Subject: [FlyRotary] Re: fun with EGT's

 

Perry,

I'm experiencing the same thing on my 3-rotor,  the center rotor runs

cooler than the other two.  (Keep in mind that this is w/o a prop, so most

of this is meaningless per Tracy's EM-2 calibration instructions.)  I've

tried changing Mode 5 rich and lean to no avail.  Last weekend, I switched

EGT sensors around, hoping that it was a sensor problem. Not! Then I

swapped injectors around, which didn't help.  I'm thinking that it might be

a result of my intake plenum design.  I have decided to wait until I have a

prop installed to do any further trouble-shooting.

 

Mark S.

 

One thing to be careful of in balancing the EGTs is to know which side of peak you are.  You may have two rotors giving the same EGT at some condition, but one is lean of peak and the other rich of peak.  I had this on my 20B on the dyno.  I don’t remember now exactly how it went, but I think rotor 2 was higher at max power mixture than rotor 3.  I was puzzled why, as I leaned out, rotors #1 and #3 would swap - #1 would go down, #3 would go up.  Until I realized they were on different sides of peak.

 

And intake plenum is also a factor.  The spread would vary with RPM; and although they remained within 75 F spread, the #1 rotor would depart from the other two as rpm increased – which correlated with the plenum being least restrictive for #1.  More air flow, same amount of fuel, leaner mixture.

 

I guess best bet is to set for the minimum spread at cruise condition (all on same side of peak).

 

Al