SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
02-20-2010, 06:19 PM
#277
RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
Evert, I was under the impression that when you set your timing to say 28 degs, that's the most advance you can get. When powered down, it's already full advanced when you set the 28 or whatever number. The difference is thrown to AFTER top dead center while running. So a 35 advance unit set to 28 will advance to 28 at above 4000 rpm. Below 4000, you'll retard to as much as 7 degs AFTER TDC depending on how low the rpms get. Anyway, maybe I'm wrong on this, I'll allow for that. This is just my current understanding.
02-20-2010, 06:32 PM
#279
RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
I don't know about the ignition being used but if I remember correctly, the CH and RCEXL ignitions only retard about 16 degrees betwee 2000 and 4000 rpm.
So with the ignition set at 28 degrees - at idle, your ignition timing would be around 12 degrees BTDC and getting up above 4,000 the advance returns to 28 degrees BTDC.
EDIT: See the post down below by TKG for the real facts!
So with the ignition set at 28 degrees - at idle, your ignition timing would be around 12 degrees BTDC and getting up above 4,000 the advance returns to 28 degrees BTDC.
EDIT: See the post down below by TKG for the real facts!
02-20-2010, 07:42 PM
#282
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RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
The CH curve is different, 26 degrees of timing change. That's why we say 28-30 BTDC. Most engines like a little advance when idling 2-5 degrees. If you engine has retarded timing it will often start backwards.... so it gets 2-5 degrees BTDC.
You really want to have the minimum advance to achieve WOT. Too much advance and the engine may knock or have a HS miss that you can't tune out with the carb. To little advance and your engine will bog when you try to accelerate it.
The whole secret to all this is to find exactly TDC.
You really want to have the minimum advance to achieve WOT. Too much advance and the engine may knock or have a HS miss that you can't tune out with the carb. To little advance and your engine will bog when you try to accelerate it.
The whole secret to all this is to find exactly TDC.
02-21-2010, 05:51 AM
#283
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RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
@TKG,
I think thats really what i've experienced. The rcexl unit gives more advancing than the CH units i guess.
When setting up the ignition at a point where the engine runs well at mid and high rpm it ends up with retarded timing at idle. Thats noticeble because of less power at transition from idle to mid range.
Also see the specs of the rcexl units here:http://www.rcexl.com/upfile/200994/2...1492067926.pdf
I've asked rcexl to send me the grafics with the curve. Hope the will do that.
Maybe i can try an other cdi unit. I have to figure out wich cdi unit has the smallest advancing.
I think thats really what i've experienced. The rcexl unit gives more advancing than the CH units i guess.
When setting up the ignition at a point where the engine runs well at mid and high rpm it ends up with retarded timing at idle. Thats noticeble because of less power at transition from idle to mid range.
Also see the specs of the rcexl units here:http://www.rcexl.com/upfile/200994/2...1492067926.pdf
I've asked rcexl to send me the grafics with the curve. Hope the will do that.
Maybe i can try an other cdi unit. I have to figure out wich cdi unit has the smallest advancing.
02-21-2010, 10:24 AM
#284
RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
That RCEXL PDF document sure speaks of a lot of timing change. It makes for a narrow realm of initial timing position.
Since back in the 90's I have followed TKG's advice and it has always worked as he said.
Since back in the 90's I have followed TKG's advice and it has always worked as he said.
02-21-2010, 11:04 AM
#286
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RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
Yep, would be nice if we could figure this out wouldn't it.
If we are able to find out what curve grafics the different cdi 's have we can do a even better job on the engine conversions.
Today i flew my Robbe Diamant with the FA80 conversion. It's better than it was in its former glow life. I can say that i'm proud about it.
( Still don't see the option for pasting a picture in this post. pfff......) 
Ohh, thats easy.......
If we are able to find out what curve grafics the different cdi 's have we can do a even better job on the engine conversions.
Today i flew my Robbe Diamant with the FA80 conversion. It's better than it was in its former glow life. I can say that i'm proud about it.
Ohh, thats easy.......
