How Ferrari is fixing Turbo Engines
F1 cars. BMW M3/M4. BMW M5. McLaren. Audi RS5. Those are just a few examples of cars whose noises lay victims in the wake of turbocharging. But they say the future is turbocharging (it's the present, really, if you look at how many cars already are turbocharged). There are a lot of technical pros and cons to turbocharging, which I won't get into here, but one of the biggest subjective downsides is the huge difference in engine noise between naturally aspirated and turbocharged engines. Some dismiss it, if the specs and the numbers are good. Some prefer all the whine, whooshing, and hissing. This probably sounds familiar...
Hammond (Noble M600) vs May (McLaren MP4-12C) on Turbo Noises - Supercars Across Italy TG Episode (S18 E1)
Some, however, mourn the death of naturally aspirated engine noises. Everyone who is familiar with what I like in cars knows I'm in that latter group. Apparently, it's a special group because Ferrari engineers (or at least their customers) are in that group as well because Ferrari filed a patent for a design that should make turbo engines sound (as well as work) much better.
The system is a hybrid between an electric supercharger system and a traditional turbocharger. Last week, DriveTribe's own Mike Fernie posted a great video explaining how a traditional supercharger works in under 5 minutes (and included a test run of a 707 hp Jeep TrackHawk). Seriously, you need to watch it.
An electric supercharger works much the same way, only it uses an electric motor to drive a compressor wheel to make boost on demand. On the other hand, traditional turbos use a turbine wheel in the exhaust connected by a shaft to a compressor wheel in the intake, where the turbine wheel extracts energy from the exhaust stream and uses that energy to compress the intake charge.
Ferrari's system uses a turbine wheel just like a traditional turbo to extract energy from the exhaust, but instead of a direct mechanical connection (i.e. shaft) to the compressor wheel, it is connected to an electric motor that is used to charge a battery. Essentially, it turns the exhaust side of a traditional turbo into a small electric generator. The intake side is basically identical to an electric (centrifugal) supercharger, where there is an electric motor that is used to power a compressor wheel to generate boost when needed.
There are obvious benefits to this system compared to both of an electric supercharger and a traditional turbo. A pure electric supercharger does not capture any energy in the exhaust, letting it all go to waste through the tailpipe(s). If used with an electric/Internal Combustion Engine (ICE) hybrid powertrain, it can run more efficiently on energy captured through a regenerative braking system instead of power from the engine, but there is still no exhaust energy recovery.
Here, the turbine wheel can capture exhaust energy and store it in a battery or a battery pack for later use. And compared to a traditional turbo, the main benefit is independent operation of turbine and compressor wheel. Energy can be captured from the exhaust whenever possible but boost can be made on demand as soon as required, so lag could be nearly eliminated completely instead of having to wait for the engine to rev up, exhaust flow to build, and output to overcome compressor wheel mass (inertia).
The only downside? A little extra weight compared to both systems, but that's a (likely, small) penalty I'll happily take. The system may also be a little more complex, but we are into turbocharging and hybrid powertrains, so simplicity is thrown out the window. Adding a couple of electric motors (or one if compared to electric superchargers) is a small added complexity that's worth the gains in my opinion, especially considering that electric motors are hugely reliable devices. So how, you might ask, is Ferrari changing the noise? This is where it gets even more creative.
Since the turbine and compressor wheel are independent, the speed of the turbine wheel and how much energy is extracted from the exhaust - both are factors directly related to noise - could be varied to control the exhaust noise without affecting the intake side. In other words, you could control the turbine wheel on the exhaust side to improve or increase the noise when you want (i.e. speed it up or slow it down) to control the "acoustic emission in the exhaust", as Ferrari calls it. If you need boost at a time when you want to slow down the turbine wheel, you could just use energy from the battery to drive the compressor wheel and make the exact amount of boost you need. That means you can get the noise and the boost at the same time, something a turbocharger can't do, and you can still capture energy from the exhaust stream, something a traditional or electric supercharger can't do.
Of course, there should be an expected efficiency loss if you're wasting exhaust energy sometimes to avoid muffling engine noise. However, Ferrari says in its filing that the “control method can only be used when desired and therefore has no relevant negative effect on the overall energy efficiency.” Read that last bit again in an Italian accent and you'll believe it.
Joking aside, I do think that, overall, the system will definitely be vastly more efficient than electric superchargers (assuming both or neither are connected to a regen braking system). It could even have the potential be a little more efficient than traditional turbos at times because you could recover energy in the exhaust and store in a battery at any time, not only when you need boost. The noise? That alone is worth any downsides. The elimination of lag is sweet, sweet icing on the cake. Just don't tell AMG engineers that they can make their engines sound even better, because they seem to rely on magic right now to continue to make their new V8's that are (twin) turbocharged sound as glorious as ever...
You can read the Patent Application in detail on the US Patent & Trademark Office Website.
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