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HelicopterEngines Plugs Mufflers Fuel › OS91C-spec PS VIPERHEAD
05-03-2005 06:29 PM  12 years agoPost 1
Raptor Rulezzz

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Rockanje, Zuid-Holland - The Netherlands

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Hi all,

I considering getting 2 dual plug viperheads for my OS91 C-specs because they should give me a bit more power and more consistent running.

Is there anyone out there who can comment on this? (who is already using this combo?)

I'm going to use 30% Wildcat helimix / 30% CY Wildcat

Thanks for the info!

Richard



Proud Member of Team QuickUK, Team Duralite & Sponsored by V-blades & 4rc.nl

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05-03-2005 06:54 PM  12 years agoPost 2
3DPP

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Vienna/Austria

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I have one, test him on OS and Webra after hole modification.
If you are using a muffler then a power increase is there because of higher compression.
Put out the shim on the OS head it´s the same effect.
If you use a pipe or MP2 there is no power increase and at most you have to add a shim too.
From idle to mid range you can run the motor a little more rich without four stroking, smoother run.

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05-03-2005 06:55 PM  12 years agoPost 3
Raptor Rulezzz

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Rockanje, Zuid-Holland - The Netherlands

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Thanks for the info already.

I forgot to mension I'm using a MP2 90.

Cheers,

Richard



Proud Member of Team QuickUK, Team Duralite & Sponsored by V-blades & 4rc.nl

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05-03-2005 09:22 PM  12 years agoPost 4
Gary

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Crosby, Texas

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I've got 2 set up with the Viper head and 2 without and I can't really say there is a difference, that I can notice anyway.

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05-03-2005 09:44 PM  12 years agoPost 5
3DPP

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Vienna/Austria

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Yes for sure there is a different in fuel consumption and with muffler power increase, but not with pipe
I had some tests and use a telemetry system, thats data during flyght and not by feeling

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05-04-2005 05:32 AM  12 years agoPost 6
Fredrik R

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Habo, Sweden

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Got one on my C-spec with MP2 and it runs very smooth with the Viperhead. But power increase, I dont know. Maybee a little.


Fredrik

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05-04-2005 08:15 AM  12 years agoPost 7
3DPP

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Vienna/Austria

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May be this feeling is from the higher torque which come with the higher compression and the MP2 isn´t a real pipe it´s a mini pipe, like the Magic Pipe from Webra or some of the Westons, which having broader resonance. But there also , if you make your compression perfect, so that it´s the same as with the viperhead, no power increase, that means same pitch at same high rpm.
With a real tuning pipe like the Hat. 970 the high compression is to much and you have to add shims, because the pipe load the motor like a turbo but in another way.
If you load to much you get predetonations from the to early ignition because of to high compression.
If you run a muffler it´s another story, because this one isn´t loading the motor, there the much higher compression has big effect.
Also the two plugs are very good for smooth him out from idle to midrange.
I have a lot of tests with dual plug heads, start was with the Bellwood dual plug head on my Webra 75.

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07-26-2005 02:41 PM  12 years agoPost 8
Ron Henry

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Atlanta area, GA - USA

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3DPP that's not necessarily true... If you shim the Viperhead to the same tolerance of the regular C-Spec head, there isn't a change in compression. From the designers mouth himself, the Viperhead broadens the torque band of the O.S. slightly. It doesn't necessarily make more power; it helps the engine to stay in it's powerband a bit better. If you're running the Blue PS head, you're accomplishing pretty much the same thing. I've been running the 970 on 30% on on my C-Spec for the last 3 months with 0 problems with detonation. The engine actually runs cooler, gets far better fuel economy and makes excellent power. There's no hanging on the pipe when I shoot autos like I commonly see with the SB-17. Probably the only downside to the 970 is you have to get a touch creative when it comes to mounting it but other than that, there is no negative to it. In my opinion it performs better than some exhaust systems costing 60 - 80 dollars more.

