Long time 4chan user, never been to auto though I am an enthusiast

I intuitively have no idea

>>17727747
Do you for sure have no idea for sure though?

fairly sure top fuel uses crossplane.

probably because merica and no other reason.

Everything can be overbuilt and I don't think either design has more strength than the other.

the best way to describe them is that flat planes have alot lower rotating mass adn good secondary balance whilst crossplane has better primary balance.
crossplanes make good smooth torquey engines that don't have to rev too high
flat planes make great responsive high revving engines

>>17727353
Read this first:
https://www.linkedin.com/pulse/flat-plane-silliness-how-crankshaft-press-release-duped-stephen-kim
tl;dr the Voodoo is great because it was engineered well, not because it has a flat plane crank. That's just marketing.

Top Fuel dragsters use crossplane cranks, for various reasons. For dragsters, you don't need throttle response, since you're full throttle during the entire run. Acceleration there is determined by the amount of slip in the electronically controlled clutch plates. Counterweights are fine and dandy, but don't matter if you're only turning 10,000 RPM. Given the massive strokes these things have (hey, you need to get a 500ci someway), the problem with internal balance lies with the conrods, not the crank. Efficiency like you're saying is a misnomer: energy is never lost, but in an engine with a lot of coutnerweight, it's simply converted into kinetic (rotational) energy, just like in a flywheel. Once you've ''filled'' the counterweights, then they don't pose a point where you're losing energy. Again, if you're starting at 8-10K RPM, that's not a problem.

>They allow for a lower CoG
No they don't.

>helps with scavenging
Irrelevant when you have 60 PSI pushing into the intake, and have extremely well-ported heads.

>they are not as smooth
And herein lies the problem. A crossplane V8 has a primary inbalance, which you can easily correct. A flatplane unit, has secondary imbalance, which you can't easily correct. This caused a lot of problems during the development of the new Voodoo V8. Guess what happens when you put 9000 horsepower through a crank with a secondary imbalance? Conrods start flying through very, very expensive billet blocks.

>>17727766
See >>17727801
Flatplanes have good primary, crossplanes have good secondary.

You can make a crossplane rev far beyond what any streetable engine ever needs, and torque is a function of how good your heads are. Flat plane crank V8's may actually need so much mass for balancing that their throttle response advantage is very,very small.

>>17727801
Fuck, I forgot to mention that scavenging is utterly irrelevant when you only have zoomies.

>>17727845

I always wonder how top fuel dragsters don't fuck with their scavenging because I know dragsters have a really, really weird firing order that's different from other cross-planes.....

yeah you just made me realize it doesn't matter, derp

>>17727877
OP here, I never thought it mattered for top fuel to have scavenging. They don't use it period some of the time, with each cylinder exhausting through individual pipes. I don't know exactly why, but the only reason I brought that up was for people that don't know what the difference between the designs are to get an idea. I don't know how intelligent you guys are her on auto.
>>17727801
The voodoo engine is actually what I was reading about when I thought of the question. Thanks for a well thought out answer

>>17728243
Oh, but apologies, efficiency like I'm talking about is not a misnomer. Energy is lost through various things like friction. The more moving stuff you have moving at high speed, the less efficient. And flat plane does allow for lower center of gravity, although this is also pretty irrelevant for top fuel dragsters. I was just pointing out for those that may not know. I don't know how knowledgeable the users here are, mostly a g/ guy, or diy/ guy

>>17728262
>The more moving stuff you have moving at high speed, the less efficient.
A crossplane crank does not have any more friction though, just more mass. Same bearings, same piston-to-wall clearances, the exact same thing, just heavier. It's not weight that causes energy ''losses'' (converted into heat, mostly), but friction. In traditional mechanics, yeah, mass causes friction, but not inside of an engine, since all of the force is generated by the combustion events. Heavier components just function as a bigger flywheel, that's all, so they inhibit throttle response.

