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Originally Posted by Dyno247365
I'm taking environmental physics as my first ever physics class so a lot of this is new to me. We recently learned about calculating Gas Mileage from Fdrag and it got me thinking. Help this thread by trying to answer my three individual questions. Notice I said try.
1. Currently, engines produce power with 33% or less efficiency. How can we optimize and increase engine efficiency for the future?
2. My homework was to calculate how much possible miles per gallon my car could make (The Camaro) based on it's Coefficient Drag and Frontal Surface Area. With the right engine, this particular shape could theoretically make 46MPG. What specific/type of engine would it need to come close to that number? Does such an engine exist today?
3. I know there was something else I wanted to ask, just focus on those for now until I replace this sentence with the real question.
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1. If you look up "carnot" efficiency, you'll see the the maximum efficiency possible depends on the highest temp that happens in combustion. If you can increase the temp, you can increase the carnot efficiency (i.e the maximum possible).
This is what abaird is talking about.
In reality the material limits, emissions and fuel limits force us to use lower temperatures.
Then you'll see the Otto "petrol" thermodynamic cycle has it's own limitations and can't get to the ideal carnot cycle.
On top of that, mechanical and fluid factors reduce your efficiency further.
33% is the best efficiency you'll get only in a very tiny operating range (speed, load, rpm, throttle position).
Diesel engines have higher efficiencies (up to almost 50%) for a few main reasons. The first is a compression ratio that is higher than petrol fuel can withstand. The second is no throttle which reduces air pumping losses and makes them highly efficient over much of their operating range.
You can sleep easy knowing that there are thousands of very clever engineers worldwide working to get the most out of our current engine designs and also exploring new ones.
2. You need a small turbocharged diesel engine. Check out european car makers (VW etc). Their engines can produce 1kwhour of shaft power on 200g of diesel fuel.