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HomeAircraftHelicopterEngines Plugs Mufflers Fuel › difference in 91 engines?
01-22-2010 02:38 AM  8 years agoPost 1
nathan211

rrNovice

st.clair michigan

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I was wondering what the difference is between os 91 with the black head and the one with the blue head? I plan on getting a trex 700. thanks

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01-22-2010 03:13 AM  8 years agoPost 2
Duckster

rrApprentice

Brunei

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the black head is hz version while the blue is sz version, the different is the blue head got the diffrent type of piston which is flat piston head and dosent have the crank case heat case, while the hz got a piston renew version which os claim that piston is being lighten and got 5 small hole on the piston head and improve lots of performance and the black head cooling system is improve added with crank case heat case at the bottom plate, but my hz i ve replace with sz piston since it cheap and am happy with the performance at the moment i ll make a review after few gallon of flight

Trex 600,700 AND 450, GY611, GY401, OS5H, OS91HZ, MGP, HS65HB, Scorpion 2221-8,

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01-22-2010 04:09 AM  8 years agoPost 3
CoronaL

rrKey Veteran

Winnebago IL

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there are Align motors with teh blue head that is really an OS HZ motor, but with the older SZ style head on it. It's got all the internals of the OS HZ, but with the blue head. The OS blue head is the SZ or some older SX's even had blue heads.

Randy!!! I am the liquor

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01-22-2010 05:18 AM  8 years agoPost 4
Against Gravity

rrVeteran

Pottstown PA

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Align Blue
Yes this question gets asked often. The answer is, All the align Motor's are OS HZ's, With blue or black head. The only difference is the head, and as far as I can tell there is no performance difference between the head's.

AG

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01-22-2010 05:54 AM  8 years agoPost 5
Dr.Ben

rrMaster

Richmond, VA, USA

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The difference between the blue and black headed engines will show up mostly in stressed or otherwise inadequate cooling installations or in cases where the engine is to be run as close to maximum output as possible. In those situations, the black headed version cools better.

Ben Minor

Peak Aircraft/Team Minicopter Team Futaba Team Kontronik USA

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01-24-2010 11:35 PM  8 years agoPost 6
Furious Predator

rrProfessor

Kitchener, Ontario, Canada

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There are actually many differences with the two engines besides the head and piston, though those are the main ones.

the carb, and crank are completely different, as well as the cylinder liner. Most of those differences being wider ports with larger chamfers to allow for faster fuel/air intake.

i have all of the differences listed in detail somewhere, i'll post them if i can find it again. But having to model in 3D both engines in every detail showed me that these are two completely different beasts.

My initial plan while modeling was to see if it would be possible to upgrad an SZ to an HZ, but to do this would require buying almost every single major part that makes up your engine.

Shawn
Team Leisure-Tech
Team HelixRC

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01-25-2010 02:52 AM  8 years agoPost 7
cheepstr

rrApprentice

Ferndale WA

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os 91 hz
I think He is talking about the OS91hp the blue head and the Os91HZ the black head. they are the same engine. I asked the same question the only dif was the head
the sz is totaly different

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01-25-2010 09:30 PM  8 years agoPost 8
Furious Predator

rrProfessor

Kitchener, Ontario, Canada

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aaah, ok.

Shawn
Team Leisure-Tech
Team HelixRC

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