- Ron Henry
http://kaizenrc.com/forum

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07-26-2005 02:54 PM  12 years agoPost 9
Jason WAI

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Hong Kong

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I'm considering the OS91 Viper too. My concern is that...... Is the increased of power worth for the added cost? The price difference between OS91 and OS91 Viper is about $100 to $120 more..... (no matter the Cspec or Cspec PS)

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07-26-2005 03:09 PM  12 years agoPost 10
Ron Henry

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Atlanta area, GA - USA

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Jason Viperhead doesn't make a night and day difference in the power dept.It does broaden the engine's torque band which will allow you to get away with loading the heli a bit harder before the headspeed starts to drop off. If substantially more power is what you're after, I'd contact OMI and ask for the Skunkworks O'neal big bore carb with the cline regulator. You'll notice a much bigger difference in power and the engine will run far more consistently. From a full main tank to 1/4 inch of fuel in the header with no change in performance.

- Ron Henry
http://kaizenrc.com/forum

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07-26-2005 03:12 PM  12 years agoPost 11
pilotError

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Long Island, NY

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OS 91

I agree, the Viper head does cool a little better, but for the money the cline system is the way to go for more power / better consistency.

Mike...

Good Judgement comes from Experience. Great Judgement comes from Bad Experience.

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07-26-2005 03:25 PM  12 years agoPost 12
Jason WAI

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Hong Kong

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Thanks Ron , Thanks Mike

sorry for asking but What is actually a " cline regulator " ? Is it a part of stock design ?

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07-26-2005 03:33 PM  12 years agoPost 13
pilotError

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Long Island, NY

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Cline

He modifies the back plate to use crank pressure (already done on the ps) and uses a regulator just like the YS motors do. He also bores the carb out.

There's some better explanations of it on here, look for a thread by rstacy within the past couple of weeks and toward the end of the thread it goes into detail about everything.

Mike...

Good Judgement comes from Experience. Great Judgement comes from Bad Experience.

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07-27-2005 02:38 AM  12 years agoPost 14
Chris.C

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Hong Kong

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I have two Cspec modified by Scott Gray and he installed the C-line regulators without bored out the carb. Both engines run perfectly.

So I guess the bored carb gives slightly more rpm but how does it affect the power and torque band of the engine?

Chris

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07-27-2005 06:55 AM  12 years agoPost 15
Fredrik R

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Habo, Sweden

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HT 970 pipe

Ron,

What length are you using on the 970?


Fredrik

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07-27-2005 07:15 AM  12 years agoPost 16
Vicky

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Hong Kong

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Hi Friend,

I am using YS91 with Funtech muffer. I am impressed by OS91 Cspec PS with Viperhead with wider torque band.

Is it suitable for F3C, especially hovering? If yes, what muffer and what % nitro of fuel do you suggest?

Vicky

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07-27-2005 01:41 PM  12 years agoPost 17
Ron Henry

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Atlanta area, GA - USA

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Raptorman, I'm using a Zimmerman header which starts out at around 180mm in length. I cut about 15mm off of it. Depending on what your target headspeed is, you may want to go a bit shorter. The engine makes more power everywhere with the bored carb. I ran the regular cline setup for a few months before getting one with the bored carb. The engine runs just as consistent, but pulls much better through heavy loading than before. I wouldn't say that anything suffers from the big bore carb other than perhaps fuel economy. You gotta feed it.

- Ron Henry
http://kaizenrc.com/forum

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07-27-2005 02:02 PM  12 years agoPost 18
TMoore

rrMaster

Cookeville, TN

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Doing the work that James does at OMI is not for the faint of heart. I just did my own carb and can tell you that it is not a quick 15 minute procedure. The machining of the bore, disassembly and modification is time consuming. You can't do it with a Dremel so don't bother unless you like buying new carb internals. What Steve and James did is nothing short of dedication. They essentially fixed the OS carb to run like it is supposed to.

Once a carb has had the cline installed it is almost impossible to extract the jet without destroying it due to the existing mods to that jet. There are no jets available to buy. So, this makes doing the big bore option to an existing Cline equipped carb very difficult at best. It might be better to start with a new carb.

In short, sending your 60K carb to OMI is the very best way to insure that your C-Spec runs to its full potential. What James O'Neal does is worth every cent, in fact it is downright inexpensive considering the work that is involved.

TM

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07-27-2005 02:14 PM  12 years agoPost 19
Ron Henry

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Atlanta area, GA - USA

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Amen brother Moore....

- Ron Henry
http://kaizenrc.com/forum

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07-27-2005 02:17 PM  12 years agoPost 20
TMoore

rrMaster

Cookeville, TN

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Ron,

Welcome to Team Blue.

Terry

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HelicopterEngines Plugs Mufflers Fuel › OS91C-spec PS VIPERHEAD
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