When it comes to mods for a Subie WRX everything is pretty well mapped out. It's known what sort of gains you'll get with an exhaust, an intake, big 'cooler, more boost, bigger turbo and all the rest of the stuff. So when George X pops the bonnet of his MY02 Rexie and you see only the dump pipe of a full 3-inch exhaust, a quick mental calculation tells you it's making somewhere around 175kW - give or take.
And then you see it launch. H-uh?
Scrounge around under the bonnet for a bigger turbo all you like, coz the additional power kick of this Rex is well and truly hidden - until you look in the boot at least. Furthermore, George wanted more go but without the response and low-down torque sacrifices associated with a bigger turbo.
The answer was good ol' giggle gas.
Once a Hi-Teck 3-inch mandrel exhaust had been fitted from the stock turbine to the tips, the Rex's backpressure had been relieved so it would be possible to make a decent amount more grunt. As you've probably heard a thousand times, the standard three-cat exhaust is a shocker in terms of flow.
Oh, and you'll also find a K&N drop-in panel filter in the standard airbox as well.
With nitrous on his mind, George entrusted his Subie to the guys at Mildura's Advanced Automotive Services - Michael and Jason. Having already nitrous'd a number of vehicles - including their own - Michael and Jason are some of the few people in Australia who really know what they're doing with N20. Jason's everyday driver - a nitrous assisted '80s BMW 3-series - packs a real surprise wallop, for example.
Michael and Jason stepped back to look at the job and decided it safest to fit the nitrous nozzle immediately prior to the throttle; this would prevent, or at least lessen, damage to the intercooler in the event of a backfire. The nozzle can
just be seen in this pic - it's the blue fitting on the underside of the pipe leading into the throttle body.
The system in service is a so-called wet system whereby fuel is also sprayed from the nitrous nozzle. The Rex is currently running an 'advertised' 100 horsepower gas shot, though this is actually a bit optimistic in this case since there is no bottle warmer fitted. A warmer is necessary to maintain the bottle at a certain temperature and gas pressure; the optimal pressure (between 900 and 950 psi) is required to give the advertised horsepower shot. Without a bottle warmer, gas pressure is reduced and so is the horsepower increase.
The kit chosen for the Rex is manufactured by NOS (Nitrous Oxide Systems) from the 'States.
As mentioned, the extra fuel necessary for burning the nitrous mixed charge-air is delivered through the single fogger. Michael tells us the nozzle has a matching pair of nitrous and fuel jets so you get the right mixtures with whatever size nitrous jet is used. Fuel is for the fogger is supplied from a tee in the fuel line that feeds the injector rails.
As noted, the fogger really is impossible to see unless you know what you're looking for.
"No, officer, all my car has is an aftermarket exhaust system..."
This deception ends when the boot is popped, however. A 10lb nitrous bottle stands proud on its custom mounting brackets in the left side of the cargo area. As you can see, there's a knob at the top of the bottle; this must be unwound in preparation for any anticipated 'action'. With the knob fully opened, the nitrous system can then be armed and triggered. A switch inside the centre console opens an electric shut-off solenoid and the engine cops its assistance whenever 100 percent throttle is used. The throttle opening trigger point is determined by a micro-switch beneath the accelerator pedal.
The boot also contains the bass drivers and amplifiers of a pretty serious sound system. A sealed enclosure is home for twin Alpine 12-inch subs and a pair of Alpine V12 amps. Note that, for the ultimate in a stealth nitrous installation, Michael told us he has previously mounted the bottle inside a dummy sub enclosure; assuming there are no obvious gas lines sprouting from the enclosure, the chance of being found out is very, very slim.
The '02 cabin also scores top-of-the-range Rockford and Focals full-range speakers - the biggest that would fit - and tunes are sourced from a Kenwood MP3 system with a retractable screen.
Cosmetically, George's Rex has been enhanced with tinted glass, some subtle A.A.S. (Advanced Automotive Services) stickers and slick Works V5 18-inch rims wearing 225/40 Bridgestone S-03s. The ride height has also been brought down thanks to Pedders springs.
With the gas a-flowin' flywheel power is estimated up to around 250kW, together with much stronger low and mid-range torque. Not bad given the nitrous kit cost only AUD$3200 installed - that's about what you pay to have a new VF-series turbo fitted and, unlike a NOS kit, you won't be able to carry it forward to your next car.
And how long does the nitrous bottle last, you ask? Well, that depends how many consecutive sets of traffic lights you need to be wasted at before you can bring yourself to accept you've been caned by a Rex with apparently nothing more than a big exhaust... In its current configuration, though, nitrous is consumed at the rate of about 1lb per 10-seconds of assistance - that's about twenty 0 - 100s.
With the kit now installed for about 12 months, George is very happy with the performance boost. "The nitrous can come on fairly noticeably depending how you squeeze the throttle and it just flies through the revs now - it feels like a completely different car," he says.
From seat of the pants George tells us it also feels quicker than his previous Rex, which pulled a high 12 down the quarter mile. Yet - somehow - the standard '02 clutch has so far survived the extra torque loading.
All this just when you thought you could predict the power and performance of a Rex with only a cursory glance over its mechanicals!
Contact:
Advanced Automotive Services (Mildura, Victoria)
+61 3 5022 8277
|