Are All Rcxl CDI units the same?
01-01-2011 | 09:11 AM
#26
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RE: Are All Rcxl CDI units the same?
This is over-simplified, but I believe it is the larger bore that causes the need for more timing advance in auto engines. That is also why full size airplane engines have two plugs per cylinder; because of the large bore. With the two plugs, the timing advance needs are lessened, and many full size airplane engines are timed at 25 degrees. The side benefit of course, is redundant ignition.
AV8TOR
AV8TOR
01-01-2011 | 10:04 AM
#27
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RE: Are All Rcxl CDI units the same?
Full scale re-cip engines have twin plugs due to a requirement for ignition system redundancy. They have twin magnetos and you can't use a single plug or plug wire for both magnetos. One of the pre-take off checks is to verify the rpm drop on each separate magneto by selecting between left-right-then both. Aside from that there is no reason a large bore engine cannot use a well designed hemispherical head to accomplish the ignition event efficiently.
01-01-2011 | 12:28 PM
#28
RE: Are All Rcxl CDI units the same?
I am not sure, but I think the mags are set to fire at 25 degrees and may be a fixed timing for less parts to go bad. Sure seems like dual CD ignitions would be just as good or better. Or have one of each...mag & CD ignition. It seems like the engines sound to far advanced for a suer smooth idle( maybe a compramise)...some sould like they have a high performace cam on idle...but I am sure the valve train is far from high lift...high duration cams in use. Just a guess....don,tt know for sure! Capt,n
01-01-2011 | 12:31 PM
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From: Tres Cantos, SPAIN
RE: Are All Rcxl CDI units the same?
RCEXL ignition manufactured for DLE engines are now labeled wit a number:
#1 is the first model intended for the DL50-DLE55 and side induction DLE30, #2 is the twin version for the 100-111, #3 is for the DLE30 V2 modified at same time than read induction, #4 for the DLE20 ....
I've seen the standard (model A01) ignition 'curve' , but i suspect the #2 and #3 models have a different static advance than #1. Maybe the rpms when advance is lowered is at hi rpm in #3 and #4 .
Regards
#1 is the first model intended for the DL50-DLE55 and side induction DLE30, #2 is the twin version for the 100-111, #3 is for the DLE30 V2 modified at same time than read induction, #4 for the DLE20 ....
I've seen the standard (model A01) ignition 'curve' , but i suspect the #2 and #3 models have a different static advance than #1. Maybe the rpms when advance is lowered is at hi rpm in #3 and #4 .
Regards
01-01-2011 | 12:38 PM
#30
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RE: Are All Rcxl CDI units the same?
Not too hard to figure out, you only have to be willing to remove an ignition from flight use and sacrifice it to dedicated test usage. Hardest part is "degreeing" the prop hub or spinner backplate after accurately marking TDC.
wesaysoracing;
I can't answer your question because it comes much too close to things I can't discuss outside of work. Anyone can figure it out butthey have to be willing to dedicate some time and resources to learn what questions need to be asked to find answers to.
wesaysoracing;
I can't answer your question because it comes much too close to things I can't discuss outside of work. Anyone can figure it out butthey have to be willing to dedicate some time and resources to learn what questions need to be asked to find answers to.
01-01-2011 | 12:42 PM
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From: Tres Cantos, SPAIN
RE: Are All Rcxl CDI units the same?
ORIGINAL: Tired Old Man
Not too hard to figure out, you only have to be willing to remove an ignition from flight use and sacrifice it to dedicated test usage. Hardest part is ''degreeing'' the prop hub or spinner backplate after accurately marking TDC.
Not too hard to figure out, you only have to be willing to remove an ignition from flight use and sacrifice it to dedicated test usage. Hardest part is ''degreeing'' the prop hub or spinner backplate after accurately marking TDC.
I've done it with many RCEXL ignitions ...
And i will do with next generation of CDI .....
Regards
01-01-2011 | 12:44 PM
#32
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RE: Are All Rcxl CDI units the same?
That is some good info. I had heard that the curve may had been changed a bit on the V2 DLE30's but had not seen anything on the forums about it. My 30 is a V1 that I converted to a V2. It runs fine on the A-01 ignition. It would be nice to find out the differences between the curves as it could impact what you set the static advance at. I know my 30 develops the greatest rpm when set at about 36 degrees. Problem is the idle is very bad with that much advance. If I drop the advance down to 26 degrees I can get it to idle down to about 1200, but then the top end suffers and I lose rpm. I ended up setting it at about 30~31 degrees. It has a good 1500rpm idle and the top end is pretty good. That is why if the ignition had the curve changed to retard the ignition more at low rpm it would enable the user to set the timing higher to gain rpm on the top end. If a change like that was made the user wouldn't be able to take advantage of it unless he played around with the timing to discover the changes. It may just be the rpm points in the curve were changed with the maximum amount of retard remaining the same as well. I use the term retard as these ignitions do not advance the timing to my understanding. The retard the ignition from what the static advance is set at when at low rpm and reduce the amount that it retards it as the rpm increases until it does not retard at all. I forget at what rpm it no longer retards it.
