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Question about Homelite conversion... - 12/18/2012 1:55 PM

1QwkSport2.5r

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I was referred to the Gas Boat section for some info on hopping up a Homelite 30cc engine. I have a low-usage 30cc with twin ringed piston. I believe it to be from the late 1990's, but I am not 100% sure. I would like to get as much power from this free engine as I can. I will most likely do away with the stock ignition system and flywheel and switch to (don't hate me...) glow ignition. Possibly CDI later, if I run into problems. I plan to use a Walbro WT499 carburetor as I plan to use methanol for fuel.

I'm looking for good ballpark numbers for Exhaust and transfer timing, squish clearance, and trapped compression ratio. I have a little more tear down to do before I degree the engine but I know the timing on this engine is pretty low.. Somewhere around 140° for exhaust duration. I'm accustomed to glow engines running with 160-180° exhaust duration and tuned exhaust systems...

Any help you guys are willing to provide will be greatly appreciated.

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RE: Question about Homelite conversion... - 12/18/2012 6:35 PM

lohring

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This is pretty much a waste of time. Homelites are over hung crankshaft engines with light duty connecting rods. Serious increases in power will overtax the engine. Even Zenoahs, a much more durable design, are starting to have rod bearing problems at the power levels they are now running. Run the Homelite as it is for fun then get a better engine when you want more power.

To give you an idea, the best modified 26 cc Zenoahs are putting out around 6 1/4 hp at 16,000 rpm. Stock Zenoahs put out around 4 hp at 14,000 rpm. Tthese figures are with tuned pipes. So far, electronic ignitions haven't been better than stock ignitions at these rpm and power levels. We have tested methanol based fuels with varying amounts of nitromethane in modified Zenoahs. There isn't much to be gained since the head volume and ignition timing are pretty fixed. We tested a 26 cc Quickdraw on standard model fuel with glow ignition. We didn't find glow plugs in our collection that would hold up for even one inertial dyno run. The engine did run well on low nitro fuel with spark ignition. However, 40% nitro burned the electrodes off. The electrodes damaged the piston and sleeve when they went out the exhaust.

Lohring Miller

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RE: Question about Homelite conversion... - 12/18/2012 8:16 PM

1QwkSport2.5r

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quote:

ORIGINAL: lohring

This is pretty much a waste of time. Homelites are over hung crankshaft engines with light duty connecting rods. Serious increases in power will overtax the engine. Even Zenoahs, a much more durable design, are starting to have rod bearing problems at the power levels they are now running. Run the Homelite as it is for fun then get a better engine when you want more power.

To give you an idea, the best modified 26 cc Zenoahs are putting out around 6 1/4 hp at 16,000 rpm. Stock Zenoahs put out around 4 hp at 14,000 rpm. Tthese figures are with tuned pipes. So far, electronic ignitions haven't been better than stock ignitions at these rpm and power levels. We have tested methanol based fuels with varying amounts of nitromethane in modified Zenoahs. There isn't much to be gained since the head volume and ignition timing are pretty fixed. We tested a 26 cc Quickdraw on standard model fuel with glow ignition. We didn't find glow plugs in our collection that would hold up for even one inertial dyno run. The engine did run well on low nitro fuel with spark ignition. However, 40% nitro burned the electrodes off. The electrodes damaged the piston and sleeve when they went out the exhaust.

Lohring Miller

For one, I'm not trying to get 10hp out of this engine. I got it for free, have the time to strip it down and convert it, and want to see what it can do. I dont really care that there are other engines out there running faster rpm and making more power. The idea with modifying the engine is to raise compression and timing to take advantage of the extra power methanol can provide that gasoline cannot and use it on something. With the right compression ratio, high amounts of nitro really aren't needed. I dont use more than 10% in my glow engines, with 5% being the predominant amount I use.

If I got it running well enough to hit 12,000rpm occasionally, I'd be fine with it. I'm not going to spend a grand or more on a hull to put a weedwacker engine in it. I'd probably be more inclined to put it on an airboat hull and run an airplane prop on it.

Glow plugs heat range is hypercritical when dealing with high amounts of nitro. At 40% nitro, any glow plug hot or cold isnt going to last real long if the carb is leaned to oblivion.

