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I am not saying that there aren't bad 4-cylinders - I recall my Dad's 1982 Mustang and my buddy's 1974 Vega had crappy 4-cylinders, very crude. My first new car was a 1990 Honda CRX Si with a 5-speed stick, and the redline was at least 6,000 RPMs, and I certainly visited the redline, and honestly there was no trace of any undue noise, vibration or harshness in that thing, it sounded very happy to be there, I used to think it sounded like a turbine. I owned a series of Honda 4-cylinders after that first one and always felt the engine was refined. Honda's CBR1000RR motorcycle engine is an inline 4-cyl with a 13,000 RPM redline, 1-liter displacement without turbocharging that makes ~ 190HP, and is highly regarded for its smoothness. If you can do that, then I think making a 4-cyl engine run well at 6,000 RPMs is a piece of cake.
How smooth or rough a four cylinder sounds depends on firing order. As they are not a balanced engine.
The answer to this question is several-fold, but mostly it boils down to efficiency:
1) The larger the cylinders, the greater their volume to surface area ratio, which means less energy is lost as heat and more turns into useful motion. A 3 cylinder will have fewer thermal losses given the same displacement as a 4 cylinder engine.
2) The larger the cylinders, the less friction there is for a given displacement, for the same reason as above.
3) 3 cylinders make better turbo engines than 4's, for reasons that are rather complicated for the scope of this post. Most 6 cylinder engines have dual turbos, each fed by a bank of 3 cylinders.
4) There is a optimal piston size to extract the most energy out of gasoline, due to the speed of flamefront. A 3 cylinder engine will be at peak efficiency at a lower RPM than a 4. Lower RPM means lower friction, lower losses.
I'm sure there are more reasons but that's what comes to mind immediately.
~
A few other things I'd like to point out:
DISPLACEMENT IS DISPLACEMENT. A 3 cylinder engine at 1.5L will produce no less power than a 4 cylinder of the same size. It might produce more, in fact, since it will have fewer parasitic losses, and peak torque will more likely be at a lower RPM.
A 3 cylinder engine is much harder to balance than a 4. Chances are good a 3 cylinder will have a heavier flywheel and larger balance shafts, and even then it will likely be a less "refined" ride.
I daily drive a 3 cylinder car. It gets phenomenal fuel economy. It also vibrates a lot more than other cars I've owned.
The coyote 5.0 makes more power than the 5.2 in the raptor, and a Lambos 5.0v10 makes more power than a Mustangs 5.0...
The coyote 5.0 makes more power than the 5.2 in the raptor, and a Lambos 5.0v10 makes more power than a Mustangs 5.0...
I should have said, "All else being equal".
Consider this: in the early 2000's, the Honda Accord had a 2.4L 4 cylinder which produced 160HP, whereas the S2000 had a 2.0L which produced 250HP. Both were naturally aspirated. Why do you suppose that might be?
But technology has come so far in the past 30 years. In the late 60's, we were big stuff if we had 425 HP. Now, my daily driver has that much, and it gets great gas mileage and is smooth as silk. I bet they are able to squeeze a lot of hp out of those little 3 cylinders these days...…..not Hemi hp, but decent hp.
Great for the power output. Some of today’s V8 performance cars get fuel economy of V6 vehicles of ten to twenty years ago when they were at or less than 200 hp.
Location: East of Seattle since 1992, 615' Elevation, Zone 8b - originally from SF Bay Area
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Originally Posted by victimofGM
Great for the power output. Some of today’s V8 performance cars get fuel economy of V6 vehicles of ten to twenty years ago when they were at or less than 200 hp.
My F150 5.0 gets 15/21, which I consider great for 385 horsepower, and with the 36 gallon tank I can go over 700 miles before having to fill up on a road trip. I had a 1972 El Camino 350 that made 330 horsepower, and only got 11 mpg.
I drove an H3 with that engine and I wasn’t impressed. It was weak and noisy.
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