V6 Engine Question

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Please un-confuse me. \:\( If you have a 90 deg V6, you either have to have offset crank pins or balance shaft/shafts. If you have a 60 deg V6, you don't need either and can use common crank pins. Or, is it the other way around?
 
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The Buick V6 started life with a common crank pin odd fire design and later on in '78 I believe went even fire with the split crank pin design. Both were 90 degree V6s and neither had a balance shaft. Not sure if the Series II got a balance shaft or not. I'm pretty sure the angle of the V does not make a difference whether it needs a balance shaft or not. I would assume and I may be wrong that the even fire V6 would be less likely to need a balance shaft but no V6 is balanced like an inline 6 is. I doubt this answers your question...
 
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I dunno, been some years since i pored over automotive books, but I'll give it a shot. Since 60 degrees goes into 360 six times and it's a six cylinder engine, seems that would work without offset (think it's called "splayed") connecting rod journals, but 60 is a pretty tight V. That may be why they go 90 degrees and then I would guess you need offsets if you wanted even spaced power pulses. Maybe 120 degrees would be better for a V6?
 
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The 90° doesn't "have" to use offset rod journals on the crank, (ala early Buick/AMC V-6) but if it does not it has extra vibration to quell, an "odd-fire" V-6 becuase its three power pulses per revoultion of the crank are not the ideal 120° apart. The Buick V-6 was made even-fire in the 70's by the split-pin crankshaft also used on the other 90° V-6's that have followed. The balance shaft was added to the '3800' V-6 to quell secondary vibrations for even more NVH reduction. Ditto the '93+ GM 4.3L, Chrysler 3.7, etc. The Chrysler and Ford V-10s were also designed in a similar manner. IIRC a 72° engine was the ideal for even-fire but yet again the simplicity of a 90° V-8 based design with a split pin crank won over.
 
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The V-angle most definitely makes a difference in engine design. The 90-degree V-angle design is a result of the desire to produce a V6 from an existing V8 design. No one in their right mind would choose the 90-degree configuration for a "clean sheet of paper" design. The split-pin configuration does help with the common-pin's unbalanced secondary rocking couple, trading one form of imbalance for another. However, you can never eliminate the balance issues of a 90-degree configuration with any kind of crankshaft change. The problem is inherent in the 90-degree design. The use of a balance-shaft would be beneficial to any 90-degree V6. From an engineering standpoint, the 60-degree V-angle V6 with a six crank-pin crankshaft is a far more appealing design. With the crank-pins at 60-degree intervals you get equal 120-degree firing intervals, just like the in-line six. You even achieve both primary and secondary balance with this configuration. Both Ferrari and Ford have used this design. A 120-degree V-angle V6, in combination with a 120-degree common-pin crankshaft, provides the same even-fire configuration. The primary difference being that this results in an engine which is shorter in height, but gains in overall width. This design has also been used by Ferrari in the past.
 
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It's horses for courses. Look at a straight 6...perfect primary and no rocking couple...cut it in half and make a 3 cyl, and you get the primary, but get a rocking couple. If you make a v-6 as two 3 cylinders, as rshunter has pointed out, you can make it work sans balance shaft. A 90 degree can be balanced as three 90 degree V-twins, but still sounds and feels rough as guts from a power delivery aspect. http://www.youtube.com/watch?v=YMDPU6XBkL8 I think (from over cubicle banter), that Yamaha have been playing with purposeful modification of crank pins to upset even power delivery lately on their GP bikes.
 
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 Originally Posted By: Shannow
I think (from over cubicle banter), that Yamaha have been playing with purposeful modification of crank pins to upset even power delivery lately on their GP bikes.
The current Yamaha R1 sportbike is using an unconventional crank-pin arrangement. Despite being described as such, it's not really a "big bang" configuration, as has been used in MotoGP racing. The design is intended to allow the rear tire more recovery time during each rotation, to aid in achieving grip. It seems to be working quite well in the FIM Superbike World Championship, in the hands of our very own Ben "Elbowz" Spies. I smell a rookie World Champ in the tire smoke!!!
 
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Wow, learned something new. I never thought there would be a signifigant difference in balance between a 60 degree and 90 degree V6. There are some guys that prefer the old odd fire design when making over 1,500hp with the Buick engines. Not sure if it's the power delivery or the fact that the common pin crank "looks" stronger.
 
