Why no 60 degree v8's

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Thread: Why no 60 degree v8's

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    3.0 Liter SIDI V6 acascianelli's Avatar
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    Why no 60 degree v8's

    GM has had pretty good sucess with the 60 degree v6. its a very compact and reliable design. why are there not any 60 degree v8 motors?

    Volkswagen has taken there 15 degree v6 design and made a w8, w12, and w16 motor out of it. Thats what gave me this idea.
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    6.2 Liter LS9 Supercharged V8 Hudson's Avatar
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    Re: Why no 60 degree v8's

    For "vee" engines to be properly balanced (in theory), they need to be at certain bank angles. The theory goes that if you take 720 degrees (the measurement from one spark to the next, four strokes) and divide it by the number of cylinders, you get the optimal bank angle for the engine.

    Using this measure, 90 degrees is perfect for a V8, 180 degrees (horizontally opposed) is the right angle for a four-cylinder, 45 degrees for a V16, and 120 degrees would be right for a V6. Since most vehicles are not designed to handle an engine as wide as a 120-degree vee, the next best thing has been to use HALF of that angle, or 60 degrees.

    If anyone has experienced the early Buick V6s, you'd agree that 90 degrees is not optimal for a V6. Later versions changed the firing sequence and made it smoother. But a 60-degree V6 is inherently (in theory) a better design than a 90-degree V6.

    Since a 90-degree V8 is the optimal design for that size engine, nearly all V8s have that bank angle. There are a few exceptions including TVR's 75-degree V8, the aforementioned 72-degree W8 (which uses banks of 15-degree "V4" engines), and Ford/Yamaha's Taurus SHO 60-degree V8 which was based on a 60-degree V6. The new Volvo V8 (designed and built by Yamaha) also uses the 60-degree V8 design.

    In many of these other-than-optimal designs, balance shafts are used to smooth out the engine. Balances shafts work but they also use take away some power.

    Odd angle engines are usually designed for cost savings or space savings. Ford and Chrysler have 90-degree V10s which, to save money, are based on V8 blocks instead of using the more desireable 72-degree design. We all know about the "Shortstar" V6, Buick's V6, and Chevrolet's V6 engines that were developed from V8s.

    And then there's VW's 15-degree V5...but that's another story.

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    3.0 Liter SIDI V6 acascianelli's Avatar
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    Re: Why no 60 degree v8's

    That theory is pretty interesting. Would it also work in the case of 2 stroke engines? Coming to think about it, aren't alot of european makers v12's 60 degree?

    Yea, the 15 degree VW motors are pretty crazy. Looking at technical drawings of the motor in the Bugatti Veyron make valvetrain look like a nightmare. Plus I never really understood how the cylinders and pistons work with angled pistons and all.
    Last edited by acascianelli; 05-11-2005 at 10:00 AM.
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    Re: Why no 60 degree v8's

    Yes, this theory applies to 2-stroke engines as well...but in that case (I assume you already did the math), you would take 360 degrees and divide by the number of cylinders.

    "Angled pistons" still operate perpendicular to the tangent (am I getting too technical?) of the crankshaft. Just imagine that each bank of cyilnders is an inline engine, and then put those inline cylinders on a common crankshaft.

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    3.0 Liter SIDI V6 acascianelli's Avatar
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    Re: Why no 60 degree v8's

    I'd like to see a 4.6L 60degree twin cam v8 based on the old 3.4 twin dam

    we could call it the southstar
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    Re: Why no 60 degree v8's

    and 120 degrees would be right for a V6. Since most vehicles are not designed to handle an engine as wide as a 120-degree vee, the next best thing has been to use HALF of that angle, or 60 degrees.
    ...
    In many of these other-than-optimal designs, balance shafts are used to smooth out the engine. Balances shafts work but they also use take away some power.
    ...
    And then there's VW's 15-degree V5...but that's another story


    Yes the VR6 and W12 are special. The VR6 has a 15 degree bank angle, but the engine is actually more identicle to an inline 6 than a V6. (Hence the name VR6, which translates to Inline-Vee-6). It uses seperate throws for each cylinder like an I6, but contrary to the shared split-pins common to V6's. Because of this the firing order of the VR6 is the exact same as an inline 6. As such, the VR6 is actually inherently smooth, and does not need or employ balance shafts.

