dinoslmn

My Feedback: (1)

correctly the formula is 2*R*Sin(20) or D*sin(20) where R or D is radius or hub diameter.
Sin (20) =0.324

Antique

My Feedback: (4)

Take the cap off the plug...Turn the ignition on..slowly rotate the crank CCW..When you hear a spark draw a line across the hub and case...Put the piston on TDC...The distance from mark to mark should be hub diameter x .244....the spark happens when the edge of the magnet passes the edge of the sensor...The width of the sensor and possition in the holder can vary, so you can't tell exactly where it fires if you try to use the other measurement method...Using the spark to do the timing is better...You won't hurt most ignitions turning it a few times with no spark plug..If you're worried about it put a spark plug in the cap...
Timing is not exact, a few degrees one way or the other makes NO difference at all..
I have only been doing this for 20 years, maybe all those engines are timed wrong ?
The timing on the Chinese ignition works out to about 28 either way....

tkg

My Feedback: (1)

The Hall trigered ignitions fire when the magnet LEAVES the sensor not centerline to center line. This is why it is important to time the spark, there may be variables due to sensor sestivity and magnet strength.
A degree wheel is much simpler to use, once you are set up, than trying to measure .XXX on a curved hub.

Tired Old Man

My Feedback: (1)

CH provides a paper protractor with every ignition they sell. Attach it to a piece of light ply that can fit the prop bolt. Make and use a bent wire pointer like CH shows in their ignition instructions. Find TDC any way you want, but doing it with the plug out is easiest. Here's the super easy part. Use the CH tester to visually see whan the ignition fires when you rotate the hub. It's a simple light diode attached to an ignition chip.

You can do all the math stuff you want but seeing when the ignition fires compared to where the piston is in it's stroke is about as easy as it gets. Don't fire the plug if it's not touching, grounded to, the engine. You can put the magnet at any location on a hub as long as the hub can be rotated to set the timing.

Too many engineers spoil the broth and make it appear much more difficult than it needs to be. It's an early part of the basic engineering courses, "making the simple difficult to justify job and security 101".

jpanhalt

Well, I put Ralph's formula into the formula I suggested (adjusted for 28 degrees instead of 40 degrees) and get 0.242 times the hub diameter....which is more than close enough and is better than I can measure

In response to tkg, yes, I understood that most ignitions fire on the falling edge, not rising edge of the Hall switch. I tried to frame my comments, however, in accord with the model proposed by the poster (gpar). Also, earlier this week, I looked at the Hall signal from a 3W and in that case, it was clearly a little more complicated. It was easy to duplicate the signal, but since the magnet was polarized with North closest to the sensor, things were a little different. I was not absolutely sure the rcexl ignition referenced by gpar followed the scheme you use or the one used by 3W; although, I suspected it was the same as yours. John

gpar

It´s no problem measuring arcs just marking on a piece of paper on the hub.

As I said before applying this method to my stock spe 26 with a different chinese ignition (from another company) I found out the static angle is just 27,5 degrees, instead of the 40 in the case of the rcexl ignition.

I wonder if such a big difference means a big tolerance for the static angle.

I think better ignition gives you more top rpm and more power, but then the setup angle should be found by moving the sensor by hand at open throttle.

Antique

My Feedback: (4)

There is no benefit to using more than 30 degrees...The 28 or 30 degrees that works best for ALL gassers was found by moving the sensor with the engine running.....NO ignition on ANY gasser works best at 40 degrees...Unless you think 25 years experience means nothing.....Experience gained from using ignitions with no electronic control...When we started there was no electronic advance, just fixed timing or mechanical control linked to the throttle shaft...ALL chainsaws and other magneto ignitions fire at 28 or 30...
Too much advance just makes heat and if carried to the extreme will result it the engine cutting out at WOT...Don't believe it ? Try setting the advance by using the point where the ignition actually fires, not some claculated measurement using the width of the sensor holder...
The older 3W and DA ignitions don't use a hall sensor and can't be set by turning the crank slowly to check the spark....The newer 3W ignitions are set by putting the piston at TDC and setting the sensor holder so the edge bisects one of the magnests in the hub...
Which most likely is 28 degrees, not anything near 40....

captinjohn

The use of a timing light will let you see exactly when it fires. I am going to use my Sears timing light on all my instalations. Capt,n

Antique

My Feedback: (4)

Timing lights work, but an inductive timing light won't work unless you can put it on an unshielded wire....I use one on 3W ignitions..My 3W test ignition is made from an old crashed ignition with the shielding off the wires and a separate ground from the ignition box to the engine case....

captinjohn

I use a paper clip and stick it along plug termenal and push cap on to hold it there. Then clip on paper clip for connection. Capt,n I guess you would say not induction on my set-up? Capt,n

CopperheadAV

[quote]ORIGINAL: RCIGN1

There is no benefit to using more than 30 degrees...The 28 or 30 degrees that works best for ALL gassers was found by moving the sensor with the engine running.....NO ignition on ANY gasser works best at 40 degrees

Correct,

Everyone is under the impression that the RCexl demands 40 degrees, Thats wrong. I will admit the instructions can be likened to a rubrics cube. The 40 degrees has to do with passing the magnet clockwise past the sensor. An engine spins clockwise. This makes up for the 10 degrees in the instructions. I do not think this method works well and you should follow Ralph's instructions on timing. Flame away guys and I would be more than happy to put it in a chart with 3 colors! The timing light??? Save your time. A couple of degrees here and there doset matter, the CDI will make up for it.

