sosic2121 wrote: ↑
Wed Jul 29, 2020 5:47 pm
Just_a_fan wrote: ↑
Wed Jul 29, 2020 5:23 pm
sosic2121 wrote: ↑
Wed Jul 29, 2020 8:42 am
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On the other hand I seriously doubt turbo engines are more efficient. IMO higher the boost, lower the efficiency. Especially in real world. When you buy aftermarket injectors, turbo application requires about 10% "larger" injector then NA, and supercharged 20%.
I guess there is a reason why Prius is NA...
Depends what you mean by "efficient". A forced induction engine will give more power per cylinder cc, for example. So it's more efficient in terms of hp/cc. Whether it's more efficient by some other metric will be for the reader to decide.
I meant fuel efficient, not volumetric
The future of high mileage engines are small, high torque, turbo engines.
If you look at your industrial applications (freight locomotives, etc.) they're all turbocharged diesel electric. It's kind of crazy it's taken vehicles this long to get there considering it's been refined for 80 years now in the industrial world.
NA / Turbo / etc, the amount of fuel burned is dictated by the type of fuel you are using. A particular blend of gasoline is going to want to be the same AFR on a NA engine as it would a turbo engine. There are efficiencies in combustion, friction, etc., but that doesn't change the AFR ratio or fuel burned, it just takes energy that was wasted via heat or friction and putting it into the crank.
An NA engine has to create depression with the piston, so there are two ways to deal with this; 1) make the engine larger 2) rev it higher.
In a turbo engine, you can artificially increase atmospheric pressure, and with the modern refinement of hybrid turbo systems, you can decouple turbo boost from exhaust pressure, improving performance at rpms lower than you could previously. There is no way around that with a NA engine.
When we're talking racing, NA engines have been noncompetitive since the 1940s in drag racing, when hot rodders first put truck type roots blowers on their engines. Bonneville, the altitude is a huge problem, as is the Pikes Peak Hillclimb (I live about 45 minutes from Pikes Peak, and walk out the door and see several 4265m+ peaks). Indy Car, they have been noncompetitive since before WWII, and the integrated head / block of the Offy, and its ability to handle huge boost loads, is what allowed it to be competitive for decades.
As for fuel, it just depends on the rules and applications. In Top Fuel racing, they run more fuel (nitromethane) through the engine 1) for cooling 2) to burn in the exhaust to create downforce (those 3m flames are for a reason). They have way more power than traction, so a dozen pounds or more of fuel isn't going to hurt them. Maybe its restricted in other series (F1 is), maybe you'll be faster if you make more power but take a weight penalty or maybe it's faster the other way. Racing is all about fitting the rules and applications.