180 degree flat crank

180 degree flat crank

Post by Max-a-millio » Sun, 01 Mar 1998 04:00:00


Any knowledgable motorheads able to discuss the pros and cons of the 180
degree, flat-crank motor?  Would it be legal in WC?  Would it be
advantageous if it were?  

It's been a long time since I read the theory on this, but basically it
results in two cylinders firing at the same time i.e., two simultaneous
firing pulses every 180 degrees of crankshaft rotation instead of the
conventional one firing pulse every 90 degrees.  I have heard V8 motors
like this run at the drags and it is some kind of weird sounding....  like
a four banger on steriods.  

What I cannot remember is what advantage this has.  Flatter torque curve?
Higher torque curve?  ???   Help.  

Max  

 
 
 

180 degree flat crank

Post by John McC » Sun, 01 Mar 1998 04:00:00

Quote:

>Any knowledgable motorheads able to discuss the pros and cons of the 180
>degree, flat-crank motor?  Would it be legal in WC?  Would it be
>advantageous if it were?  

As far as I know, it's legal.  Jr Johnson & others have experimented with
such engines in the past.  I have to assume it's not advantageous,
since no-one is using it now.

Quote:
>It's been a long time since I read the theory on this, but basically it
>results in two cylinders firing at the same time i.e., two simultaneous
>firing pulses every 180 degrees of crankshaft rotation instead of the
>conventional one firing pulse every 90 degrees.  I have heard V8 motors
>like this run at the drags and it is some kind of weird sounding....  like
>a four banger on steriods.  
>What I cannot remember is what advantage this has.  Flatter torque curve?
>Higher torque curve?  ???   Help.  

I beleive there are two percieved advantages, one being that the exhaust
can be tuned more effectively (which would give a higher torque curve).
Unfortunately it is _extremely_ difficult to fit the exhaust headers needed
to be effective with a flat crank engine into a typical stock car (unless you
move the engine forward, which is usually a very bad thing from a
handleing perspective).

A second perceived advantage, which still seems to be the subject of
much debate as to whether it really exists, is that tires seem to have
slightly more traction with a flat crank engine.  The idea is that the tire
has a brief moment between torque pulses to "recover".  This was a
popular idea in motorcycle racing a while back, and also on the
Mercedes Indy engine (the "stock block" version that ran at Indy,
not the CART engine).

John