RunRyder - Engine setup woes

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Beginners Corner > Engine setup woes - ideas ?

Eolo Boy
Heliman
Location: Lancashire, UK

I've lost my needle settings for an engine (webra 35F/promix carb) which I've just refurbed. Both main and low speed needles are fully clockwise (i.e. no fuel flow) The engine is installed in a model equipped with headloaders so adjustment should be straight forward. How do I get it running and the tuned ? How would you guys approach the situation (assuming that the manufacturers default settings are unknown) ? Is it something like

* 3 turns on each and try and start it
* adjust low speed with engine idling
* adjust main at full throttle
* twiddle with both at hover/mid setting ?

thanks

06-15-2008 10:55 AM

nivlek
Elite Veteran
Location: Norfolk England

http://www.webra-austria.at/download/en/motor.pdf

At the end of the day , it gets dark .

06-15-2008 11:44 AM

Mike0251
Senior Heliman
Location: Hills of the Blue Ridge VA

http://www.webraengines.com/download/en/motor.pdf
Has exactly what you are looking for.
top of the day nivlek! we posted within minutes of each other...lol.

06-15-2008 11:48 AM

Eolo Boy
Heliman
Location: Lancashire, UK

Thanks guys, I found the link just after posting the question. With the carb set at the factory settings (3-3.5 low, 2-2.5 main) absolutely nothing

I'm using CP 0% plus enya 3 (high compression engine plus pipe). The engine didn't attempt to fire, not even once. After a bit of head scratching it appeared to be wayyyy to rich. Backed the main and low to approx 2 turns and bingo

Headloaders are great, really easy to see the transitioning from low to high speed needles. They engine is nice and smokey and runs at about 90 degrees according to my non-calibrated finger. The question is, how much smoke is right ?

thanks

06-15-2008 08:03 PM

speeddemon370
Veteran
Location: Spruce Grove, Alberta, Canada

Imo, you should be able to see the smoke when you're flying but just barely. However, I don't like to tune engines based on smoke and I learned that lesson the hard way from dirt bikes. Too much smoke and you're going to start fouling plugs. I'd reccomend getting it to the point where you feel it's running on the rich side but still running well and bolt it up to fly. Once flying expect to land frequently and adjust the mixture until you get that nice crisp throttle response but it dosen't remain at high rpm once you cut the throttle. (that means it's too lean) And it dosen't bog terribly once you gun the throttle (that means it's too rich). On heli's throttle response isn't that important. It's more of an indication of fuel settings but a throttle "punch" shouldn't stall it. During all this check you're temps. If you're using a gun try aim it right around the plug or the backplate. Don't measure by the exhaust, carb, or crank. 200-210deg f is absolutely perfect so if you can get it to be at that range when it lands and perform properly during the throttle movements stated above you're good to go.

with 2 ears and 1 mouth you should listen twice as much as you talk

06-15-2008 10:54 PM

HOMEPAGE

Eolo Boy
Heliman
Location: Lancashire, UK

Wow, thanks speeddemon370, what a reasoned scientific approach to engine setup. Can the adjustments be based on temperature alone or does lubrication still play a part in the equation (is this a daft newbie question?) Could the idea be extended to selection of nitro content / plug based on temperature

thanks

06-16-2008 08:10 PM

speeddemon370
Veteran
Location: Spruce Grove, Alberta, Canada

For the most part you need to be set up based on temperature. There are a couple ways to get cooler performance so to speak but nothing to really worry about. If you're not getting the proper lubrication you're temps are gonna skyrocket so they temps and lube go hand in hand. So to answer your question, yes. You can base all this on temperature and not worry about anything else. However, what you'll find is that you'll still be able to make your engine run quite nice and remain on the cooler side of the 200-210. This may sound great but you're actually cheating yourself out of the last approx 15-20% of the available horsepower right when you hit the tuning sweet spot. You'll know when you get it. Everything just smooths out and has that nice crisp "bark" to it when you snap the throttle. Patience is the key. Remembor at any given moment you can be a 1/8th turn from peak performance while still being completely safe with your engine.

