Why not use crankshaft weights on any vee engine?

Because consumers don't want a car that shakes like a Harley!

Actually, there are some very SUCCESSFUL odd-firing engines out there. The Viper V10, for example, has a slight odd-fire because its a v10 built on a 90-degree bank angle. There are degrees of odd-firingness, for lack of a better word. The v10 doesn't have a very large difference in crankshaft rotation between the "close" cylinder pairs and the "far" pairs. You can't even really feel it, although you can hear the dual tones in the exhaust note. An odd-firing 90-degree v6 with a 3-throw crank, on the other hand, has a very large and noticeable difference between the close and far pairs, so that the engine seems very rough. The manufacturers splay the crankpins and reduce the difference to something manageable. They're still slightly odd-firing, but not so extreme as a true 3-throw crankshaft would be.

Take a look at the early 231 Buick for an odd fire V6. Even the later ones with split journals are not real smooth.

Exactly...

Smooth enough to be GM's most successful v6, if not one of the better and probably the most successful v6 engines of all time.

No v6 is ever going to be a smooth as an inline six or v8, but since the length of an inline six is incompatible with most modern small car designs and a v8 is too inefficient when made that small, it comes down to a choice of v6 or inline 4. Given that, the v6 handily wins the smoothness contest.

Steve wrote in news:jJKdnWp7PLqHkqXUnZ2dnUVZ snipped-for-privacy@texas.net:

firingness,

the early alumun buick v6 was a 60 degree v and just as smooth as any v8, only the 90 degree v is odd fire. KB

So are many current car v6 engines, but not all the vibration comes from odd-firing.

Not true. All v6s have a slight higher-order vibration that inline sixes and 90-degree crank v8s don't have. But it is less noticeable than the

2nd-order "bounce" that inline 4s have without balance shafts. You have to almost go feeling for it to notice it but it is there.

Ibeg to differ. When GM split the journals 43degrees (IIRC) they became way smoother, and when they finally got EFI they got silky smooth.

I wonder what a 2.5L V8 would sound like. Would it still sound like a V8?

Ray

I reckon it would :)

Neat. I'm assuming that's like a 1/4 scale or 1/8 scale RC dragster motor? Now, if only Pontiac made a G5 with rwd and a 3L V8....

a 2.5 V-8........ methinks a Daimler-SP250 has one that size. It uses the old 60's aluminum Buick V8 that GM sold them. Sounds pretty good too. The sound produced by any engine is directly related to some ratio having to do with the connecting rod length and the engine stroke.

.....gotta take that back about the GM engine, but a few British models did use it... the Daimler had it's own design ..

Well.... that, and cam timing, lobe-center separation, ramp rate, intake/exhuast event timing, ignition timing, firing order, exhaust valve configuration, intake plenum volume, intake/exhaust port size/shape, exhaust manifolding, downstream exhaust plumbing.....

In the grand scheme of things, rod-ratio really is a fairly minor contributor to engine sound.

What truly amazes me is that with all these variables, all 90-degree crank v8s still manage to have an identifiable sound that says "I'm a

90-degree crank v8."

I'm not much of a Brit-car guru, but I was thinking that the Daimler v8 was a hemi-head engine with throguh-the-valvecover plug tubes similar to a Chrysler hemi, unlike the Buick/Rover v8 that showed up in various Triumphs and Range Rovers over the years.

And I know I'm not alone when I say "and it's a glorious sound."

Seriously, I'm all for high tech... but what is it about the sound of a V8 that just sounds so pleasing?

:)

Hello, Take another look at the crank in the link below.

Notice the 2 crank throws outside of the outboard main journals? Those hammerhead looking lumps are balance weight.

*Every* crank on *every* modern engine has some form of counter balance, even if its just Mallory metal pressed into the rod journal. Your best bet for complete understanding of balance dynamics is to find your local machine shopor spped shop that does balancing, take the guy a 6pack and ask him to let you look over his shoulder while he's doing one and have him 'splain it to you. I did that with the guy who does the cranks on all my race cars (I do all the pistons and rods before-hand to save a few bucks). I would also suggest posing this question on the forums at eng- tips.com There is a wealth of info there. HTH, Ben

*unless* it has an even-firing exhaust (e.g. Ford GT-40)

nate

Taurus 3.0's and later SHO's have balance shafts....

*unless* it has an even-firing exhaust (e.g. Ford GT-40)

Any chance you know of a website with a pic of a GT40 crank? I'd like to see it. Thanks, Ben