Cross plane crankshaft conversion?

[Chapap]

Is there such a thing as a cross plane crank conversion? You'd have to find someone who makes a crank and cam. I'm guessing that you could get proper spark with a cleverly designed tone ring/ harmonic balancer.

 

[85_Ranger4x4]

Dunno but there is a whole 'nuther level of harmonics for a block not designed for it to deal with it.

Assuming this is for a V type engine...

 

[don4331]

Most V-8s are "cross plane" to begin with.

Only a few of them exotic cars get flat plane cranks.

A flat plane crank will allow the engine to accelerate slightly faster - so if you have a 700hp Cosworth in your F1 Lotus, and are making 40+ shifts per lap, it makes a fraction of a second difference. And that matters in F1. If I'm not mistaken, it actually costs power (with fancy tuning, you can get the power back, but it has been theorized that the Ford Mustang flat plane engine would have made more power as a cross plane. I just wouldn't sound as exotic....​

But for the rest of us mere mortals, the reduced harmonics of a cross plane cranks allow for longer longer service, lives.

Most I-4s are flat plane to get even firing impulses.

I don't think I'd want to do flat plane for I-5 - it would shake itself apart, same for I-6. A V-6 flat plane would have uneven firing.

The whole point of a v-12 is to use the cross plane crank to eliminate both primary and secondary vibration issues, so wouldn't do it there either.

Just remembered: There is/was a Yamaha I-4 bike with cross plane crank. There are advantages to duration without power on a bike as it allows the rear wheel to hook up better. Harley's have similar setup but for different and now historic reasons.

 

[Chapap]

I guess the actual question is if it’s possible to change it. I had 4 cylinder in the mind when I wrote that. I want to hear a cross plane 4. I only know of one that was made. Some Japanese motorcycle I think.
I imagine this idea is one of my more practicable ideas. Spend a few grand on a crank and cam (I’m pretty sure you can find people who will mill it) and trick the timing.

 

[Blmpkn]

What kinda race rig you building where it's a 'worth it' kinda thing to do? Having a one off crank and cam made won't be cheap.

 

[rubydist]

A cross plane crank in an I-4 engine will have uneven firing and a lot more unbalance issues than a regular crank, so that's going to be expensive wasted effort.

 

[Chapap]

A cross plane crank in an I-4 engine will have uneven firing and a lot more unbalance issues than a regular crank, so that's going to be expensive wasted effort.

Probably why there’s only one out there, but it’s supposed to sound good. I guess I’m wondering why it’s not a popular thing to do for V8s. As far as I can tell, the main advantage is even firing order. Apparently a standard V8 has one exhaust pulse that isn’t evenly timed with the others on at least one bank.

BUT…. All the super cars have flat plane, so why not convert?

 

[Ranger850]

I love the way the new flat plane crank mustangs sound.

 

[Blmpkn]

I love the way the new flat plane crank mustangs sound.

They intentionally don't sound like flat plane cranks though.

Ford designed their exhaust to make as close to a cross plane sound as they could.. because they figured most Americans would prefer the classic American v8 sound over the far superior wail of a flat plane motor.

Probably why there’s only one out there, but it’s supposed to sound good. I guess I’m wondering why it’s not a popular thing to do for V8s. As far as I can tell, the main advantage is even firing order. Apparently a standard V8 has one exhaust pulse that isn’t evenly timed with the others on at least one bank.

BUT…. All the super cars have flat plane, so why not convert?

Flat plane cranks ARE super popular, but as you said... usually only in supercars.

They're used in supercars because everything in a supercar is made to the extreme. A flat plane motor will be happy revving more than a few thousand rpm higher than a cross plane motor would.. and make more HP.. the trade off is less torque. Nobody wants a Ferrari that has a 6200 rpm rev limit... you don't wanna have to shift that bad boy until after 9k.

The reason why most of our American v8 sports cars don't have flat plane cranks is pretty much because the people making those kind of decisions are uncultured swine.

 

[don4331]

Flat plane cranks ARE super popular, but as you said... usually only in supercars.

They're used in supercars because everything in a supercar is made to the extreme. A flat plane motor will be happy revving more than a few thousand rpm higher than a cross plane motor would.. and make more HP.. the trade off is less torque. Nobody wants a Ferrari that has a 6200 rpm rev limit... you don't wanna have to shift that bad boy until after 9k.

The reason why most of our American v8 sports cars don't have flat plane cranks is pretty much because the people making those kind of decisions are uncultured swine.

Less torque = less horsepower. You measure torque and rpm to get horsepower: HP = Torque * rpm/5252

The Voodoo in the Mustang GT350R makes 526 hp as a flat plane engine. Note: The Voodoo has a different flat plane than most, so sounds different even without the tuned exhaust.

The Aluminator - same block and heads as Voodoo but with cross plane crank makes 580 hp! Over 10% more than the flat plane.

The American engineers designed their engines the best for the car American masses can afford/their driving style. Not many Italian mountain roads/German Autobahns in USA (Although, I have enjoyed the no speed limit of Montana back in the day in Mustangs).

Flat plane cranks in v-8 are useful in super light open wheel racers, but like carbon fiber brakes belong on the race track, not on the street.

 

[Blmpkn]

Less torque = less horsepower. You measure torque and rpm to get horsepower: HP = Torque * rpm/5252

The Voodoo in the Mustang GT350R makes 526 hp as a flat plane engine. Note: The Voodoo has a different flat plane than most, so sounds different even without the tuned exhaust.

The Aluminator - same block and heads as Voodoo but with cross plane crank makes 580 hp! Over 10% more than the flat plane.

The American engineers designed their engines the best for the car American masses can afford/their driving style. Not many Italian mountain roads/German Autobahns in USA (Although, I have enjoyed the no speed limit of Montana back in the day in Mustangs).

Flat plane cranks in v-8 are useful in super light open wheel racers, but like carbon fiber brakes belong on the race track, not on the street.

Less low end power I guess is how I should of worded it, the things are more like rotaries with a flat plane in em.. they wanna be revved.

No autobahns may be the more reasonable answer... but I stand by my uncultured swine comment

 

[Ranger850]

They intentionally don't sound like flat plane cranks though.

I still like it. It clearly sounds different than a Cross Plane Crank.

 

[Ranger850]

The Voodoo in the Mustang GT350R makes 526 hp as a flat plane engine. Note: The Voodoo has a different flat plane than most, so sounds different even without the tuned exhaust.

Maybe this is why]