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HomeRC & Power✈️Aircraft🚁HelicopterEngines Plugs Mufflers Fuel › Curious Comparision of OS Engines
04-21-2009 05:54 PM  10 years ago
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rocket_33

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Mount Pleasant, Michigan USA

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Curious Comparision of OS Engines
I was curious to ask those of you who have had both engines, how would you compare the power and smoothness of a current OS Max 91 HZ engine to the old OS Max 91 CSpec engine (assuming the proper muffler for each one). Is there truly a power difference, where is the power band between the two engines, what about the smoothness of the two engines?

Any other comments as to the comparison?
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04-21-2009 05:59 PM  10 years ago
Dr.Ben

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Richmond, VA, USA

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The HZ is noticeably more powerful, and that's in comparison to a fully tricked out, Cline Big Bore mod'ed C-Spec, not a stock one. The HZ is also noticeably smoother. The powerband of the HZ will allow to to make good hp at a higher peak rpm than the C-Spec. Thus C-Spec tuned mufflers are ill advised on HZ or SZ engines.

The HZ is truly a great engine. OS got it right.

Ben Minor
Peak Aircraft/Team Minicopter Team Futaba Team Kontronik USA
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04-21-2009 06:04 PM  10 years ago
rocket_33

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Excellent information, thank you for the post. You mentioned that it makes hp at a higher peak RPM.....what is the peak RPM on the motor?
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04-21-2009 06:12 PM  10 years ago
Dood

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Wescanson

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OS removes their discontinued engines from their products page so it's hard to find the specs.

The HZ shows a peak output of 3.4hp @ 15,000 w/ a practical RPM of 2,000-16,000

The SZ (stock), if I remember, is 3.3hp @ 15,000 w/ a practical RPM of 2,000-16,000

I have no idea what a stock C-Spec was rated at, much less a fully tricked-out C-Spec
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04-21-2009 06:26 PM  10 years ago
Roby

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Slovenija, Europe

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The C-Spec(stock) is 3hp@15.000 w/ a practical RPM of 2,000-16,000
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04-21-2009 06:36 PM  10 years ago
BarracudaHockey

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Jacksonville FL

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As I'm sure Ben would agree with (or I'd hope anyways)

Those HP ratings look pretty on the specs page but the only way to tell is to fly it because unless they put them on a dyno with the same fuel and weather and muffler, the comparsions are nothing but just numbers, even more so when you cross manufacturers.

To be honest, I'd be shocked if someone told me the published figures were anything more than a mathamatically modeled estimate.
Andy
AMA 77227
http://www.jaxrc.com
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04-22-2009 12:36 AM  10 years ago
jsenicka

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Eagle River, WI

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Agree with Dr. Ben 100%

I have CSPEC on 60K with OMI/Cline, CSPEC with BB 60K OMI/Cline and HZ with OMI/Cline.
I have run all on SB18 and SB18 1900rpm versions.
The HZ on the SB18/1900 is noticeably more powerful and smoother than my best BB CSPEC. I run the HZ engines at 15,750 on my TREX 700N's and they are amazing.

CSPEC was great with all the OMI work. The SZ made better power, but was also going to shake my R90's apart. The HZ is flat out awesome.
Jim Senicka
Team Manager, GrandRC Flight Team
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04-22-2009 12:46 AM  10 years ago
rocket_33

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Mount Pleasant, Michigan USA

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Thanks Jim

Your response really was what I am looking for in terms of info and your comparision because my CSpec is configured the way you described and I was actuall thinking of an HZ with the Cline mods as I have been really happy with it on my CSpec.

Do you know with the carb on the HZ are they doing any mods or just adding the regulator?
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04-22-2009 01:00 AM  10 years ago
jsenicka

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Eagle River, WI

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James has to make mods for the regulator to work. You need to increase suction at Wide Open Throttle to open the demand regulator. I know he does spraybar mods and some porting changes on the fuel passages.
I have mutt engines. SZ case, HZ crank, piston and pin, and my OMI modified 60M carbs from the SZ.
A true HZ has better porting to broaden the power band a bit more than mine, so it would be even better.
Jim Senicka
Team Manager, GrandRC Flight Team
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04-22-2009 01:57 AM  10 years ago
rocket_33

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Mount Pleasant, Michigan USA

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When you say he also does porting changes on the fuel passages are you referring to cylinder porting or that to the carb? I ask because the last time he did work on my CSpec it was strictly carb work.
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04-22-2009 04:49 AM  10 years ago
jsenicka

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Eagle River, WI

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He does work inside the carb to allow better fuel draw to pull the regulator open at WOT.
If you just bolt on a regulator it will run fine except at WOT when suction drops off, and it would then go lean.

My comment on "porting" was in relation to a true HZ motor having a different liner than my mutt SZ/HZ Hybrid. The new liner changes port timing on intake and exhaust to give a wider power band.
Jim Senicka
Team Manager, GrandRC Flight Team
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04-22-2009 06:00 PM  10 years ago
Dr.Ben

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Richmond, VA, USA

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Though the printed hp ratings for any mfg's engines are SO dependent on fuel, exhaust, and climate, I do know that OS's R&D facility does indeed have dyno equipment. There facilites have been described to me by someone who has seen them as something just short of what you'd associated with a NASCAR or INDY auto racing engine builder's facilities.

Ben Minor
Peak Aircraft/Team Minicopter Team Futaba Team Kontronik USA
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04-22-2009 07:01 PM  10 years ago
BarracudaHockey

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Jacksonville FL

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Thats interesting. I wondered, thanks.Andy
AMA 77227
http://www.jaxrc.com
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