Subaru Impreza WRX STI CAR

DIFFERENCES IN THE IMPREZA CARS

There are differences between the Japanese domestic WRX and the world version. When the reasons for these differences are taken into account, it is hard to fault our version of the Impreza WRX as in some way being a little sister to the Japanese WRX. It is as close as regulations have permitted.

There major changes in the way the new model WRX is marketed. The new STI cars now have have significant mechanical and structural differences compared to the normal WRX. The Japanese STI body shell has light weight panels and other weight savings, separate interior options and of course the now well documented six-speed gearbox and huge Brembo brake option. The most significant differences between the STI cars and the standard WRX are the high power 280hp+ EJ207 motors and the new six speed transmission. The STI type "RA" version is known to put out an easy 320hp. In sharp contrast all WRX cars in Japan have 250hp and worldwide have 228hp EJ205 engines and 5-speed gearboxes.

For 2001 Japan model year, the standard model Japanese WRX has been detuned considerably from its earlier 280hp 1997-2000 versions. The new standard WRX is fitted with a less powerful 250hp EJ205 motor very similar to what is now in the US and other export WRX models. Japanese engine EJ205 version has less horsepower, but substantially the same torque as the older WRX-STI version EJ207 engines. It still goes pretty good. The domestic WRX has a variable valve timing, which the world export cars do not get. It also runs a much better gas than we get here. This is the main factor for its higher power output and variable valve timing. It was felt that the benefits of variable valve timing would not be significant on low octane fuel combined with the mileage and emissions restrictions.

The Japanese 4-door WRX continues with the earlier mid-close TY754 model transmission and 4.44 final drive introduced in 1999. The 5-door wagon continues with its 3.9 final drive wide ratio transmission. This wide ratio gearbox is in all 4 or 5 door export versions currently sent to the US, Europe and Australia. Australia for 2003 will receive the closer ratio 4.44 drive train at the insistence of the importer. I suspect that our EPA mileage restrictions will preclude introduction of the 4.44 gearbox in the US.

Of the actual drive train and brakes, very little was changed. The new 5-door suspension is essentially the same as the old car, other than the need for different spring rates and shock valving. The four-door has longer control arms and drive axles to accommodate the wider track. There are larger front brakes on the turbo models for greater safety. Both cars can easily accommodate 225/45-17 or 225/40-18 tires. The 4-door will go even wider with careful wheel and tire selection.

We did not get the high bolstered seats of the Turbo WRX model or European WRX models, rather we have the seats from the Japanese "2.5RS" model. The reason is simple. There was no quick way to have side impact bags fit to the traditional high bolster WRX seat and the EPA crash dummy also comes into play. The Japan market WRX has the same brakes as we do, but gets 16x7 wheels instead of our 16x6.5. The Australian and European models are fitted with 17x7 rims and have the four pot front brakes as standard. What is going on here?!!

All but the Japanese and US/Canada markets are controlled by independent importers and they were given the choice of brakes and wheels. Japan and US/Canada are Fuji companies and they are just too conservative in their outlook to 'go for it' in our market yet. Our 16x6.5 wheels are no accident. It prevents the average owner from installing four pot brakes, comes on really bad tires to keep speeds down and encourages the wealthy Americans to sport for a proper set of wheels. Not to mention that all those 17 inch wheels Prodrive was stuck with until they sold them to the Tirerack when European WRX came with 17x7 wheels. The rest of the car is all pretty much the same world wide.

It is the body shell and interior that received all the attention. There have been years of evolutionary development of gear box synchronizer and gear arrangements, steady engine management evolution every two years, a major revision of the motor intake layout and a minor front end and interior facelift, but it finally came time to re-tool the production line, so why not incorporate chassis design insight and freshen up the car while you are at it?

The new WRX car has gained weight, but with this weight has come strength and rigidity in the chassis. The WRX chassis is vastly stiffer and slightly larger than the previous Impreza. It is certainly a more refined car. Solid is the best description. It has a total lack of chassis resonance that is a tribute to a computer analysis make over of the old chassis design. Consisting of little bits of added plate there, a more complex pillar shape, smooth hydro- formed large panels and other subtle changes have added substantial weight to the car in trade for its increased stiffness and strength. All these subtle changes translate to a quieter cabin and better handling transitions. It also makes the car harder on its brakes.

In comparing the power to weight ratio of the RS to the new WRX, if you account for the increased weight factor it looks like the new WRX develops a weight factored 200 hp, the other 27 hp is needed to carry around the new found weight. This statement obviously does not account for the much greater midrange torque of the turbo motor. You may sleep comfortably knowing a 200hp RS is not going to say with you, but the weight gain is telling in the acceleration department compared to the old WRX. Along this line of thinking we can also point out the Japanese WRX has considerably more torque and shorter gears than the world export models and will leave our WRX in the dust, especially above 50 mph.