Topic Subscribe
WATCH  2 pages [ <<    <    ( 1 )     2     NEXT    >> ]3438 viewsPOST REPLY
Thunder Power RC . Mikado . Futaba-RC
. .

Engines Plugs Mufflers Fuel

 >

OS.91SZ-H PS-Hyper vs OS.91SX-H 'C' Spec PS

alchemist

Veteran

Auckland,New Zealand

Can someone please explain the main differences and usages between the OS.91SZ-H PS-Hyper and OS.91SX-H 'C' Spec PS

I'm looking for the ultimate 3D 90 engine setup, OS is one obvious choice for reliability and support. I see a few differences like the pump mounts and carbs. What is unusual is the Hyper is posting a 3.3hp output and the 'C' Spec a 3.1hp output, however the 'C' Spec is more expensive.

Why is that?

Which one is the better engine for 3D in your opinion?

If money was not a consideration would you choose something else?

OS.91SZ-H PS-Hyper

VS

OS.91SX-H 'C' Spec PS

Cheers

01-24-2008 Over year old.
HOMEPAGE  
jsenicka

Elite Veteran

Hampton VA

Best choice (in my opinion) is an SZ-H, non pumped, with a OMI modified carb with Cline regulator.
The SZ PS has had some reliability issues with the pump. The C-SPEC PS is very finicky and difficult to tune.

Jim Senicka
Team Manager, GrandRC Flight Team

01-24-2008 Over year old.
JR-ric

Veteran

newport news VA

i agree......91 szh is the way to go with the OMI mode.....but if you didnt have the choice or the time to get OMI you can get pump but later on when you realize that the OMI is the way to go...you wont be able to with the pump unless you the the plate and carb to buy....but if you get a none pump...you will have the choice of geting the omi made in the future.....but the SZ-H is the way to go

Ricardo Maldonado
Team Curtis Youngblood Enterprise

01-25-2008 Over year old.
Dr.Ben

rrProfessor

Richmond, VA, USA

Right now,

SZ-H NON pumped + OMI/Cline system (or even bone stock if you can stand to run a toucher richer).

Ben Minor

01-25-2008 Over year old.
ehaga

Senior Heliman

Bærum, Norway

I find the OS 91SZ-H PS hard to tune. It runs on almost any needle settings, but it is hard to find that optimal needle-settings. The C-spec runs bad until you find the optimal needle-settings.

The SZ has more power compared to C-spec.

Have a look at YS 91SR. More like the C-spec in tuning, but with more power.

01-25-2008 Over year old.
alchemist

Veteran

Auckland,New Zealand

Thanks for the info

Sounds like simple is best...often the case.

So the OMI modified carb with Cline regulator is a fuel regulator bolted on the side plus a re-bore of the carb to 10.8mm?

If I was interested in going down this route I assume I just email James at http://www.oneals.com/Omitro.html and then send off my engine?

01-25-2008 Over year old.
HOMEPAGE  
Raptile

Senior Heliman

SLOVENIA-Logatec (EU)

Where can I buy the OMI/Cline system ???

Tnx

Futaba FASST 12FG | Raptor 90 V-Max V-BAR 4.0| Henseleit TDR 4.0 | PiroFreak =)

01-25-2008 Over year old.
Dr.Ben

rrProfessor

Richmond, VA, USA

James doesn't bore the SZ carbs. They come stock just 0.2mm smaller than the 10.8 bored ones. The performance difference from that size difference is basically undetectable. The SZ nonpumped carbs are thus a much better value to have OMI mod than the older 60K carbs were.

James doesn't "do" email much. Call him. Let me repeat. Do NOT email him; CALL him. I don't have his number handy right now.

Ben Minor

01-25-2008 Over year old.
rstacy

Elite Veteran

Rochester, NY

Where can I buy the OMI/Cline system ???
I'm looking for the ultimate 3D 90 engine setup, OS is one obvious choice for reliability and support
The ultimate can come in two flavors. Either the C-Spec with the OMI set up or the SZ-H with the OMI set up including Viper head. Awesome power!

With that said, I have had very good results with the OS.91SZ-H PS-Hyper. I find it to be easy to tune and it produces great power out of the box.

01-25-2008 Over year old.
HOMEPAGE  
Rymps

Key Veteran

Indianapolis

I am running an OS SZ pumped with a hyper head. I have no problems tunning. my settings are: main needle 1.5 open and the mid needle closed and the idle screw about 3-5 degrees rich. I am flying at 5000 feet. on warm days the main needle will be 1.5 on cold days 40-60 i set it to 1.2. I am also runng .016 on my head shims. I was thinking of running .012 at 5000 feet to see if it would be better.

