Flat-plane Crankshaft for Cobra Engine
 

HI All,

So... the new Ford GT350 has been recently advertised with much press and attention. Among the obligatory technical upgrades is the continual mention of an anticipated Flat-plane Crankshaft V8 engine. Quite a bit of the reference is to the sound the engine will make, and the potential for a higher rev limit.

I'm wondering, does anyone use a Flat-plane crankshaft in the cobra? I'm really curious to know what this would sound like. Most of the auto OEMs have such engineered exhaust sounds (Ford to Ferrari) that sometimes it's a bit difficult to anticipate what this would sound like with our large and unfiltered side pipes.

If anyone has video, media, or otherwise even a confirmation that this is their setup I would be very thankful to see this (even a link to another posting). I'm thinking of specing out another SB stroker engine for this spring and this is my first consideration for such.

Thanks!

Flat plane crank
 

It will shake so bad your teeth will fall out.

^what he said

Oh very funny :) Fortunately my wife is a dentist... and she's a bit of a stickler too... so I'm guessing if they fall out, she'll put them back in while I sleep.

Yep. I'm really surprised that Ford is toying with this. Has been proven to be bad design for decades.

Other than a lack of secondary balancing, are there other reasons the design is bad? There have been some high end cars that have used flat plane cranks, though I can't think of any daily driver type cars.

Vibration/harmonics. You're lighting off two cylinders on one bank at once. In addition, it's been proven by several well-known builders/racers (think Warren Johnson, Smokey Yunick, etc. etc.) to not offer any performance benefit.

I have owned two flat crank V8s, and while I'm aware of the reputation for excessive vibration, I did not find that to be the case in the cars I owned (Ferrari 360 and F430). And oh my would they rev. In the case of the F430 it made nearly 600 hp from 262 ci, normally aspirated. I think the flat crank Mustang sounds very intriguing.

I think Ferrari even spoke of the 360 and F430 having a different vibration....

Would be nice to have a flat cranked 360 and a cross cranked 360 to compare.

I'm thinking you'd also need a new cam to go with the flat plane crank. Another area of deal with would be changing the ignition system to fire two cylinders simultaneously, rather than sequentially.

As far as the sound, it seems to me a Ferrari or Maserati with flat plane crank might be a good indicator of what to expect. Here's one link ([ame]https://www.youtube.com/watch?v=RLPOpgP9pEk[/ame]), but there are plenty of choices on YouTube.

Sounds great....I bet the Mustang will start quicker though. :D

Looks like I need to research it a bit more....

Flat Crank
 

Yes, the crank is very light compared to conventional cranks but not generally used in larger engines because of vibrational forces. I suppose you could use balance shafts but that would negate some of the advantage. I am surprised they didn't go with Ti rods like GM and a light weight aluminum flywheel with small multi-disk clutch. That combination would rev very quickly too and not have vibration issues. Atlantic cars I owned had similar vibration issues and would crack brackets and loosen fasteners at an alarming rate. Lots of safety wire and Loctite were required. Sometimes the mirrors would go into resonance too, and it was difficult to see at certain rpm.

Lingenfelter made an LSx, it was back in 2011 I couldnt find any updates since. More Flat Plane Action Lingenfelter Race Engine Dyno Video

Still doesnt sound like a ferrari or maserati, might just be the turbo exhaust setup they were using.

Great explanation on flat planes

So several magazines have mentioned the possibility of a "Flat Plane Crank" which most people don't know very much about, and some recognize it as the style of V8 used by Ferrari and in the new Lotus, but that's pretty much all they know. Well Im going to try and explain how it works, the problems that go with it, the benefits, some history, and whether or not I believe it would be feasible for Ford to put one in a mustang.

WHAT'S THE DIFFERENCE?


Now the first thing one might notice is that the flat plane; also called a 180* crank, doesn't have the large counter weights. This means that the crankshaft is much lighter, but I'll get into that later. Now the design for this style of crankshaft is very different than the cross plane, so you couldn't just swap a flat plane crank into a standard coyote, it will require a new engine design entirely.

