Ignition Only

[Eric Bryant]

> From: Buchholz, Steven [mailto:Steven.Buchholz at kla-tencor.com]
> Subject: RE: Ignition Only
> 
> As far as the concerns about misfires on the wasted spark system, the
> immediate response that comes to me is the fact that 
> motorcycles have been
> using this technique for decades.  Motorcycle engines 
> characteristically
> have a relatively high specific power output and are high 
> revving ... I
> don't seem to hear much about problems there.  I guess there 
> aren't too many
> supercharged MC engines though.  

I'm coming into the discussion a bit late, so forgive me if I'm repeating
something or not understanding the topic completely.

Motorcycles predominately uses a waste-spark DIS setup, with certain engine
configurations being the exception (the 70-degree V4 in my Vmax uses a
180-degree crank, so no two pistons are at TDC at the same time).  The
production CBR250RR has a redline of 19,000 RPM, and it's running two coils
as a waste-spark setup on an inline four.  As far as I know, that's the
fastest-spinning four-stroke in production.

There's not a whole lot of supercharged motorcycles, but there's a fair
number of turbocharged motorcycles out there that run stock ignition systems
without problems (at least there's no problems until the timing needs to be
retarded with increasing boost levels).

A fairly-common problem in carburated motorcycles is fouled plugs, and
fouling one plug on a waste-spark system can mean a misfire on two
cylinders.  The other plug on the shared coil can foul very quickly in this
case, and now you've dropped two cylinders instead of one.  On a
four-cylinder, this does tend to impact the power just a bit.

Eric Bryant
mailto:bryante at ghsp.com
http://www.novagate.com/~bryante 



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