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  1. #1
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    The Flat Plane Crank explained

    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.

    DISCLAIMER
    I gave it my best shot in hopes to help clear things up for people, so everyone can stop getting off-topic on threads with Q and A. If you have any questions, I can try my best, maybe someone can chime in, or google is your friend. If anything is inaccurate feel free to correct me. I do not claim ownership of any pictures or information presented, nor do I claim accuracy or accountability to what I have said.
    Last edited by specizripn; 10-28-2013 at 03:01 PM.

  2. #2
    Yield right!!!! GTSpartan's Avatar
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    Great write up man.

    I don't see Ford spending the amount of money it would take to make this happen on a car model that will in all likelihood sell less than 50K units annually. Moving the F150 5.0 to this style doesn't appear in the cards, so you lose a lot of scale there. The engine already makes plenty of power and RPM, and is easily capable of more with much more minor changes in comparison. An 8K+ engine can also create shifting issues with conventional syncro trannys.

    You never know though.....

  3. #3
    Car Czar OH3Cobra's Avatar
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    thanks for the explanation.
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  4. #4
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    Perfect explanation! thank you

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  5. #5
    The GYROMEISTER
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    Its much more clear now. Thx OP!

  6. #6
    Crazy SVT Poster NELCO's Avatar
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    OP, Nice explanation. Ford rocks they will always build a better motor. They seem to be the most innovative............... Turbo's Blowers..................I love my 13 GT 500 Go Ford
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    Last edited by NELCO; 10-28-2013 at 11:04 PM.

  7. #7
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    I believe that Ford may put this technology into whatever model will replace the Boss. That would make it a beast on a road course

  8. #8
    Crazy SVT Poster blackvette101's Avatar
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    Quote Originally Posted by GTSpartan View Post
    Great write up man.

    I don't see Ford spending the amount of money it would take to make this happen on a car model that will in all likelihood sell less than 50K units annually. Moving the F150 5.0 to this style doesn't appear in the cards, so you lose a lot of scale there. The engine already makes plenty of power and RPM, and is easily capable of more with much more minor changes in comparison. An 8K+ engine can also create shifting issues with conventional syncro trannys.

    You never know though.....
    they want to put it in the specialty models like the BOSS or the GT350 supposedly. Probably closer to 10k units annually.
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  9. #9
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    Quote Originally Posted by GTSpartan View Post
    Great write up man.

    I don't see Ford spending the amount of money it would take to make this happen on a car model that will in all likelihood sell less than 50K units annually. Moving the F150 5.0 to this style doesn't appear in the cards, so you lose a lot of scale there. The engine already makes plenty of power and RPM, and is easily capable of more with much more minor changes in comparison. An 8K+ engine can also create shifting issues with conventional syncro trannys.

    You never know though.....
    Id agree that it would be very expensive and unlikely, but its not impossible. Porsche made a great 6 speed for the GT3 RS4.0 which has a 9k redline, the Audi/Lamborghini and Ferarri manual boxes were also able to handle 8.5-9k with minimal isuues, but the current Mustang gearboxes would definitely have some issues. You are right though, Ford would definitely need to find a system with some sophisticated syncros. I'm thinking if ford were to come out with this car they would have to have a GT500 sized pricetag on the car. A much lighter curb weight and similar power could yield the same straight line performance as the 13-14 GT500 without the heatsoak and with much better handeling characteristics, so who knows, it may even be worth the money. This is all up in the air because no one really knows how reliable the source for this rumor is.
    Could be complete fantasy, but we will just have to wait and see if anything turns up!

  10. #10
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    Quote Originally Posted by specizripn View Post
    Id agree that it would be very expensive and unlikely, but its not impossible. Porsche made a great 6 speed for the GT3 RS4.0 which has a 9k redline, the Audi/Lamborghini and Ferarri manual boxes were also able to handle 8.5-9k with minimal isuues, but the current Mustang gearboxes would definitely have some issues. You are right though, Ford would definitely need to find a system with some sophisticated syncros. I'm thinking if ford were to come out with this car they would have to have a GT500 sized pricetag on the car. A much lighter curb weight and similar power could yield the same straight line performance as the 13-14 GT500 without the heatsoak and with much better handeling characteristics, so who knows, it may even be worth the money. This is all up in the air because no one really knows how reliable the source for this rumor is.
    Could be complete fantasy, but we will just have to wait and see if anything turns up!
    As much as I said this will never happen, I would love to see it.

    If we do see it, my guess is it will be *significantly* more than the GT500 $$$ wise. Porsche GT3 RS 4.0 is a fantastic car... so rare.
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  11. #11
    Procharged! 97desertCobra's Avatar
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    Nice explanation. I see Ford making a flat plane crank engine for R&D purposes but not mass production in a mustang. There is plenty of room for the coyote to grow and increase power over the next decade. Now, an exotic flat plane in a new FGT would make sense but I don't think that is going to happen.

  12. #12
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    The Flat Plane Crank explained

    Changing the crank design and the cams to match in an existing block is not expensive for ford. Getting it to rev to 8000 is not that hard for low volume engine, they are already at 7500 rpm.

    The real issue is getting vibration under control, Ferrari, I believe hAs a balance shaft to do this. The next issue is the emissions and all the engine controls to make it work as well as being able to predict reliability. But on the plus side the 5.8l shows amazing technology in an engine that only sold 10000 units over two years and is being (likely) retired.