IS IT BETTER?
It has its benefits. Due to the design of the crankshaft, a flat-plane V8 can have an alternating firing order, meaning the pistons will fire R-L-R-L-R-L-R-L. This means that the exhaust manifolds will be able to more efficiently scavenge exhaust gasses thus improving efficiency. In order to properly scavenge with a Cross Plane crank you will need a "Bundle of Snakes" style exhaust manifold, which is more expensive and very difficult for packaging constraints. In addition to the scavenging efficiency, the lighter crankshaft means the engine can rev quicker, higher, and make more power. Counter balance weights add a large amount of rotational weight, which means the engine has to spend power moving the crank before the power can be put to the ground, and the force required is amplified the higher you go into the rev range. With a flat-plane, the engine can rev easier, and will be able to keep revving higher, as well as free up some power that would normally be wasted turning the crank. I would also like to add that cross plane engines are technically more refined than the flat plane due to the weights and balancing properties.

WHERE IS THE TORQUE?!
One of the first things people notice when comparing engine styles is that flat plane V8s typically don't make as much torque as an american V8. Now although this is somewhat controversial, there is a good reason that most don't make the same torque. Typically these engines are in exotic supercars that rev to the moon. The motors are tiny with a short stroke to aid in high rpm abilities. Now, if you ever paid attention in science class as a kid, or if you've used a breaker bar, you will understand that more leverage means more turning force(torque). The same logic applies to a motor. A longer stroke will aid in more torque, and the tiny cross planes typically have very short strokes. While this is not the only factor, it is too complicated to point at one cause, but a flat-plane can make just as much torque as a cross plane, it comes down to how the engineers design it, and how much torque they want to give up for higher rpm capabilities.

BALANCING ISSUES?
Many people are aware that without counter weights it is very hard to balance an engine, and a bigger flat plane, would be very difficult to do. I keep hearing people say it is impossible. Now those people are also forgetting that Ford managed to balance a 3 cylinder engine... If they can do that, I'm sure with a enough time and light enough rods and pistons, ford will be able to manage the task.

HISTORY
For those of you who don't know, Ford has already built a flat plane crank V8. In the 60's the Ford Motor Company was testing race cars with 180* cranks, but set the idea to the side. If ford could do it in the late 60's, there is no doubt they could create one stable enough for a road car nearly 50 years later.

DRIVABILITY ISSUES
Another problem with the flat planes, is the tendency to vibrate like hell. This is a result of the difficulty to balance such a motor. Now with research and development this can be eliminated entirely. The Ferrari 458 Italia has absolutely no vibration and the motor is only a liter smaller than the rumored engine for the specialty (GT350/Cobra/Boss) mustang, which means that it is possible to balance one well enough that it isn't even noticeable.

IS IT POSSIBLE WE WILL SEE ONE IN A FUTURE MUSTANG?
Is it possible? Certainly. Will we see one? Maybe. Ford has the ability, experience, and ingenuity required to create such an engine, but will it be worth it financially for them? I don't know. The answer to that may lie in the Euro market. If Ford were to ever bring a V8 into the European market, this would definitely be the one to do it with. Many Americans would also love the high revving; powerful motor, and it would definitely spice things up in the world of American V8s. The only way it would be worth engineering is if they could keep the motor around for a couple decades. If they want to do this, everything will have to be perfect, which could explain the rumor that Ford would wait a few years after the initial release of the S550s to release this engine choice, so they can enhance it.

I'm intrigued by the engine. I imagine Ford did their homework on this one and I wouldn't mind selling my dart blocked 427w and going this route at some point.

The sound of a V8 at very high revs is intoxicating! Listen to this old flat-crank Ferrari. Have a good pair of speakers and turn em up!

[ame]https://www.youtube.com/watch?v=0YPabCzxMXM[/ame]

As stated a couple of times, Ferrari uses the flat plan crank design in the V8's since the F430 (also used in their current 458 and California). They make a very unique sound that is commonly associated with Ferrari - when one hears the exhaust, it sounds distinctively Ferrari.

So, the question is: who would want a Cobra that sounds like a Ferrari?

I think there it might be worth experiencing what that setup would sound like through our long and large side pipes.

Love that idle, choppy, quick, poppy.