Driving the XR8

Posted on September 11th, 2005 in Opinion by Julian Edgar

Drove a car the other day that’s a good example of a fundamentally excellent design ruined by some strange decisions. The car? A Mark II BA Falcon XR8 – that’s the one with the 6-speed trans.

So what is wrong with it? Well firstly – and probably most critically – the gearing is simply way too tall. The very sweet 260kW 5.4 litre DOHC-per-bank engine has peak torque (a massive 500 Nm!) up at 4250 rpm. That’s not a problem in itself, because the engine is also superbly mapped, being tractable and progressive at any rpm. However, with an engine like this, you can’t run ultra-tall gearing and expect a strong performer. Not unless you drive around always two or three gears lower than ideal.

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Like, while the engine would pull 6th gear at just 60 km/h, there was also zero response. Fair enough – 6th is after all the highest gear. But even in 4th gear at 60 km/h, the grunt when you buried it wasn’t very good. In fact, to get what I’d call acceptable 260kW V8 response, at 60 the XR8 had to be in 3rd gear. The same story was repeated at other speeds – best to be in 4th gear at 80 km/h, 5th gear at 110 km/h, and so on.

The gearing made what should have been a powerful and responsive car feel at times lethargically slow.

Then there’s the suspension. This model runs 18-inch wheels and 40 series tyres, together with springs stiffened over the previous car. The ride? Well, it’s lousy. Over short, sharp bumps like potholes, the car shudders as the vibrations pound into the cabin. On larger amplitude, gentler bumps, the car feels underdamped, body oscillating after the bump has been left behind. As you’d then expect, getting the power down on tough roads is difficult – on one demanding stretch of bumpy back-road bitumen being driven hard in second gear, the traction control light was lit almost continuously.

And talking about the traction control, it is clearly not optimised to the tyre and suspension tune of the car. Even on smooth roads it activates as soon as the rear even thinks about losing cornering grip. In fact, with the system switched on, the car feels nervous, the system telling the driver the rear wheels have little grip. The silly thing is, switch off the traction control and you’ll find that the rear-end has plenty of grip! In fact, its power-oversteer characteristics are superbly benign and well-telegraphed. Like a big Mazda MX5, this is one rear-wheel drive car that you can easily understeer-in and oversteer-out, without the slip angles ever becoming excessive and while going bloody fast. But with the traction control system on, you can’t do a thing – something very different to Honda and Audi and (Euro) Holden traction control systems…… 

Other poor aspects of the car? Well, the steering changes in feel dramatically as the wheel is moved away from centre, the diff in the test car developed a Godawful rumble at freeway speeds (it sounded like a subwoofer thumping away), the (optional leather) seats lack lower back support, and the driveline makes clunking sounds on every low speed gear change.

But I think the engine is superb, being fantastically flexible at the bottom of the rev range and developing a howling thrust of power over 4000 rpm. It also gives much better fuel economy than the Commodore V8 (and I don’t think that’s all in the gearing!).

Put in some better dampers (and/or soften the springs), go back to the higher aspect ratio tyres fitted to the previous model, lower the final drive (perhaps by fitting the Turbo’s 3.73 ratio), re-calibrate the traction control system and fix some quality control issues, and you’d have an outstanding car for the money.

And that’s not said in irony: at times the XR8 showed just how good it could be – and then the car would fall into a pothole, or you’d miss filling a gap in traffic because of the lack of immediate engine response, or the bloody rear axle ‘subwoofer’ would start pounding…

On paper the Falcon XR8 is a killer package – quad cam V8, 6-speed manual trans, good suspension design front and rear. But on the road it’s simply disappointing.

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As it happens, on one of the days that I was driving the XR8, I was at Redcliffe Dyno and Performance in Brisbane. RDP has developed a supercharger conversion for the XR8, but it wasn’t the blown engine that excited me. (Perhaps that’s because performance test driving of the supercharged car was unfortunately not possible on this occasion.)  Instead, what got me going was a good look at the XR8’s standard airbox.

It’s a bloody ripper.

A bit like the turbo XR6 Falcon cat converter (which as we’ve previously mentioned, is amongst the best flowing of factory cats you’ll find), the XR8 airbox is a fantastic design. I don’t have flowbench figures to support that statement, but as was found on the dyno at Xeding Expectations, removing the airbox makes no difference to the measured power output of the engine – a very respectable achievement.

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There are a few things that make the airbox so attractive, especially for fitting to other cars. Firstly, it’s a compact barrel shape – 210mm in diameter and 250mm long. Secondly, it has a huge diameter outlet duct, no less than 100mm in fact. Thirdly, it uses a cylindrical filter design which – as aftermarket filter designers know – allows a very large surface area of filtering medium to be fitted in a small volume. Fourthly, the filter comes with an aerodynamic spreader located at one end. Fifthly, the air inlet is a wide-mouthed slot located near the base of the assembly. And finally, factory quality airfilters are easily obtainable.

Put all these things together and it’s the ideal filter box to go into the front guard of a lot of cars, nestling behind the bumper in front of a wheel. (Or of course, if there’s plenty of underbonnet space, in the engine bay.)

Inspecting the XR8 airbox was made easy at RDP – as part of the supercharger conversion, the workshop removes the airbox and doesn’t re-use it. So there one was – a near-new Falcon XR8 airbox sitting on the bench, unloved and unwanted. But I sure wanted it and asked the cost. Despite my stuffing cash into his face, Steve refused to take any money for it, suggesting it’s the sort of thing he usually puts in the rubbish skip.

In my application the airbox will be flowing less than 20 per cent of the air that the Falcon engine demands. On that basis, I think I can be pretty confident that there will be near zero pressure drop through the filter box and that the filter won’t need changing very often!

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