Flat plane crank
Discussion
Hi all,
I know it's only the AJPs that have flat plane cranks, but I'm just curious about why they're supposedly better for racing.
Also, do they have some wierd firing order, like on Ducattis where there are two firings, then a long pause, then two firings (apparently to improve the impulse recovery in the tyres). Do 4 cyls fire at once, followed by the other 4 or some such?
I know these beasts have a different exhaust note to the Rover unit, and I wondered what was actually going on in them.
Cheers
Jon
I know it's only the AJPs that have flat plane cranks, but I'm just curious about why they're supposedly better for racing.
Also, do they have some wierd firing order, like on Ducattis where there are two firings, then a long pause, then two firings (apparently to improve the impulse recovery in the tyres). Do 4 cyls fire at once, followed by the other 4 or some such?
I know these beasts have a different exhaust note to the Rover unit, and I wondered what was actually going on in them.
Cheers
Jon
Ah, so the idea is to combine 2 exhaust pulses so that while they are travelling down the exhaust system they effectively siphon more mixture into a cylinder that is just starting it's intake phase with the exhaust valve still open (overlap)?
So I guess the slightly different sounds inthe exhaust nbote are caused by two cylinders firing at once with a *tiny* difference in times.
So I guess the slightly different sounds inthe exhaust nbote are caused by two cylinders firing at once with a *tiny* difference in times.
Big bang stuff is only really relevant for motorcycles with their tiny contact patch, i.e. the new Ducati V4 that fires just like a V2. More cylinders means more valve area which means more power.
The Ferrari V8 is also a flat plane crank, so it's not exactly that you can't make them sound nice... but the Cerbie one is even weirder because of the 75 degree angle - irregular periods between firings. I think it's lovely
danny
The Ferrari V8 is also a flat plane crank, so it's not exactly that you can't make them sound nice... but the Cerbie one is even weirder because of the 75 degree angle - irregular periods between firings. I think it's lovely
danny
Two cylinders dont fire at the same time. A typical firing order would be 15486372, numbering up the side of the block.
The single plane crankshaft provides 180 degree exhaust pulse intervals between adjacent cylinders and with simple manifold modifications this can be extended to 360 degrees before pulse interference can occur.
The 2 plane crankshaft (like that of a Ford or Chevrolet V8) has a dynamic state of balance far superior to that of the single plane crank, and for this reason is more popular.
The single plane crankshaft provides 180 degree exhaust pulse intervals between adjacent cylinders and with simple manifold modifications this can be extended to 360 degrees before pulse interference can occur.
The 2 plane crankshaft (like that of a Ford or Chevrolet V8) has a dynamic state of balance far superior to that of the single plane crank, and for this reason is more popular.
Interesting site. Reinforces my previous statement.
As for all V8's being 90 degrees, well there are 2 that I know of in common use. The Ford Windsor 302 and 351 cubic in V8's are 60 degree engines, not 90.
They are a very compact unit and seem to perform as equally as well as their 90 d counterparts.
Ford also make the same engine as a 90 degree unit. They are the 302 and 351 Cleavland.
As for all V8's being 90 degrees, well there are 2 that I know of in common use. The Ford Windsor 302 and 351 cubic in V8's are 60 degree engines, not 90.
They are a very compact unit and seem to perform as equally as well as their 90 d counterparts.
Ford also make the same engine as a 90 degree unit. They are the 302 and 351 Cleavland.
I'd imagine (and this is purely speculation!) that a rotary (not Wankel) configuration simply has crank pins spread at equal distances around the crank. The advantage of course is perfect balance should be acheivable as the pistons all travel in different directions, and you should be able to get equal and opposite forces cancelling each other - like a boxer engine only more so.
quote:
Since you've cracked the flat-plane crank problem, can anyone explain how a rotary engine (aeroplane, not Wankel) works? I can't see how the con-rods don't go straight through the crankshaft!
I think you're referring to a Radial engine, where the cylinders are arranged in a circle. The conventional 'in-line' design of each con rod having a separate big end bearing onto its own crank on the crankshaft wouldn't work, because all the cranks would have to be in the same place. Having all the con rods connecting on a common crank wouldn't work either, because they would get knotted up!
How this actually works is, there is one 'master' piston with a normal con rod and big-end bearing onto a crank. All the other pistons have modified con rods that connect onto the end of the master con rod. Hence the big ends move round in a circle but don't rotate (if you see what I mean).
OK cr*p explanation and you probably need a picture, but I don't have one. Sorry!
Cheers,
Peter Humphries (and a green V8S)
quote:
quote:
Since you've cracked the flat-plane crank problem, can anyone explain how a rotary engine (aeroplane, not Wankel) works? I can't see how the con-rods don't go straight through the crankshaft!
I think you're referring to a Radial engine, where the cylinders are arranged in a circle. The conventional 'in-line' design of each con rod having a separate big end bearing onto its own crank on the crankshaft wouldn't work, because all the cranks would have to be in the same place. Having all the con rods connecting on a common crank wouldn't work either, because they would get knotted up!
How this actually works is, there is one 'master' piston with a normal con rod and big-end bearing onto a crank. All the other pistons have modified con rods that connect onto the end of the master con rod. Hence the big ends move round in a circle but don't rotate (if you see what I mean).
OK cr*p explanation and you probably need a picture, but I don't have one. Sorry!
Cheers,
Peter Humphries (and a green V8S)
They had one at duxford that looked like it was being set up for a display. No cylinders on it for show etc. very compact.
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