Wednesday, November 30, 2005


Despite all the technology going into engine and engine research these days, there seems to be very little progress in turbocharging for whatever lame reasons. FINALLY, an auto manufacturer is going to try some new technology to enhance turbochargers on their production cars.

This isn't the same as the old Garrett aerochargers which had a variable size for the compressor housing. It seems they're changing the actual angle of attack of the compressor wheels blades. My hope is that it really works well to allow high RPM flow and greater top-end power that is typically sacrificed as much of the low and mid-range punch of smaller turbos. My worry is that it isn't nearly as efficient aerodynamically and you have reduced power and torque in comparison your high-tech non-variable solutions.

Basically the way it should work is that as you change the angle on the compressor blades, it's effectively like how tuners and the aftermarket clip the blades, removing material from the blades to allow greater airflow rates at high engine speeds and compressor speeds.

Why would this work? Well, what happens on a typical small or medium-sized turbo? The compressor (essentially a giant fan) speeds up more and more from increased exhaust flow to try and supply that constant pressure in the intake stream. That means more and more air must flow through the turbocompressor quickly to be pressurized.

You now encounter either or both of two possible problems that limit turbochargers. Heat from pressurization or limit of airflow capacity. Heat from pressurization is always going to be present which is why intercoolers are so crucial for high pressure turbocharger or supercharger systems since there is a limit to which you can minimize heat increase from pressurization, that's just simple science.

While change the angle of the compressor blades does somewhat change the aerodynamic compression efficiencies of the fan, Porsche's VTG isn't directly addressing this. Rather, it seems to be addressing flow issues. By changing the angle, you change the maximum airflow capacity through the compressor housing. Less angle and thus less restriction and greater airflow thus greater capacity to maintain that pressure at high engine speeds = better top-end.

So, Borg Warner isn't making big turbos spin up that much quicker. It's making smaller turbos more efficient at the top-end. I think if this could be implemented at a reasonable price for the massive automotive aftermarket, it would be a boon. I see so many tuner cars out there that are simply built for top-end power... "I put down 500 wheel horsepower dawg!" but when you're doing anything other than wangan (top speed) or drag racing, top end is of limited use.

Opening up good mid-range punch into the top-end means better overall balance... this means the car is easier to drive on the street and on the circuit. You don't have to constantly be in the exact proper gearing and drive to maintain engine rpms in a small range... shifting down, shifting up, shifting down, etc. Just hit the gas and you'll get acceleration.

If you've never had the joy of experiencing a high power turbocharged car, you're missing out... if you know me, pester me, maybe I'll finish fixing up my 400hp monster and give you a ride :)


Post a Comment

<< Home