More nitro content is going to be hotter. It will also predetonate (go boom before it's supposed to @tdc) easier than a lower nitro content. This is where shims and plugs come into play. A shimmed head is generally all you need when going up 10% or more in nitro content. However, as the engine gets old and looses compression you can adjust the combustion point of the engine by playing with the temp of the plug. Both shimming and plugs can achieve the same thing. Just depends on personal preference and what works. There's no replacement for displacement are the words that I live by. In otherwords, i'll play with shims till I'm blue in the face and use a different plug as more of a fine tuning last resort type of thing.

I read over what I wrote and I'm not sure I'm making alot of sense. It's pretty hard to describe but if you look up octane and ron/mon as well as compression ratios and the overall logistics of a diesel engine. You should be pretty well educated on the subject and be able to expirement with confidence. Remembor that nitro engines are a lot more similar to a diesel than a 2 stroke.

with 2 ears and 1 mouth you should listen twice as much as you talk

06-16-2008 11:53 PM

HOMEPAGE

nivlek
Elite Veteran
Location: Norfolk England

Quote
However, what you'll find is that you'll still be able to make your engine run quite nice and remain on the cooler side of the 200-210.

With zero nitro , you won't have a prayer of good power at those temps .

At the end of the day , it gets dark .

06-17-2008 07:23 AM

Eolo Boy
Heliman
Location: Lancashire, UK

Thanks nivlek and speeddemon370

Quote
With zero nitro , you won't have a prayer of good power at those temps

It's not good power which I seek but something more ellusive...good knowledge. I feel that I have a fairly good grasp of model helicopters, excepting delta offset but that's another subject, but engines and tuning seem to be a bit of a black art

Do you know of a good online resource for theory and operation of two-strokes ?

The theory of operation is probably well documented but it's the practical side of operation which I'd like to understand. So here's a hypothetical situation which I'd appreciate feedback on, outlining the thought process.....

You are the "engine guru" in your local club and turn up to the field to meet a group of disgruntled fellow heli-nuts huddled around a latest aquisition. It's a top of the range, mechanically perfect heli, setup to perfection but fitted with an unknown engine which steadfastly refuses to start. No markings on the engine, no idea if its ABC/AAC/RING, no manufacturers settings available on the planet. You examine the engine and note that it is piped and that the low and high speed needles are fully clockwise (off). The gauntlet has been laid down and not being one to resist a challenge you note that between you, you have 0%,10%,20% and 30% nitro fuel and a three plugs ranging from cold to hot. You have been told that unless the heli wins at the competion the following day, your flying site will become home to more lucrative car boot sales from now on. Incensed, you grab fuel, plugs and starter motor and head towards the heli...

OK what happens next (and no you can't swipe someone elses engine)

06-17-2008 08:09 PM

nivlek
Elite Veteran
Location: Norfolk England

One way to get a feel for tuning is to buy yourself a little aero engine , say a 15 , bolt it on a bench , fit a prop and learn what does what !
Maybe someone should write some tuning software for one of the sims !

At the end of the day , it gets dark .

06-17-2008 08:46 PM

speeddemon370
Veteran
Location: Spruce Grove, Alberta, Canada

To answer your hypothetical situation. I'd fill the tank with 20%. Put in the medium plug. Check for fuel leaks. Check for compression and exhaust pressure/fuel pressure, turn the low needle 1.5 turns out and the main needle 2 turns out. Check for crap and debris in the carb or throttle body. Start turning it over while manually choking it and using my handy dandy thumb as a throttle servo holding at approx half to 3/4 throttle. I'd take the main needle out at quarter turn increments until it sputtered to life even just barely, If i got to 3.5 or 4 turns out i'd return to 2 and start turning it in to see if it helped. If it hasn't started by now it'll be time to take the plug out and let things dry out in there because it will most certianly be flooded. If it's not flooded then there's obviously a fuel delivery issue that has to be corrected so proceed accordingly. This will also be the time to go over a couple more basics, maybe spray in some carb clean, check for leaks around the carb/cylinder head, twiddle your thumbs and turn red because you can't seem to make the friggin thing start! If that still didn't work I'd go back to 4 out and carry on with this method until it started or I gave up out of sheer frustration. Then i'd fine tune the main needle so at about half throttle everything sounded somewhat good. Then I'd set the low needle so there was no sputtering or leaning at low throttle, set the idle, punch the throttle a couple times and see how "snappy" it is and adjust from there. Get everything running as smoothly as I could and then check the temp, and start test flying. Be careful though! No wide open throttle on the bench or under "no load" conditions.

