Electronic Ignition Conversion on US 41cc????
 

Hi Everyone!
Haven´t flown yet my extra 300 25% with an US 41 cc on it. Weight is at its limits for an aerobatic plane at 12lb/ 6kg. It was suggested to me at the field to consider a conversion to electronic ignition for the engine, that way I could gain power and get rid of some weight.
Did any of you done this conversion on this engine already???
How well does it work out? How much weight can we actually get rid of (after considering the extra batt pack for the ignition spark)???? Can it run a larger prop, what was your gain in rpms? Is it worthed the cost, or better save and get a high performance engine????
Any thoughts would be appreciated
Happy flying
Cris

RE: Electronic Ignition Conversion on US 41cc????
 

I had my Zenoah G23 converted to elect ignition by Ralph at RCIGNITION and it has proved to be one of my better decisions. The engine lost about one lb. in weight and idles much smoother than before, but most of all, it's so easy to start.

Just a couple flips of the prop and it's running. It has picked up a few hundred rpm, but I can't say for sure if it was all from the ignition change or just the engine continuing to break-in.

The only additional weight is the switch and the 600mAh nicad ignition battery pack which gives about two hours running time. Going to elect ignition certaintly transformed my engine for sure.

Karol

RE: Electronic Ignition Conversion on US 41cc????
 

The battery weight is not "additional". You'd actually be trading the weight of the stock flywheel and coil for an aluminum hub, ignition box, hall sensor, battery pack and switch. There will be a weight reduction after the conversion, but I don't remember exactly how much I got with mine. Another thing to remember is after the conversion, the weight is not all on the engine. The ignition box, battery pack and switch can all be positioned in the fuselage (as long as it's not near radio gear) to help with balance. Cris, I believe you mentioned you added a fair amount of weight to the aft end of your airframe. This conversion will allow you to lose a good portion (or maybe all of) that weight via better balancing (less weight at the very front on the engine) for an even higher net weight-loss. Not to mention you can also dump the spring starter as well if you have one installed. Won't need it. ;)

You will definately get more power if the ignition used is an auto-advance type. Because the magneto ignition is static (no advance), it uses "mild" timing for good all around performance and handling. With an auto-advance system, the timing will be mild for smoother low speeds and for easy starting, but can give you full timing advance for much better full-throttle output compared to a mildly timed static system.

So from my experience with the US41, there's both a weight advantage AND a power output advantage to converting this engine.

Oh, and by the way, I installed a B&B muffler for it with smoke taps and it works perfectly. So much nicer than the piece of junk that comes with the US engine. Here is the link to his web page: http://www.bennettbuilt.com/page3.htm

RE: Electronic Ignition Conversion on US 41cc????
 

Crismedicatrix,

I converted my US41 some years back. Bought a CH Ignition and installed it myself. No problem. I estimate 10-12 ozs. saved with the ignition battery pack. You HAVE TO remove the spring starter as it cannot be used with electronic ignition, but as stated above, you don't need it. Easy hand starts.

I disagree with above statement. There is no noticable performance improvement at the top end. There is a smoother, more reliable idle.

You won't get much weight shift by moving the ignition battery pack back, 'cause you will start getting too close (stay at least 11" away) to radio gear. Can't move the ignition module back. It has a short spark lead and doesn't weigh anything anyway.

Have fun!

Bedford

RE: Electronic Ignition Conversion on US 41cc????
 

If you didn't get any performance improvement, then you don't have full timing advance. Did you create your own hub to replace the flywheel? Where was the magnet position (degrees before top-dead center)? Is your CH iginition the "syncro-spark" type? If not, then all you did was convert from static magneto ignition to static electronic ignition. Your only benefit in that case would be the weight savings as you pointed out.

As for weight and balance, typically the iginition box is behind the engine on the firewall somewhere. Yes, it doesn't weight much, but what weight is there is probably 4 to 5 inches further back than the front of the engine where the flywheel and coil was. The battery pack can be even further back inside the front end of the fuselage for even more balance improvement. 11 inches is overkill unless you have some kind of defect or a poor performing receiver. You can definately get closer than that. However, I do agree that the futher from the radio gear, the better. Just make sure to range check thoroughly.

I could have used my spring starter just fine on my engine after the conversion. However, it wasn't needed since the engine started so easily by hand. I chose to lose the weight instead. Removing it was purely an option, not required. Maybe the CH conversion kit you bought installs on the rear end of the crank shaft. If that's the case, then yes, the spring starter will have to go.

Cris, If you go with the conversion kit that Bedford is describing, see if you can get one with the timing advance feature. The CH product is called "syncro-spark". If you're going to do the conversion, you might as well get the power benefit as well as the weight savings. There would be virtually no difference in weight between the CH static unit and the CH syncro-spark unit. There will be a cost difference though.

RE: Electronic Ignition Conversion on US 41cc????
 

A definite plus with the Zenoah ignition conversion from Ralph is that the entire ignition system is housed in the rear of the engine case cavity and is protected by the aluminium mounting plate.

