Automobile performance can be expressed in many forms. There are the ultimate performance cars for racing, “dyno queens” with impressive numbers; and then there are the true performance cars that can be driven on the street in traffic. My involvement with performance upgrades is pretty much in the past tense, so to research this article I decided to go to the experts. Looking around the Puget Sound region, I was able to find a lot of shops that can modify cars, but only a handful that have the expertise to modify cars that can perform in daily use.
Subaru builds a great stock performance vehicle and, with all-wheel drive, some basic concerns like traction and handling are built into the original design. Numerous aftermarket companies make products that can enhance that stock performance and tailor it to any desire from “mild” to “wild.”
Balancing ultimate performance within legal parameters and practicality is what Z Sport (www.zsport.com) is all about. I spent several hours being shown their clean and well-equipped shop in Everett, WA. Manager Charles Damewood and Owner Gary Watts both were very helpful in explaining what it is that Z Sport does, and how their shop makes sure that the customer is happy with the final result – whether it’s regular service or modifications (see Photo 1). The entire staff was willing to take the time to show and tell me about some of the unique aspects of the work they perform.
In business for nearly 30 years, and 15 years at their present location, Z Sport started as a shop devoted to the Nissan Z car. As the client list grew, other car lines were added, and today the shop is committed to providing service, repair and performance upgrades for all makes of import cars, as well as some domestic and vintage vehicles.
Of particular interest during my visit was the “project” car that is being developed in the shop. A Subaru WRX/STI (see Photo 2) that has already been modified for better handling, stopping and comfort, while retaining a relatively stock appearance, is the basis for an ultimate performance “daily driver.” Since this vehicle is not yet complete, I will highlight the performance upgrades that are being done, and will need to do a follow-up article to show how it all comes out.
Too many shops will increase engine performance without ever considering the rest of the car and its ability to cope with the additional power. This is obviously a recipe for disaster. A discussion of the need to modify the whole vehicle is an integral part of any performance “build.” This particular car will be Damewoods’ daily driver when completed so, in this case, the project was planned with total performance in mind.
Subaru provides decent brakes by using four-wheel disc brakes on all of its factory performance models. Since the late 1990s, the front brakes have had dual-piston calipers and vented rotors. With heavy use the stock rotors have a tendency to warp, so an upgrade to grooved, cross-drilled, dimpled or a combination is suggested. The project car already has grooved and dimpled rotors along with premium pads at all four corners (see Photos 3 and 4).
As with all standard or performance brake repairs, matching of components and care in installation is essential to proper brake function and safety. Proper lubrication of caliper components and a full break-in procedure are part of any performance upgrade as aggressive driving will demand even more of the brakes.
There are literally hundreds of various suspension systems (see Photo 5) available for these cars, and deciding what will work best on a given car will take some research to find the best compromise for all of the expected uses a particular car might endure. The stock Subaru suspension will handle minor upgrades for performance driving, but with higher engine output and demanding driving, some more focused changes will be desirable.
The project car has infinitely adjustable struts at all corners, along with upgraded sway bars and urethane bushings. The front suspension has been modified with a Positive Steering Response System (PSRS) (www.perrinperformance.com) that relocates and stiffens the rear mounting of the lower control arms to provide significantly more response to the steering and less suspension lift on acceleration. The system achieves this by adding additional caster to the front end alignment and using less-compliant bushings.
The boxer engine in a Subaru is a different challenge for modifications. The design limits the amount of displacement that can be added, but a displacement increase can be accomplished by increasing the stroke, while the bore is limited to a cleanup or a change of the block.
Z Sport’s master technician and engine builder Mike Larsson gave me the specifics of the engine for the project. Since there are some weaknesses in the 2.5L engine, he decided to stay with the 2.0L base (see Photo 6) and increase displacement through the use of a 2.5L crankshaft. Mike says that the stock crankshaft is strong and suitable for a performance engine (see Photo 7), but both the main and rod bearings in stock form are weak. This is not a place to use substandard parts and aftermarket parts are available to keep the lower end together. Aftermarket pistons and custom rods allow the use of the longer stroke crankshaft. All fasteners in this engine will be aftermarket premium parts.
With four valves per cylinder (two intake and two exhaust), breathing is OK once the ports are opened up slightly (see Photo 8); 1mm oversize valves are being installed for an extra measure of air flow. Care should be taken to not get too carried away removing material from the ports (see Photo 9) and avoid polishing the intake ports for a street driven car, as the low-end performance will suffer.
The stock camshafts for the factory turbo engines are also well designed and don’t need to be replaced. A tuned header exhaust will be used to open up the exhaust for better breathing and high rpm flow.
The biggest improvement in horsepower will come from the Garrett turbocharger kit (see Photo 10). The increased size of the turbo, with larger injectors and better flow through the cylinders, is expected to produce between 350 and 400 horsepower at the wheels.
Mike indicated that additional things to consider are upgrading the oiling system with the late-model oil pump and using only the MLS (multi-layer steel) head gaskets as specified by the manufacturer.
Z Sport is equipped with a set of hub-mount Dynapack (www.dynapackusa.com) dynamometers (see Photo 11) that tuner Chuck Watts uses to dial in the engines after modification (see Photo 12). This part of the performance modification is critical to getting maximum flexibility, driveability and even economy. This mobile dyno system is also a hit at local car events where participants can actually see what their own rig will do compared to others. These units attach directly to the hubs (see Photo 13) and use a hydraulic load brake system to accurately measure the power output.
Obviously, since the engine is still being built and isn’t in the car yet, I can’t close out the whole story on this project. Z Sport has invited me to come back once the engine install and setup are completed.
I can’t wait to see what this little engine will do with the modifications being made. Charles has every intention of using this car to make quick runs for groceries on a regular basis once he gets it back on the road.
I’d like to thank the whole crew at Z Sport for their help in getting this article together, and inspiring me to maybe start thinking about making some mods to one of my E30 Beemers.