RunRyder - Webra 91 P5 Hi, Nitro conversion

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Gasser Model RC Helicopters > Webra 91 P5 Hi, Nitro conversion

Fixit
Key Veteran
Location: UK

Webra 91 P5 Hi Nitro conversion

I have two of these Webra 91 P5 Hi engines and it’s been made very clear they aren’t fit for purpose and even though they still leave a very bitter taste in my mouth after all this time I was thinking as the carbs have both dropped in bits would they run on nitro if I fit a OS carb and change the head or adapted it to take a glow plug.

01-16-2008 10:10 PM

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Fixit
Key Veteran
Location: UK

Not sure how this is going to workout but I've managed to fit a glow head and carb tonight, just need to give it a run and maybe stand back

01-17-2008 01:49 AM

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BeltFedBrowning
Senior Heliman
Location: Albany, MO USA

Keep the pictures coming. I'm curious to know how this works.

01-17-2008 02:29 AM

copperclad
Elite Veteran
Location: ..

hi
it looks great , i agree , a OS carb , i am thinking the metering in that webra carb has to be way different for gas , that engine might finally get to run , dana

01-17-2008 11:42 AM

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nadman
Heliman
Location: ...

Hi Fixit,

I did try the 91i with glow fuel when I had the engine in the R90 (15% oil no nitro). I didn't change anything other than needle setting. You need to open low/high needles.
As you know 91i is in my Trex600N now, haven't tested it yet. I still think the only problem with this engine is the Carb. It needs a real gas engine carb not a VERY SLIGTLY modified glow carb. I believe because of the carb design, this engine will run better with glow fuel.

01-17-2008 02:02 PM

Fixit
Key Veteran
Location: UK

Hi nadman

01-17-2008 03:23 PM

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Fixit
Key Veteran
Location: UK

purrs like a kitten

Hi nadman
I used a modified OS 91C-spec head and carb for this trial and did think about trying it on gas with the OS carb and webra head but I don’t think the rubber seals would last two minuets with gas.

I didn’t want to spend too much time building this engine into an airframe again

just in case I was wasting my time so I rigged it up in the vice with a 60 muffler and a 90 fan then just turned it over with the starter cone on the fan and hey presto it starts first time every time and purrs like a kitten on idle, it was very responsive using 20% but I couldnt rev it much with not having any load on it at all,it did sound nice though

The next thing is to try it in the T-rex 600 and see how it runs.

01-17-2008 03:37 PM

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nadman
Heliman
Location: ...

Fixit,

Glad to see its fine. We paid a lot for these engines, the least is to use them as glow engines. Which head and carb did you install?
I think I will end up converting mine to glow also.
If you decide to use the original head, you will need to cut the fan casing a bit.

01-17-2008 03:49 PM

Fixit
Key Veteran
Location: UK

nadman
Thanks for the tip,
Your right we did pay a lot of money for these engines and Webra should have recalled theses but instead they chose to leave us stranded and well out of pocket and bring out a bigger gas engine instaed.
The thing is I didn’t want another Nitro engine but apart from using my webra gas engine as a paper weight running it on nitro is the only other option unless like you say another petrol carb can be found that works.

I used the OS 91 Max SX head and OS 60K carb, the head just needs the lower skirt removing (easy job) then use the sleeve from the webra carb on the OS 60 K and that’s it but don’t forget I've still to fly it before I can tell you what it performs like.

PS
Did you have to cut the crank down to fit it in the 600 just like all the other guys

01-17-2008 04:26 PM

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nadman
Heliman
Location: ...

Fixit,

Yes, installatioln is just like YS80/90.

I tried starting the 91i. No such luck. There seems to be somthing wrong with the ignition. No spark. That is it. I will either machine a adaptor to fit a regular glow plug or just get a new 91 glow head and use the engine as a very over priced glow engine.
I don't think the 150i is any better. Looks like every one is staying away from it.
Seems my Cuatro (Zenoah conversion) is going to be my only gas heli.

