bestrcpilot

After checking 3 ignitions from 3w I find that the advance built in to them is only 10 degrees. The 3W ignition will not spark until 800 RPM
The first spark is at 18-19 degrees btdc. and full advance is 28 degrees btdc
I'm getting full advance at 2300 RPM Now this is at the point the the mid range Burbler is in a stock 3W twin.

The C&H Ignitions show a advancer of 24 degrees in two degree step until 5200 RPM

So the Question is
Is the Mid Range Burbler really in the Carb or is it from the Timing advancing to fast ?

Antique

My Feedback: (4)

Timing is not a factor..There are thousands of fixed timing engines out there with no problems...The manufacturers are using carburetors calibrated for chain saws..They could spend a little money to get Walbro to make a specific carb for each engine, but that would cut into their profit ....
Does running rich in the midrange cause a problem with the plane or is it just in the mind of the pilot ??
Or get someone to make a fuel injection system..
Never heard of a syncro spark that was at full advance at 5200 rpm..Either 4000 or 6000, depends on where it's set when installed...Maybe your tach is off ??
You out there Ed ???
there are two different electronic modules being used..Maybe the other one is 5200, never checked...
OOPS..Reichmuth (now D&B made) and Pro spark don't use the snycro spark module...Their advance is different..Reichmuth uses two sensors and switches from on to the other somewhere between 2 and 3 thousand rpm...Have not tested a Pro Spark...

Diablo-RCU

My Feedback: (1)

Please explain how you checked the timing advance of 3 ignitions. Did you use a degree wheel and pointer on the crankshaft and a timing light? I am quite surprised that you measured only 10 degrees of advance. I swapped a DA ignition onto my 3W-100 and was told by DA that the ignition operated exactly like the 3W ignition. The performance was the same on my motor using the 2 different brands and I did not reposition the sensor. The ignition that ZDZ uses has 20 degrees of electronic advance (from their instructions). I'd be surprised that DA and 3W both chose to use only 10 degrees of advance - just doesn't make sense.

Antique

My Feedback: (4)

Foreign manufacturers in their infinite wisdom don't mark their ignitions for timing..Maybe they don't want us Yankees fooling around with their stuff..All U. S. made electronic ignitions will spark at 1 rpm, unlike the foreign makes that require some rpm to fire..Makes it hard to time a 3W or one of the others..I have an old 3w ignition with the braid removed from one side to allow the use of an inductive timing light. The pickup fits over the wire..You can mark the hub and case at TDC..Some are already marked, but usually where you can't see the mark when the engine is running..Multiply the diameter of the hub by 3.14, divide by 360 to get the distance for 1 degree..Make some marks for 5,10,15,20.etc....You can get a pretty good idea what the advance is by interpolating between the numbers illuminated by the timing light with the engine running..
28 degrees, normal timing, works out to .244 times the hub diameter...Example..
Hub 2"
X 3.14= 6.28, circumfrence of the hub
divided by 360 = .0017, 1 degree
X 28 = .488, distance around the hub for 28 BTDC
OR ......244 X Hub diameter....
WATCH OUT FOR THE PROP!!!!!!!!!!!

bestrcpilot

The test of the ignitions was done using a test stand that turns an old prop hub from a 3W .
This Hub is turn by a DC motor that will spin the hub from 100 RPM to over 30,000 RPM. We mounted a flywheel in place of a prop. The flywheel has two slots cut out of .
The Hub has been marked in 2 degree increments. A timing light was used, the timing light is a new snap-on model that can be used between the plug cap and the spark plug. The tack used is a "Glow Bee" digital.

The C&H ignition that was tested was a older C&H with a Timing Stick.

