People just love bolt-on goodies - and with good reason. The more power you can get from things like exhaust systems, boost controllers and air intakes - without peeling off the engine's factory seal of freshness - the better. And there's one route to extra power that seems pretty big in the 'States but that we Aussies haven't yet taken much notice of - underdrive pulleys.
The main principle behind these things is simple. A smaller than stock, lightweight pulley is fitted to the crankshaft, literally driving your engine accessories (ie alternator, water pump, etc) at a lower speed than standard. Some power gains come from the slower speed at which the accessories are driven, but most power comes from the lighter weight and smaller diameter of the new pulley (similar in effect to a lightened flywheel). So technically speaking, an underdrive pulley delivers a reduction in parasitic load due to its lower rotating inertia and the slower turning of the accessories that it is driving.
US companies such as Unorthodox Racing manufacture a large range of billet aluminium pulleys as direct factory replacements, and these (obviously) must go on with a new, appropriate length belt (which most companies also supply). And by simply bolting on an underdrive pulley and a revised belt, Unorthodox claims that a 1996 Dodge Neon ACR DOHC can achieve 8.2hp (6kW) and 5.6 ft-lb increases over stock.
Check out these graphs for yourself - not too bad for a simple pulley eh?
Independent testing also quotes that a US-spec Ford Probe GT scores an extra 4hp (3kW) and 6 ft-lb (peak) improvement over the standard flywheel figure (which would be somewhere near our Oz-spec Probe's 121kW). Or, to put it another way, there's a peak gain in this case of a couple of percent.
But of course, there must be a downside to running your engine accessories at a reduced speed. They take less power... and so they also generate less power, or water flow, or power steering pump flow, or air con cooling .... It's for this reason that Unorthodox Racing strongly caution against too much underdrive. In the case of the alternator, for example, underdriving it can cause obvious problems. One website we located quotes, "Some have reported that with a normal idle, the alternator has difficulties keeping up under heavy load (headlights, brake lights...). Cranking up the idle to 1000-1100 rpm solves this." Hardly great for fuel consumption, engine wear, emissions and - without a doubt - it'd get a bit annoying as well!
So where does all of this leave us? Well, I guess it would depend on the mass of the currently-fitted crankshaft pulley, the severity of parasitic loadings on a given engine, and the amount of under-driving you can get away with without having any ill-effects. In most cases - modern engines especially - I'd reckon if you bring these factors together, the margin for extra power would be small. On a road car, the principle of underdriving may also cause potentially severe problems - especially in areas where there are extreme climates. A water pump driven at a reduced speed on a car in Australia's red centre isn't exactly a nice thought. But on a racecar - where there's no trade-offs to anything other than outright power - it could easily turn out to be a free lunch.
http://www.unorthodoxracing.com/pulleys.html
Adelaide came alive for me the other weekend (on one of those fairly rare and notable occasions!) Adelaideans, many of whom - including me - are still mourning the loss of the F1 Grand Prix, put on a show for the Clipsal 500 spectacular. Conducted over the three days between April 7th and 9th, a major portion of the city's once F1 track hosted yet another great race - with the main focus this time being on local produce V8 Supercars. But there was yet another series of racing that seemed to be taking off big-time too. Attending each day's competition, I couldn't help overhearing a noticeable interest in the Century Batteries GT-P Championship - a group of cars people can tag as reasonably similar to those parked in their home driveway.
Starting at P-plater level, the Class E (four cylinder tourers) buzzed around the concrete barriered city track and were the cars most frequently holding up traffic. Each time it zipped around, I couldn't help but think that the Suzuki Swift GTi was now looking positively old - especially next to the Civic VTi-R and Vectras, with which it was competing. Don't get me wrong, they still looked reasonably quick and composed, but - damn it - when will Suzi give us a replacement hot hatch?!
Somewhat intriguingly, it was the Class D six cylinders that I heard most people commenting on. And we're talking positive comments here, not sinking in the proverbial boot. Toyota's Camry CSi V6 was the one that got most people's brows walking off the top of their face. Visually, though, the Camry, Magna and EL XR6 all seemed fairly well matched (they were all quick given their humble base), but the poor old Mazda 626 seemed way, way off the pace. It looked like a handful too as it waffled and understeered its way through tight bends. In contrast, Mitsubishi and Toyota really captialised on the opportunity to push the performance of their bread-and-butter cars.
Then there were the big Aussie V8s - three VT SSs, one VS SS, one VS V8 Exec and a sole AU XR8. Ford - in case you haven't noticed - are really getting caned by Holden/HSV in the high performance sedan stakes. And when was the last time you saw someone brave enough to wear a once-worshiped Ford jacket? He-he. One thing that really showed up on the track was that each of these cars is a big weapon to handle. The drivers' lines through corners were much more calculated and they needed a-l-l of the width. But, jeez, they looked quick and they still sounded as horny as ever!
The B classers were the Sports Touring Cars. There's a real mixed bag in this group, with front-drive V-TEC Integra Type Rs, rear-drive BMW 323is and a MX5 and even a couple of rear engine'd/driven MR2 GTs. Another car that looked about as old as Grandpa was the wedge-shape BMW 323i. But then, none of these cars are especially new - a fact probably due to the generous regulations in regard to the vehicle's age. And again, the aging Mazda sporty looked slow in comparison to the rest of the class.
Looks of wonder were exchanged between many-a-spectator whenever the Type R Integras came around - they sounded totally insane! Their poor V-TEC motors would have been feeling lucky when they were momentarily allowed to go down to 5000 rpm! They screeeaaamed all the way!
But the elite bunch of the GT-Pers is the Class A High Performance cars - yet another smorgasbord of manufacturers and designs. It's in this class where many Gran Turismo faves come alive in the form of WRXs, STis, RX7s and Evolution 5 RS Lancers. I'm still not sure on how the Evo is allowed to compete given that it's never been manufacturer released here - but anyhow...
It was the flame-belching RX7 that set the pace along with some strong lap time, tussling with an on-the-limit 5.7 litre R8 Commodore. It was back in the pits where the reason for this became clear. Many of the turbo cars had been stung with a (low) boost pressure limitation - to the point where some cars were reputed to be competing on less boost than factory! No wonder the mighty Evos weren't sling-shotting out of corners and stretching their legs on the straights.
Of course, it'd be nice to see what they can really do - but once again it all comes back to making the racing closer and drawing in spectators. Let's just hope that it doesn't continue on this way and we all end up getting fed a misrepresentation of how quick these cars are.
GT-P racing is terrific so let's not let it get too politicised. Pretty pleeaase.