    So very feasible to do and the only way to beat displacement is with rpm's, so since mustang is limited on engine size, if they want to compete without FI, they need rpm's
    Last edited by NametoShowOther; 11-03-2013 at 01:33 PM.

  13. #13
    CORPSMAN UP! USNjocson's Avatar
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    excellent write-up thanks OP
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  14. #14
    Slower than ever Fenixfire's Avatar
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    Ford is co-developing a 10 speed auto with GM.......could it be used with the flat crank engine?
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  15. #15
    SVT God Quicktime_GT's Avatar
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    Just thinking about the flat plane R1 engines and their very odd sound.. I wonder if a flat plane V8 has a weird sound?
    --

  16. #16
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    Quote Originally Posted by Quicktime_GT View Post
    Just thinking about the flat plane R1 engines and their very odd sound.. I wonder if a flat plane V8 has a weird sound?
    Listen to a 458 Ferrari. It would sound very similar to that

  17. #17
    Crazy SVT Poster ibismojo's Avatar
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    Quote Originally Posted by Quicktime_GT View Post
    Just thinking about the flat plane R1 engines and their very odd sound.. I wonder if a flat plane V8 has a weird sound?
    To me, they sound like two 4 cylinders put together....which it is. They only sound decent when you open it up.

  18. #18
    Rookie SVT Poster BADBOSS's Avatar
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    don't mean to pop the bubble and be a naysayer but it won't happen. Too expensive of an investment for extremely limited upside return potential. Remember Ford is a corporation with shareholders that need to see $$$. Besides the current 5.0 is amazing HP to displacement ratio, reliability, gas mileage and oh btw has paid for itself already from an R&D perspective. I would rather see further R&D monies spent to further refine and push the current 5.0 platform further from FORD. Direct injection, turbo charging, and improved manual transmission would be a much better investment win win for shareholders and mustang enthusiasts.

  19. #19
    Crazy SVT Poster CW1343's Avatar
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    Good write up man, very informative. Thanks

  20. #20
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    Quote Originally Posted by Quicktime_GT View Post
    Just thinking about the flat plane R1 engines and their very odd sound.. I wonder if a flat plane V8 has a weird sound?
    Quote Originally Posted by specizripn View Post
    Listen to a 458 Ferrari. It would sound very similar to that
    Flat plane crank V8s sound nothing like the classic American V8, I would almost wonder if that factor alone would put off some from buying a Mustang if it used that type of engine.

  21. #21
    Crazy SVT Poster THE_EVIL_TW1N's Avatar
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    Quote Originally Posted by Aftrbrnr View Post
    Flat plane crank V8s sound nothing like the classic American V8, I would almost wonder if that factor alone would put off some from buying a Mustang if it used that type of engine.
    Or it could be a positive for the same exact reason and guve people a reason to look at a Mustang where they wouldnt have before.


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  22. #22
    Camaro5's Most Wanted thePill's Avatar
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    Quote Originally Posted by GTSpartan View Post
    Great write up man.

    I don't see Ford spending the amount of money it would take to make this happen on a car model that will in all likelihood sell less than 50K units annually. Moving the F150 5.0 to this style doesn't appear in the cards, so you lose a lot of scale there. The engine already makes plenty of power and RPM, and is easily capable of more with much more minor changes in comparison. An 8K+ engine can also create shifting issues with conventional syncro trannys.

    You never know though.....
    This should be copy, pasted and quoted in the original post. The flat plane crank explanation was spot on fantastic...

    ...we should also be made more aware of what you are suggesting...

  23. #23
    The Shocker IUP99snake's Avatar
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    Would it be possible for someone to make an aftermarket flat plane crank for an existing cross plane engine such as a 302, modular, or Coyote, granted matching cam(s) are used to accommodate the different firing order. Or are there differences in the block and cylinder layout that would make it impossible for the two different types of cranks to interchange?

    Curious.

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  24. #24
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    Quote Originally Posted by Aftrbrnr View Post
    Flat plane crank V8s sound nothing like the classic American V8, I would almost wonder if that factor alone would put off some from buying a Mustang if it used that type of engine.
    I don't think I would be "put off" if my Mustang sounded like this...

    Engine sound Ferrari 458 Italia - YouTube

    It doesn't have the nice lub dub lub dub idle of a cross plane V8 but listen to that high RPM wail when it gets opened up.

    It makes the hairs on the back of my neck stand on end.

  25. #25
    SVT God tt335ci03cobra's Avatar
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    Sound is very tunable, just as you would imagine.

    Check out this 358cid lingenfelter flat plane v8, it does have a little twang, but isn't like the tuned in sound of the 4.5L in the 458 Italia.

    Lingenfelter 358 CID LSx Flat Plane Crank Engine - YouTube

    http://youtu.be/PEcnq3Is0Q4

    http://youtu.be/MJ_qucrWZFs

    Now mind you I've never been in love with ohv sound in general (it can be epic though, header/cam ls7!) but these give an idea that the pitch/sound is very tunable.
    -------

    Lots of great vids on a flat plane design, once there, search their YouTube video search tab for "flat plane"

    http://m.youtube.com/user/LingenfelterVideo


    http://youtu.be/5SHRPOo31Xg

    ------

    Video showing a v8 flat plane

    Ferrari does it differently to get that pitched Ferrari sound, America could easily fall in love with the more familiar (brassier) sound of a decently angled v8 with a flat plane


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