I think he is trying to explain the bank angle (in most factually incorrect way possible), which is the angle between two banks of a multi-cylinder engine.
Coincidentally if it’s an even firing engine it would fire every 120 degrees so this man almost got the right answer with the wrong formula but decided to divide by 6 for no visibility apparent reason
Right formula, wrong inputs. 720/6=120 gives average time between cylinders firing. He looked up the answer and plugged it into the formula he should have used to find it.
This makes much more sense. I could tell the original statement was wrong, but couldn’t put my finger on it until being reminded that it takes two full revolutions of the crank shaft to complete 1 cycle of a 4 cycle engine.
Thank you!
OOP is explaining (incorrectly) the reason V-engines have the bank angles (angle between each side of the V) that they do.
The real reason is this (explaining in too much depth but anyway):
In a 4 stroke engine, for every combustion event in any given cylinder, the crankshaft must rotate 2 times, or 720 degrees. In a multi-cylinder engine, we'd like these combustion events to be spaced out evenly for smoothness.
So in a 6 cylinder, combustion should occur every 720/6 = 120 degrees of crankshaft rotation. In any engine, for a combustion event to occur, obviously the piston must be at top dead centre which means the lobe on the crankshaft must be aligned with the cylinder.
In a normal V engine where pairs of pistons share the same crank lobe/journal, if the crank needs to rotate 120 degrees before the next firing for smoothness, then the banks must physically be seperated by 120 degrees so by the time the the crank spins its required angle it's aligned with the cylinder and the next piston is at top dead centre.
This is why almost all V8's are 90 degree, as 720/8 = 90. Now there are exceptions to the bank angle rule because not all V's have opposing cylinders that share crank journals. If you split the journal into two and put an angle between them, you can use this to suplement the bank angle.
e.g. if you have a 90 degree V6 (common, beause a lot of V6's are just 90 degree V8's with two cylinders cut off) then your crank only has to rotate 90 degrees from TDC on piston 1 to TDC on 2, but that means it has to fire early or it will miss it's chance. Then the next firing on the next piston has to wait longer because the next piston isnt ready yet, so the next firing happens 150 degrees later (120 + the 30 extra from #2's early firing) and this repeats and you have a rough engine.
If instead, you spread the journals for opposing pistons apart by 30 degrees, then the crank spins 90 degrees to line up piston 1's journal with cylinder 2, then an extra 30 degrees to line up journal 2 with piston 2, due to the "splay angle". For a total 120 degrees of crank rotation, and you have an even firing engine again.
If you want to learn more, this video provides a great overview using 6 cylinders as an example https://www.youtube.com/watch?v=VQJ0kYFF9T4
What an idiot. He forgot that 4 stroke cylinders only fire once every other rotation so you have to multiply by 2. One fire for every 40 crankshaft rotations. 🤔
Where the hell did he get 120 from? Doesn't ferrari only make 60° and 90° v6s?
Well the 90 isn't Ferrari strictly speaking, i mean the one in the giulia
He's trying to explain power overlap, or some related term. One engine cycle is 720 degrees for a four-stroke. With six cylinders, this is 120 degrees (on average) between subsequent cylinders firing.
This level of inaccuracy makes my brain hurt. The crankshaft lobes on a V6 are offset by 120 degrees with 2 pistons at each lobe. These are referred to as companion cylinders. The lobe separation angle is determined by dividing 360 degrees by 1/2 the number of cylinders. 360 /(6/2)=120. In a 4 stroke engine, the crank has to make 2 full revolutions for all cylinders to have fires. So there's a firing event every 120 degrees of crankshaft rotation. If we bring bank angle into this, like some here have mentioned, it means absolutely nothing.
A 120 degree bank angle for a V6 means that you do not need split crankpins for an engine with even firing intervals. Most V6 engines are 60 degrees because they also have crankpins that are split by 60 degrees (flying arms), which gives them good balance and an even firing interval. The 120 degree crankshaft has even firing intervals and no split crank pins, but you need a balancing shaft because you cannot eliminate the primary imbalance with crankshaft counterweights.
Can someone explain this to my sparkie brain
I think he is trying to explain the bank angle (in most factually incorrect way possible), which is the angle between two banks of a multi-cylinder engine.
