Julian Edgar, 50, has been writing about car modification and automotive technology for nearly 25 years. He has owned cars with two, three, four, five, six and eight cylinders; single turbo, twin turbo, supercharged, diesel and hybrid electric drivelines. He lists his transport interests as turbocharging, aerodynamics, suspension design and human-powered vehicles.
Driving Emotion
On a recent trip to Melbourne I had interesting conversations with Terry Wilson of AVO, APS’s Peter Luxon and David Innal (yes, the latter of twin turbo four wheel drive Falcon fame), and Simon Gischus of Nizpro.
Without a doubt these men are fiercely competitive – in a small market they each want to be seen not just as pre-eminent but also the first choice of people modifying their cars. They know each other – if not personally then certainly by reputation – and you could expect them to have significantly differing views on not only the ways of achieving performance outcomes, but what those outcomes for a performance road car should be.
But on that last point you’d be wrong. For each of these men stated the same thing repeatedly, perhaps best summarised by “It’s not the peak power that counts, it’s the breadth of the torque curve.”
The reason that this came up in conversation is that each of these companies has recently purchased a BA Falcon Turbo and each is well down the path of developing performance parts for the car. And significantly, each man loves the new Falcon. Simon Gischus suggested he was thinking of buying another for family car duties. Peter Luxon said that the Falcon was the first Australian car that he would ever consider driving as one of his own cars. Terry Wilson complained about the build quality (kinked pressure regulator hose, missing dome light cover, window that falls down with a loud bang as he drives along – and we could all hear the front suspension clunk) but thought the car was a very good package.
To gain universal praise from such a disparate trio of modifiers is amazing.
But what did all of them think the best aspect of the car was? Its torque curve. The fact that it develops good power at low revs (power is just torque times revs with a division thrown in) and yet still has a strong top-end.
A car with flexibility and power.
Unfortunately, most car enthusiasts simply don’t understand the significance of a broad torque curve. It’s power that accelerates cars – not torque – but in flexibility and the real-world of street driving, having good power available at all revs is worth a lot. A real lot. Like, I’d much rather drive a car which was 50kW down over a 200kW competitor yet had 80 per cent of the available torque from 1500-6000 rpm, compared with say only over 3500-5500 rpm. In road driving the better throttle response (in its broadest sense), the lack of required gear changes and the stronger urge gained without having to be at peak revs will all give a faster and more enjoyable car.
It’s a frustration that a workshop that very carefully modifies a car to retain this driveability and lower rpm power will be fighting a publicity race against another company that is prepared to sacrifice this in order that a bigger peak power number can be stated. As an example, the current STi Impreza WRX (here in Australia, at least) is a car with an extremely narrow power band. I’d just laugh at any company that told me it’d put on a bigger turbo (unless of course they’d also increased capacity and/or comp ratio to try to get back some of that off-boost urge.) In fact, it’s quite likely that a smaller turbo would result in a car that’s faster on the road.
And it’s not just turbo cars. Simon Gischus took me for a ride in a 6.3-litre Gen III Commodore that they have developed. The car (covered previously in AutoSpeed at “Big Bore Bruiser”) now features head work in addition to its new inlet manifold, greater capacity and MoTeC management. It apparently makes as much top-end power as a full-house local NASCAR engine – but it is supremely driveable. After demonstrating its ability to spin its huge tyres through first and way into second gears, Simon gave a fantastic demonstration of its torque curve – trundling up a hill in sixth gear at 1100 rpm. The engine had serious grunt everywhere – it was a very, very good thing. No doubt another couple of hundred horsepower could have been extracted at higher revs with a radical cam, short trumpet manifold, new internals – stuff like that – but the aim was always to have a usable car.
In fact I asked Simon if any of his many stove-hot Nissan Skyline GT-Rs had ever had this much response right through the rev range – and he immediately replied ‘No.’
Of course at 6.3 litres it’s a helluva big engine, and so it bloody well should go hard everywhere! But the fact that it did is indicative of a particular modification philosophy, one built around a broad torque curve and not a peak power figure.
So where does that leave you if you’re looking at modifying your car? That’s not easy to answer. Most (although as the STi demonstrates, not all!) factory cars are set up with as broad a torque curve as the engineers can easily implement – manufacturers almost universally realise the benefits of this approach. (Although it must be said that few cars succeed as well at it as the turbo Falc.) Modifications should not aim at picking up top-end improvements at the expense of bottom-end losses – instead the ability of the engine to breathe at high revs should be an addition.
Specifics? Well, in power increases of up to 30-50 per cent, be wary of swapping-in a larger turbo. In naturally aspirated cars, confirm that a new cam grind doesn’t slash the bottom-end power. Intake manifold changes should be undertaken with care and cam timing alterations (especially in variable cam timed engines) should be proved with an eye on the totality of the power curve.
I guess the best approach is to talk to the workshop. If they look doubtful – or don’t even understand – when you say that you’d like a power gain but without sacrificing the flexibility and torque spread of the engine, think of going elsewhere. Workshop staff who understand the concept are likely to grab you by the arm and start shrieking “yes, yes, yes!”.