01-25-2008 Over year old.
Conrod

Veteran

Melbourne, Florida

I'd go for the YS & 30%Coolpower. easy to tune and plenty of power has always been my experience. Another plus is that your main tank fuel line will last much longer.

01-26-2008 Over year old.
ferincr

Veteran

sometimes in Costa Rica sometimes in the US

Well, it seems like some people actually like the pumped version.
I'm also looking for a 2nd OS 91 engine to upgrade my R60 to a 90 and still not sure what to get.
I have a non pumped on my R90SE but since I'm pretty new and I don't know anybody that flies helis here I have nothing to compare it with.
I'm flying at 4800ft ASL so I'm in the hunt for power too.
So far I read a lot of no so hot comments on the pumped SZH (actually when I got my R90 Heliproz suggested me to get the non pumped which I did) but according to this thread there are few very good comments on the pumped one.
Another question...
Is there any difference between the black plastic pump that comes with the SZH and the one on the SX C spec on the pic above???
Thanks,

Intelligence chases me, but I'm a lot faster! Fernando

01-26-2008 Over year old.
Brett Horton

Key Veteran

---------

I am running the new OS.91SZ-H PS-Hyper in a Sylphide, no muffler pressure. I flew with Wayne Mann a couple weeks ago, He flew the machine as well and stated that it was the best running stock OS he had ever seen!
Purrs like a kitten. I have about 9 gallons through it at this point.

01-26-2008 Over year old.
ferincr

Veteran

sometimes in Costa Rica sometimes in the US

So it seems to be a hit or miss type of engine or am I wrong?

Intelligence chases me, but I'm a lot faster! Fernando

01-26-2008 Over year old.
RAK402

Key Veteran

Alhambra, CA

I have 11 flights on a pumped OS Hyper. The first five were spent tuning it.

It is still running rich (but I always run the rich). Lots of power, and good throttle response, so far (with the exception of transition from idle when first throttling up-which is a bit too rich-I am still tweaking).

At any rate, I like it so far.

I will know more over time.

01-27-2008 Over year old.
Rymps

Key Veteran

Indianapolis

the pumped is fine. i like mine better then the C=Spec pumped. If the pumped was so bad Bobby Watts would not be flying the pumped motor. check out his web site.

01-27-2008 Over year old.
Dr.Ben

rrProfessor

Richmond, VA, USA

When you have a PS engine that runs well, it runs well. I'll never dispute anyone that says that theirs work well. The problem is that the PS system unequivocally varies from engine to engine. Above there is a post from a gentleman who is having great luck with a PS engine in a Sylphide. I also know of a gentleman who helped design the PS system for OS that could never get it to work on his particular Sylphide. Then you'll have guys that can get it to work just fine, but they have to use muffler pressure. This can be on the exact same kind of model as another guy who doesn't need muffler pressure at all. Finally, you'll have those whose PS engines run fine for a few months to a season, and then the pump starts going south, typically manifested by a propensity to run lean by the end of the tank. There are countless threads on RR that reflect varying results with the SZ engines, and the variance is almost INvariably tied to the PS version ONLY. You just can't tell exactly what every one of the PS engines is going to do every time. It is for this reason that if I have to put my name on the line and suggest what I know will pretty much work 99.9% of the time, it's going to be either a bone stock SZ-H or that engine with a OMI/Cline reg attached.

Ben Minor

01-27-2008 Over year old.
WiscHeli

Veteran

Wisconsin USA

would a OS .91 SZ-H Hyper w60M-C Carb w/No pump just muffler pressure make a good reliable sport flying 91 engine

T-Rex450seV2,, 600N-Pro ..500CF... Jr 9303 Syn 72Mhz

01-27-2008 Over year old.
Rymps

Key Veteran

Indianapolis

Good Point Dr Ben

I did not know that the pumps very from motor to motor. I am running muffler presure with my pumped motor. why would you not? I havent tried to run the motor with out muffler presure.

01-27-2008 Over year old.
Dr.Ben

rrProfessor

Richmond, VA, USA

The whole reason for a pumped engine is to avoid the annoyances of muffler pressure and for absolute needle consistency. If I need to run pressure to make the pump work, I'll just run muffler pressure alone or a uniflow set up and keep it simpler still.

Ben

01-27-2008 Over year old.
WATCH  2 pages [ <<    <    ( 1 )     2     NEXT    >> ]3438 viewsPOST REPLY
HeliProz . Boca Bearings . ExperienceRC
. .

Engines Plugs Mufflers Fuel

 >

OS.91SZ-H PS-Hyper vs OS.91SX-H 'C' Spec PS

 Print TOPIC Advertisers 

Topic Subscribe

Tuesday, July 22 - 7:57 pm - Copyright © 2000 - 2014 runryder.com | email | runryder needs cookie