01-01-2011 | 12:51 PM
#33
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RE: Are All Rcxl CDI units the same?
To add to that I am not sure at what point preignition would start to become a problem at high rpm with so much advance. More advance, higher rpm, and higher ambient temperatures all add up to higher engine temps and problems start to develop. Pat would know more about this than all of us put together.
01-01-2011 | 02:09 PM
#35
RE: Are All Rcxl CDI units the same?
Lots of ideas and opinions abound .
FWIW - sometimes an advance of up to 50 degerres is required on some 4 strokers .
The amount of advance is related to the pressures developed in the combustion chamber -and WHEN they are best ignited
No secret.
Also in some engines, the pistons spend far more time as they travel over the top- than they do as they travel thru the bottom of a stroke - (has to do with relative rod to stroke length) and these types can take advantage of INCREASES in timing.
No secret
Al;so once th e engine reaches max torque point - furthe increases in rpm DECREASE pressures in th cylinder
no secret
further increase in advance does not cause pre ignition
THAT occurs when the charge ignites too early along the piston's advance to TDC
and OR temperatures are too hight (which further increases pressures )
All this has been common knownedge since probably 1900 AD
In our model airplane ignition systems we are working with fairly low compressions and a fairly low energy ignitions that are pretty similar . The curves available are sometimes grossly over advertised in theitr value
I guess (don't know ) that the one in question, stays at low advancetill abour 3500rpm? the nshifts on up to max
ZDZ made some that had variable curve in order to minimize the typical out of balance shudder at 2500-3000 on singles
I used to measure the ignitions on a big ol SUN machine - then just stuck with cut n try to balance setups for thengine - w/wo tuned pipes etc..
FWIW - sometimes an advance of up to 50 degerres is required on some 4 strokers .
The amount of advance is related to the pressures developed in the combustion chamber -and WHEN they are best ignited
No secret.
Also in some engines, the pistons spend far more time as they travel over the top- than they do as they travel thru the bottom of a stroke - (has to do with relative rod to stroke length) and these types can take advantage of INCREASES in timing.
No secret
Al;so once th e engine reaches max torque point - furthe increases in rpm DECREASE pressures in th cylinder
no secret
further increase in advance does not cause pre ignition
THAT occurs when the charge ignites too early along the piston's advance to TDC
and OR temperatures are too hight (which further increases pressures )
All this has been common knownedge since probably 1900 AD
In our model airplane ignition systems we are working with fairly low compressions and a fairly low energy ignitions that are pretty similar . The curves available are sometimes grossly over advertised in theitr value
I guess (don't know ) that the one in question, stays at low advancetill abour 3500rpm? the nshifts on up to max
ZDZ made some that had variable curve in order to minimize the typical out of balance shudder at 2500-3000 on singles
I used to measure the ignitions on a big ol SUN machine - then just stuck with cut n try to balance setups for thengine - w/wo tuned pipes etc..
01-01-2011 | 02:41 PM
#36
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RE: Are All Rcxl CDI units the same?
That had to have been a long and painful process. Imagine what could have been done if you could have observed all the various the impacts of changes in timing as they occurred using a high output, remotely programmable ignition. The exhaust system is indeed an important part of the performance equation.
01-01-2011 | 03:12 PM
#38
RE: Are All Rcxl CDI units the same?
ORIGINAL: Tired Old Man
That had to have been a long and painful process. Imagine what could have been done if you could have observed all the various the impacts of changes in timing as they occurred using a high output, remotely programmable ignition. The exhaust system is indeed an important part of the performance equation.
That had to have been a long and painful process. Imagine what could have been done if you could have observed all the various the impacts of changes in timing as they occurred using a high output, remotely programmable ignition. The exhaust system is indeed an important part of the performance equation.
I always used my ear and a tach
mostly my ear -
Often I would get asked - "how can you tell it's running faster?
the sound - faster is a higher pitch (relatively)
I have perfect relative pitch (as opposed to perfect pitch) developed as a musican from the time I was a little kid.
Lots of musicans have developed this
Here is a little aid which demonstrates why there are so many timing setups: take some poster board an make up a crank throw of 1" (simulate a 1" stroke)
now make a con rod which is 2" long and one which is three" long
With a piece of graph paper -assemble either rod to the throw (using straight pins) and turn the throw 360.
measure and mark the top of the rod for every 20 degrees of rod revolution.
change rods and do the same thing again alongside this first set of marks on the graph paper -
Note that the markes are now spaced differently vertically , as the throw rotates
You can also use this to demonstrate a DeSax cylinder arrrangement whre the crank is offset to one side a little bit
The piston -during the last 20 degrees before and after top dead center will rise at a different rate per each degree of crank rotation
This makes a BIG difference in when you want the spark to occur
-It also enables the designer to INCREASE compression when using a a longer rod to stroke arrangement !
