[DML] Re: "Odd-firing" engine

["BRUCE BENSON" <delornut@xxxx>]

It's related to crankshaft rotation. In a vee type engine it's quite common to have two opposing piston rods share the same crankshaft journal. In the case of the DeLorean the vee configuration has the cylinder banks 90 degrees apart. This all works out to the two cylinders sharing the crankshaft journal rotating the crankshaft different degrees of rotation. When the first cylinder fires the crank rotates 120 degrees. The second turns the crank 60 degrees, the third 120, the fourth 60 and so on. When a V-6 is banked at 60 degrees it becomes an even firing engine. When a 90 degree vee becomes a V-8 it becomes an even firing engine. It's just the way the math works out. If youwent to the expense of casting a crankshaft with a separate journal for every cylinder then even the 90 degree V-6 could be made even firing. The most obvious detriment to odd firing is an inherent engine shake. The DeLorean doesn't shake but it's not particularly smooth at idle because of this. Some manufacturers have added a counter rotating balance shaft to overcome this.

 

Bruce Benson

 

The Delorean Shop Manual refers to the PRV engine as an "Odd-firing" engine. 
Can someone shed some light onto this term and what it means compared to an
"Even-firing" engine?

Thanks,
Steve
VIN 2650

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