02-21-2010, 02:38 PM
#287
RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
Really nice. I'm glad we were able to help here in this thread.
I'm still curious just what kind of engine could have effectively used that 35 deg advance ignition unit.
Now, what is YOUR process for posting pics here? I"m always looking for easier ways of doing things. Thanks.
I'm still curious just what kind of engine could have effectively used that 35 deg advance ignition unit.
Now, what is YOUR process for posting pics here? I"m always looking for easier ways of doing things. Thanks.
02-21-2010, 03:25 PM
#288
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RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
ORIGINAL: Pull Up Now!
I'm still curious just what kind of engine could have effectively used that 35 deg advance ignition unit.
Now, what is YOUR process for posting pics here? I"m always looking for easier ways of doing things. Thanks.
I'm still curious just what kind of engine could have effectively used that 35 deg advance ignition unit.
Now, what is YOUR process for posting pics here? I"m always looking for easier ways of doing things. Thanks.
I download pictures to my gallery. From there just cut and paste in de post.
02-22-2010, 01:03 PM
#289
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RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
This is the grafic i received from rcexl. I know my english isn't very clear sometimes but this is the chinese -english answer from rcexl:
Angle is delayed mode,Started is delayed to 3-5 degrees to start the engine
Reached after the 4000 rpm, without delay, direct ignition spark.
I do not know Can you understand that.
In addition, you can refer to the CH company's website. Which have a more detailed description of the modification.(www.ch[/b]-ignition[/b]s.com)
Thank you very much.
Best Regards
Xu Liang Company President
HTTP://WWW.RCCDI.COM HTTP://WWW.RCEXL.COM
Thank you very much.
Best Regards
Xu Liang Company President
HTTP://WWW.RCCDI.COM HTTP://WWW.RCEXL.COM
This curve is different as it shows at the datasheet from rcexl.
Since they are referring to ch-ignitions it has probably the same curve.
In my case : i've set the ignition timing at 22 degrees. If i'm right that means at 2000 rpm idle i still have 6 degrees advancing.
02-22-2010, 05:53 PM
#290
RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
These are the instructions you should be using with your RCEXL ignition
Set up the static timing at 28-30 degrees BTDC
The auto retard feature will bring the timing back down to 2-8 degrees BTDC when you briskly flip the prop once.
http://www.ch-ignitions.com/timing.html
Set up the static timing at 28-30 degrees BTDC
The auto retard feature will bring the timing back down to 2-8 degrees BTDC when you briskly flip the prop once.
http://www.ch-ignitions.com/timing.html
02-22-2010, 10:18 PM
#291
RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
Evert,
Thanks for publishing that advance curve graph rcexl sent you. It's interesting. There is one glaring problem. Rcexl's own published data sheet says their curve maximum is 35 degs at 4k rpm. Yet the graph shows 28 degs. So your engine performance, and how you set your timing is greatly dependent on which it is.
Remember I said I wondered what kind of engine 35 degs of advance would be good for? Question still is a good one. Maybe an extremely high rpm engine. Except the curve still tops out at 4k. I could see maybe 35 degs at 25k rpm. Combustion doesn't get any faster at high rpm. So you have to spark earlier when it's spark ignition. In the real world, you run out of steam really before then.
I actually wonder if the data sheet (not the graph) is an error, or a type. Wouldn't be the first time a Asian supplier had the wrong data. Or maybe that was "revision 1" software and it didn't work out well in the field, but they never updated that datasheet on their website? I don't know, just speculating. If you communicate with them again, maybe you could ask about the inconsistency.
Why don't you put a old automotive timing light strobe on your engine and then you can tell if you have a 28 or a 35 ignition unit? I'd bet it's 28, in which case you should follow W8ye's advise.
The only other thing is that, as TKG said, a little advance at idle is good. In this case, yes, it would be good about 6 degs assuming you idle around 2krpm. My Saito conversion was idling at as low as 1300 rpm. The big issue is that at WOT you're only going to get 22 degs of advance. That may not be optimized for max power. If static is set up at 22 degs, you used up 12 of the 28 (see the graph) total available to get to 2k rpm and 6 degs BTDC. There are 16 degs left available now. They (the degs of advance) will be all used up at 4k rpm. The original 12+16=22 degs. From 4k rpm up thru WOT, your advance is max'd out a 22, which may rob you of some power at WOT.
