Re: how many rotations of crankshaft does it take to fire all cylinders of v8 engine

That seems wrong; assuming a 4-stroke, any given cylinder, assuming that it fires at zero degrees, will fire again 720 degrees later. lessee...

1 - 0 degrees 8 - 90 4 - 180 3 - 270 6 - 360 5 - 450 7 - 540 2 - 630 1 - 720

yup, that's more like it (for everything but F*rds, anyway... don't ask me what a F*rd firing order is, they number things weird)

So the short answer is, for pretty much any 4-stroke, "two revolutions" but to be strictly accurate, all cylinders actually fire within

720-(720/(number of cylinders)) degrees. For a 2-stroke, it'd be "one revolution" or, again, more strictly accurately, 360-(360/(number of cylinders)) degrees.

nate

You know It seemed wrong while I was posting it but....

Bit of a bummed mood anyway. This past month has been a real BIT%^... Lost my 9 year old puppy to kidney failure and internal bleeding, wifes Blazer ate it's cat, then the radiator split a tank. Got it all together and then one of my friends over in the sandbox was hit and killed.

Then just to make it interesting I get the flu, and this is after I got both flu shots!!!!

I will be real happy when December gets here....

God speed Steve , you will be in tonights prayers.

"Steve W." wrote in news:hev82b$ecm$ snipped-for-privacy@aioe.org:

Ouch. It never rains as they say . Here's to a very happy Christmas for you and yours.

Because it is ;-)

Assuming even firing and 4-stroke, you're right, its every 90 degrees. IF its a Detroit 8V71 two-stroke, then its one every 45 degrees, which is why Detroit Diesel 8v71s sound like they're turning 5000 RPM when they're really only turning 2500

Steve, please, no! let us not delve into even versus odd-firing!!! :) That is a whole-'nother topic.... :)

(exercise -- an even-fir> Nate Nagel wrote:

Ooh! Ooh! (raises hand) split crank pins!

nate

An even firing v6 should be a 120 degree engine

Didn't Felix Wankel invent the Wankel engine? I think NSU (Germany) was the first to sell Wankel engine cars.There was at least one German motorcycle with a Wankel engine.There have been advancements in Wankel engine technology over the years.Do any auto companies build and sell Wankel engine vehicles nowadays? Wankel engine model airplane engines are available nowadays, I think so. cuhulin

yes, the Mazda MX-8 still has a rotary engine. Not sure if there are any others or not. Which is a shame because the RX-7 was so pretty and the RX-8 has so much more power and looks like a SUV mated with a Transformer.

nate

Of course I meant RX-8. Don't know what I was thinking, or not.

nate

Swashplate Engines

There are many different kinds of engines.Some of them I have read about many years ago. cuhulin

Awww but its so FUN!! :-)

Splayed journals on each throw of the crankshaft. The problem is that if you splay the journals far enough to make it *truly* even firing, then the crank is significantly weakened by the lack of metal overlapping between the two adjacent journals. So most 90-degree v6 engines are a compromise- they splay the cranks enough to bring it CLOSER to even firing, but not so far as to make the splayed journals fail to overlap and thus weaken the crank. I'd have to go look it up to be sure, but I think the Chrysler 90-degree engines (the old 3.9 and the current 3.7) have something like 128 and 112 degree intervals instead of perfectly even 120-degree intervals. Thats decidedly better than the 90° and 150° intervals of a non-splayed crank 90-degree v6 like the first Buick v6.

As you add more cylinders, odd-firing becomes less of a problem. The Dodge Viper V10 doesn't even have splayed journals, its just got so many cylinders that is very smooth feeling even with the inherent odd-firing of a 10-cylinder 90-degree V engine. Gives it a really gnarly exhaust note, though.

True or false: Even- or odd-firingness has nothing to do with engine balance.