Does Size Matter? Engine Displacement….How Low Can They Go?
- Thread starter dkryan
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I got to do some troubleshooting on a very original BMW Isetta yesterday. 300cc single, 12hp.
Fiat still makes two cylinder engines! Straight twins under a liter, both with and even without a turbo! Not even as a range extender (which would be an excellent use of the TwinAir), but as the sole power source for the whole car 
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Not if you can only get it out from underneath...
Flipping that around, many years ago when I was teen, a coworker at my part-time job was convinced that a Datsun 240Z had a 240 c.i. engine.Imagine when a BMW 330 refers to a 330cc engine.
Or a Lexus gx550 refers to 550cc engine.
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It's very easy...
For decently modern normally aspirated gasoline engines, my personal standard is 1.25 pounds per 1cc engine volume.
And my idea of decently modern is 90hp and up per 1000cc for cars, 60ish for econo/base/utilitary/specialized vehicles.
So ballpark - 4000lb vehicle should end up at 4000/1.25=3200cc and ~290ish hp for a decent vehicle.
I would allow some play with turbochargers, except - I wouldn't apply any equivalents below 2000cc for cars that weigh the average. Meaning - I'm ok with a turbocharged 2000cc & 280hp engine hauling a 4000lb car, but not ok with a 1000cc & 140hp engine hauling a 3000lb car. I'd maybe consider it on a 2000lb small sporty thing.
Something about a 1.5l turbocharged engine hauling an Accord gives me a sinking feeling. Not sure if I'm right. I wasn't giving any reliability credit to Tdi engines when the first golf trip was released, and yet they turned out to be a good enough future.
For decently modern normally aspirated gasoline engines, my personal standard is 1.25 pounds per 1cc engine volume.
And my idea of decently modern is 90hp and up per 1000cc for cars, 60ish for econo/base/utilitary/specialized vehicles.
So ballpark - 4000lb vehicle should end up at 4000/1.25=3200cc and ~290ish hp for a decent vehicle.
I would allow some play with turbochargers, except - I wouldn't apply any equivalents below 2000cc for cars that weigh the average. Meaning - I'm ok with a turbocharged 2000cc & 280hp engine hauling a 4000lb car, but not ok with a 1000cc & 140hp engine hauling a 3000lb car. I'd maybe consider it on a 2000lb small sporty thing.
Something about a 1.5l turbocharged engine hauling an Accord gives me a sinking feeling. Not sure if I'm right. I wasn't giving any reliability credit to Tdi engines when the first golf trip was released, and yet they turned out to be a good enough future.
Or retard the timing so much, the engine becomes a choked dog.
I went to Germany a few years ago and had a VW T-Cross rental which had the EA211 1.0T 3 cylinder. I was very impressed with that engine, it felt more than adequate for the vehicle and with the DSG it felt even sporty. I've also driven a Japanese Kei car with a 668cc engine, and that was also plenty adequate for city streets. Americans are just now realizing what the rest of the world has known for decades, small engines can be more than enough.
The issue with those ended up not even the belt itself but the belt tensioner would fail. The belts had issues too but most of the failures were actually due to the tensioner falling apart.
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And Japanese never realized that you can't castrate and tame small engines ad infinitum and expect Americans to keep buying them.
The defense will present exhibit A: the CRX that morphed into the DelSol then into nothing but 20 years of bland civic juice (1999 civic sedan, anyone), with a monstrosity-shaped Type R parachuted to defend the realm with a front wheel drive in a sea of quattros, stis and evos. In a time when even Ford managed to get good looking hot hatches.
I would argue that Honda and Toyota have demonstrated your assertion to be wrong with how many Civics, Corollas, Yaris, Fits etc they've sold in the US over the years.
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My assertion is about them having done it along with going up in engine displacement. Civics and Corollas bread and butter went from 1600cc average in the early 90s to 1800-2000cc+.
Smallest Civic non-hybrid engine in the US from 2000 to 2020: 1700cc.