01-17-2008 05:11 PM

Fixit
Key Veteran
Location: UK

Hi nadman
Both my ignition systems have packed in one was repaired at webra and the other is still broken, just couldn’t see the point in battling with them over it because the carbs have also both fallen apart.
nadman, you could spend hours setting the engine up and sometimes it might even run a fast idle but the very next day it wont start and you just spend hours again trying to start it.

I do hope the 150i is a better engine for the buyer’s sake but I very much doubt it, the carb looks the same for a start and we all know the problems you have with those.

The Nitro heads are a bit pricy new but you should be able to find loads of people with an old 91SX-H C Spec wanting to get rid of it, put a wanted add in the classified.

http://www.modelhelicopters.co.uk/a.../OS_91SX_H.html

New price for C Spec Head

29054110 : Heatsink Head (Gold) - 91SX-H C Spec
Heatsink Head (Gold) - 91SX-H C Spec

Price: £48.94 £57.50 Including VAT at 17.5%

01-17-2008 05:28 PM

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nadman
Heliman
Location: ...

Thanks for the info.

01-18-2008 06:16 AM

Fixit
Key Veteran
Location: UK

nadman
I've fit the webra in my 600 today and if you do use the C Spec head you will have to trim the fan shroud like you said but also grind a small amount off the cooling fins to allow the shroud to fit, the front skid also needs trimming before it will fit back on.

I also found the clutch wouldn’t fit if I used a washer under the crank nut, I think the webra nut is deeper than the ones OS use.

I will try and take some photos showing the head in place and the front skid after trimming.

01-18-2008 06:28 PM

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nivlek
rrProfessor
Location: Norfolk England

I would have used the Webra glow head , the OS and Webra 91 have slightly different bores which may well effect the combustion chamber shape , particularly the squish band . The compression ratio may also be disturbed . I'm not saying the conversion it won't work , but I wouldn't be suprised if it doesn't .

At the end of the day , it gets dark .

01-18-2008 06:50 PM

aarinsingh
Veteran
Location: Thompson, MB

I have a C-spec that has given me quite a bit of grief. If somebody wants it for parts or trade for something I can use I'm sure we can work something out

01-18-2008 06:54 PM

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Fixit
Key Veteran
Location: UK

Hi nivlek
I can still use the webra head but I would need to find a reducer from the spark plug to a glow.

If it doesn’t work it hasn’t cost me anything, just filling some time really

01-18-2008 07:34 PM

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nivlek
rrProfessor
Location: Norfolk England

How about using an adapter to fit one of the OS bioethanol plugs .
You could buy bioethanol at your local Morrisons and add some oil .
OS use 10% oil in their bioethanol engines , so it would be a compromise between a petrol and methanol engine !

At the end of the day , it gets dark .

01-18-2008 07:41 PM

Fixit
Key Veteran
Location: UK

I have never heard of RC engines using bioethanol until now, would I find one of these plugs at my local model shop?

01-18-2008 08:09 PM

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nivlek
rrProfessor
Location: Norfolk England

I doubt that they will have them in stock , but may be able to get them .

http://www.os-engines.co.jp/english/index.htm

At the end of the day , it gets dark .

01-18-2008 08:40 PM

Fixit
Key Veteran
Location: UK

Webra 91 P5 Hi running on glow fuel

Hey nivlek, I had the T-Rex600/webra 91 out today and after 15 min's messing with the needles the webra 91 preformed very well, the engine has never been run in so I'm still running it rich but at +14 pitch and a head speed of 1790 the climb out was unbelievable, no heating problems so far and a full tank returned 7mins flying time on a very rich setting. It’s still early days but it seems like the OS head and carb might not be such a bad match after all,

01-19-2008 10:01 PM

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Gasser Model RC Helicopters > Webra 91 P5 Hi, Nitro conversion

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