It was sorta kinda explained to me in a round about, watered down half assed way.

As i recall, I3's were good, V8's were good, V6 bad. whats different about it? if i recall it was something about the harmonics.

just trying to recall this explanation as I just heard someone saying "V6 is just a terrible configuration for a powerhouse motor"

 

um.....gn's and 300zxtt's dont have any probs making big power with a v6........whats wrong with them?

 

As I understand it, One thing that makes a v-6 less of a performance engine is the balance of the engine... As a v-8s pistons are cycled, there is a balancing effect by the other pistons, creating a smoother acceleration. A v-6 has less pistons therefore the balancing effect is greatly lessened.
For the same reason, a v-12 is an amazingly smooth engine (for the most part)



It also depends somewhat on the V-6. The 60 degree v-6's and 90 degree v-6's are two completely different motors..... The 60degree offset is very hard to balance out.

 

v-12's can be very smooth engines if you treat each bank of six as separate. Inline sixes can be naturally-balanced (the harmonics of one moving assembly - pistons and rods- balances against the harmonics produced by another moving assembly), and a smooth v-12 is just two smooth sixes.

Since hemholtz resonators work best on 3 an 4 cylinder engines, treating the intake and exhaust as 4 separate banks of 3, can get you some very high specific output (check the hp/L numbers on Lambo's).

 

What's bad is your starting out 2 cylinders short of a V-8 that's what's bad about V-6's! If you only want to race other V-6s you're fine but otherwise you've given away two intake and exhaust ports so at even the same inches you cannot make as much power. Now a V-12 is another story!

 

Previously mentioned but worth saying again.......GN.

 

Yes sir, the buick V6 has already broken the 1500rwhp barrier. Pretty stout if you ask me. I'm over 400rwhp at 25 psi and the valve covers have never come off (even the factory springs are still in there). As far as vibration and balance, it's a heck of a lot smoother from idle to redline than my LT1 and any other V8 I've driven. Even moreso than the Triton 5.4 in my dad's F-150.... and those modulars are about as smooth as you can get. I guess the firing order and such play that big of a role in any engine configuration when it comes to harmonics. If designed properly each one will be equally smooth.

Where's the 'Old one' at? He'll be able to shed more light on this.

 

V6 vs. V8. It depends on where you or the OEM want to go and how deep the money hole is. If you have a 5.7 liter V8 with decades of development time and tooling amortized to zilch, and you want a 3/4 sized powerplant at minimum expense, lop of two cylinders. Viola! The 4.3 liter 90 degree GM V6. The same scenerio worked for Buick. It also worked for DC with the Viper V-10, which is a 90 degree, not 72 degree V-angle.

Why the 90 degree V angle? Cylinder block transfer line machining. Building a new line costs hundreds of millions. It's a lot cheaper to use the 90 degree (V8) tooling, along with many of the same parts and fix the problems. Sometimes both engines can be run down the same machining lline.

An extreme example is the 4 cylinder Pontiac Tempest slant 4 engine of 1961-1963. It was literally a 389 V8 with the left bank of cylinders removed. Virtually all the inner bits were the same, except for crank and cam. It ran down the same lines, produced about 1/2 the hp of the equivalent 389, and, at 3.2 liters, shook horizontally something fierce. The thing that made it work was the torque tube and transaxle: the engine had front mounts in the normal side-of-block location, and rear mounts at the rear axle, about 9 feet aft. The front mounts were very soft side-to-side, so the engine could move a inch or so without problems. The next torque tube/transaxle combination in GM was the C5 Vette. I had a new one of each, and the C5 is much nicer!

One more "war story". Pontiac spent about $600,000 total to develop and tool the slant 4. (1960 dollars). Buick and Olds at the same time designed, developed and tooled the all aluminum 215 cube V8 to the tune of about $65 million. Both engines ran about 3 years and maybe 300,000 of each. If you amortize the tooling over the number of engines, it's about $2/engine vs. $200/engine. To be fair, GM sold the 215 tooling to Rover/Leyland/BMC to recoup a fraction of the original cost. The engine still powers the Rover SUV, and has been used in many Brit cars. They have stretched it from 3.5 to 4.5 or 4.6 liters. IMO, that was one of the automobile world's "best buys"!

The big problem here is vibration. For even firing, divide 720 degrees by the number of cylinders. That's 120 degrees for a 6. You can use multiples like 0, 60, or 180 (inline, V, and boxer layout) and not have problems. If you use a 90 degree V6, you either have an odd-firing engine, or with split crank pins, an even firing engine with some funny vibration modes. Add a balance shaft, and its hardware and most of them are gone.

If you have a clean sheet of paper...oops, a "clean screen", and you need a nice 3-4 liter, short (for FWD or small cars) V6, do a 60 degree engine. The GM 2.8/3.4 L is a good(?) example. It's wasn't a bad design, with canted valves, etc, but it's small bore spacing limited it's maximum displacement to around the 3.4-3.5 liter range. Too bad.

As far as power goes, hp/l and torque/l really don't depend on number of cylinders. At the high end, tons of development has been done on 2-valve 700 cc cylinders (350 V8), 1000 cc cylinders (ProStock V8) and 300 cc cylinders (F1). Busch V6's around 5 L made great power/L , and with somewhat lower inertia innerds, and llighter engine weight, actually were competitive with V8s on short tracks and road courses. IMO, cost, and fan appeal drove the move to V8s. The V8 sound is great!

If you want to compete with 350-400 inch V8s in 3000+ lb. cars, you could do it with a V6, but it would necesarily either be very exotic (Ferrari-like), or Buick GN (turbo). Even GM when they wanted to go after BMW's M-customers with the CTS-V chose the LS6. Sure money was important, but who wants a blown V6 400 hp Caddy when they could have a V8?

My $.02.

 

The current Rover SUV is powered by a BMW 4.4L V8, which is not derived from anything GM came up with.

Unless there are multiple Rover SUVs and we're talking about different ones!

 

About time they got something interesting! The 4.4 appears to be about 60 hp stronger than the old 4.6 pushrod "Buford" which lasted until 2002, I think. I guess 40+ years finally wore out all the tooling.

Thanks for the update.

 

i am suddenly reminded of your last email