Originally Posted by gkamysz

Your needle setting will depend on what you're comfortable with here.

Greg

And THAT.... is what I am trying to figure out....
I simply am not yet experienced enough with this ignition stuff, to know what it exactly is that I am comfortable with....

But finding out is half the fun...

EDIT: one more question: i know from professional background, that retarding ignition increases EGT, and decreases max combustion pressure (thus also power, and to an extent, vibration levels)
As you stated, timing should be rather 34 degrees. I take it that is from experience on airplane engines
Since I am running the engine in a helicopter and I am not sure what is the influence of that application, how do I recognize if timing is too advanced?
las year, when I was setting it up, I could not really notice too much difference in running behaviour if I shifted the timing a few degrees forward or backward....

Brgds, bert

With a pressurized fuel system and regulator I run as lean as possible. With a regular setup you must allow for a near empty tank with the needle. That is all. This varies by engine and tank installation, so you'll have to sort it out. I'd look to see if you have any significant change from full to empty tank and go from there.

I've observed basically the same in regards to timing. A few degrees here or there is not significant. The larger engines are more critical of timing, and in a larger engine a small change in RPM is a much greater change in power. Most of my spark ignition running has been 46-52 size four stroke.

I do have one engine which still baffles me. An FSa-81 I converted to spark makes less than half the power it should with gasoline fuel. It ran as expected in stock form.

Greg

Then I guess, since I am running a .90 and that is bigger than most your engines, I will for now keep it as it is.

How do you regard the muffler temp of close to 300 degree C? That is the stock OS "muffler" by the way, actually more a place to fit the tank pressure connection than a muffler as it is loud as hell, and there is no prop-wash to cool it.
And what are your measured head temperatures? just to have an idea of where i am standing...

My fuel tanks (it is a Bell 47 GII with functional tanks) are mounted with the bottom at needle level. I never fill them completely since that is almost a full Quart of fuel Usually I fill close to two inches above the needle, and because its fuel level is not clearly visible in flight, I stop on the timer. Usually the level is still 1 inch above the needle. No pressure is used in the tanks, no pump, just natural draw.

Brgds, Bert

Originally Posted by Brutus1967

I have the impression, that EGT was the same or slightly lower compared to glowplug operation.

Not to be a nuisance, but are you sure about that 34 degrees? Currently I am running 26 to 28 degrees before TDC. The guy who sold me the system, Pe Reivers, was absolutely convinced it should be 26~28 degrees, no difference between gas and methanol according to him.


Brgds, Bert

I am speaking from 4-stroke experience. I'm not sure of you are using a 4S or 2S.

Retarded ignition timing on an air cooled motorcycycle engine will turn the pipes blue from the excessive heat in the exhuast.Perhaps due to the combustion still taking place as the exhaust valve opens.

As far as gasoline & methanol needing the same ignition timing?

Methanol burns slower than gasoline & thus needs more ignition timing advance.

http://www.voc.uk.com/net/docs/7.1/7.1-654-20.pdf

BTW: All of my CDI converted engines are .91 or larger.

1-.91, 1-1.50, 2- 1.8 & a 3.00 twin.

II am using the ignition on a 4 stroke, but will most probably convert my three flightschool helicopters (Rossi .60 2 stroke) as well.

OK, will try and advance the ignition by 4-6 degrees.

Brgds, Bert

Originally Posted by Brutus1967

II am using the ignition on a 4 stroke, but will most probably convert my three flightschool helicopters (Rossi .60 2 stroke) as well.

OK, will try and advance the ignition by 4-6 degrees.

Brgds, Bert

My Saito FA91S was turning the same RPM on CDI as GI when the timing was @ 28* BTDC.

Advancing to 34* gained 200 RPM W/the same prop.

Larger engines (1.5/1.8) gained RPM even W/the 28* CDI setting over GI but still gained some RPM as the timing was advanced further.

I wish i had saved the link There was a heck of a good article on reading spark plugs. You could look at the ground electrode and determine where the timing was, by a faint line on the strap. Well at least get in in the range you need.
with glow fuel, I don't think it would work as there is too much oil. Still an interesting read.

If it were me I would advance the timing until I stop seeing a gain in RPM. Then back it off a degree or two. The same goes for the fuel mixture. Richen or lean for max RPM then slightly rich, just like you've always done. You might have to go back and forth a couple of times to optimize the setting. Once you have this back off the timing and slightly richer on the fuel. If you left it at the high setting as the days change you would have to fuss with it more than is necessary. Of course, you must have a tach to do this. This is nothing more than a poor mans dyno. The prop is the "dyno" or load on the engine. It would be nice to be able to play with compression also, but that can be a chore on a 4C engine. 2C is a snap with head shims.