Smallest in Europe: 1000cc.
Corolla:
US - 1800cc
Europe - 1.3 (1.2 if you count turbos).
Your Yaris and Fit examples are excellent as well - the Yaris never got the 1.0 or 1.3 engines in the US, just the 1.5 one. Same for the Fit, it only came to the US with the largest engine available. And both were in a market bracket orders of magnitude smaller than the Civic/Corolla one.
To to me the answer would not be "are we going to see 1L engine in America" but rather
1) Are we going to see a powerful 1L engine pushing today's sellable vehicles passing emissions that people want?
or
2) Is 1L engine of such power going to be cheaper, lower emission, better fuel efficient, or more durable than just a slightly larger simpler engine for such vehicle?
I don't think American will go back to smaller vehicles as we get better at cost of vehicle purchases. We are not in oil crisis like the 70s and our cost of living are more in the housing, medical, and higher education than in automobile fuel expense. Less powerful engine is not going to be as big of a cost saving today when we already commoditized other stuff like variable valving, hybrid, more advanced transmission with more ratios (or CVT even), direct injection (or dual injection), better engine control, more durable turbo, etc. We can't even convince people to buy smaller cars and everyone just want at least a crossover or SUV today.
About small engine with turbo vs bigger engine, the trade off was huge back when we can only reliably do 4 speed auto so we need to design engine to rev if we want smaller engine to save fuel, or regulation in foreign country taxing displacement. Today I think it is more about regulation in emission or mpg, so it is possible we will have 1L turbo with CVT pushing a crossover in some model due to regulation but not if those regulation go away due to politics. Saving 5mpg at 40mpg is not as big of a deal as saving 5mpg at 20mpg. And if people want extreme mpg they can always get hybrid, and the fact that hybrid still uses larger displacement engine means 1) it is better to run larger displacement at Atkinson cycles than smaller engine at Carnot cycle like regular car, and 2) it doesn't save you much manufacturing cost making smaller engine when economy of scale is not there, as in you share the same engine family's manufacturing infrastructure and platform if possible.
We may see some of those 1L engines in the US if they sell a lot of them in foreign countries first, and that would likely come from brands with many foreign R&D and sales.
1) Are we going to see a powerful 1L engine pushing today's sellable vehicles passing emissions that people want?
or
2) Is 1L engine of such power going to be cheaper, lower emission, better fuel efficient, or more durable than just a slightly larger simpler engine for such vehicle?
I don't think American will go back to smaller vehicles as we get better at cost of vehicle purchases. We are not in oil crisis like the 70s and our cost of living are more in the housing, medical, and higher education than in automobile fuel expense. Less powerful engine is not going to be as big of a cost saving today when we already commoditized other stuff like variable valving, hybrid, more advanced transmission with more ratios (or CVT even), direct injection (or dual injection), better engine control, more durable turbo, etc. We can't even convince people to buy smaller cars and everyone just want at least a crossover or SUV today.
About small engine with turbo vs bigger engine, the trade off was huge back when we can only reliably do 4 speed auto so we need to design engine to rev if we want smaller engine to save fuel, or regulation in foreign country taxing displacement. Today I think it is more about regulation in emission or mpg, so it is possible we will have 1L turbo with CVT pushing a crossover in some model due to regulation but not if those regulation go away due to politics. Saving 5mpg at 40mpg is not as big of a deal as saving 5mpg at 20mpg. And if people want extreme mpg they can always get hybrid, and the fact that hybrid still uses larger displacement engine means 1) it is better to run larger displacement at Atkinson cycles than smaller engine at Carnot cycle like regular car, and 2) it doesn't save you much manufacturing cost making smaller engine when economy of scale is not there, as in you share the same engine family's manufacturing infrastructure and platform if possible.
We may see some of those 1L engines in the US if they sell a lot of them in foreign countries first, and that would likely come from brands with many foreign R&D and sales.