side of the bay to the right, meaning that a pre-’96 MIVEC head, when flipped, would bolt directly to the later model 1800 turbo 4G93 block without too much hassle. The hassle would lie in getting it to function: “Everything was a nightmare internally.”
This work began with a set of custom cams, as they are different lengths due to the internal MIVEC solenoid. The oil feeds that activate the MIVEC also had to be modified to enter the opposite end of the shaft. The later model trigger system had to do a complete 180. The list of required modifications just goes on and on, to the point that nothing on, or in, the motor is factory. Talk about a commitment to making it happen! Not all the work was simply to get it functioning, though; performance was also a focus. The head was heavily ported and the valve seats reshaped in preparation for a rev-happy valve train, while the block internals were replaced with custom forged parts to create a combustionmix-crushing 12.5:1 comp. Was all the effort worth it? We’d say hell yes, as the power figures of 165kW and 203Nm would make an equivalent Honda B-Series run and hide for cover.
With a rev limit currently sitting at 10,000rpm, that in itself created a unique problem with resonance. “It’s a very, very aggressive motor,” Cam tells us. “I couldn’t keep anything on it. I originally had a lightweight crank pulley on it, and I’d do a track day and be missing a bunch of bolts and stuff would be broken or cracked [at the end]. Alistair from Macbilt Engineering told me to put a factory crank pulley back on, which removed the resonance.” Even the intake manifold suffered, splitting almost entirely in half due to the vibration. Seizing the opportunity, a new set of Jenvey quads replaced the 4GAE items, with Alistar putting together a new manifold. Alistair’s signature can be found all over the Mirage — from the eight-point roll cage to the custom headers — and he is someone who Cam credits with getting the car to work as well as it does.
The forged rotating assembly is topped off with custom 12.5:1-compression JE pistons that have been Teflon and ceramic coated. The crank itself was knife edged before being nitrided, while the rods are Argo items The only off-the-shelf Mirage-specific performance part on the build is the Monster Sport carbon bonnet
The head is a seriously trick piece of kit, with custom cams, JUN valve springs, titanium intake valves, sodium-filled exhaust valves, and titanium retainers. The valve seats have been shaped and a heavy dose of porting has taken place Although still registered and warranted, the Mirage sees very little street running these days The hybrid motor combo has been dubbed a ‘4G9X’. The head’s from an early MIVEC 1600, while the block is a later model 1800 turbo unit. This made reversing easier, as the head bolted directly on, but that was where the easy stopped. Extensive custom work ensued to get the combination working, leaving no factory parts to be found
Which was no easy feat given the custom nature of the build. Off-the-shelf upgrades just don’t exist, although many parts meant for the Mirage’s boosted big brother, the Evo, were able to be repurposed — parts like the Racefab World Rally Championship (WRC)–style cross members, tubular arms, and Evo VI suspension. It’s all the stuff that you simply can’t see at a glance but which makes for proper race car underpinnings in a vehicle that weighs only 910kg wet. Given that there is very limited power on offer, Cam had to be pedantic about weight. Anything that went in had to come out elsewhere. The fact that it tipped the scales at 1040kg in factory trim and now has a 70kg eight-point cage yet still comes in 130kg lighter than factory should be a good indication of just how far this has been taken. But being so light also means that Cam needs to bring his A-game come track time. “It’s so light in the rear [that] you just don’t get away with anything,” he says.
With some more consistent time on track, he should be able to really dial his times and show the true potential of the latest configuration. But dreams of running the car competitively, which were the focus in those early days, at least for now have taken a back seat to track days at his local, Manfeild Circuit. However, that hasn’t stopped Cam from dreaming up the next round of upgrades, focused on extracting some serious power from the 1800 and spurred on by what guys running in the World Time Attack Challenge are doing with superchargers and K24s, making upwards of 450kW. Given the engine’s new layout and its forged internals, this would not be a hard task at all to make work. But, for now, Cam will be more than content to stalk some Hondas out there on track and continue to have people scratching their heads any time the carbon bonnet is popped on this worldfirst combination.