You already know it - the WRX is the best car performance bargain ever. Jut whack on an exhaust, tweak the boost and you're able to wipe the smile off pretty well every other driver on the road. But is everything about the Impreza as good as it's meant to be? Talk to Rex owners who pedal their car hard and a disturbing story of broken gearboxes, smoking clutches and even stuffed engines can come to light. We decided to get the story from a man who works on standard and modified WRXs pretty well every week - Bill Keen of Adelaide Turbo Services. Here's what he had to say:
Value for money the Subaru is the best performance road car on the road - no question. But at the end of the day it's still a shopping trolley. It's still designed to cater for the mass public and so like every road car, it's a compromise. They've built them to a price - and they're a fantastic product at that price. The overall feel of a WRX on the road is terrific. All of them - Liberty RS's, WRXs - are very good packages with well-balanced handling, good braking, good performance.
But their weakness is as soon as you start pushing them a little bit, we're talking broken clutches and gearboxes. The rear diff doesn't seem to be a problem, but the clutch and gearbox really do seem to be weak links. The drivetrain simply hasn't been over-engineered - in this area all of the Subarus through the whole range have been inherently weak - and I dare to say that the '99 will be no better. If it is better, it won't be that major over-engineering step that really needs to happen to cater for the guys that are pushing them harder than they were intended to go.
In standard form the WRX engine is a good, strong reliable package. Even with the usual mods of putting on an exhaust, changing the intake and moderately turning up the boost, the engines are good strong units - no problems at all. But even with that amount of modification it over-accentuates the gearbox and clutch problems. Driving a standard WRX moderately hard gives a life of somewhere around 100 - 120,000 kays for the clutch and the gearbox. The gearbox would need synchro rings and bearings around that distance. Whether it's modified or not, we give that undersized gearbox the best possible chance by putting in the best lubricants. That's anything that's synthetic and is recommended by the oil manufacturer - whether it's Mobil, Castrol or whoever. We use Castrol Syntrax or the Mobil synthetic here and have good results.
Someone who drives their modified WRX hard could expect in the clutch and gearbox area a life as little as 20,000 kilometres from a brand new car - it could even be shorter if common sense has gone out the window. A car like this needs to be driven with some degree of respect. Anything mechanical can be broken - and can be broken fairly quickly - and so there's got to be some driver education brought into it. You have to drive the car with some degree of sensibility to expect reliability. Hard launches over four-and-a-half-grand are ridiculous. Abusive gear changes and hard launches - these two areas are the killers.
We have seen nothing that will make clutches and gearboxes in hard-driven WRX's last. If you want to start going into rally-proven parts and spend the sort of money that the rally guys do - whether it be for straight-cut gears, gearbox coolers, or multi-plate clutches - it will be lots and lots of money. Multi-plate clutches are somewhere around the $3000 mark for a clutch and flywheel; a good gearbox is anywhere from $7000-$10,000 - it's all a lot of money. Certainly there's some degree of reliability but you need to bear in mind that if it's race developed, it's also high maintenance. It's designed to come apart after every race or every rally. So sure it will take the punishment, but it needs the maintenance - so again it doesn't become cost-effective for the general road user.
We've tried quite a few combinations of clutches over the years. We try to judge the clutch that is required by the type of driver - for example, whether we can afford to get away with the softest clutch to help the driveline. Clamping forces up around 1050 - 1100kg seems to be as much as we get out of them comfortably inside the standard cover. Remember that the clamping force relates to load on crankshaft end-float, so there is a limitation as to what you can do without harming the engine. We use all of the different combinations - Kevlar, ceramic, sintered bronze, or full organic. We can vary the combinations - even using different materials on the different sides of one paddle. You can have Kevlar on one side and sintered bonze on the other. Picking a clutch becomes very difficult because it's still a road car that has to carry passengers - you don't want the passengers holding onto their false teeth when you've let the clutch out!
We're also seeing engine problems with WRXs up around 17-plus pounds of boost. With a very high compression motor and with fuel varying in consistency from week to week, there's a prevalence of detonation, whether it's audible to the driver or not. Detonation will kill anything. In the Subaru, pistons melt or ring lands break- that's generally where it starts. We've seen probably in the vicinity of half a dozen WRXs with piston problems. I've not seen or known of any crankshaft breakage or rod bending - that area seems to be okay - the problems seem to be concentrated in the combustion area. You look at the STi versions - factory forged pistons. It's something that the factory's recognised as being an area that can certainly be improved.
There's also been some reports where WRXs have thrown legs out of bed when they have been hydraulic'd. Water injection after the intercooler without the correct shut-off valving can allow water to siphon into the chamber. When this happens it can be the end of the motor. We've also seen problems with water injection where the pumps haven't been sufficient to overcome boost pressure and are just blowing bubbles in the tank. Water's a corrosive product - we've seen MAP sensor failures because of water contamination. Unfortunately water injection relies on maintenance by the owner and it's susceptible to failure. Pump failures are pretty common, as is just running out of water! Good fail-safe measures have got to be in place to prevent any excessive boost if you're out of water.
You always find that the Japanese tuners - whether it be GReddy, APEXi, or one of the others - produce products that are generally well researched and very, very well made. And they're probably two years ahead of us, because of the fact that the cars have been available that much longer. By the time that the vehicle finds its way here, there's a good product on the market that's been developed by the Japanese. The stuff's always aesthetically spot-on and works very well. When you get back to traditional ways of addressing detonation like lowering induction temperature, a better intercooler from one of these companies is needed.
The standard intercooler is located under the bonnet and there's nothing worse than a heat sink sitting on top of an engine. Sitting at the lights, where does the heat go? - up! It heats the intercooler, you take off for that quick blast to blow your mate off, and all you've done is pump hot air into the engine. So if you're really serious, you need a front-mount intercooler. Convenience says to use a replacement top-mount intercooler - and it's certainly an improvement when there's the airflow. But in city driving stop-start conditions, there's the downfall.
With an exhaust, intake mods and 15-15.5 psi we're seeing utter reliability in the engine department and moderate wear in the driveline. But people need to realise that there're not buying a race car. If they want a race car, use the WRX as a tow car and buy a Formula V!
Contact:
Adelaide Turbo Services
+618 8377 2511
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