More power can now be made with less chance of preignition or detonation
(That's a bitoversimplified but basically true)
DA notes this setup in their advertising
01-01-2011 | 03:46 PM
#39
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From: Golden,
CO
RE: Are All Rcxl CDI units the same?
ORIGINAL: rmh
Not too bad -
I always used my ear and a tach
mostly my ear -
Often I would get asked - ''how can you tell it's running faster?
the sound - faster is a higher pitch (relatively)
I have perfect relative pitch (as opposed to perfect pitch) developed as a musican from the time I was a little kid.
Lots of musicans have developed this
Here is a little aid which demonstrates why there are so many timing setups: take some poster board an make up a crank throw of 1'' (simulate a 1'' stroke)
now make a con rod which is 2'' long and one which is three'' long
With a piece of graph paper -assemble either rod to the throw (using straight pins) and turn the throw 360.
measure and mark the top of the rod for every 20 degrees of rod revolution.
change rods and do the same thing again alongside this first set of marks on the graph paper -
Note that the markes are now spaced differently vertically , as the throw rotates
You can also use this to demonstrate a DeSax cylinder arrrangement whre the crank is offset to one side a little bit
The piston -during the last 20 degrees before and after top dead center will rise at a different rate per each degree of crank rotation
This makes a BIG difference in when you want the spark to occur
-It also enables the designer to INCREASE compression when using a a longer rod to stroke arrangement !
More power can now be made with less chance of preignition or detonation
(That's a bitoversimplified but basically true)
DA notes this setup in their advertising
ORIGINAL: Tired Old Man
That had to have been a long and painful process. Imagine what could have been done if you could have observed all the various the impacts of changes in timing as they occurred using a high output, remotely programmable ignition. The exhaust system is indeed an important part of the performance equation.
That had to have been a long and painful process. Imagine what could have been done if you could have observed all the various the impacts of changes in timing as they occurred using a high output, remotely programmable ignition. The exhaust system is indeed an important part of the performance equation.
I always used my ear and a tach
mostly my ear -
Often I would get asked - ''how can you tell it's running faster?
the sound - faster is a higher pitch (relatively)
I have perfect relative pitch (as opposed to perfect pitch) developed as a musican from the time I was a little kid.
Lots of musicans have developed this
Here is a little aid which demonstrates why there are so many timing setups: take some poster board an make up a crank throw of 1'' (simulate a 1'' stroke)
now make a con rod which is 2'' long and one which is three'' long
With a piece of graph paper -assemble either rod to the throw (using straight pins) and turn the throw 360.
measure and mark the top of the rod for every 20 degrees of rod revolution.
change rods and do the same thing again alongside this first set of marks on the graph paper -
Note that the markes are now spaced differently vertically , as the throw rotates
You can also use this to demonstrate a DeSax cylinder arrrangement whre the crank is offset to one side a little bit
The piston -during the last 20 degrees before and after top dead center will rise at a different rate per each degree of crank rotation
This makes a BIG difference in when you want the spark to occur
-It also enables the designer to INCREASE compression when using a a longer rod to stroke arrangement !
More power can now be made with less chance of preignition or detonation
(That's a bitoversimplified but basically true)
DA notes this setup in their advertising
Thanks......great info on this post and your previous post too.
01-01-2011 | 04:55 PM
#41
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From: Salem,
OR
RE: Are All Rcxl CDI units the same?
Just to throw it in the mix, I program GM engines at work for boat and industrial use, every engine requires a different spark map to be optimal. One engine tops at 15 degrees at 4500rpm, but is 35 degrees at that speed and lower load, others are in the 25 degree range at full load/speed. The timing tables I use are a little fancier than just a curve though, they change with manifold pressure and speed instead of just speed. For a plane, a prop load curve is close enough to just use a curve though.
01-01-2011 | 05:43 PM
#42
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RE: Are All Rcxl CDI units the same?
Well TOM, I can't find my reference material that explained about how full size aircraft engines and their large bores used dual ignition to control combustion and prevent detonation, and I'm too tired to go searching for the info on the internet.
Been a pilot and aircraft mechanic (full size) for nearly 40 years...
Yes, a large bore engine could be designed with a combustion area that would do fine on a single ignition source, but nobody wants to pay what it would cost to get the FAA to certify it. (Millions) That's why we are stuck with 1940's technology on full size airplane engines.
