Aircooled VW South Africa

just so you know, the 917 is a 180deg V engine, not a horizontally opposed.

Tony Z wrote:just so you know, the 917 is a 180deg V engine, not a horizontally opposed.

and the Ferrari 12 cylinder 'boxer' is also technically a 180deg V

Porsche Boxer 4 crank - perfectly balanced as you put it



917

MINCE wrote:

Tony Z wrote:just so you know, the 917 is a 180deg V engine, not a horizontally opposed.

and the Ferrari 12 cylinder 'boxer' is also technically a 180deg V

Technically a boxer engine is not a engine type anyway
What is commonly referred to as a boxer engine is a Horizontally opposed engine design.

The Ferrari boxer is a 180deg V-12. Nothing technically about it.

well there you go again, laying the knowledge smack-down!
Legend you!

MINCE wrote:Thanks Tony for clearing EVERYTHING UP. Now I believe we are all on the same page.

MINCE wrote:well there you go again, laying the knowledge smack-down!
Legend you!

Sarcasm isnt your forte

I wasn't being sarcastic. I was been sincere, I was in quite an awesome mood today

But thanks dude, I learnt a lot

In that case you are welcome

http://moto2-usa.blogspot.com/2010/09/s ... shaft.html

The picture shows what a crank of an 180deg v4 would look like. As you can see it will we lighter than a boxer crank, as less material would be needed and also shorter. The crank housing would also be shorter and lighter. Also see picture of a similar design http://www.esportbike.com/forums/showth ... p?t=140664

I have done a fair bit of thinking about this, since your question does make sense. And yes, a V4 would probably work. The timing would have to obviously change to 1-3-4-2 or 1-4-2-3, but that is part and parcel of designing a new engine.
Here comes a few thoughts....
1-4-3-2 firing order might not be such a good idea with the center mounted single carb. The fuel will constantly be changing direction as each inlet stroke is on a different side of the engine. So having the firing order 1-3-4-2 would bring it back into touch with the stock idea of having 2 intake strokes per side to get more fuel deeper into the manifold before it tries to change direction.
Crank flex, vibration and firing order go hand in hand. I dont know enough to comment on this, but I do know it is a fairly big design item. And remember, a car crank will flex more than a bike crank because of the power per stroke. A bike makes power through the use of revs.

I cant stop thinking though that by making the crank shorter, the cylinder spacing will be closer and thus the cooling will not be as good. For the bigger more robust aircooled engines (T4) VW made the crank and block longer and moved the cylinders further away from each other to improve cooling.
I suspect that will be the biggest issue with changing it for a 180deg V4

and it just hit me.... a 180deg V4 wont work!!!

Simple reason. The beetle uses a center mounted camshaft which only has 4 lobes. Each opposing cylinder shares the lobes. So being a 4 stroke, each opposing cylinder NEEDS to have its power stroke 360deg (crank) apart - which equates to half a rev of the cam. Which puts on pair of opposing cylinders either at TDC or BDC when the crank gear is at zero. This is not possible with a V4 as the opposing cylinders will be 180 crank degrees out of synch with each other, not 360deg as in a H engine.
It can work with overhead cams or an individual cam per side of the engine. But as the beetle was designed to be cheap, it has to be horizontally opposed to use the single camshaft.

The V4 cooling issue can be solved by a longer center main bearing, bringing it back to stock length.

next thing you guys are going to start digging into flat-plane & cross-plane cranks

eben wrote: next thing you guys are going to start digging into flat-plane & cross-plane cranks

If I am not mistaken, that has to do with the inlet manifold, not the crank - correct me if I am wrong

Tony Z wrote:

eben wrote: next thing you guys are going to start digging into flat-plane & cross-plane cranks

If I am not mistaken, that has to do with the inlet manifold, not the crank - correct me if I am wrong

No it has to do with the crank layout on V8-plus engines

http://en.wikipedia.org/wiki/V8_engine# ... aft_design

big article....
I was thinking about single and dual plane manifolds.