Why don't we see more flat-plane V8's?

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I'm just curious. I know they each have their own inherent advantages and disadvantages, but you hardly ever see flat-plane (aka 180 degree) V8's. I'm surprised we don't see them in a greater number of high-performance cars. Any thoughts? By the way, they sound awesome
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Originally Posted By: Eddie
Not a smooth running engine.

^^ This.

Here is an explanation based on my understanding:

Flat-plane crank V8s inherently generate 2nd-order vibration. They work best when they have super-lightweight internals, a short piston stroke, and a high rod/stroke ratio, because those make the vibration much less severe. Those attributes are best suited to small, lightweight engines with stratospheric redlines and lots of top-end power -- in other words, race engines.
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Street engines tend to put a higher emphasis on low-end torque, low NVH, and cost control, so a cross-plane crankshaft is better suited. Balance shafts can eliminate the NVH problem for a flat-plane crank V8, but they are complicated to implement and their extra mass largely cancels the benefits of having a flat-plane crank in the first place.


Now, all of that being said, I share your wish for more flat-plane crank V8s. I would happily give up some low-end torque and tolerate some extra vibration in exchange for a huge redline and a screaming top-end.
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I believe the OP is speaking of the "flat plane crankshaft". This has nothing to do with the vee angle of the block. This is specifically related to the connecting rod journal placement in which all journals are going to be set at 180º apart from each other.

Compare the flat-plane crank to a cross-plane crankshaft which will set the journals at 90º placement. This design does afford a much smoother operation when dealing with high reciprocating masses.
 
Originally Posted By: FowVay
I believe the OP is speaking of the "flat plane crankshaft". This has nothing to do with the vee angle of the block. This is specifically related to the connecting rod journal placement in which all journals are going to be set at 180º apart from each other.

Compare the flat-plane crank to a cross-plane crankshaft which will set the journals at 90º placement. This design does afford a much smoother operation when dealing with high reciprocating masses.


Yes, this was precisely what I was referring to. Not the layout of the engine block, but the crankshaft.
 
that would be two 4 cyls running off the same crank. 180 phasing is not good for low rpm operation due to the cyl firing with all other pistons "locked" at TDC/BDC. This is of course archaic thinking from the days of 6/1 comp ratios and 300CUIN 4 cyls with 2800 rpm "redlines" but usable torque at 600 rpm and up. Remember now, with thoughts of lugging in your head (in our heady days of 5000 rpm peak torque PC engines!) that each cyl fires 10 times a second at 1200 rpm. That's fourty firing pulses a second at a luggardly 1200 rpm in a 4 cyl. ( 1200 rpm = 20RPS /2 = 10 power strokes/second/CYL ) There was torque to be had down low but its mainly vanished due to advertising BIG HP bragging rights to no ones advantage.
 
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Originally Posted By: mechtech2
Car mfrs want to consolidate space in engine compartments.
And weight.
V engines do this inherently.


Yes, but again, I'm not referring to flat/boxer 8 cylinder engines. I'm referring to flat-plane aka 180 degree crank shaft V8 engines.
 
Ferrari, Audi, and BMW. Those are the three biggies that I come up with who are using flat-plane V8s that aren't a niche manufacturer (did I just call Ferrari a mainstream manufacturer?).

Now, looking at the automakers who are using cross-plane V8s, lots of they are also using them in trucks, with a few exceptions. It doesn't make sense to build two completely separate engine families, one for performance cars and the other for non-performance sedans and trucks.

When you study at the overall horsepower, torque, and rev capacity in the Ford Coyote and GM LS7, it seems to me that those that do use cross-plane V8s for performance applications are doing just fine with them.
 
Originally Posted By: MrHorspwer
Ferrari, Audi, and BMW. Those are the three biggies that I come up with who are using flat-plane V8s that aren't a niche manufacturer (did I just call Ferrari a mainstream manufacturer?).

On the US market, Ferrari and McLaren are the only major manufacturer that have flat-plane crankshafts in their V8 road cars (and McLaren only has one production model right now). ALL others have cross-plane crankshafts. You can tell when you hear them.
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Originally Posted By: d00df00d
Originally Posted By: MrHorspwer
Ferrari, Audi, and BMW. Those are the three biggies that I come up with who are using flat-plane V8s that aren't a niche manufacturer (did I just call Ferrari a mainstream manufacturer?).

On the US market, Ferrari and McLaren are the only major manufacturer that have flat-plane crankshafts in their V8 road cars (and McLaren only has one production model right now). ALL others have cross-plane crankshafts. You can tell when you hear them.
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Yeah, they have a VERY distinctive note that sounds a lot like a 180 degree 4 banger to me.
 
I knew there were two different cars in the first 20 seconds of video. correct me if I am wrong....
Plate that ends in 815 is a cross plane, plate that ends in 070 is a flat plane?
 
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