What are some common RS/WRX engine failures?
"Pistons - people running too much boost and detonating them. In some instances you can stick your finger through a hole created in the top of the piston, or it blows the side of the piston away near the compression ring. I've seen that happen on cars running anything from 16 psi boost onward."
"People ask us what boost level is safe - we tell them standard boost is safe, but we believe 16 psi is relatively safe because some factory Subaru models hit 16 psi and then creep back with revs. If you hold 16 psi - as long as the turbo and exhaust can flow enough - you have a quick and fairly reliable vehicle. Above 16 psi it's shades of grey on the amount of risk you take."
Which pistons are most prone to failure?
"Typically it's the one closest to the turbo because that's the one that runs hottest and can run lean because of an inadequacy in the standard fuel rails."
Tell us about the fuel rail upgrade you sell.
"We now have an all aluminium one to suit GD-chassis Subarus and we do a small modification kit that fits earlier model Rexes. What it entails is running twin regulators on the rail system; it's designed to fix a harmonic pulse in the rail. We've developed it from R&D and talking to rally teams."
"It significantly reduces the risk of one cylinder running lean. If you've got a car running a bit more boost than it should, a rail upgrade is our recommendation - it won't give any more performance but it's good insurance."
What is a good, cost-effective upgrade for the Subaru driveline?
"If it wasn't for the cost of installation, a lightened flywheel is a really good way to upgrade RSs and WRXs. Not only does it give better acceleration (because there's less dynamic weight) you can feel the difference in braking and you can change gears faster as well - the synchros don't have to work as hard. When a customer first drives their car with a lightened flywheel they'll typically miss a couple of gears or stall the car. It is easier to stall, but you soon get used to it - the benefits more than make up for it."
And what are your views on certain types of clutches in Subies?
"We stopped using Kevlar clutches about three years ago because they don't last in normal road use. These days we offer button and full-face clutches; if you want to drag race you really need a button clutch, because it is the only type that will take considerable abuse and get good hook-up. But a button clutch is no good if you're towing something or you've got a steep driveway - they are not designed to be slipped. In these instances we go to a heavy-duty full-face clutch with a higher clamp load. I can't remember how much extra clamp we use but it's not enough to feel the difference with pedal effort. I'd say 70 - 80 percent of the clutches we sell are full-face heavy-duty."
Once you've prevented clutch slip is the chance of gearbox damage dramatically increased?
"It depends how abusive you are and which gearbox it is. A good rule of thumb; if the drivers of RSs or WRXs change gears fast and hear a thump in the centre tunnel they've let the clutch out too fast. What you're hearing is the gearbox cross-member and/or tailshaft centre bearing bottoming out in its joint and making a thumping noise through the chassis. That means it's getting too much shock load."
"I've never seen any evidence of Subaru gear failure purely through application of torque. I suppose some cars that have enough grunt to do that kind of damage; a Daihatsu Charade with a twin-cam turbo - if you're making decent grunt - you can put in 5th gear and squeeze the juice it'll just shatter. But you're talking teeny-weeny gears there - I don't think that would happen in a Subaru."
"You can drive a really big horsepower WRX and have no gearbox problems or you can drive a standard WRX and have problems. It all comes down to the driver."
How should you launch an AWD turbo Subaru?
"Let's take a worse case scenario - if you've got your foot to the floor and it's bouncing off the rev limiter and you slide-step the clutch, the shock loads are huge. If you let it out gradually there's no shock load, but you can torch the clutch and it won't hook-up. It needs to be somewhere in between - a fine balance."
"The optimal launch is hard to describe and about as hard to demonstrate - just remember to bring the load on as smooth as possible."
Tell us about the hub dyno you have coming to your workshop.
"Well, we're pretty excited about it. Obviously it's a lot of money, but it's brought upon by necessity because we're doing so much R&D - it is so accurate it will detect the difference in power when changing tailpipe length. We considered a lot of different dynos and we chose the DynaPac hub dyno primarily because of its accuracy and, second, there's no tyre noise. You can also do more work in a shorter period of time because you can start in, say, 4th gear - there's almost no inertia. It also takes up little space."
And what new products do you have coming?
"Well, we're still putting a lot of work into EcuTeK - that's a big responsibility for us, since we cover New Zealand and Australia. We're also putting a lot of effort into the new 2.5-litre STi that goes on sale in the US and, now that we've finished our exclusive alloy fuel rail kit, there are a few other things we're working on. I can't really talk about those projects just yet!"
