90 degree V8s with 180 degree cranks

[Route666]

Ferrari is running them, and I know it's in the realm of "Not really classic tech, more current tech" but I was wondering how hard it would be (discounting money from how hard things are to do) to get a crank for a Windsor motor made in 180 degree throws.

Why does Ferrari run 180, and not 90? There must be a benefit to it, like balance. In effect it seems it would be like two 4 cylinder motors connected to the same crank at a 90 degree seperation.

And wouldn't it be just sweet to have the Ferrari V8 sound. mmmm

Of course you'd need an "all-in-one" header so you can properly balance exhaust pulses, but that wouldn't be any harder than getting the crank.

EDIT: And what orientation should the crankshaft have? staggered throws, or the two centre ones on the same side and the end ones on the same side?

 

[Max Power]

Not sure why they would do that. 90 degree should be much smoother.

 

[ron67fb]

The 180 "flat" crank is more suitable for high rpm. I would imagine a 300+ CI V8 with a flat crank would have a hard time idling below 2000RPM. The Indy V8s used flat cranks, but they run very small displacements at really high RPMs. What's the Ferrari's displacement on that V8? Probably a lot less than 300 I'm guessing?

I don't see the point for the street, since I thought that the reason race teams went flat crank on a V engine is because 180- and 360-degree headers were against the rules. Making an equal length, 180- or 360-degree header to fit a chassis is a lot easier and cheaper than a custom flat crank, hence the GT40's "bundle of snakes" exhaust. On a front engine car (which aren't exactly "real" race cars), I doubt the benefits of either method is of much use compared to the complexity and cost. Good headers and an X-pipe seems to work fine for us.

 

[Route666]

That's right the Fezza engines are 3.6L, and recently moved to 4.3L, so are quite small, so a higher idle is ok with them I guess.

And I thought about the headers and thought hang on, it should be easier to make a better exhaust for them, since it's like two 4-cylinders (if you use the non-staggered design) and you just confirmed that.

Damn I dunno about a 90 degree crank running smoother either because the firing order seems all over the place in either 302 or 351W sticks.

With a 180 crank, I've worked out that you could just run it like two 4 cylinders with one backwards, so the firing order is

1-8-3-6-4-5-2-7
EDIT: cylinders are numbered differently to what I thought.

Visualise it on

I think it looks more spread out, a cylinder still fires every 90 degrees, because it has eight cylinders, but the order looks more evenly spread out.

 

[Route666]

Or if you ran it like a four cylinder, with two cylinders firing at once, they seem to be staggered away from each other enough to not stress it too much, but maybe the total displacement is too much with even a 302.

 

[D.Hearne]

Are we suffering from Cabin Fever route666?

 

[C0V3R]

I suppose the big problem is getting a crank and a cam to make it run that way?

 

[Route666]

I don't think I've got cabin fever, I just like to think/hypothesise etc about all this stuff, you should know that. Or perhaps I've always got the fever?

Actually getting the crank and cam is a major hurdle, but if it's not going to run as well as a 90 degree crank then there's no point bothering to get it either.

What wouldn't you want to do to the crank and bearings, say would it be bad to have 5 fire 90 degrees after 1, or 2 90 after 1, and what would fatigue the crank a lot?

 

[C0V3R]

That would probably not be a good thing (compared to oposing end firing) to do as youd be putting alot of force into one end of the crank in a short(er) period of time.

As far as the crank and cam - I'm sure if your pockets are deep enough you could get a custom crank made out of a billet by the guys that make up serious drag internals.

Another related question - did the cranks change when the firing pattern change through out the windsor series?

 

[Route666]

No it didn't, you can use either cam in any 302/351W

Yeh it'd require relatively deep pockets, but I dunno how much more than a standard billet crank though. I've emailed SCAT, asking them a couple of questions about it.

 

[Max Power]

I guess I don't understand your graphic above. You said it would fire every 90 degrees, yet it's still a 180 degree V-8? I'm confused as to what you mean.

The degree number assigned to a engine, as far as I remember, refers to the degrees of crankshaft rotation between cylinder firing pulses. The closer the firing is together, the smoother the engine tends to be. That's why the V-12s, which fire every 60 degrees, are so smooth and rev so high, a fact not lost on Ferrari.

180 degree engines have been used in a number of applications, mostly twin motorcycle engines, since with two cylinders, 180 degrees is the best you can get with a 4 stroke engine design. Many motorcycle mfgs got around this by going to two strokes, which fired twice as often. When Honda experimented with a 360 degree twin, they had problems with smoothness and crank stress from loads due to firing both cylinders at the same time. It ran like a thumper on steroids.

