-----Original Message-----
From: kevin lane <n3773@comcast.net>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Sun, 22 Jul 2007 11:01 pm
Subject: [FlyRotary] last time, i promise - carb vs EFI



I still never got an answer to my original question;  how much more power comes from EFI vs. carb?  or is it a case that efi is just better tuned at all rpms since it has so many easily controllable parameters?  does efi produce an optimum mixture and finer fuel droplets that can't be matched by the carb?  if it does produce more complete burning and efficiency, how much?  I hear these type stmts, but never numbers.  are we talking 5%, 10%, 20%?    kevin (renesis in my future :-)

Kevin,
 To properly answer your question, It depends on lots of other factors. If you use the same engine and manifold set up and have the exact same level of restriction, (slide throttle vs. slide throttle) the difference will be minimal at WOT. When they were testing on the big dyno at Kawasaki the difference at WOT,(unning 4 cycles) was about 3% in favor of TIMED PORT EFI. They tested some of the 2 cycles that actually did better with carbs. The thought was there was dampening of the reversed pulse at the time. Also PORT EFI was hard to get to work on 2 cycles due to the flow reversals. Most of the 2 strokes went to direct injection which was better, albiet somwhat more complicated. On the 4 cycles EFI had a advantage almost everywhere else. Sometimes a drastic advantage in mid-range operation. The dyno guys also liked the remote tuneability of the EFI which made it much easier to tune new engine combinations. Interestingly the worst thing for EFI on bikes was trying to get it to be smooth at low throttle openings. The earliest ones were so sudden off the like I thought they would pull your arms out of their sockets! Later versions were de-tuned at idle speed to improve this area.

Bill Jepson
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