Flat-plane Crankshaft for Cobra Engine

[J.Jensen]

But would it sound like a Ferrari with the larger? displacement and side pipes?

[RedEye]

For my personal taste, the goal would not be necessarily to sound like a Ferrari. I'm working on a winter project engine build in the 8K RPM range and would like to match the fast rev and idle of this flat crank concept. At least what I have heard so far.

[Gary(SF)]

Originally Posted by Randy Rosenberg

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?

My understanding is (not 100% sure but pretty close) that all mid-engine V8 Ferraris are flat plane crank engines, so 308 and on.

[maurice19]

Sound is beautiful for a Ferrari, but I like the sound of my 511 ci Shelby better.

Maurice

[Cobra #3170]

Originally Posted by maurice19

Sound is beautiful for a Ferrari, but I like the sound of my 511 ci Shelby better.

Maurice

This small block sounds pretty good to me, and it has some torque too.


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

[Randy Rosenberg]

Originally Posted by Gary(SF)

My understanding is (not 100% sure but pretty close) that all mid-engine V8 Ferraris are flat plane crank engines, so 308 and on.

You're right. My mistake. I got the "flat crank" with "timing belt vs. chain" change mixed up.

[Jac Mac]

Originally Posted by RedEye

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.

With that Cobra side pipe deal its going to sound like a stroked /bored 2.3 pinto on each side with one of the two engines 90° out of phase to other. To get the GT40/Ferrari sounds you will need under car exhaust with both tailpipes in close proximity, but due to the longer pipe lengths and larger capacity it will sound heavier/deeper.

[Mark IV]

Originally Posted by Cobra #3170

This small block sounds pretty good to me, and it has some torque too.


https://www.youtube.com/watch?v=XODKScxUDjk

The Roush T/A cars have a 180 degree undercar crossover exhaust system. I was at Roush when the first ones were dyno tested.....wicked sounding! Jack was a happy camper.

[maurice19]

Sounds great,Bruce.

I have always loved the Trans Am series.

Maurice

[fordracing65]

Originally Posted by Cobra #3170

It will shake so bad your teeth will fall out.

I would pull all my teeth to have this engine in a COBRA...lol

[Jac Mac]

Originally Posted by Mark IV

The Roush T/A cars have a 180 degree undercar crossover exhaust system. I was at Roush when the first ones were dyno tested.....wicked sounding! Jack was a happy camper.

It also runs the exhaust into a single tailpipe which goes a long way toward the 'sound'.

[twobjshelbys]

I think with the straight pipes on a Cobra you might be disappointed in the sound. Based on alternating right/left side firing order you might need a blended system - X- or H- pipe to get the best sound. Like was mentioned, this would mean an under-the-car exhaust system.

[eschaider]

There is a lot of urban legend surrounding flat plane cranks. Most of it is just that, urban legend! There are two couples or forces in two different planes that a conventional non-flat plane crank makes easier to resolve (balance out). With a flat plane crank the balance in one of those planes remains unresolved. It is typically the horizontal plane.

While you might possibly detect the out of balance condition it is more likely you will not. The fasteners on the vehicle that are not Loktited® however will and without some type of thread locker they can, over time, potentially loosen.

While the design of the crankshaft has caused some to speculate the V8 versions of a flat crank motor fire two cylinders simultaneously that is most often because the appearance of two pistons at TDC simultaneously is for some reason more visible. In fact out 90˚ degree cranks also bring two pistons to TDC simultaneously and God knows we don't light both of them at the same time! They get lit 360˚ apart from one another — same thing on a flat crank engine as someone has already pointed out.

The V8 version of the engines sound like two synchronized four cylinder engines on each side of the car because that is essentially what is happening. The staccato note in our exhausts is caused by a successive cylinder firing but not on the same side of the engine. With a flat crank there is a firing pulse form each cylinder, on each bank, every 90˚ of crankshaft rotation. Not so on a traditional 90˚ crank.

