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10-27-2017, 10:12 AM
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Join Date: Oct 2010
Location: Phoenix, AZ
Posts: 2,820
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When I took the ROTAX course the instructor had a home made setup using the manifold pressure gage from a twin engine aircraft. It worked great, but the Carbmate seems to have a better resolution than what you can see on the analog gage. On the other hand maybe ?close enough? is good enough.
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10-27-2017, 02:26 PM
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Join Date: Jul 2009
Location: Coeur d'Alene, ID/Casa Grande, AZ
Posts: 654
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Quote:
Originally Posted by RFSchaller
When I took the ROTAX course the instructor had a home made setup using the manifold pressure gage from a twin engine aircraft. It worked great, but the Carbmate seems to have a better resolution than what you can see on the analog gage. On the other hand maybe ?close enough? is good enough.
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Richard...what airfield are you based @ in Phoenix?
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Ric Dickison
307 (CAB) Phantom
Search and Destroy (Can Tho RVN)
Distinguished Flying Cross Society Member
CH-47 & UH-1H "Driver"
Rotax 9 Series Service IRMT
RV-12 Kit#729 "N312RD" is now a full functioning fun machine!! Thanks Van for fulfilling my dream😎
2018 Dues Paid
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10-30-2017, 01:00 PM
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Join Date: Oct 2010
Location: Phoenix, AZ
Posts: 2,820
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Glendale. Desert Hangar Owners Hangar #24.
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10-30-2017, 02:28 PM
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Join Date: Sep 2013
Location: Fall City, WA
Posts: 138
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I am seeing a 0 to 56 degree delta (right side higher).
I was told (at my 200 hour / annual) this was good and no balancing was necessary by the mechanic doing the work. Is this consistent with what you are finding?
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B2RV12
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10-30-2017, 02:46 PM
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Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,035
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Personally I don't consider EGT as a reliable indication of carb. synch/balance. If it was reliable I think Rotax would have put it in the maint. documentation.
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.
Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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10-30-2017, 04:27 PM
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Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 2,065
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I balanced my carbs with two vacuum gages. When I was satisfied that they were closely synched I then transferred the vacuum gages L>R to make sure they was no gage bias. I then looked at EGT's for idle and off-idle and they are very closely matched. I frequently monitor the EGT's and will re-balance if differential ever changes...
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Jim Stricker
EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 622 
LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father & CFI) - USAAF 1st Lt. Captain B-17H
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10-30-2017, 09:19 PM
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Join Date: Oct 2010
Location: Phoenix, AZ
Posts: 2,820
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Above about 4000 RPM the intake manifolds will have the same pressure unless your throttle cables are completely out of whack, so I would not expect cruise RPM to be a good indicator of synchronization. The ROTAX instructor told us that is why you do the ignition check at 4000 RPM: to eliminate carb synch as a factor in rough running during the check. It makes sense considering the throttling profile of a butterfly valve. After about the first 50 degrees of rotation they have little restriction to airflow.
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06-07-2018, 06:39 PM
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Join Date: Oct 2006
Location: St Louis, MO
Posts: 323
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Quote:
Originally Posted by RFSchaller
Above about 4000 RPM the intake manifolds will have the same pressure unless your throttle cables are completely out of whack, so I would not expect cruise RPM to be a good indicator of synchronization. The ROTAX instructor told us that is why you do the ignition check at 4000 RPM: to eliminate carb synch as a factor in rough running during the check. It makes sense considering the throttling profile of a butterfly valve. After about the first 50 degrees of rotation they have little restriction to airflow.
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Hi, can changing spark plugs or prop dynamic balancing or adjusting/correcting prop blade pitch affect carb sync?
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06-07-2018, 08:33 PM
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Join Date: Oct 2010
Location: Phoenix, AZ
Posts: 2,820
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I would hardly call myself the ROTAX expert, but I don?t see how prop pitch or spark plugs would affect carb balance.
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06-07-2018, 09:12 PM
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Join Date: Jul 2009
Location: Coeur d'Alene, ID/Casa Grande, AZ
Posts: 654
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Quote:
Originally Posted by RFSchaller
Above about 4000 RPM the intake manifolds will have the same pressure unless your throttle cables are completely out of whack, so I would not expect cruise RPM to be a good indicator of synchronization. The ROTAX instructor told us that is why you do the ignition check at 4000 RPM: to eliminate carb synch as a factor in rough running during the check. It makes sense considering the throttling profile of a butterfly valve. After about the first 50 degrees of rotation they have little restriction to airflow.
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I?ve tried several dual gauge set-ups; but I like best the dual-needle gauge like Tony uses. Set your off-idle adjustment first @ 3800 rpm. Then adjust idle sync & idle rpm with your idle screws....she?ll purr like a kitten.
__________________
Ric Dickison
307 (CAB) Phantom
Search and Destroy (Can Tho RVN)
Distinguished Flying Cross Society Member
CH-47 & UH-1H "Driver"
Rotax 9 Series Service IRMT
RV-12 Kit#729 "N312RD" is now a full functioning fun machine!! Thanks Van for fulfilling my dream😎
2018 Dues Paid
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