Hope to post some Pic of the test stand if I can get the new computer to talk to the Camera

Scott Yeo

tkg

My Feedback: (1)

The Timing Stick is NOT a CH product. Lets keep the apples and oranges in the right barrel.

bestrcpilot

OK I guess I goofed, It is really called a External Syncro Spark Computer timing module. But here in the hills we just call it a timing stick.
Sorry if that is wrong.
Scott Yeo

Antique

My Feedback: (4)

Sounds like a good test setup...Don't know for sure, but " syncro spark" is connected only to one electronic timing module..If the name wasn't copyrighted it should have been..
..The timing stick is the reason for the 5200 rpm advance....
It is only connected is series with the C&H ignition, and is not in any way related.....
In my humble opinion the syncro spark module can't be surpassed. The prop looks like it's stationary at ANY rpm..Try that on the others.....

Ed Vollmer

My Feedback: (14)

To post #1: After checking 3 ignitions from 3w I find that the advance built in to them is only 10 degrees. The 3W ignition will not spark until 800 RPM
The first spark is at 18-19 degrees btdc. and full advance is 28 degrees btdc
I'm getting full advance at 2300 RPM Now this is at the point the the mid range Burbler is in a stock 3W twin.

It is hard to believe that starting a large engine at 18 or 19 degrees BTDC would not produce some very sore fingers. I have both 3W and DA engines and they are very docile to start and have very good idle characteristics. My findings are that around 8 to 10 degrees BTDC is the upper end of the safe operating range for starting a large engine. 2 to 4 degrees seems optimum.

I have not done timing checks on my 3W, DA, ZDZ, or RCS engines so I cannot confirm or refute your findings. Perhaps I can do that someday when the weather and time permits.

IMO, 2300 is pretty low for full advance considering that most idle RPM's are 1000 to 1200 RPM. All that would do is assure starting and idle at a retarded setting and not provide a smooth transition to full throttle. However, I do not think this causes "burble". IMO, "burble" is caused by the throttle disk passing from the idle jet to the high speed jet. Some of this can be "tuned out" and some carbs are better than others for reducing this characteristic. The opposite of "burble" (rich setting) is "surging" (lean setting) and somewhere in between is the best we can hope for.

To post #2: Or get someone to make a fuel injection system..

AMEN!

Never heard of a syncro spark that was at full advance at 5200 rpm..Either 4000 or 6000, depends on where it's set when installed...Maybe your tach is off ??
You out there Ed ???

Correct, Ralph. 4000 or 6000, 26 degrees or 20 degrees. Default is 26 degrees at 4000 RPM.

To post #7: OK I guess I goofed, It is really called a External Syncro Spark Computer timing module. But here in the hills we just call it a timing stick.
Sorry if that is wrong.
Scott Yeo

OUCH, Scott, that really hurts<G>.

Ed Vollmer

My Feedback: (14)

To post #1: The 3W ignition will not spark until 800 RPM

I forgot to mention this in my prevoius post. Our testing (done in the mid 1990's - so I am drawing from memory), suggests that an 800 RPM flip would require Superman to do. We found that at least 300 RPM is required sustain enough inertia to reliably start an engine. The maximum RPM I could generate by hand flipping even a small (ST 2500) engine was under 700 RPM. (And I have been flipping props for 41 years <G>).

Your methodology of testing seems excellent, so I would only question the accuracy of your instrumentation.

BBW Walt

My Feedback: (11)

I have a new QS-100- 106 in transit from A.I. I received a phone call explaining the new Ignition module. 3W has completely redesigned the modules which includes an RPM wire for future accessories "Gee" IT also incorporates a L.E.D which shows the user when the ignition is ready to fire. I have been told this new system uses 2 hall sensors instead of 1. Operator must turn on the ignition and the L.E.D. will light. Upon propping the engine the L.E.D. will go out indicating that the ignition is set and ready to fire. Supposedly this system was designed this way for safety reasons. I hope the reliability has been improved upon, a little more precision would help also. I anticipate arrival in a day or 2 and a test run will be in order. 3W claims 30-10 props have been spun with this engine. This information came from a phone conversation so I can only relay what I have been told. I should know shortly whats up with this new system...I waited 3 months for this new engine.

Antique

My Feedback: (4)

So much for the K.I.S.S principle....Looks like a race to see who can put the most unnecessary technology into a product..
RPM wire ?? Get a TNC tach and you can check ALL your engines...