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RE: Question about Homelite conversion... - 12/19/2012 12:59 AM

Tidnab

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Did you look in the Engine Conversions section. There's guys converting them to glow from gas and some do modifications to them. http://www.rcuniverse.com/forum/forumid_92/tt.htm

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RE: Question about Homelite conversion... - 12/19/2012 1:35 PM

1QwkSport2.5r

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quote:

ORIGINAL: Tidnab

Did you look in the Engine Conversions section. There's guys converting them to glow from gas and some do modifications to them. http://www.rcuniverse.com/forum/forumid_92/tt.htm

I did; the conversion "guru" as I call him told me I should check with the guys in here. He claimed "the boat guys rave about them" ......

Most if not all of the airplane guys converting these engines for glow ignition are using a gasoline/glow fuel mixture. 66.6% gasoline and 33.4% 10% nitro 10% oil glow fuel. This is how they can use the normal factory Walbro or Zama carbs without having to modify them. Glow fuel needs something like 30-40% more flow rate through the needles/jets to run at proper mixture and I think the Walbro WT499 is the only carb that will flow enough for straight alky fuel. The Gas/Glow mix has proven to be very reliable, produce more power than gasoline alone and give a lower idle than on ignition... But I hate the smell of gasoline, thus my reason to run all glow fuel.

I'll have to look elsewhere on the internet to find the information I am looking for.

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RE: Question about Homelite conversion... - 12/19/2012 7:53 PM

lohring

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Modify away. I tried to alter a Fugi engine that Tower Hobbies once sold to try to approach the power of a stock Zenoah. It was a big waste of time. I managed to move the power peak into a higher rpm area, but it still had 1/2 the power of a stock Zenoah. These days Tower sells its gas mono with a Zenoah, a much more expensive engine. There's a reason when you consider the cost of returns. Boat engines run at least twice the rpm of airplane engines. Power levels that make fliers happy are much less than boats, operating in a high drag medium, run.

Our problem with glow plugs was seal failure. We managed to blow the center out of a variety of plugs. There was no point in getting into heat range refinements. All I'll say is you should be able to get an engine to start and idle on low nitro fuel if it has enough compression. Our Quickdraws had 1.8 cc head volume. I have no idea if the 2.4 cc head volume of a Zenoah would be low enough. Good luck in reducing the head volume significantly on a one piece cylinder.

From Jim Nissen five years ago, "I've run plenty of Homelite's Butch and yes they hold together for awhile and do real well. I ran a 30cc for years and it was competitive with Zenoah G23's. It was a chore to keep it running like that though. I'm not saying you can't make a powerful Homelite, just saying for less cost long term the Zenoah or Sikk is the way to go. "
The stock Zenoah G 23 had around 1/2 the power of a stock G260 Zenoah and its clones.

From Scott Schneider, talking about generic weedeater engines, "I would stay conservative,
leave transfer port height stock , Widen exhaust port if you can too 60% of bore diameter & raise to @ 165/170* open duration, Widen intake port as you can making sure piston skirt still seals on the edges, Cut intake side skirt of piston as needed to get @ 140/145* open duration.

Just do this and it's going to run a LOT better. "

Lohring Miller

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RE: Question about Homelite conversion... - 12/21/2012 7:11 AM

MrMikeG

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It will run over 13k on petrol, so why bother?
It will run over 13k on petrol with no tuned pipe, so why bother?
At about 13,5 or so the standard crank and rod max out, so why bother?
Some guys on here can get them to 15K with cast cranks and certain rods with pipes on petrol, so why not ask them how to modify your FREE engine for the most power?

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RE: Question about Homelite conversion... - 12/21/2012 1:08 PM

1QwkSport2.5r

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quote:

ORIGINAL: MrMikeG

It will run over 13k on petrol, so why bother?
It will run over 13k on petrol with no tuned pipe, so why bother?

Because methanol makes more power, and is almost $1.50 per gallon cheaper than 'petrol'.

quote:

At about 13,5 or so the standard crank and rod max out, so why bother?
Some guys on here can get them to 15K with cast cranks and certain rods with pipes on petrol, so why not ask them how to modify your FREE engine for the most power?

