Quote:
Originally Posted by afterburn 549
Ford has made this the new big deal as of late.
I think Ferrari has used these now or in the past?
I will admit my ignorance with this program.
Its not that I have not read all I could, and tried to assimilate as much of it as posable.
It is all pretty foggy to me.
I know they were not possible at one point as I understand it?
Yet, now they are.
Its harmonics, balance, firing order etc.
It would be great to attempt to bat this back and fourth few rounds.
I would like to steal some insights.
|
All 90° V8 Ferrari use a single plane(180°) crank. As do the Porsche V8s used in the Spider RS.
what the flat crank does in a 90° V motor is change it from odd fire to even fire.
Odd fire V8 has a very distinctive exhaust because they always have 2 cylinders firing consecutively on each bank and they have irregular firing intervals
for an older(Pre LSx) series setup like this
L 1-3-5-7
R 8-4-6-2
w/ this firing order 1,8,4,3,6,5,7,2
Left__collector: B1-S0-S0-B3-S0-B5-B7-S0-B1-S0
Right_collector: S0-B8-B4-S0-B6-S0-S0-B2-S0-B8
or
L-R-R-L-R-L-L-R
on the left side 5 & 7 fire consecutively and on the right side 8 & 4 do the same. Ford uses a similar setup on both old and new small blocks, the firing intervals on the left side are 180°-90°-180°-180° and 180°-270°-180° on the right
the LS series has the same setup as far as cyl #s but the firing order is 1-8-7-2-6-5-4-3
S0-B8-SO-B2-B6-S0-B4-S0
R 2-4-6-8
L 1-3-5-7
B1-SO-B7-S0-S0-B5-S0-B3
This firing order reduces crank torsion
or L-R-L-R-R-L-R-L w/ firing intervals of 180°-90°-180° on the left and 180°-270°-180° on the right w/ only one set of consecutively firing cylinders on the right side
The Shelby 5.2 Voodoo V8 w/ flat crank
L-R-L-R-L-R-L-R
In a 90° V a 180° crank leads to vibration issues and displacement restrictions as a result
Porsche H6 is also an even fire design but w/o the 90° V restrictions because the intervals are also evenly spaced
B1-S0-B2-S0-B3-S0
L 1-2-3
R 4-5-6
S0-B6-S0-B4-S0-B5
or
L-R-L-R-L-R w/ 240° intervals between pulses on each side
flat plane crank is also also used in most I4s
Interestingly enough the firing order issue of a 90 V8 w/ 90 crank can be overcome simple by redesigning the exhaust, one cyl. from each bank has to cross over to the opposite side collector, if the right cylinders are chosen the exhaust at least is now even fire. however this does nothing for the irregular firing intervals inherent in these engines