Cheers,

Antique

My Feedback: (4)

Clockwise from behind the engine, CCW like most of us do, looking from the front

tkg

My Feedback: (1)

I'll run a dregree wheel and a timing light Monday. But as I remember the total timing movement is in the 25 degree range.
We use 30 deg BTDC as the base timing on 95% of the engines we work on.

Tired Old Man

My Feedback: (1)

Terry,

Is it just me or is this timing thing, which is a VERY simple process, being made difficult unneccessarily? Too much advance (more than 30, +/-2 or so) and the prop will bite the hell out of you. Not enough and you suffer a lower top rpm. That's about it, right?

Antique

My Feedback: (4)

Anyone that can start a magneto gasser will have no trouble with kickback on a EI engine, you just have to use a serious flip....
If a EI engine was timed at 40, the timing at start up would still be only about 15...Hardly enough to bite very hard....

tkg

My Feedback: (1)

Timing is like Model T technology, but its fun to pretend that its rocket science
If we were racing Indy cars then timing is very important, but for us 28-30 degrees is right about 95% of the time. The next 4% need LESS timing. Only seen one engine that liked 33deg.

gpar

If I replace my carb for another one with a bigger venturi, Should I replace the electronic ignition as well ?

Antique

My Feedback: (4)

Nope, the igniton doesn't care what the carb is....Unless the carb was too small in the first place, a bigger carb makes no difference at all.....

PlaneInsane

My Feedback: (5)

Ralph, I just mounted my sensor on my 3W100 and when standing in front of the motor the sensor is now hanging to my right. In other words I remounted the sensor to the right. Looking from behind the motor the sensor is mounted to the left of center.

Since this whole thread has been confusing and no instructions were provided with the RCEXL I'm taking it that I SET my total advance and the unit retards only.

Is this correct?

CopperheadAV

This is correct.

Go here for more info: http://www.venomengines.com/Comersus/store/index.asp

PlaneInsane

My Feedback: (5)

Thanks! That's exactly what I was looking for.

shaunmichaeljohnson

sorry to bring up this old thread again[:@]
i have been recomended a CHXL ignition by terry from CH.
but what i have not understood from this thread is where to set the ignition timing.
if i'm right, if i set the hall sensor @ 28 BTDC then i get a maximum automatic retard of 2 BTDC right?

and if i had it at 40 BTDC i would get a max retart of 15 BTDC (but from what i have read above 28 BTDC does not reak any benifits)

thanks,
shaun

pe reivers

I bought an ignition from Ralph (RCexcl), and tested it vis-a-vis a vlach ignition.
The chinese ignition has a very nice advance (or rather, delay) curve between 2000 and 4000 rpm. In the Vlach the range is much shorter.
The chinese ignition fires at full speed (tested up to 10,000 rpm) like set. Above 500 rpm, delay gets to a max of ~22 degrees, so when set at 28 degrees, the spark will be at ~6 degrees when starting. A lazy flip like the Vlach allows, will kick back the prop, because then the timing is at full advance.
Ralph is dead right in setting these ignitions at 28° BTDC

The Vlach ignition works with advance.
The advance sets in at ~1900 rpm, and is at full at ~2500 rpm. This makes the engine rpm a bit sensitive around this mark.
Advantage is, that even a very lazy flip will never bite you.

Side note:
Because I had to bare the HT wire for my voltage clamp to work, strange things started to happen in my work shop.
When testing the Vlach, the transmitter and receiver I used to regulate rpm on the electric test motor went wild! My Schulze battery charger made clicking noises switching on and off. This was about the same experience I had when testing automotive appliances for radio disturbance resistance. These high power radiations play games with our electronic devices like transmitters and receivers.
So be careful to not damage the shielding in any way, or you may crash your plane.

shaunmichaeljohnson

i have now ordered the CHXL single ignintion.
but correct me if i am wrong...
the first fire of the igntion is @ 28 BTDC and after that on a steady idel it will be @ 2+ BTDC right?
so the first fire is set at maximum advance adn after that the idel is at a retarded rate?

shaun

tkg

My Feedback: (1)

The CHXL does NOT measure RPM for starting. It measures the dwell time of the magnet under the sensor. From the time it caculates the rpm to see if your turning fast enough to get full retard. So a vigorous flip and your timing retards.