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 Originally Posted By: BuickGN
Wow, learned something new. I never thought there would be a signifigant difference in balance between a 60 degree and 90 degree V6. There are some guys that prefer the old odd fire design when making over 1,500hp with the Buick engines. Not sure if it's the power delivery or the fact that the common pin crank "looks" stronger.
There are Jeep guys who prefer the old Dauntless v6 (which happens to be what AMC called the odd-fire Buick v6 when they owned and produced it before selling it back to GM) for similar reasons. GM had a way of selling off good Buick engines to other companies- the v6 to AMC and the aluminum V8 to Rover. They bought the v6 back and are still running with it, but they never did pry the v8 away from Rover.
 
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 Originally Posted By: rshunter
From an engineering standpoint, the 60-degree V-angle V6 with a six crank-pin crankshaft is a far more appealing design. With the crank-pins at 60-degree intervals you get equal 120-degree firing intervals, just like the in-line six. You even achieve both primary and secondary balance with this configuration. Both Ferrari and Ford have used this design.
I was going to bring this up also- most 60-degree v6 engines out there don't actually use common crank pins (3-throw cranks), even though they could do so. I don't know much about the GM 60-degree v6 engines, but I'm pretty sure all the Chrysler v6 families (pushrod 3.3/3.8, SOHC 3.2/3.5/4.0, DOHC 2.7) are built this way. In fact, I suspect that the list of 3-throw-crank 60-degree v6 engines on the road is a lot shorter than the list of 6-throw-crank 60-degree v6s.
 
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 Originally Posted By: 440Magnum
 Originally Posted By: rshunter
From an engineering standpoint, the 60-degree V-angle V6 with a six crank-pin crankshaft is a far more appealing design. With the crank-pins at 60-degree intervals you get equal 120-degree firing intervals, just like the in-line six. You even achieve both primary and secondary balance with this configuration. Both Ferrari and Ford have used this design.
I was going to bring this up also- most 60-degree v6 engines out there don't actually use common crank pins (3-throw cranks), even though they could do so. I don't know much about the GM 60-degree v6 engines, but I'm pretty sure all the Chrysler v6 families (pushrod 3.3/3.8, SOHC 3.2/3.5/4.0, DOHC 2.7) are built this way. In fact, I suspect that the list of 3-throw-crank 60-degree v6 engines on the road is a lot shorter than the list of 6-throw-crank 60-degree v6s.
I certainly wouldn't take a bet against your suspicion. I'd chart global production at... 90* V6 > 60* 6-pin V6 > 60* 3-pin V6 As in most things, the easy and cheap option often trumps the best one. I do find it interesting that Ford has been doing it the correct way for a very long time...
 

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Wow. Yes, very interesting. I have a 2008 GM 4.3 V6. My son in law made the comment of how much smoother it was than the V6 in hes big Chrysler Van. He said it much have offset(splayed) crank pins and balance shafts. GM makes a big deal of advertising the balance shaft and I must say it is extremely smooth. I had a Buick with a V6 engine, in 1965. It was a Special convertible with a very stout V6 but a lousy transmission. The man that owns one of the area mom and pop gas, tires, oil, and AC places has a old Chevy Nova body with a 3.8 V6. I think the block is the only stock part as it has aluminum heads with full needle bearing rockers, needle bearing roller cam followers, aftermarket crankshaft, huge headers, and a Holly 3(three) barrel carb. He said it was around 260 HP and was very comfortable with 6000 RPM. He said he choose that block because it did not need balance shafts. I am very sure he also said some version of the Buick 3.8 was used in some class of race cars. I think he said Indy, but, that is hard to believe.
 
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 Originally Posted By: FrankN4
I am very sure he also said some version of the Buick 3.8 was used in some class of race cars. I think he said Indy, but, that is hard to believe.
He's correct, a turbocharged methanol-fueled version of the Buick 90* V6 was run at Indianapolis in the mid-80's under their stock-block regulations. In '85 it took pole-position as well as the number two starting spot. That was an achievement that hadn't been made by a production-based engine since Duesenberg did it way back in 1931, IIRC. Durability over 500 miles was their Achilles heel, though.
 