>And flat plane does allow for lower center of gravity, although this is also pretty irrelevant for top fuel dragsters.
No it doesn't - why would crank layout matter in terms of how heavy your block is, and where the weight is distributed?

Center of gravity for any component in a dragster chassis is pretty improtant though, since it controls how the weight will transfer during initial acceleration. This weight transfer is especially important in the Top Fuel monsters where there is no traditional suspension - the entire chassis is tuned to flex just right when they accelerate.

>>17728305
Well, to start off the counterweights themselves cause some drag through the oil air mist inside the crankcase. I don't understand how this is actually an argument, racers have been messing with this stuff for decades
As for center of gravity, a counterweight sticks out farther than the stroke of the piston needs. No counterweights means smaller diameter of crank rotation which means you can use a more shallow oil pan which means you can mount the engine lower on the car which means lower center of gravity overall

They've been around for a while. Most of automotive technology was all invented and explored way back in the first half of the 20th century.

Mostly it's about engine reliability vs. performance. All a racing engine has to do is last the length of the race. Who cares if it needs rebuilding after the race? A person buying a DD probably wants something that won't need a rebuild quite so soon. Ferd claims they can build one that doesn't need to get rebuilt? We'll see. Check back in 5 years and see what people are saying.

File: AAEAAQAAAAAAAATGAAAAJDJhZWIzNGNiLWZmNzctNDA4Mi04MDJkLTk5NDYyYmM2OWY4MQ.jpg (81KB, 779x800px) Image search: [Google]

81KB, 779x800px

>>17728823
You don't increase the frontal area of the counterweights though, you increase the angle of the counterweights (like cam angle, actually). Pic related though: does the Voodoo crank (left) look like it's got less counterweights than the crossplane Modular crank on the right? Not really. Besides, windage isn't significant compared to friction.

Again, counterweights don't stick out further than the diameter of the crankpin journals, since that would cause excess windage (and inbalance), just compare pic related again. For any given stroke, a crossplane and flatplane crank will have an identical outer diameter, which means you theory of a more shallow oil pan doesn't work. Also, it's irrelevant on anything with a dry sump. The linear acceleration that dragsters cause, actually requires dry sumps, so your point would be useless even if it were true (it isn't).

>>17728831
At the pricepoint those GT350's are going, and by the amount they'll appreciate, nobody's going to care about engine rebuilds. It's a fantastically characterful engine (amazing considering it's heritage), with one of, if not the, best marketing departments in the automotive world behind it. It's an instant classic, for all the right (and a few wrong) reasons.

>>17728305
Oh, and the only reason I say center of gravity is a bit of a moot point is because my question really pertains to the structural integrity of flat plane vs cross. That question I think we both agree on, it doesn't seem possible to run one in a top fuel dragster. The rest I only said to give a basic idea of the differences for people not necessarily familiar with the designs to understand the topic of discussion.

>>17728854
>The rest I only said to give a basic idea of the differences for people not necessarily familiar with the designs to understand the topic of discussion.
So, yourself?

>>17728848
Huh, you're right. Ive never actually seen the difference in person, just read about it. My real knowledge of this stuff comes from car repair as I'm a mechanic, and I've never had them come into the shop. I see your point now though.

>>17728864
Well, yeah I guess. See>>17728865
But I do have something aha

>>17727353
A quick google search probably wpuld have answered your question. Just found it on wikipedia:

Billet steelcrankshaftsare used; they all have a cross plane a.k.a. 90 degree configuration and run in five conventional bearing shells.180 degree crankshaftshave been tried and they can offer increased power. A 180 degree crankshaft is also about 10kg lighter than 90 degree crankshaft, but they create a lot of vibration. Such is the strength of a top fuel crankshaft that in one incident, the entire engine block was split open and blown off the car during an engine failure, and the crank, with all eight connecting rods and pistons, was left still bolted to the clutch.

>>17729508
>and the crank, with all eight connecting rods and pistons, was left still bolted to the clutch.
This pretty much summarises 90% of engine failures in Top Fuel.