Can you use a timing light on these small ignitions? I would assume you could. That would make your settings repeatable, providing you can mark the trigger in degrees as a reference.

Ken

That is my problem: it is in a helicopter.
Hovering you can use an optical tach, but that has the accuracy of the tach multiplied by the gearing ratio (9.2:1) and the slip of the clutch, BUT that is not full power so completely useless for determining max RPM.
Full climbing there is too much influence of it being absolutely vertical or not to do an accurate reading.
And you can't really keep a close eye on the engine while doing a full climb: if something goes wrong (overheating for example) you can not readily back it off to protect the engine, you still need to bring the helicopter back, which unfortunately means the engine has to do its job at near full load for a little more(the helicopter is "a wee bit" underpowered so the engine is actually straining almost all the time).

That's why I need to learn about all the old fashioned little tell-tale signs, because I cannot rely on the old habits the engine had when it was still a glow...

B

Originally Posted by Brutus1967

That is my problem: it is in a helicopter.
Hovering you can use an optical tach, but that has the accuracy of the tach multiplied by the gearing ratio (9.2:1) and the slip of the clutch, BUT that is not full power so completely useless for determining max RPM.
Full climbing there is too much influence of it being absolutely vertical or not to do an accurate reading.
And you can't really keep a close eye on the engine while doing a full climb: if something goes wrong (overheating for example) you can not readily back it off to protect the engine, you still need to bring the helicopter back, which unfortunately means the engine has to do its job at near full load for a little more(the helicopter is "a wee bit" underpowered so the engine is actually straining almost all the time).

That's why I need to learn about all the old fashioned little tell-tale signs, because I cannot rely on the old habits the engine had when it was still a glow...

B

Could you secure the heli to a bench & use a digital tach tapped into the hall sensor lead W/a "Y" harness? You could then use long aileron extension to get the readout module far enough away from the rotor blades.

I thought they had hall effect sensors for some of the telemetry stuff. You can hook up a sensor to read the timing sensor magnet on the gasoline engine for a tachometer too.

You can't tie a helicopter down: that is not what the airframe is designed for and any windgust or similar will provoke a gyroscopic response from the rotor that will try to tear the thing apart.

Otherwise it would be easy, because the RCElx has an output for a tach, and their tachs are cheap.

I did advance the timing a bit, by 4 degrees. Did not measure the actual timing, but it should be around 30~32 degrees before TDC.

RPM was not noticeable increased, but I had the impression that it was climbing a tiny bit better.
Further I noticed that in cold condition, idle had improved significantly, but when hot, it seemed same as before, if not slightly worse: if you set the helicopter down and reduce to idle, you have to raise idle or it will die.

I was not able to get good consistent temperature readings, but it seemed, the EGT has increased instead of lowered: I was measuring a constant 300 degrees throughout the readings.
The running gear seems to run slightly cooler (55 degrees on the backplate) and the oil seems to come out slightly less turbid. But the amount of oil caught after the crankcase breather seems not to change, even if oil content has gone up from 10 to 15%.
The cyinider temp seemed to have gone down slightly (90 degrees) and the head I could not get decent readings of, but I have seen 110 degrees.

All in all, I made 36 minutes of flying, and the 2% Nitro and 15% Oil did not seem to harm (with glow ignition, the engine would have overheated from too little nitro ant too much oil) and it is not only approx 30% cheaper, but also a lot more convenient to have only one type of fuel at the field, so I think I will stick to this fuel, and leave the settings as they are at the moment.

Thinking about converting the flight school helicopters (.60 2 stroke) to spark ignition too.
They should earn themselves back in approx. 1 year.

Brgds, Bert

The RPM of a prop increases because the torque output has increased. I would guess 20RPM on the head would be difficult to observe. The extra torque could be felt like you said with better climb. What do you use for EGT sensor?

Greg

No EGT sensor....
I hoover for some minutes, and land and try to measure the outside temperature of the exhaust as quick as possible. For that I use an IR gun, and I need to stop the rotor for that. That takes approx 15 seconds.
That is not very accurate, I know, but I have no other option at the moment.

Yesterday I noticed those measurements showed a slight decline, today they were pretty consistent at 300+ degrees, but that van also mean, EGT at idle is just higher.

From the normal signs like smell and smoke, I do not get the impression things have really changed, but that is not an accurate indicator as well.

Brgds, Bert

Did I read in a previaous post that you are still running the same needle settings W/CDI as when you ran GI?