Karol

RE: Electronic Ignition Conversion on US 41cc????
 

Your milage will vary:D Some users of the US41 syncro conversion report power gains in the 200 rpm range, others 0 rpm increase, BUT both report much improved manners.
The variable may be the skill of the installer in setting the timing correctly
Using a spring starter with a CH ignition is VERY DANGEROUS, simply because a CH ignition will fire in eather direction. If you were not paying attation it can fire and jerk the prop out of your hand. Trust me that smarts, cause its going to wack you on the back of your hand.

RE: Electronic Ignition Conversion on US 41cc????
 

Hi Everyone!

Thanks here for all the imputs.
You all agree that there is a weight reduction installing electronic ignition, and on power gain it will depend on adjusting the timing probably.
It is good to know though that the engine can improve and will save weight. I think it will be a plus to have the sychro type of electronic advancing module even though it is a bit more costly, it is still better than replacing the whole engine for better performance. I wish I knew all this a few years ago when I bought the engine and wanted to go into large scale planes. It took several years to actually get the plane ready. Maybe it will be a good idea to leave the engine to last in the next project...
Great flying to all
This weekend we had spetacular weather over here in Brazil and lots of fun too!
Thanks again
Cris

RE: Electronic Ignition Conversion on US 41cc????
 

You can also gain some good power using the carb from a Q-52, and a Bennett muffler (loud). Add in the electronic ignition, and you can have pretty strong & fairly liteweight engine.

RE: Electronic Ignition Conversion on US 41cc????
 

Thanks for the backup Terry (TKG). I timed my unit per your instructions and though I did not have hard performance data before and after, the perception is certainly nil increase. Running is overall improved, however. I said what I did about the spring starter because CH was very explicit with their warnings regarding the sparking. It is definitely not needed.

I do recommend the CH unit for their quality and backup of the product.

Have fun!

Bedford

RE: Electronic Ignition Conversion on US 41cc????
 

Hi TLH:

Did you try installing a Q-52 carb in yours? did it pick up extra power?
Where can find one of these carbs? Do you have the ref numbers???
Might just try this before doing the conversion to igniton! What do you think?
Thanks
Good flying
Cris

RE: Electronic Ignition Conversion on US 41cc????
 

Cris:
I have converted the 41 on two occasions......The update is a Walbro #144 carb, or a Walbro carb of 13.2 mm..You must also toss the restricting can muffler..I use the B&B muffler and it made a big difference....I also use Poulan synthetic chain saw oil at 40-1..With these changes you can pick up 4-500 rpm...These little engines are super reliable..

RE: Electronic Ignition Conversion on US 41cc????
 

Hi Eugene:

Thanks for the conversion numbers on the wallbros´ carbs. On the muffler... I bought the US41 at Tower Hobbies when they still sold it, and it came with a different muffler than advertised. They call it the Alluminum muffler, which is round and has the two pipes. Looks better than the can one, it is lighter and is louder too. So I am not sure if this works already for increasing final rpms.
Thanks again, I am starting to like this engine every time more, so many possibilities!!!!
Great Flying
Cris

RE: Electronic Ignition Conversion on US 41cc????
 

I have not run the mods on a 41, but have seen a couple, and they were strong engines. Saw one an American Eagle Spitfire, with 84" w/s, & it pulled it around with authority. You can get the carb & muffler from B&B Specialties: http://www.bennettbuilt.com/eng10.htm
I have seen the new style muffler you mentioned, I believe it would be about the same as the B&B muffler, or close.

RE: Electronic Ignition Conversion on US 41cc????
 

Hi Eugene:

Finally called B&B and talked to Bennet himself. He told me the walbro #144 are outdated and I cannot get them anymore. So he told me about the WT 76, but could not tell me if it is the 13.2mm carb. Do you know if this new walbro carb will work on the US 41???
Thanks
Great Flying
Cris

RE: Electronic Ignition Conversion on US 41cc????
 

Cris,
Yes, that is correct... B&B is very competent and experienced with gas engines, and you can rely on his information.. Matter of fact, my first US41 was purchased new from Bennett, with the set up I described....

RE: Electronic Ignition Conversion on US 41cc????
 

Pretty sure it is a 13.2 mm carb. My Brison, & A&M 3.2s and 2.0 have WT 76A carbs and they work really well.

RE: Electronic Ignition Conversion on US 41cc????
 

Thanks Again Eugene and Terry:

Well, let´s give it a try then to the wt 76 and see what happens with this US 41
Happy Flying
Cris

RE: Electronic Ignition Conversion on US 41cc????
 

Eugene,
Dick Bennett is a very good resource. I go to him for lots of info and parts. I just bought a WT76 from him for my 41 and it works real nice, but you don't get the extra wallop from the Q52 carb and they are very hard to find. I have one in my H9 Giant Cessna 182 and allowed me to go to a larger prop at the same RPM. So, find that 52!!