Honda did experiment with odd-fire cranks in there GP motorcycle program, as there was a real problem with the new radial tires the GP bikes were using. The power would come on in such a rush that the rear tire would suddenly snap out when accelerating out of corners, and then the driver would let off the throttle, causing the rear tire to grab again and high-side the rider.

Honda combated this by going to the odd-fire crank, which dramatically flattened the torque curve, eliminating the high-sides.

When Honda went Indycar racing in the early 90s, they tried the same formula for odd firing cranks for the cars. It failed miserably. They were well down on HP and they broke a lot.

 

[ron67fb]

Don't forget that the firing phases are usually tied with how the cylinder banks are angled. 60-degree V12s have 60 degrees between the cylinder banks, for example.

A 90-degree V8 would have a hard time using a 180-degree crank. Once a cylinder fires and that piston hits BDC, the crank has to rotate another 90 degrees before another cylinder can fire. This would cause some serious vibrations if you could get it to idle at all, which limits it to small displacements with high rev ranges.

There's a reason you don't see any flat cranks for our engines. It just isn't worth it, and building 180-degree headers is cheaper and easier. A flat crank V8 is made to circumvent the "no 180-degree headers" rule, and nothing else. Bikes and two-strokes are a different story. Rules non-withstanding, it would be smarter and cheaper to turbocharge your engine and gain over %100 more power than to fart around with $3000+ custom flat cranks for an extra 5%.

 

[brianj5600]

Hasn't the pushrod Corvette been pretty successful against the red cars you speak of? WJ showed up at Ennis in the late 80's with a car that sounded almost like a 6 cyl. It ran ok, but it was a V8. I don't know, but I guess he was messing with phasing. 90* cranks with 90* v are naturally balanced. I believe 180* cranks require extra counter balancers to keep vibration in check. Ditto on the turbo idea. Tons of bottom end and tons of top end.

 

[Route666]

Well, I'll try and explain it, you need pictures really, and I'll try and find some links.

Max, it's still the same 90 degree block, but with a 180 degree crank.

When looking at the engine from the front, the crank spins clockwise. (I actually don't know which way they spin lol, but let's say it's this way, it works either way, just reverse things) - Now, the first and last rod journals are at 0 degrees, and number 2 and 3 are at 180 degrees, making it like a 4 cylinder crankshaft, only there is two rods connected per rod journal.

For simplicity's sake, lets say the engine fires at TDC.

So number one gets to TDC and fires, then the crank rotates 90 degrees. This puts number 5 and 8 at TDC, whether it is on the end of the exhaust or compression stroke is up to the camshaft, just like it is with normal windsors.

So to spread things out, let's make number 8 be at the end of compression. So number 8 fires, 90 degrees later, rod journals 2 and 3 are at TDC on bank 1 (being the bank with number 1 cylinder) so to continue that bank's 4-cylinder firing order, number 3 fires, another 90, and rod journals 2 and 3 are at TDC on bank 2, where number 6 fires (being number 3 on the reversed 4-cylinder bank)

Now, 90 degrees later, journals 1 and 4 are back to TDC on bank 1, continuing the 4-cyl firing order, number 4 fires, 90 degrees pass, and number 5 fires.

Another 90 and journals 2 and 3 are back to TDC on bank 1, and 2 fires, being the last on that bank. 90 degrees later and 7 fires. 90 degrees later and 1 and 4 journals are back to TDC on bank 1, number 1 cylinder to fire again.

Whether going back and forth between the banks like this would have more vibration than a standard setup I don't actually know, but it looks more even than the windsor firing orders, that sometimes have a couple next to each other firing, either on the same bank, like number 1 and 5 at the same time.

I see what you're saying Ron, and it has been said that 180 cranks aren't good for low rpms, but those motors using them fire two cylinders at once, making it a big displacement 4 cylinder in effect. I propose that the flat crank should have inherent internal balance, plus should be smoother if run like two 4 cylinder motors alternating sides. In the firing order I came up with, no two cylinders on the same bank fire in a row, they are always bank 1, 2, 1, 2, ... and no two cylinders on the same rod journal fire right after each other either - the folloing cylinder fired is at least staggered by bank and by rod journal. Whereas if you look at standard windsor firing orders, you have two on the same bank, next to each other firing one after the other, and cylinders on the same rod journal firing one after the other.

EDIT: Here we go,

The crank would be like the 4 cylinder one in the top left.