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HomeAircraftHelicopterEngines Plugs Mufflers Fuel › OS 91 SZH and CY30% which shims
02-12-2006 09:30 PM  12 years agoPost 1
Rappy30

rrApprentice

South Riding, VA - US

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Which shims should I be using for the new 0s 91 SZH when run with 30% fuel?

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02-12-2006 09:33 PM  12 years agoPost 2
DOKEY

rrProfessor

Northamptonshire UK

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as it comes, 0.2mm.

(I am running WC 30%)

Ryan.

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02-12-2006 11:41 PM  12 years agoPost 3
Eury

rrProfessor

Dover NH

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There's a thread on one of the other sites that says that on 30% in warm weather, you should run both .2 shims. Apparently the performance isn't any different, but the engine runs cooler with no detonation.

I just installed a new SZ-H in my Freya, and I run CY 30% as well. I put the extra shim in. If nothing else, reducing the compression ratio should cause the engine to be easier to tune, and make it last longer. Personally, I just dropped $330 on this engine, any increase in longevity is welcome, so the extra shim is in.

Nick Crego

Citizen #0168

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02-13-2006 12:49 AM  12 years agoPost 4
Jerry Sudimick

rrVeteran

Connecticut

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.016" for the stock head with most 30% fuels. (2 thick shims)

.024" for the stock head with Magnum. (3 thick shims)

Jerry

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02-14-2006 04:38 AM  12 years agoPost 5
mkeigwin

rrApprentice

Marietta GA usa

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i just changed over to the mag 30% and would like to know if i should also add a shim to the os 50 also . i have not done it yet in the 91 sz but when i did change fuel i had to richin it up alot on the 91 . the 50 only has be run with the mag 30% . still breaking in the 50 .

Trex 600Pro
TTRed Line 53
ATG
Solid G
9252's
12 FGH

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02-14-2006 04:54 AM  12 years agoPost 6
ToXcell

rrNovice

Central California

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Correct Shims.....
Jerry,

Recomendation for 30% nitro and a Viper head?

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