The design is so poorly thought of that you will find it in F-1 engines competing (very effectively) with other F-1 engines that use 90˚cranks! The flat crank while possible to manufacture w/o counterweights is infact, in all modern implementations, manufactured with counterweights. The flat crank design allows for a small but measurable reduction in both engine weight and rotating weights which in highly competitive classes like F-1 can potentially translate into a performance advantage.

There are those who will also argue that the more uniform bank to bank firing order of a flat crank allows for an intake manifold tuning advantage not available to the more conventional 90˚ crank designs. In supercharged applications the intake manifold design issues / considerations tend to be different than for similar n/a engines. Any resonance dynamics available to n/a engines because of the crankshaft design, for all intents and purposes, do not translate over to the supercharged versions of the engines.


Ed

[HealeyRick]

That motor sounds pretty nice in the new GT 350:

[ame=http://www.youtube.com/watch?v=JtGHjfQRaFU]2015/2016 Mustang GT350 SVT on Nurburgring (Extended Cut) - YouTube[/ame]

[rodneym]

Call me crazy but the good 'ol cross plane sounds much, much better to me.

[vatdevil]

Ferraris opinion


FLAT-PLANE CRANKSHAFT
The engine’s flat-plane crank (with 180° between throws) epitomises Ferrari’s uncompromising design approach.
Eight-cylinder engines with a 90 degree angle between their cylinder banks are a relatively recent addition to Ferrari history.
Apart from the engine sported by the 1956 World Championship-wining F1 car, which Ferrari inherited from Lancia after the latter pulled out competition, and the one mounted to the 248 sports prototype in the early 1960s, it was 1973 before a Ferrari would be powered by an engine with this specific architecture.
Characteristically flat-plane crankshaft engines have a crankshaft with crankpins angled at 180 degrees to each other or “flat” i.e. on the same plane.
Ferrari_F430_Crankshaft
Ferrari_F430_Crankshaft
Generally speaking V8 engines have a 90 degree angle between the cylinder banks with each crank pin offset at 90 degrees from the adjacent ones i.e. they are “crossed” at 90 degrees. Hence the cross-plane name. Whether a flat or cross-plane crankshaft is chosen depends on what kind of performance is required. To get maximum performance from the engine, the flat-plane must be used but for all-round functioning the cross-plane is best. This why all Ferrari V8s engines (from the 308 to the 328, the 348 to the 355,the 360 to the 430,and the special high performance GTO series, the F40 and the recent California, our first front V8) use a flat-plane crankshaft.
The advantages of the flat-plane crankshaft over the cross-plane one can be summarised as follows:
A flat-plane crankshaft is lighter than a 90-degree, or cross-plane crankshaft, and, having a lower rotating mass than the latter, provides sharper response as well as allowing higher maximum revs, useful when seeking higher power outputs. Another advantage of the flat-plane crank is that it allows more efficient exhaust manifold design.
CLOSE

[Jac Mac]

While we are waiting we could always do what these guys did a few decades ago...

Flatheads - Crankshafts

[Richard Hudgins]

I had a Traco 5 liter 90 degree sbc in a Lola T330 (A long time ago) and I bought a HRE flat crank motor as a replacement as the Traco was getting long in the tooth and the HRE motor was cheaper.

The car was 100-150 rpm down on the back straight at Road Atlanta with all settings the same (Wing and gears) but I was 1.5 seconds a lap quicker.

Much faster turn one through seven. Accelerated like a banshee.

I did notice that the rivets on the engine pontoons were getting a bit loose after the first two practices and qualifying. But this was a Lola after all and they were flexible flyers anyway.

The engine also went through rod bearings rapidly. We replaced them after every 1.5 hours running. (This was from oil analysis results. Never showed copper but real close.)

I liked the motor....

[mdross1]

Funny how it always boils down to personal preference with our toys/hobbies. I do love the sound of exotic engine designs, but for my cobra only one will work. My first impression of these amazing muscle cars will live on with the American BB Ford nestled between the frame rails.

[RedEye]

Originally Posted by HealeyRick

That motor sounds pretty nice in the new GT 350:

2015/2016 Mustang GT350 SVT on Nurburgring (Extended Cut) - YouTube

The motor in this video reminds me of some of the recent renditions of the Mercedes AMG / Black cars.