Despite the stellar improvements in handling and chassis response wrung out of our Project MR2 Spyder, there has been little fighting over who takes it home for the night or out for a weekend thrash. With a wide variety of equally fun and eminently more practical hardware available for our daily drives, it takes more than just fabulous handling to pique our jaded interests. Of course, the fact that it sat for almost a year at XS Engineering (waiting for a new engine, rag top, and turbo kit) made it that much easier to avoid. But we're back behind the wheel with a vengeance.
Able to deliver 1.03gs of gut-shuffling lateral stick while snaking through the 600-foot slalom at nearly 73mph, it's clear that Project MR2 delivers world class chassis dynamics. But the stock 1.8-liter engine's uninspired performance brings sighs, musings and mostly doubts regarding our lofty goal of beating a Lotus Elise at this game.
Installing the turbo on the MR2 ends up being a lot easier than on many other cars once the rear cosmetics have been removed. There's plenty of room to pull off and bolt on the hardware.
A quick review of the SAE 'white paper' on Toyota's design objectives for the MR2's 1ZZ-FE engine reveals only two of the six major goals outlined by the engineers had anything to do with performance: a flat torque curve and class-leading low weight. The rest had to do with friction, emissions, noise and cost reduction. It's an interesting read, outlining the innovative ideas Toyota incorporated to achieve those goals. From a nerd's point of view, the text on improving the combustion stability and volumetric efficency is fascinating, but geeks need testosterone-pumping, class-leading horsepower and torque as much the next guy, and there was little of that in the paper, as the final product illustrates. For reasons best known to Toyota, it created the perfect powerplant for an appliance instead of a sexy two-seater. Yawn.
Perhaps the lack of muscle is excusable when considering the MR2's low mass of 2250 pounds. It's amazingly light for a regulations-strapped, mandatory-safety-equipment-laden modern car that's not made from glue and sheet aluminum.
The heart of the XS turbo kit is the IHI VF23 with a P20 exhaust housing and internal wastegate. The turbo not only uses a ball-bearing center section, but is also water cooled. The kit uses a 2ZZ sil-moly smooth flow cast-iron manifold.
We repeated baseline measurements with the fresh engine (one without spun bearings) on XS Engineering's Dynojet 248E, where 115 wheel-hp and 115lb-ft of torque was pumped out with all the drama of a Singer sewing machine ripping out a topstitch. Even when considering the MR2's lack of bulk, the power to weight ratio still ends up at a nap-inducing 19.6:1.
Few relatively simple or economical options exist for better motivating the 1ZZ motor, since the usual bolt-ons can't change or disguise the fact that the combustion chamber was designed by someone who might be better suited to accountancy. A common solution is to dump the engine altogether and drop in the higher-revving 2ZZ motor shared by the GT-S Celica and Lotus Elise, but even that engine is not so receptive to simple mods.
The 2ZZ is peaky, with a narrow powerband and not the most pleasant to drive. Furthermore, the costs and headache - not to mention our brand new engine - make any swap impractical.
The turbo is a straight bolt-on with plenty of tool clearance. The manifold studs are replaced by bolts in the kit and the water and oil lines are all provided.
The Turbo
To get the most streetable bang-for-the-buck power, our eyes turned toward forced induction. After much nagging and cajoling, we convinced Eric Hsu of XS Engineering to consider turbocharging our car as part of the development for a line of bolt-on XS Engineering turbo kits for the platform. Turbocharging is good simply because it gets the greatest gains with the least amount of fuss. Done properly, it would also give us the widest powerband and the most flexible power delivery. Normally, it's the pricey alternative compared to bolt-ons, but since none of them do wonders for the 1ZZ, a turbo system is our best (and only?) option. The good news is that the XS kit will come with an exhaust, intercooler and intake, which should save a good chunk of change versus buying the parts separately. The production kit will also look a lot better than our prototype kit pictured here.