Tracy Crook wrote:

Paul, I must have misunderstood the idea of the trailing hole mod. In

the earlier versions of the engine, (read I go back to the distributor era)
the split timing was always used. In must of the electronic ignition cars I
have worked on the split timing was used by the factory. Is the intent to
use two separate ingition modules and coils firing at the same time just to
have redundancy? I didn't meant to set off a firestorm here but we will lose
power by not firing the trailing plug retarded. If firing both plug at the
same time is the intent I can at least understand it. Both plugs would need
to be totally independent of course. Dual coils dual ignition modules etc.

 In a related info item several of the ignition systems I have seen use

the dual lead coils. I am not sure what Tracy is using. If the dual lead
coils are used to fire two plugs it isn't dual ignition, since the dual lead
coils are 1 coil with a floating secondary, ie 1 secondary winding. If the
coil fails both plugs go dead. In the motorcycle business the 2 lead coils
are used all over on 4 cylinders wasting a spark in the ex stroke. I only
mention this since we found there were some interesting spark plug failures
since one plug fires backward. On the 2 lead coils Kawasaki recomended NOT
using fine wire electrode plugs (platinum or whatever) singe the reverse
spark would mess up the center electrode on the one firing backward. Just an
FYI. Hope I wasn't too redundant myself. Bill Jepson

Not trying to discourage experimentation with the enlarged hole but just
relaying my experiences.

Advancing the trailing plug timing does not result in a power loss.  In
fact, I gained a small amount and the EGT went down about 20 degrees.  The
emissions may have been affected since the goal of retarded timing was
reduced emissions from the reading I've done.  Powersport runns the same
timing on both plugs the last time I checked.  Everett Hatch did extensive
dyno work on the trailing ignition timing and confirmed the power increase
with advanced timing.

I am currently using the stock 86 - 91 Mazda coils (lead is a double ended
coil as described by Bill).  I've never noticed any difference in plug wear
with the reverse polarity.  Never used platinum plugs though.   I am getting
ready to change over to the LS-1 coils but not for redundancy (I already
have that).  Lower weight is the main advantage.

Tracy Crook
tcrook@rotaryaviation.com
www.rotaryaviation.com

 
The AirCraft Rotary Engine NewsLetter.  Powered by Linux.
ACRE NL web site. http://home.earthlink.net/~rotaryeng/            
Copyright 1998-2002 All world wide rights reserved.