This technology will start showing up in production vehicles soon (I believe VW will be first). Their intent is more of using the supercharger to get the car going with instant power, and the turbocharger will of coarse help the top end. The main job of the turbo, however, is to actually help in fuel economy at cruising speeds.

 

Indeed...I have seen twin charging a handful of times. Like previously stated it is done to utilize the low-end power increase of the supercharger, and the high-end power gain of the turbo...it's a "best of both worlds" idea in regards of the powerband. I believe it would be much much more common if it wasn't for the opportunity cost of building such a setup. Generally, the added cost I assume scares people away.

Its been around for a long time. 2-stroke diesels will have ports at the bottom of the cylinders. A roots supercharger actually forces air into the cylinders via these ports (opposed to intake valves) at the bottom of the pistons stroke . They then stack on "X" number of turbo chargers to aid in creating the boost levels they require. If you've ever seen one of the infamous burnout semi vids, I believe they run dual Detroit 2-Stroke engines, each engine has a large roots supercharger and 4 large Turbos...high cool factor...

 

I don't think a vacuum would form between the two. Any increase in pressure of the air that the supercharger will get will be a plus.. HOWEVER this is a 4 cylinder and I don't think that the increase in back pressure PLUS the power drain from the supercharger would represent a great setup.

 

Little 4 cylinder and diesels is were this setup will be most beneficial because of there slow low-speed acceleration characteristics. When you have a well-built 6 or 8 cylinder motor, you need a supercharger to get the car moving. The motor can do that on it's own.

 

Come to think of it, I thought I just saw some little econobox concept car with both in one of those "driving shoe" magazines.

 

Nothing would sound cooler than belt whine and turbo spool....i wish someone could post some more pics on this topic

 

and then that bov

 

The roots blower in a 2 stroke diesel is just there to scavenge the cylinders and blow exhaust out. They are not set up at the clearances required to actually boost the intake charge. The turbocharger does all the pressurization.

 

i cant speak for the car you saw, but thats not how i would imagine it was set up.

it should be.......turbo----->supercharger----->motor.

at low rpm the positive displacement blower can draw air through the centrifugal turbo. then once the turbo spools up and is moving more air than the supercharger is, it is basically boosting the SC.

make sense?

 

That's the way that I've seen it done, including on that 65 Nova that whassisname built; that started the pro-street trend back in the 80's.

 

I've seen this done on a few performance cars, but its not actually twin charging its more sequential charging.

The roots type blower does its thing on the low end and ususally has a magnetic clutch that will disengage the blower and bypass it once the turbo starts making boost so it is not drawing power on the top end.

The big thing about the turbos is that you can now run a much bigger turbo than you would normally. Say you've got an engine with X amount of liters and a blower running 7psi. Your turbo will now be sized for a 1.5X L engine because that is what is spooling the turbo(the exhaust side for sure, compressor may vary). This lets you run a much bigger exhaust housing and will actually gain you some extra hp in the top end.