AV8TOR
Been a pilot and aircraft mechanic (full size) for nearly 40 years...
Yes, a large bore engine could be designed with a combustion area that would do fine on a single ignition source, but nobody wants to pay what it would cost to get the FAA to certify it. (Millions) That's why we are stuck with 1940's technology on full size airplane engines.
AV8TOR
01-01-2011 | 05:57 PM
#43
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RE: Are All Rcxl CDI units the same?
I hear ya where the certification process is concerned. A lot of good stuff has been lost because of that process alone. It's amazing what happens to the cost of a relatively simple alternator once the FAA certification process has been encountered. The $65.00 one will work just fine but the one that's legal for use ends up costing $800.00, before labor.........
I don't doubt the dual ignition prevents detonation. With the plugs indexed as they are it can't help but prevent it. I wonder if that was secondary to the redundant mag requirement though.
I don't doubt the dual ignition prevents detonation. With the plugs indexed as they are it can't help but prevent it. I wonder if that was secondary to the redundant mag requirement though.
01-01-2011 | 06:35 PM
#45
RE: Are All Rcxl CDI units the same?
here is some serious offset
If you look around -there are some really quirky engine designs - which usually had too may faults to make em popular
If you look around -there are some really quirky engine designs - which usually had too may faults to make em popular
01-01-2011 | 08:51 PM
#46
Senior Member
RE: Are All Rcxl CDI units the same?
Look at no#4 with a timing light and tell me you see.I need some one else to check this and tell me I haven' lost it.I have sent parts to Ralph so he can check this.
BCCHI
[quote]ORIGINAL: mpascual
RCEXL ignition manufactured for DLE engines are now labeled wit a number:
#1 is the first model intended for the DL50-DLE55 and side induction DLE30, #2 is the twin version for the 100-111, #3 is for the DLE30 V2 modified at same time than read induction, #4 for the DLE20 ....
I've seen the standard (model A01) ignition 'curve' , but i suspect the #2 and #3 models have a different static advance than #1. Maybe the rpms when advance is lowered is at hi rpm in #3 and #4 .
Regards
[/quote
BCCHI
[quote]ORIGINAL: mpascual
RCEXL ignition manufactured for DLE engines are now labeled wit a number:
#1 is the first model intended for the DL50-DLE55 and side induction DLE30, #2 is the twin version for the 100-111, #3 is for the DLE30 V2 modified at same time than read induction, #4 for the DLE20 ....
I've seen the standard (model A01) ignition 'curve' , but i suspect the #2 and #3 models have a different static advance than #1. Maybe the rpms when advance is lowered is at hi rpm in #3 and #4 .
Regards
[/quote
01-02-2011 | 06:48 AM
#47
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From: pmburg, SOUTH AFRICA
RE: Are All Rcxl CDI units the same?
[quote]ORIGINAL: bcchi
Look at no#4 with a timing light and tell me you see.I need some one else to check this and tell me I haven' lost it.I have sent parts to Ralph so he can check this.
BCCHI
ORIGINAL: mpascual
RCEXL ignition manufactured for DLE engines are now labeled wit a number:
#1 is the first model intended for the DL50-DLE55 and side induction DLE30, #2 is the twin version for the 100-111, #3 is for the DLE30 V2 modified at same time than read induction, #4 for the DLE20 ....
I've seen the standard (model A01) ignition 'curve' , but i suspect the #2 and #3 models have a different static advance than #1. Maybe the rpms when advance is lowered is at hi rpm in #3 and #4 .
Regards
[/quote
RCEXL ignition manufactured for DLE engines are now labeled wit a number:
#1 is the first model intended for the DL50-DLE55 and side induction DLE30, #2 is the twin version for the 100-111, #3 is for the DLE30 V2 modified at same time than read induction, #4 for the DLE20 ....
I've seen the standard (model A01) ignition 'curve' , but i suspect the #2 and #3 models have a different static advance than #1. Maybe the rpms when advance is lowered is at hi rpm in #3 and #4 .
Regards
[/quote
01-02-2011 | 06:50 PM
#48
RE: Are All Rcxl CDI units the same?
I will place my airplane on my airplane test stand and put a timing lught on the engine soon. If things go good.. I should learn and post.some data here. Hope this photo uploads...pretty hard to do lately!
Capt,n
Capt,n
01-02-2011 | 07:05 PM
#49
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RE: Are All Rcxl CDI units the same?
I find to make them load without them coming out full size I need to post one picture and then go back and edit. Each time only adding one more picture. If I attach them all at the same time the first picture is fine, but the rest are huge.
01-02-2011 | 07:09 PM
#50
RE: Are All Rcxl CDI units the same?
Did you notice that some photos that are large....when you click to enlarge them....tthe photos then go smaller!!!!!! Very strange indeed. capt,n