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 Originally Posted By: rshunter
 Originally Posted By: 440Magnum
I was going to bring this up also- most 60-degree v6 engines out there don't actually use common crank pins (3-throw cranks), even though they could do so. I don't know much about the GM 60-degree v6 engines, but I'm pretty sure all the Chrysler v6 families (pushrod 3.3/3.8, SOHC 3.2/3.5/4.0, DOHC 2.7) are built this way. In fact, I suspect that the list of 3-throw-crank 60-degree v6 engines on the road is a lot shorter than the list of 6-throw-crank 60-degree v6s.
I certainly wouldn't take a bet against your suspicion. I'd chart global production at... 90* V6 > 60* 6-pin V6 > 60* 3-pin V6 As in most things, the easy and cheap option often trumps the best one. I do find it interesting that Ford has been doing it the correct way for a very long time...
If you count number of units sold, you're probably right just because of the huge numbers of Chevy 4.3 and Buick 3.8 90-degree engines out there. But if you talk about the number of individual engine designs out there, 60-deg 6-pin might win. Ford had a 90-deg 3.8 that was based on the Windsor block, didn't they? I seem to remember it being the base engine in Mustangs for a long time. Also 90-deg v6 engines really don't make bad pickup truck/SUV engines where torque trumps smoothness and high-rpm capability. The Chevy 4.3 and Dodge 3.7 (4.7 v8 minus two cylinders) are 90-degree truck engines that do what they're asked very reliably and cheaply.
 
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Even the old Volvo V6 was a 90* design. They had been planning on producing a V8, but the oil crisis of the '70s doomed the idea. In order to salvage the work that had been put into the project Volvo decided to chop off two cylinders and use the V6 in their larger cars. Think about that, a V6 design ham-stringed by a V8 engine that never existed. Even funnier is the fact that Ford's 60* six-pin Cologne V6 was actually derived from their Taunus 60* V4. An engine which achieved what is probably its greatest fame disguised as a SAAB. Thus, they derived a V6 by grafting on two cylinders, rather than the more common practice of chopping two off...
 
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 Originally Posted By: rshunter
. Even funnier is the fact that Ford's 60* six-pin Cologne V6 was actually derived from their Taunus 60* V4. An engine which achieved what is probably its greatest fame disguised as a SAAB. Thus, they derived a V6 by grafting on two cylinders, rather than the more common practice of chopping two off...
I'll go you one further- How about the Ford/Yamaha Taurus SHO 60-degree V8 that was basically the previous SHO v6 with two cylinders added. Now *THAT* was bass-ackwards engineering! But it worked.
 
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VW got around the limitations by creating a 15 degree V6 (Called VR6) which had the same firing order as an inline 6. They also created a way to use 2 cams to separately control the intake valves and exhaust valves just like a DOHC inline 6. Later they made a 11.6 degree VR6 which had the same advantages as the earlier engine. That is why I love the VR6 so much. Almost all the smoothness of an inline 6 without a balance shaft, and without much challenge fitting it under the hood. I don't like V6 engines because of the balance issue. That is the one reason I do not like the new Nissan GT-R the same way I like the older ones.
 
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Some of the V6 blocks are V8 blocks with two cylinders cut off.The GM 4.3 engine block is a 350 engine block with 2 cylinders cut off.The 3.9 Chrysler engine block is a 318 engine block with two cylinders cut off.The Vortec 4.3s,3800s have a balance shaft in the lifter valley and are needed.
 
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 Originally Posted By: rshunter
 Originally Posted By: FrankN4
I am very sure he also said some version of the Buick 3.8 was used in some class of race cars. I think he said Indy, but, that is hard to believe.
He's correct, a turbocharged methanol-fueled version of the Buick 90* V6 was run at Indianapolis in the mid-80's under their stock-block regulations. In '85 it took pole-position as well as the number two starting spot. That was an achievement that hadn't been made by a production-based engine since Duesenberg did it way back in 1931, IIRC. Durability over 500 miles was their Achilles heel, though.
Got one of those blocks in the faster of the two GNs. Where mine is a ticking timebomb, my father's will run full throttle all day long with over 200 more hp than mine. Where Buick ran into trouble was trying to push the engine over 13,000rpm. Valvetrain reliability was a major problem. Here's a neat article on Buddy Ingersol in Pro Stock with the Buick V6. http://www.gnttype.org/misc/ingersoll.html
 
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