Steve S. Helland

My Feedback: (15)

I have a question about gas engine performance with a magneto type ignition vs. auto advancing electronic ignition.
Let's start with a stock Zenoah G-38 on a mag type ignition. The timing stays the same from idle all the way up to full throttle with no advancing or retardation of timing.

If I was to upgrade the ignition to let's say an RC X-cell electronic auto advancing ignition on this engine would I get more power out of it? More RPMs using the same propellor?
Question: Say the engine is idling and the spark plug is firing at 6 deg. BTDC, does the timing advance a little at higher RPMs? Or does it retard?
Would an auto advancing electronic ignition just make it easier to start or increase performance throughout the throttle range? Use less fuel?

Background: I run both styles of ignitions on different planes, I just need information from someone who knows more than I about this so I can make the right decision on my Big Bingo w/G-38

CK1

My Feedback: (60)

Steve ,

The engine will be easier to start when changed to an electronic ignition . It will not gain any real noticeable power . There will some loss of overall engine weight with the removal of the flywheel for the conversion ,but some weight is regained by adding a battery to power the ignition .I have not noticed any change in the fuel consumption. Its a give and take deal but basically the biggest change will be the ease of starting .

av8tor1977

My Feedback: (6)

If you are replacing a fixed timing magneto setup with an auto-advance unit like the RCEXL, besides easier starting, you will also notice a slower, smoother idle. Power does often increase slightly as well, especially if you take the time to adjust the timing for best power. People often say there is no weight difference, but I find by using an 800 mah 4 cell nimh battery, which is more than sufficient, that the electronic ignition is indeed a lighter setup. There is no need for a big 2500mah 6 cell battery like many people use for their ignitions.

AV8TOR

pe reivers

Ditto

Jezmo

I third AV8TOR and Pe's comments.

Steve S. Helland

My Feedback: (15)

So,
If my common sense is serving me correctly (based upon the corespondence in this thread) I can fairly assume that our electronic ignitions are slightly retarding the timing to make the engines easier to start? Then once started the electronic ignition automatically advances the timing? I have always set them according to spec timing using a wheel and all that but never knew how and why.

Also, could someone explain why the idle is so much smoother when using an electronic ignition? Is it because of a hotter spark? Is it because the timing is automatically retarded somehow?

w8ye

My Feedback: (16)

The timing is automatically retarded for the idle

pe reivers

It is better not to speak of retard or advance. The ignition has a timing map that sets the timing according to engine rpm, either by retarding OR by advancing, depending on ignition type. Therefore, the initial timing (to be set by the user) of brand 1 need not be the same as brand 2, even when they have the same "map".

Steve S. Helland

My Feedback: (15)

That answers it! The how, why, & when.

Thank you all.
PS. I don't usually like to talk about retarding either because usually if I talk about it too much it sinks down to my thumbs...

pe reivers

didn't know the thumbs could ride the small bus

tkg

My Feedback: (1)

Slightly retarded timing??? The timing movement on most of the modern ignitions is in the 24-26 degree range. That much will make a BIG difference in how an engine idles or runs at WOT.

captinjohn

A quote

Also, could someone explain why the idle is so much smoother when using an electronic ignition? Is it because of a hotter spark? Is it because the timing is automatically retarded somehow?
<hr />
Smoother than what? Some engines idle smooth with flywheel mags. Some do not. Some flywheel mags have advance too. I have seen the advanceon a timing light. My Mac MB 290 will idle as slow and smooth as just about any stock CD ignition. Tunning the carb real good and a more heavy prop &amp; spinner will help to produce a slow idle. Sometimes no exhaust back pressure will effect the idle.

Too really learn about your engine you got to run it at different RPM,s and try various needle settings to get a "ear" for the correct sound when the engine is running. Also it helps a lot to get a engine broke in for the best running....but plan on learning how to tune a engine. Get around someone who has a good ear for tuning. Chances are some will never use a tack to even check RPM. Its done by ear. Hey when you get your engine/airplane combination running like it should....why waste time wondering if more RPM can be had. The main thing is...get some experience and learn. Capt,n



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pe reivers

A strobe lamp will be fine, and is much better than the ear.
At idle, there is so much more time for combusting the now much diluted charge, that a very late ignition pouintwill be better than an ignition at about 28&deg;BTDC. Objective is to have peak cylinder pressures just after TDC. That will make a smooth running engine.
Many mags indeed have some form of timing adjustment, due to the simple fact that the faster the magnets move, the quicker the charge needed to trigger the spark is reached. So they advance with higher rpm. In most mags, the patent (pending) number is engraved. Look it up to see how the electronics (!) inside are arranged.

Some engines have idle ignition at about 5&deg; BTDC. They can idle as low as 850rpm if the prop is heavy enough to get the piston through compression. A mag ignition will have problems producing a proper spark at these low rpm, as well as even getting that low in the first place.
A zenoah 62 on mag idles a typical 1800 rpm all day. Put a good electronic device on it, and that same reliable idle can be as low as 1400 rpm, or even down to 1200. Now remember that the zenoa likes to rev up, which makes it harder to idle that low.

Steve S. Helland

My Feedback: (15)

I have recently purchased an RC xcell Ign. for my G-62. I have not installed it yet but anxious to try it out. I was thinking of upgrading my G-38 as well.

clivemc

pe, well said, it is too often overlooked Zenoahs like to rev!!! dont compare their top RPM to other engines, they should be propped smaller (smaller dia, higher pitch)than other engines and allowed to rev, that is where their power is. Other engines will produce their power differently and allow bigger props to be swung at lower rpm. I do use RPM to compare engines but use it to compare a zenoah against another zenoah, or DLE vs DLE. you just cant compare zenoah to 3w for the same application.

pe reivers

That is exactly why it is harder for a Zenoah to compete with other brand engines when noise is an issue. Forcing them to the required lower rpm with extra long headers does their power bandwidth no good.

Steve S. Helland

My Feedback: (15)

Right now my G-38 Mag ignition with Slimline smoke muffler runs righteous as long as I use one of the heavier 18-10 propellors such as MA Classic, Zoar Laminated, APC.
I purchased a Bolly Carbon 18-10 and the airplane and the engine did'nt like it. What I mean is that the vertical and overall performance of the airplane was better using a propellor of the same size just more mass. Would a 20" carbon propellor perform better on this engine? I don't want to buy one @ $50 bucks just to find out it won't work well either.

captinjohn

If your G38 runs good now....why change props? I had good luck too with a Wood 18x6-10 Zinger.

Capt,n

tkg

My Feedback: (1)

Thats why they make so many propellers. What matters is not what everybody says is the hot ticket, but what makes YOUR plane fly best when YOU fly it.
If your happy with a MA Classic stay with it, their cheap and tough. Just remember to balance it cause most aren't even close