V6 TDI With Electric Turbo

Audi is working on a twin turbo V6 TDI but with a twist. One of the turbos is electrically driven. Audi claims a quicker response and more torque at lower RPM, "distinct boost in performance." Supposedly the electricity recovered during coasting will be used to power the electric turbo. This makes sense as this assist would be most needed after a slowdown.



http://www.worldcarfans.com/112092048467/audi-electric-bi-turbo-engine-revealed

Performance must be the #1 goal of this design, because half the reason for turbochargers is to recover energy otherwise wasted in the exhaust gases, not use electrical energy taken off the engine.

While a normal turbocharger does recover wasted energy from the waste exhaust gas, it does sound interesting to have immediate turbo boost out of the gate as an electrically driven turbo would have max torque to spin up to speed and apply boost as soon as electricity was applied to the motor.
The German engineers always take an interesting look at a problem and hit it from 90 degrees out. I think that it would be fun to have that power available off the line. It would probably quiet many DSG drivers complaints of hesitation off the line when they floor their TDI's.

I'm gonna watch this spot....

You mean all those ebay electric turbos might actually be on to something?

There are neat things you can do with a motor/generator on a turbo spool. Quicker spool in some cases, energy recovery in others.

Still hatin' on v6's with all that exterior exhaust plumbing. Put exhaust in valley like Ford did.

Edit: Looks like that is nothing more than an electric centrifugal compressor, no turbine.

LRTDI said:

You mean all those ebay electric turbos might actually be on to something?

Click to expand...

Nope. Here is a fun video about those.

http://youtu.be/cbGWgvJN1_8

From the diagram this looks like a real snail shaped turbo and not an oversized CPU fan.

Jalopnik has had a drive in the A6 powered by this engine. Pretty awesome stuff.
http://jalopnik.com/5946247/audis-secret-super-diesel-electric-turbo-prototype-is-fast-as-hell

My favorite part of the article is the following comment:
But what is the advan-
Torque.

But tor-
Yes it does. Horsepower is measured from torque.

But I never use torq-
Yes you do.

But I don't care abou-
Then you're an idiot.

This almost gives me goose bumps... I haven't even driven it, so I don't know what that says about me.

I did some sketches on this concept in the late 1980's. I don't have the background to really know how to actually make it work. I guess that makes me like Al Gore and his invention of the Internet. Just another Lame-Oh.

So this is really more like an electric supercharger than a turbocharger...

EDIT: Okay, so there is a turbocharger and an electric supercharger, essentially. Interesting. They could easily use regenerative braking to power the supercharger... just have a flywheel that gets spun up due to inertia during braking, it continues to spin and used to spin up the supercharger at initial acceleration. I guess with that setup you lose the ability to spin up the supercharger during other times, unless you still have an electric drive, as well.

It looks like the electric turbo is sped up with no load then engaged after reaching RPM... Pretty neat.

Seems like an electric-powered supercharger. In any case, I doubt this will ever see the light of day in the US with a manual transmission, so I can stop dreaming about it now...

The only V6 diesel in the A6 with a manual is the 200hp version with front wheel drive. The higher powered versions are quattro/DSG or quattro/8AT only.

if you look at the picture there is what appears to be a regular turbo and a electrical one. the electric one is probably used to help lower rpm boost and power, it would probably help cause the larger turbo to spool up alos.

What's the diff between turbo and supercharger? Just the source of motive power (exhaust versus electric driven)?

Turbo is more accurately described as a "exhaust turbine driven supercharger"

A supercharger is any machine that forces air into engine above atmospheric pressure.

So both a turbo and a supercharger are "superchargers". The turbo is a sc driven by an exhaust turbine, the audi thing is driven by an electric motor, others can be driven by belts etc from the crankshaft.

All are superchargers.

Ski in NC said:

A supercharger is any machine that forces air into engine above atmospheric pressure. So both a turbo and a supercharger are "superchargers". The turbo is a SC driven by an exhaust turbine, the audi thing is driven by an electric motor, others can be driven by belts etc from the crankshaft.

Click to expand...

Got it and thanks.

booksgamesvideos said:

What's the diff between turbo and supercharger? Just the source of motive power (exhaust versus electric driven)?

Click to expand...

Most superchargers look a lot different than turbos. Most superchargers look like the one on the Audi 3.0T and have two rotors. Here is how the most popular OEM supercharger looks like

http://www.caranddriver.com/features/prime-cuts-eaton-tvs-r1320-supercharger-feature

That's a Roots-type supercharger. Some OEMs do use centrifugal-type superchargers. I think the Mercedes 4-cylinder supercharged engines were/are (still in use in the natural gas Sprinter and E-Class) all using a centrifugal-type supercharger.

Roots type blowers are positive displacement type machines. Very different behavior than a centrifugal machine, but they both pump air. The roots blowers were used as a scavenging blower on two stroke Detroit diesels. Hotrodders found they could steal them and slap on top of a V8 gasser and get gobs of power. Not terribly efficient, but they sure won races.

cardinalkellz said:

Jalopnik has had a drive in the A6 powered by this engine. Pretty awesome stuff.
http://jalopnik.com/5946247/audis-secret-super-diesel-electric-turbo-prototype-is-fast-as-hell

My favorite part of the article is the following comment:
But what is the advan-
Torque.