"We've just launched some adjustable rear strut tops for GC and GD Impreza models - nobody else in the world offers them to fit both models. We also have the new WRC replica wing and, by sheer demand, a bigger bonnet scoop for '97 - '00 Rexes."
What are your biggest selling parts?
"Obviously EcuTeK is taking off well now - we've put a lot of work into that. We still do heaps and heaps of exhausts, intercoolers are very popular and our brake master cylinder support bracket is a common and cheap upgrade. We work a lot with Whiteline and we push their products - like swaybars and anti-lift kits - pretty hard in the US."
What affect do splitters, high-rise scoops and tilt kits have on standard top-mount WRX intercoolers?
"In all honesty we've never compared high-rise scoops but common sense tells that it has to make a difference - STi wouldn't have made theirs bigger otherwise. We do replicas of the STi '03 scoop and it's huge - something like a big bird catcher..."
"The splitters make a difference but we find it difficult to get them to work in conjunction with a water spray. The trouble is that the splitter sits behind where the water nozzles are mounted and stops water getting to the back of the core - that's where it's hottest. I've seen testing done on splitters and I think it makes some difference."
"Michael South is a big protagonist of tilt kits and, from what I know of Michael and his efforts, I would have to say that it would make a difference. It's not something we'll be looking at in the future because it's easy for people to make one for themselves."
Do exhaust dump pipe splitters make much of a difference?
"It does - to bottom-end performance when the car is coming up on boost and the wastegate is starting to open. The engine is trying to push gas as fast as it can to get the turbo up on boost and, at the same time, there is wastegate creep. When that happens in a standard Subaru turbo exhaust system - or an aftermarket wide mouth system - air is blown across the back of the turbine. Fitting a splitter means the wastegate and turbine gasses don't collide and they flow in the same direction."
"The silly thing is, some workshops promote twin or split dumps but often they're just two separate pipes welded onto a flange - there's nothing to meet up against the inside of the turbo. It looks fancy but, really, it's a waste of time. The other thing people don't realise is the length of the splitter varies depending on what turbo you're bolting it to. The VF30 has a different distance between the flange and the back of the casting to, say, a TD05."
"A dump pipe splitter probably makes some kind of difference to top-end as well, but it's not measurable - it's more for coming up on boost."
Branching away from Subaru stuff, what are your opinions of Gen 3 Holden Commodores and Ford XR6 Turbos?
"The Gen 3 is great fun from a torque point of view but the car overall is very disappointing. I haven't driven a Falcon Turbo, but we might consider doing something with those in the future."
Do you think Subaru has progressed - technically speaking - in the past few years?
"Subaru as a company, yes - the bug eye WRX took a bit of flack because of its looks and weight, but it is much more secure and better in terms of handling. I think where they're going with engines is pretty exciting as well."
How do you compare the current WRX/STi to 200SXs and Evo Lancers?
"Ah, gee, I could get myself in a hole here! A WRX is bloody good value for money. The 200SX is damn easy to make go fast, but its downside is traction and fear factor - although it is a lot of fun. The Lancer Evo is a fantastic car but it costs a whole lot more."
"It will be interesting to see what Mitsubishi Australia does with the Evo 8 compared to what they're doing in the US. I think they really dropped the ball with the Makinen special - it all happened too late. I think this year is going to be pretty interesting."
"At the end of the day you get what you pay for. I don't think the fit and finish of a WRX is as good as an Evo, but the Evo costs a lot more. People don't buy a WRX because it has Audi quality, though - it's all about value and bang for bucks."
Why do you not cater for 200SXs?
"We actually do quite a lot of other cars, but we don't advertise it because we've got so much Subaru stuff. We have done quite a few 200SXs but, because we're seen so active in the worldwide market place with Subarus, we sort of get pigeonholed. We get a lot of people coming to us with other cars but you can't be all things to all people. We try hard not to ignore opportunities of spreading our resources into other cars, but - at the same time - we won't ignore the Subaru market."
"There aren't many workshops that offer grunt, handling, brakes and a bit of looks all in the one place. They might be a very good engine builder or suspension outlet, but they don't bring it all together. These days, typical customers don't want to go to a number of different places - they'd prefer to go to one workshop with their budget and get their mods done. And that way they get the best value."
Contact:
MRT Performance
+61 2 9809 2110
info@mrtrally.com.au
www.MRTrally.com.au
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