Thanks for publishing that advance curve graph rcexl sent you. It's interesting. There is one glaring problem. Rcexl's own published data sheet says their curve maximum is 35 degs at 4k rpm. Yet the graph shows 28 degs. So your engine performance, and how you set your timing is greatly dependent on which it is.
Remember I said I wondered what kind of engine 35 degs of advance would be good for? Question still is a good one. Maybe an extremely high rpm engine. Except the curve still tops out at 4k. I could see maybe 35 degs at 25k rpm. Combustion doesn't get any faster at high rpm. So you have to spark earlier when it's spark ignition. In the real world, you run out of steam really before then.
I actually wonder if the data sheet (not the graph) is an error, or a type. Wouldn't be the first time a Asian supplier had the wrong data. Or maybe that was "revision 1" software and it didn't work out well in the field, but they never updated that datasheet on their website? I don't know, just speculating. If you communicate with them again, maybe you could ask about the inconsistency.
Why don't you put a old automotive timing light strobe on your engine and then you can tell if you have a 28 or a 35 ignition unit? I'd bet it's 28, in which case you should follow W8ye's advise.
The only other thing is that, as TKG said, a little advance at idle is good. In this case, yes, it would be good about 6 degs assuming you idle around 2krpm. My Saito conversion was idling at as low as 1300 rpm. The big issue is that at WOT you're only going to get 22 degs of advance. That may not be optimized for max power. If static is set up at 22 degs, you used up 12 of the 28 (see the graph) total available to get to 2k rpm and 6 degs BTDC. There are 16 degs left available now. They (the degs of advance) will be all used up at 4k rpm. The original 12+16=22 degs. From 4k rpm up thru WOT, your advance is max'd out a 22, which may rob you of some power at WOT.
02-23-2010, 09:52 AM
#293
RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
It seems as thought the graph is difficult to understand. The ignition is designed to give no delay above 4000 RPM. In the graph the sensor was set to spark 28°BTDC. So at 2kRPM you still have 12°BTDC timing. My little FS-52 ran just fine on an RCEXL ignition at an eyeballed 28° advance. Now I have a Runtronic ignition on it. Half the size and many options for advance/RPM. They are fairly expensive. I took a chance on one off of thEbay for almost nothing.
02-23-2010, 10:56 AM
#294
RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
Greg,
you said "In the graph, the ignition was set to 28 degs BTDC". You probably know this, but I thought I'd mention the graph has nothing to do with where the sensor is set. They're independent from each other. The graph just represents a program table in firmware, and it will look the same no matter where you place the hall sensor.
you said "In the graph, the ignition was set to 28 degs BTDC". You probably know this, but I thought I'd mention the graph has nothing to do with where the sensor is set. They're independent from each other. The graph just represents a program table in firmware, and it will look the same no matter where you place the hall sensor.
02-23-2010, 11:37 AM
#295
RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
Correct. The graph is poor. I think it should look more like this. The graph above makes it look like spark timing will be at 28° regardless of the sensor position. That is not the case.
02-23-2010, 08:12 PM
#296
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RE: SMALL DISPLACEMENT FOUR STROKE GLOW TO GAS CONVERSION
Hi guys,
I am thinking on converting a YS 120NC to gas. Can any one that has experience with this engine explain the supercharge system and how it works. I tryed to find a drawing/diagram on how the flow goes inside the engine.
Second, For a Saito FA 180 a WT 456-1 will work or is to small.
Thank You
Adrian
I am thinking on converting a YS 120NC to gas. Can any one that has experience with this engine explain the supercharge system and how it works. I tryed to find a drawing/diagram on how the flow goes inside the engine.
Second, For a Saito FA 180 a WT 456-1 will work or is to small.
Thank You
Adrian