But tor-
Yes it does. Horsepower is measured from torque.

But I never use torq-
Yes you do.

But I don't care abou-
Then you're an idiot.

Click to expand...

Yes, great reply!

About a turbo recovering lost energy from exhaust. This kind of a grey line statement to me but im also not as smart as Al Gore.

The exhaust is to some extent being pushed out of the cylinders by the piston and that force in turn pushes on the turbine. Now you are not really gaining anyhing here. And again on the intake side the pressurized air is trying to push the turbo backwards which in turn makes it harder for the piston to push out the gasses through the turbo.

So far this is all wasted energy you havent recovered anything from the exhaust gasses. The only thing that makes this all worth while is the extra oxygen that just happens to be in that intake air. This random oxygen that comes from the atmosphere is what give the the multiplier.

I just think that is kind of a misleading statement.

Thanks
Tony

rex, when exhaust gasses leave the cylinder, they're still hot and there's quite a bit of pressure left in them. A portion of the gasses are pushed out by the piston, indeed, but most rush out by their own pressure. This energy is completely lost normally, and some of it is indeed recovered by a traditional turbocharger.

That said, auto diesel turbochargers have the main purpose of improving power and speed of Diesel engines (an aspirated diesel need a long cylinder to achieve sufficient compression, which limits it's speed).
Often, fuel is burned late in the combustion phase specifically to reheat the exhaust gasses to drive the turbo, which improves responsiveness but costs fuel.
An electric compressor will probably eliminate the need for such post-injections and allow the turbo to work in a regime where it uses only waste heat and pressure, actully achieving the energy recovery it was meant for.

I understand that there is pressure left at the bottom of the stroke when the exhaust valve opens. I also get that this pressure is going to help push the turbo. However this pressure would be releived faster and with less obstruction if the turbo wasnt in the way.

Im sure with about twenty pages of math that contains mostly letters and symbols somone could prove this all to me but in my simple mind it takes energy to spin the turbo with the side affect of oxygen that gets pushed into the intake.

Without the advantage of that oxygen to burn fuel it would be like mounting a wind generator on top of your prius to charge your batteries.

Thanks
Tony

It's an idea that could make an advantage. Does look like it would be a bear under the hood as far as piping. Also the added maintenace issues along with diagnostics if there was an issue would be enhanced. Looks like most Audi additions adding to high miles headaches for owners. A great idea as far as the engineering concepts.

chewy said:

Most superchargers look a lot different than turbos. Most superchargers look like the one on the Audi 3.0T and have two rotors. Here is how the most popular OEM supercharger looks like

http://www.caranddriver.com/features/prime-cuts-eaton-tvs-r1320-supercharger-feature

Click to expand...

I agree if my old school learning holds. Super chargers have two spinning rotors and are driven from the crank shaft. In my state they were out lawed for street gasoline engine automobiles in the early 1970's. Therefore could not be added as a street performance part. When I was young A few could be seen with ram air intakes. When I took my diesel courses we were told the difference as far as air intake advantages. Also different componants. The talk of super chargers brings back memories for me. I remember the old Car Craft magazines always had a write up of the latest what they called blender designs back then and horse power stats for the after market manufacturer's designs of these. They were outlawed in Ohio in the early 1970's after the Ohio State Patrol had some bad run ins with gear heads that kinda blew their intercepters %^%$ away.

Guys, "supercharger" is a generic term that refers to any device which achieves forced air induction, i.e. makes air at above-atmospheric pressure available at the cyclinder intake port.

"Turbo-charger" is a supercharger driven by a gas turbine device. The "turbo" is in fact a gas turbine driving a centrifugal compressor. It is the most common type of "supercharger" because it's the simplest design (only one moving part, save for VGTs) and takes it's energy from the waste heat of the exhaust.

There are many other setups, both where the driving energy is concerned (belt drive off the crankshaft, electrical drive) and where the compressor construction is concerned (ceantrifugal, screw-type, etc...)


rex: I get your thinking, but what you need to understand is that it is a small proportion of the exhaust gasses which needs to be "pushed out" by the piston, most exit with force and just expend their energy expanding out into the environment. Consider that the engine only converts up to 40% of the energy released by combustion into mechanical work through the crasnkshaft! The rest just goes out the tailpipe.

Exhaust gasses are not "lost energy" but unused energy. It is true that putting any restriction (turbo) will have some effect on engine efficiency, but in the case of a turbo it allows more engine power than it consumes. One other common mis-conception is that exhaust gasses are "pushed" out of the cylinder, a more correct statement is that they are "pulled" out by the tendency of different pressures to equalize. Direct-drive positive displacement superchargers consume large amounts of power to operate, but again usually allow a net gain in engine power. It is estimated that the Roots-style superchargers on Top Fuel dragsters consume more than 1000 Horsepower, but on the other hand allow the engines to produce 7000-8000 horsepower.