Mailing List flyrotary@lancaironline.net Message #36154
From: <wrjjrs@aol.com>
Subject: Re: [FlyRotary] Re: Engine noise and changes in timeing and mixture.
Date: Tue, 13 Mar 2007 15:22:52 -0400
To: <flyrotary@lancaironline.net>
Enerest, Please note I mis-typed the line and I believe the noise will increase again as the tuning improves. There are many factors here, timing, mixture and exhaust tuning. If all the other factors remain the same I have found that ported engines are usually quieter when too rich. This is anecdotal, I haven't recorded it with a DB meter. My personal explaination is that the cylinder pressures are higher when better tuned and the sudden port opening in a rotary or 2-cycle causes a louder "bark" The rotary is particularly bad in this respect.
Bill Jepson
 
 
-----Original Message-----
From: echristley@nc.rr.com
To: flyrotary@lancaironline.net
Sent: Tue, 13 Mar 2007 8:53 AM
Subject: [FlyRotary] Re: Engine noise and changes in timeing and mixture.

WRJJRS@aol.com wrote: 
 
> For Tracy, 
> When I was actively tuning race cars we had a truism that I often > used, "everything changes everything". This was a drastic > oversimplification, but none the less was true. If you have an engine > running very well, a seemingly minor change WILL change exhaust note > or timber. On the dyno you would find some adjustments did little, > others a great deal. The fact is as you get the mixture closer to > right I am afraid you will hear the exhaust not come back up in volume. 
> Bill Jepson 
 
Maybe not, Bill. Without the snubbers, there would be some unknown and possibly variable delay in the closing. There would also possibly be varying delays between different injectors. This variability might not be enough to feel a vibration, but the exhaust pulse would be slightly stronger from one chamber than the other. It would only be detected as more noise and would express itself as a slop factor in tuning. Remove the variability and the tuning can be more exact since the same amount of fuel will be delivered every time, giving Tracy that extra 100RPM. 
 
Possible? 
 
--   ,|"|"|, Ernest Christley | 
----===<{{(oQo)}}>===---- Dyke Delta Builder | 
  o| d |o http://ernest.isa-geek.org
 
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