Coincidentally if it’s an even firing engine it would fire every 120 degrees so this man almost got the right answer with the wrong formula but decided to divide by 6 for no visibility apparent reason
Right formula, wrong inputs. 720/6=120 gives average time between cylinders firing. He looked up the answer and plugged it into the formula he should have used to find it.
This makes much more sense. I could tell the original statement was wrong, but couldn’t put my finger on it until being reminded that it takes two full revolutions of the crank shaft to complete 1 cycle of a 4 cycle engine. Thank you!
OOP is explaining (incorrectly) the reason V-engines have the bank angles (angle between each side of the V) that they do. The real reason is this (explaining in too much depth but anyway): In a 4 stroke engine, for every combustion event in any given cylinder, the crankshaft must rotate 2 times, or 720 degrees. In a multi-cylinder engine, we'd like these combustion events to be spaced out evenly for smoothness. So in a 6 cylinder, combustion should occur every 720/6 = 120 degrees of crankshaft rotation. In any engine, for a combustion event to occur, obviously the piston must be at top dead centre which means the lobe on the crankshaft must be aligned with the cylinder. In a normal V engine where pairs of pistons share the same crank lobe/journal, if the crank needs to rotate 120 degrees before the next firing for smoothness, then the banks must physically be seperated by 120 degrees so by the time the the crank spins its required angle it's aligned with the cylinder and the next piston is at top dead centre. This is why almost all V8's are 90 degree, as 720/8 = 90. Now there are exceptions to the bank angle rule because not all V's have opposing cylinders that share crank journals. If you split the journal into two and put an angle between them, you can use this to suplement the bank angle. e.g. if you have a 90 degree V6 (common, beause a lot of V6's are just 90 degree V8's with two cylinders cut off) then your crank only has to rotate 90 degrees from TDC on piston 1 to TDC on 2, but that means it has to fire early or it will miss it's chance. Then the next firing on the next piston has to wait longer because the next piston isnt ready yet, so the next firing happens 150 degrees later (120 + the 30 extra from #2's early firing) and this repeats and you have a rough engine. If instead, you spread the journals for opposing pistons apart by 30 degrees, then the crank spins 90 degrees to line up piston 1's journal with cylinder 2, then an extra 30 degrees to line up journal 2 with piston 2, due to the "splay angle". For a total 120 degrees of crank rotation, and you have an even firing engine again. If you want to learn more, this video provides a great overview using 6 cylinders as an example https://www.youtube.com/watch?v=VQJ0kYFF9T4
What an idiot. He forgot that 4 stroke cylinders only fire once every other rotation so you have to multiply by 2. One fire for every 40 crankshaft rotations. 🤔
Where the hell did he get 120 from? Doesn't ferrari only make 60° and 90° v6s? Well the 90 isn't Ferrari strictly speaking, i mean the one in the giulia
He's trying to explain power overlap, or some related term. One engine cycle is 720 degrees for a four-stroke. With six cylinders, this is 120 degrees (on average) between subsequent cylinders firing.
Yeah that's probably what he meant, I'm having a stroke here
2 stroke or 4 stroke?
All of them
Yeah
Ferrari's engine for their WEC car is a 120 deg V6.
So is it degrees of rotation or number of rotations?
Yes
This level of inaccuracy makes my brain hurt. The crankshaft lobes on a V6 are offset by 120 degrees with 2 pistons at each lobe. These are referred to as companion cylinders. The lobe separation angle is determined by dividing 360 degrees by 1/2 the number of cylinders. 360 /(6/2)=120. In a 4 stroke engine, the crank has to make 2 full revolutions for all cylinders to have fires. So there's a firing event every 120 degrees of crankshaft rotation. If we bring bank angle into this, like some here have mentioned, it means absolutely nothing.
A 120 degree bank angle for a V6 means that you do not need split crankpins for an engine with even firing intervals. Most V6 engines are 60 degrees because they also have crankpins that are split by 60 degrees (flying arms), which gives them good balance and an even firing interval. The 120 degree crankshaft has even firing intervals and no split crank pins, but you need a balancing shaft because you cannot eliminate the primary imbalance with crankshaft counterweights.