PS, this is the EXACT same procedure (with the exception of glow plugs and fuel pressure) that I use for stubborn weed eaters, chainsaws and lawnmowers.

with 2 ears and 1 mouth you should listen twice as much as you talk

06-18-2008 12:28 AM

HOMEPAGE

speeddemon370
Veteran
Location: Spruce Grove, Alberta, Canada

With zero nitro , you won't have a prayer of good power at those temps .
[quote]

I'm not sure if I understand what that was supposed to mean. With 0% nitro you don't make any power period. Regardless of temp. Engine probably won't even run. Explain?

with 2 ears and 1 mouth you should listen twice as much as you talk

06-18-2008 12:30 AM

HOMEPAGE

nivlek
Elite Veteran
Location: Norfolk England

Quote
I'm not sure if I understand what that was supposed to mean. With 0% nitro you don't make any power period. Regardless of temp. Engine probably won't even run. Explain?

What's not to understand ?
He has said that he is using Coolpower 0% nitro .

Quote
I'm using CP 0% plus enya

The Webra is a high compression engine and can produce good power without nitro , but at the temps that you quoted it would be running way too rich .
As for the "Engine probably won't even run" comment .......
However tuning would be easier with 5 to 10% nitro .

At the end of the day , it gets dark .

06-18-2008 06:58 AM

Eolo Boy
Heliman
Location: Lancashire, UK

Thanks for the info guys. My (mis)understandings from discussion are

1. Nitro is more volatile/powerful so detonates more easily and thus advances the timing. Does this mean the engine "pinks" like a car engine and sounds like ball bearings rattling around in the exhaust ?

2. This advance can be offset by using a cooler plug ?

3. The engine temperature is proportional to nitro content. The more volatile the fuel the more energy is dissipated as heat ?

4. and here's the bit I can't quite figure out

Quote
The Webra is a high compression engine and can produce good power without nitro , but at the temps that you quoted it would be running way too rich

based on the above assumptions 0% nitro means lower operating temperature. Would an engine running rich, run cooler due to excessive oil/lubrication not hotter ? so only a leaned out engine would reach these temperatures

sorry for asking these dumb questions but it's all part of the learning curve

06-18-2008 08:25 PM

nivlek
Elite Veteran
Location: Norfolk England

Quote
based on the above assumptions 0% nitro means lower operating temperature. Would an engine running rich, run cooler due to excessive oil/lubrication not hotter ? so only a leaned out engine would reach these temperatures

If the engine was fully peaked out for maximum power , it would run hotter with more nitro . However , in helis , it is not usual to have the engine fully tuned in especially on high nitro . In fact the engines run on high nitro are run rich which keeps the temperatures down . An engine running on high nitro will still run well even at these rich settings and still produce good power.
Typically heli engines run on high nitro are still using a hot plug , this is because the of the rich setting , if the engine was peaked out it would require a much cooler plug .
The high nitro , being more tolerant of being run rich also makes tuning easier .
Nitromethane has less energy than methanol (about half of it) , but it only requires about a third of the air that methanol requires to burn . This means that you use the fuel quicker (even if the engine wasn't being run rich). So in a given time you have more oil cooling the engine compared with an engine run with low nitro (plus high nitro fuels often have a higher percentage of oil ) , and you have unburned fuel cooling the engine with mixture being rich . The latent head of evaporation of methanol is very high (nitromethane is even better) .

When running straight fuel you don't have the luxury to run the engine that rich because the engine won't run smoothly , won't transition well and will have little power . Tuning the engine requires the tuning to be closer to perfect , you may only be able to go a couple of clicks on the needle richer than optimum power .

At the end of the day , it gets dark .

06-18-2008 08:59 PM

nivlek
Elite Veteran
Location: Norfolk England

Just in case you are wondering , adding more oil to straight fuel doesn't seem to work , I've already tried it . In fact , if anything the temperatures ended up higher .
There is an argument that reducing the oil content may work better because you then have a higher percentage of methanol which may allow you to run the engine slightly richer , in fact I used to use a fuel with 15% oil 85% methanol and had no problems (even on OS and YS engines) .

At the end of the day , it gets dark .

06-18-2008 09:13 PM

Eolo Boy
Heliman
Location: Lancashire, UK

Thanks for the info, things are somewhat clearer now

06-22-2008 08:56 AM

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Beginners Corner > Engine setup woes - ideas ?

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