    The W12 is two VR6 engines put together in a similar manner, so it too is inherently balanced and smooth. This is not true of the W8 however...

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    Re: Why no 60 degree v8's

    AVS:

    The VR design is not "inherently smooth" in any case. It is still a "vee" engine which produces vibrations at angles, no matter how many throws the crank has. In an inline engine, all of the pistons move in the same direction, but this isn't so in the VR5, VR6, W8, W10, W12, or W16 designs.

    In a "balanced" vee design, each power stroke of a piston is offset by one in the opposite direction. For a 15-degree vee engine to work, you'd have to have 48 cylinders.

    Because of the narrow angle of the engine, the vibrations may be minimalized, but they're still there.

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    3.0 Liter SIDI V6 acascianelli's Avatar
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    Re: Why no 60 degree v8's

    Quote Originally Posted by Hudson
    ...
    For a 15-degree vee engine to work, you'd have to have 48 cylinders.
    ...
    Yes please... :p
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    Re: Why no 60 degree v8's

    Just imagine the valve size!!!
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    3.0 Liter SIDI V6 acascianelli's Avatar
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    Re: Why no 60 degree v8's

    Quote Originally Posted by 1BadPig
    Just imagine the valve size!!!
    Thatd be 192 valves if it was 4 valves per cylinder. Imagine the intake manifold and exhaust setup.
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    Re: Why no 60 degree v8's

    Very interesting! I'm glad that I reviewed this thread.

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    3.0 Liter SIDI V6 acascianelli's Avatar
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    Re: Why no 60 degree v8's

    I never noticed how compact the 60 degree v6's are until i saw pictures of a 3400 and a 3800 both with no accessories side by side. It would be awesome if they made the blocks out of aluminum instead of cast iron so they would be light enough to put in j-bodies like the cavalier and sunfire.
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    3.0 Liter SIDI V6 acascianelli's Avatar
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    Re: Why no 60 degree v8's

    sorry, should have specified, i meant the last revison of the j-body
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    6.2 Liter LS9 Supercharged V8 Hudson's Avatar
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    Re: Why no 60 degree v8's

    You were COMPARING the 3400 and 3800, right? Because the 3800 is a 90-degree V6.

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    Re: Why no 60 degree v8's

    V6's pretty much all have balance shafts since they aren't 120 degrees, hence they have a natural disadvantage against inline-4's and 90 degree V8's.
    I used to feel you should either have an I4 or V8 (not considering I5 or I6), to get either good gas mileage or lots of power, with V6's not getting much better gas mileage than V8's and producing not much more power than I4's (because of balance shafts), but really they are a happy medium (Chrysler 3.7L V6, GM 3400 & 3800, Ford ...). My dad got 30 mpg highway in his '93 Buick Park Avenue with the 3800, yet it made what 200 HP and 250-ish lb.-ft torque. Amazing motor, especially when supercharged. Chrysler's Slant-6 was amazing too. The 30 deg. slanted I6 has several advantages from the slant, including more room in the engine compartment/smaller engine compartment necessary, almost-equal-length intake and exhaust runners, and optimal power vs. economy. Cheap maintenance repairs keep the motor running 4ever! I'd say the 3800 and slant 6 are the most reliable 6-cylinder engines of all time. The slant-6 was introduced in 1960 BTW, replacing the old flat-head 6-cylinder.
    Whoops, sorry for getting off on a tangent... :P
    Anyways, the point is that this balancing issue is largely what caused Cadillac's 4-6-8 to fail. I imagine you could have a 2-4-6 on an inline-6 though and be successful. The 2-cylinder mode would just be for idling/coasting (cruising but no throttle).
    Last edited by dodge_man; 11-19-2009 at 09:19 PM.

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