Flat (180deg) V8 crankshaft questions

Makes the engine have that lovely exhaust tone!!!!

 

Just to dovetail onto your observations:
I've always wondered if an exhaust H or X exhaust crosspipe on a flat crank V-8 makes as much of a positive difference as it does on a conventional V-8.

All of us that have lost ignition on one bank of a Ferrari V-8 can verify that it runs extremely smoothly on just one side's 4 cylinders...

 

True...and that is the reason for the flat crank: with a 90 degree crank, you have 2 firing cilinders after another at one side, then 2 at the other side. Not front-rear-front-rear bank etc, but front-front-rear-front-rear-rear-front-rear etc, this leaves less air-fuel mixture for the cilinder in one bank that fires right after the other cilinder in that bank. (hope you understand, it sounds even confusing in my own language)

 

Here's a couple of tutorials that help explain the ins and outs of various engine/crank designs:

http://autozine.kyul.net/technical_school/engine/smooth4.htm

http://www.e31.net/engines_e.html

 

From Ludvigsen - Ferrari, The Factory pp 98:

Crankshafts for the 308 Dino V8 were forged rather than machined from the solid. Fully counterweighted, they were of the "flat" or 180-degree pattern usually used in racing engines to create a lighter, stronger crankshaft with better exhaust tuning than was allowed by the 90-degree crankshafts customarily used in production engines.

So there were probably a couple of factors:

Forging vs. billet - forging probably a bit cheaper
Exhaust tuning
Lighter and stronger

 

This information is wrong. All Ferrari cranks that I've ever seen (72 forward) are machined from a forged billet. It has been Ferrari's "thumbprint" for a long time. _Inside Ferrari_ has pictures of the process. It starts with a forged cylinder billet that is machined into a crankshaft. The billet is forged, so therefore the end crankshaft is forged... just not die forged to shape. I've never personally handled a 246 crank, so I can't speak to those. AKAIK all 3x8, 355 and 360 cranks are (were) made with this process.

 

Depends upon what you call big: a flat-plane crank does have about 4X the vibrational energy of a cross-plane crank; but does 4X smooth == rough ? And the energy has different spectral signature. I find the off-cadence burble of the cross plane cranks at least as anoying to my ear as I find the vibrational pattern of the F355 engine to my butt.

 

This is USUALLY true. The reason is that the exhaust scavenges better allowing better cylinder fill. There are a lot of tricks used on 90 degree moters to try and make them as good like "H" or "X" pipes. The same is somewhat true for the intake manifold, they tend to flow better in a 180 degree engine, also increasing torque.

This is USUALLY true again. Since a flat crank engine flows and fills the cylinder better, it can make power at a higher rpm the a 90 degree engine.

 

So, an X or H pipe is not really neccesary on a flat crank engine as the exhaust pulses are already evenly timed on both sides, right?

 

I think that's right, it should not help.

 

This is not the only reason. The other reason a flat plane crank revs better is because it is lighter!, refer:

If you have to add balance weights to a crank it gets heavier and thus does not permit revving as well.

Pete

 

I would be very surprised if Ferrari still machine from a forged billet and do not move forward and forge their cranks correctly. A proper die forged crank will be stronger than a machined from billet crank I would have thought ... unless you have to add impurities to enabling the forging process (?).

Pete