Engine Displacement and Cylinder Count Explained

[@skpro_jects]

Great topic. This is something I will actually be real world testing with both of my cars. One has a turbocharged 2L I4 engine while the other is turbocharged but a 2L I6 engine (4G63 and RB20 respectively). By default they are very similar in specs however due to the extra 2 cylinders on the inline 6, I am expecting to not only be able to rev a bit higher without overstress on the rotating assembly, but also each cylinder should theoretically allow for an increased (advanced) timing for air fuel ignition, thus resulting in more torque for the same amount of A/F and charge volume.

[@BoostandEthanol]

Interesting! Would love to know your results from testing! Is the more advanced ignition timing just because of the higher RPM, or is there another property I’m forgetting about?

[@skpro_jects]

@@BoostandEthanol The ability to run more timing on the straight 6 vs the 4 would be that for the amount of power I will be making, the load would be spread out more over 6 cylinders than 4, assuming the dynamic charge pressure is the same between both engines. Thus, there will be more leeway to run more timing before hitting MBT (maximum brake torque) before running into the detonation limit. When I looked at both stock timing maps on both engines, I noticed the straight 6 had by default around 8-10 degrees more advanced timing in the same load/RPM cells compared to the inline 4, similar boost pressures. All this is further supported by the arguments you made in your video. Simply put, having more cylinders does allow for more (safer, smoother) power, even if the displacement stays the same. P.S Also you're right, at a certain point, the higher the RPM gets, the more we need to advance timing in order to prevent detonation so the flamefront can keep up with the pistons.

[@Dave12753]

This video really helped. I was struggling to figure out if a 10.1 litre inline 6 and a 10.1 litre v12 would get similar fuel economy. Now that I know cylinder count doesn't really matter and it's all in displacement, I know that we can use the pistons in a 6.7 powerstroke to make a 10.1 litre semi truck engine theoretically. I already send the idea to ford and I hope they respond.

[@lowercase.]

nice engine names at 1:04 2:02 3:59

[@Ludo66X]

No replacement for displacement!

[@d0va316]

so a 3L inline 4 could have the same torque as an inline 6, a V6 and a V8?

[@MJ-rr4hd]

5L V8 vs 4L V10/V12 who is more efficient ?

[@colebiggs7296]

So a 2 litre v6 can rev higher than a 2 litre i4 because the bore and stroke are less stressed. So how much higher can a 2 litre v6 rev compared with a 2 litre i4?

[@BoostandEthanol]

There's no nice and easy number, since there are so many variables that affect the bottom end strength and maximum revs. The best I can offer is that, if you know the maximum piston speed of a bottom end design, you could probably be able to figure out the maximum RPM of different size strokes. Actually, there are piston speed calculators online that can do exactly that. Say if you knew a crank/conrod/piston could survive up to 7000RPM, and you've got a stroke of 86mm, that's 20m/s piston speed. If you then could take that exact design and downscale it (without having any negative effects), to say, a stroke of 80mm, at 7000RPM, that's a piston speed of only 18.67m/s. To hit that 20m/s limit I used as an example, you'd need to rev the 80mm stroke engine up to 7500RPM. Bleh, engines are complicated but maybe this helps a little

[@godgirlsguitars]

I like putting big engines in vehicles with a real low cam profile. A big lazy engine that never has to strain so that I can get a million miles on the original engine. This is what I don't like about today's engines in real life, emissions are getting tighter so car makers are putting smaller engines and trying to make up for the power loss by adding direct injection and turbos which both increases pressure in the engine and something has to give, usually head gaskets or a cracked head or engine block. These little engines get strained so hard that they don't last long.

[@superben2000]

In automation best engine for cheap easy efficieny power is i5 turbo

[@BoostandEthanol]

That's extremely vague, like you haven't listed engine size, or year at the minimum. As I said in the video, displacement matters not cylinders. Even then in later years you can get away with less cylinders than in earlier years because the components are stronger. The "best engine" for something varies by year.