It fails at the racetrack because its complication has made it unreliable.
Many if not most classes of motorsport ban forced induction.
For other classes of motorsport such as drag racing and Bonneville, massive low end torque and crisp throttle response are worth nothing.
Where twincharging really shines is hillclimbing, road racing, and rallying, and that is where you find many twincharged cars. Pikes peak has seen a lot of twincharged entrants over many years.
Then there were the Group B rally cars that were twincharged.
Check out the Lancia Delta S4, these 1.8 litre cars were routinely putting over 500 Hp through all four wheels, and nothing at the time could catch them.
Today, 500 Hp does not seem such a big deal.
But twenty five years ago, 0 to 60 Mph in 2.3 seconds was sensational performance.
Unfortunately the very high speeds this produced on dirt roads led to a large number of fatal high speed crashes, and Group B was then discontinued as being far too dangerous.
Nothing wrong with the cars, or the technology, or the reliability, they were just too powerful and too fast for racing in gravel and mud.
There have been several production twincharged cars too. The Nissan March, and VW GTi, just to name two.
The VW example was built for economy not performance. It is probably too expensive to go into very wide production, a larger capacity engine is always going to be cheaper than an engine + turbo + supercharger.
I was just reading a road test of a the new 2011 model Audi A1 Sport that is twincharged, I doubt if they would have done that if it did not work or was unreliable LOL !!
For road racing, nothing can beat twincharging for a wide flat torque curve, plenty of top end power, and fast throttle response.
It is something the wider petrol head community mostly still do not know about, although twincharging has been around as long as both the supercharger, and the turbocharger, at least a hundred years, it is nothing new.
It is just cheaper for the manufacturers to build a much larger capacity engine than to build a twincharged smaller engine.
But if you wish to build a small light weight race/road car with a really compact and powerful engine, it is well worth investigating the benefits of twincharging.
When you do, one thing will immediately become very obvious.
Most of the available power in the lower gears will be completely unusable without four wheel drive.
A moments thought might convince you that the mid (rear) engined Lancia Delta S4 could never have achieved 0-60 in 2.3 seconds with two wheel drive.
I have been building, and helping others to build some very successful (and reliable) twincharged engines for a very long time, it is not all that difficult.
All this is exactly why I am currently building what will very likely be the first four wheel drive Hot Rod in Australia, unless someone else beats me to it, which is fairly unlikely.