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Date: Sat, 31 Jul 2004 08:19:51 -0400
From: Mike Robert <pmrobert@bellsouth.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Turbo and the EC2
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DaveLeonard wrote:

> That's great data to have Rusty, thanks for the contribution.
>  
> Now I just need to figure out a way to make it useful.
>  
> Dave Leonard
>
>     -----Original Message-----
>
>     It could be that   with faster combustion wave propagation that
>     you would want the timing of the lead and trail closer in timing
>     rather than further or possibly vice versa {:>). 
>     . 
>     Ed Anderson
>      
>     Exactly right Ed, or vice versa  :-)
>      
>     Through the miracle of copy and paste, I'll attach the timing
>     split from my old FD engine computer.  Keep in mind that this is
>     NOT the stock Mazda timing, though it's probably close to it.  The
>     top row is the scale in RPM, and the first column is the scale in
>     inches of mercury.   The numbers in the box represent the
>     difference in degrees between when the leading, and trailing
>     ignition will fire.  Positive numbers indicate that the leading
>     fires before the trailing. 
>      
>     It's interesting to note that aside from the idle range, the
>     timing split is 0 until you get to around sea level pressure. 
>     From there, it quickly increases to about a maximum level for the
>     rest of the boost range.  From this, I would assume that
>     increasing the split reduces the chance of detonation.  
>      
>     Still hard to say how important this is for us.  How much greater
>     is the chance of detonation?  How much power would you lose if you
>     had to run on trailing ignition only with the split built in?  
>      
>     Cheers,
>     Rusty (doing my turbo duties, though I'm not sure why) 
>
The auto people generally converge on a zero split at 100 kpa then head 
for an 8 degree split under any significant boost. An 8 degree split at 
idle makes for smoothness. I use L-32 T-30 degrees timing at max load 
(>80 kpa MAP, > 6K rpm) in a ported NA 12A - that's dyno proven to make 
the best power. One must remember that there are significant changes in 
emissions related to the split, the factory ECU parameters are more for 
emissions than max power and reliability. I have a Mazda authored SAE 
paper here somewhere that explains this in detail, I'll be looking for 
it. There was tons of good stuff in it that was written by the actual 
engineers that developed the rotary.

     -Mike