That is the point of me starting this thread.

You know.... If I was a brand new guy to the RC boating hobby, I'd consider a different hobby like stamp collecting based on the way some of you guys have replied to me. Some of you guys are downright crabasses. Sorry, but whats wrong with just answering my questions?

Sheesh... I remember now why I got into airboats and not "the other kind" of RC boats.. I think I'll stick with my original plan.

Thank you lohring for your information in your latter reply.

Thanks guys, you're the best and I wish you the best of luck in 2013.

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RE: Question about Homelite conversion... - 12/21/2012 5:08 PM

lohring

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I was just trying to save you a lot of time. However, playing around with your Homelite will still be instructive. Modifying an engine is a hobby all by itself. The worst thing that will happen is that you will ruin a free engine. That's what happened with my Fugi. It's all a learning experience. Guys like Jim and Scott have been playing with gas engines since they were first run in boats. I won my first NAMBA National championship with a gas cat in 1998. We're just trying to give you an idea of what we all learned the hard way. Having said that, there's nothing like failure to teach a lesson. I've wrecked a lot of engines.

Lohring Miller

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RE: Question about Homelite conversion... - 12/22/2012 10:35 AM

1QwkSport2.5r

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I don't intend to get into this hardcore. I don't need a hotrod race engine. That's what my Jett glow engines will be for. Is my task worth your time? Probably not. Is it worth mine? Maybe... Maybe not. I don't really care.

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RE: Question about Homelite conversion... - 12/22/2012 10:47 PM

MrMikeG

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"Crabasses" Huh, you're the one coming onto a Gas forum and telling us your going to make one of our beloved little engines run better.
Have you really looked at the Homelite yet?
All we have been trying to tell you is it isn't the best built engine, and if you try to modify it the way you intend it will probably gernade on you.

quote:

Because methanol makes more power, and is almost $1.50 per gallon cheaper than 'petrol'.

You do realise that you will be burning more than twice as much at the same RPM?

BTW since your a nitro guy, can you tell me how much I need to cut down my X482 prop to get it to run on my A mono?

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RE: Question about Homelite conversion... - 12/23/2012 3:06 PM

1QwkSport2.5r

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quote:

ORIGINAL: MrMikeG

''Crabasses'' Huh, you're the one coming onto a Gas forum and telling us your going to make one of our beloved little engines run better.
Have you really looked at the Homelite yet?
All we have been trying to tell you is it isn't the best built engine, and if you try to modify it the way you intend it will probably gernade on you.

I came here asking the question to you folks because that was what was suggested by the aero conversion guys to do. Evidently it was wrong to do so. I understand its not a major power house. Just about any engine will benefit from modifications; guys have been doing it for years. The homelite 30 turns 2000rpm faster on an air prop with mods than they do stock. They do not grenade at 10k, and its been said by others that they will survive to 13k in short bursts. Just because it will take 13k doesn't mean it will be run that fast all the time. All I asked is what mods need to be made to make a little more power, nothing more.

quote:

quote:

Because methanol makes more power, and is almost $1.50 per gallon cheaper than 'petrol'.

You do realise that you will be burning more than twice as much at the same RPM?

It's closer to 30% more fuel, but the power gains from the higher compression and the fuel together make it worth it IMO.

quote:

BTW since your a nitro guy, can you tell me how much I need to cut down my X482 prop to get it to run on my A mono?

Just because I'm a "nitro guy" doesn't mean I'm a "nitro boat guy". You should ask the nitro boat guys this. I run nitro cars and nitro airboats.

I think it's great and wonderful that I asked a simple question, and instead of just getting the question answered, get told its not worth my time and its a waste... Being told to get a Zenoa or other purpose-built engine because it makes more power is NOT answering my question.

With all due respect guys/gals, I withdraw my request for any further help. I'd rather not be chastised for simply asking a question.

I wish you all a very Merry Christmas, Hanukah, Kwanza, or whatever other holiday you folks celebrate. May 2013 be a joyous and prosperous year for you all.

Thank you for the help you all provided, I learned a great deal from it.

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*Real* glow fuel is made with Methanol, Nitromethane, and Castor oil.

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