SrTelemaster150

I get so much resistance from "dyed in the wool" glow driver users when I suggest that CDI ia a much better alternative to OBG.

They seem to think that CDI is complicated, bulky, heavy, expensive & unrelibale.

Here is a picture of a typical McDaniels single cylinder OBG. It retails in the neighborhood on $85.





Now compare that to this picture of a single cylinder C&H CDI system The retails for about $115.




Granted, the CDI system doesn't include the charger, but you use the same type of charger/ switch/charging jack that you use W/your RX & the same 4.8/6.0/7.4v battery packs.

Looks to me like the CDI is a wole lot less complicated than an OBG. The weight will be about equal but the CDI will take up less room in the airframe.

As far as cost? The CDI will use about 20% less fuel to make 6% more HP so the fuel savings outweigh the $30 added cost.

So CDI is simpler, less bulky, not any heavier, the added cost will be made up for in fuel savings, but what about reliability?

I have 2 C&H systems that were put into servive in 1997. One of them has survived several crashes, one crash was straight in @ WOT from about 100' up. They both still operate flawlessly.

The spark plugs last almost forever. The idea that CDI is somehow unreliable is ludicrous as it is emplyed on almost every kind of IC engine you can imagine W/great reliability.

So, so far it looks like CDI has some advantage over OBG.

Now, lets look @ the added bonuses of CDI over OBG.

OBG is still a glow ignition system W/all of the drawbacks of glow ignition.

That is, the ignition timing will fluctuate W/the fuel mixture, nitro content, ambient temperature, barometric pressure, humidity, etc, etc.

W/CDI the ignition event timing is exactly the same every time & it can be programed to retard/advance as the engine RPM dictates.

You will get about 5-6% more HP, (200-300 more RPM @ peak) you will be able to run about 25% longer on a given tankful of fuel, the engine will be super easy to flip start, the reliable idle speed will be about 300 RPM less, (easier landings) & the overall user friendlyness will be much better W/CDI. Oh yeah, W/CDI you can totally eliminate nitro W/O affecting reliability or user friendlyness.

Given all of these factors, it would seem that OBG has nothing to offer over CDI & CDI is a much better option W/lots of added features..

Here are some clips of both of my 16 year old C&H Synchrospark CDI sytems taken last summer.

[youtube]http://www.youtube.com/watch?v=5xaiAR8Yelc[/youtube]


[youtube]http://www.youtube.com/watch?v=vdmLu13UJzs[/youtube]



Here is the latest developement from C&H Ignitions.

A single module, single hass sensor CDI for 3 cylinder radial engines.

[youtube]http://www.youtube.com/watch?v=iERCMNum7XY[/youtube]

C&H also has CDI sytems for 5 cylinder & 7 cylinder radials in developement.

TFF

I like ignition on glow fuel, but I will play devils advocate. If you are using onboard glow to cover up an airframe or tuning problem, it is a no no. A person who does will be the same one who cant get the ignition to work reliably. If you are just using it for a way to not hook up external glow or lower idle for a scale job it will be a wash. more hp with ignition, but when you have a problem you have to have to have more than just a glow plug to get going again if you are willing to light the glow plug with an external drive. Its a hobby and there are a lot of neat ways to do things.

Hobbsy

My Feedback: (102)

In this picture you can see the same McDaniel unit on my Joss Stik, I later removed it as it was not needed once I hit the sweet spot on the LS needle. More correctly you can see the wires and the connectors.

SrTelemaster150

You are absolutely correct. if ya can't get it right on GI, (unless it's just a tempermental finger biting engine like Hobbsy's high compression FA150) you would have an even worse time W/CDI. Another example of an engine that is very difficult (I'm told) to get right on GI is the FA450R3D. Since the advent of single module/single sensor CDI systems for radial engines, it should be easier to get the full potential out of these tempermental powerplants.

I think there's over 7HP on tap W/CDI & some induction improvements. The FA450R3D is being fed by a tiny 120 size 8mm carburetor. W/an 11mm 220 Big Bore carb on a direct, through the case induction modification, it should have the potential for a dramatic increase in HP.

Perhaps the biggest drawback W/CDI is that it does require some skill/knowledge to set up.

It's not difficult, but if one isn't familiar W/the process it can be intimidating.

Once it is set-up, it's a hands off proposition unless the prop hub needs to be removed.

That's probably why Saito uses a pinned prop hub & relies on the limited adjustment on the hall sensor mount. It's nearly impossible to get the Saito system far enough out of time to prevent @ least mediocre performance.

I started this thread to try to dispel some of the mythes about CDI. IMO, if the airframe is large enough for OBG, it's large enough for CDI.

On some 40 sized airframes it would be hard to house either.

A 40 size Cub would probably be the lower limit.

I have a (supposedly 40 size) Wingsmaker (Worldsmodels) 84" 1/5 scale Cub J-3 that will get my FA91S W/CDI.

Actually I'm thinking about purchasing an FA82 to take the place of the 91S. It should make just about the same power & have less hanging out of the bottom of the cowl.

As far as having to work on the ignition sytem @ the field? I always keep some spare plugs on hand. The only failures that one is likely to encounter is fouled plugs on the initial start up for the day. When I get a fouled plug, I replace it & soak it in acetone when I get home. An overnight soak in acetone followed by a shot of compressed air makes 'em good as new. I always keep the little vials that the plugs come in to carry the spare plugs.

If the engine is not cowled, it's no harder swapping out a spark plug than it is a glow plug. The 1/4 X 32 spark plugs even use then same glow plug wrench.

Hobbsy

My Feedback: (102)

I am still going to do that but I need the 120 degree spark plug connector, the 90 I have is just too hard to get on and off. I got a picture of the 120 degree adapter.

Sport_Pilot

On board glow is used for inverted and multi cylinder applications. The latter of wihich would be more complicated with CDI.

Some engines are difficult with inverted applications because of oil drowning out the glow plug.

SrTelemaster150

Where on earth did you get the idea that inverted engines are "more complicated with CDI"?

I ran my FA150 inverted in my Dynaflite PT-19 W/great reliability.

All you have to do is pay attention to how you orient the engine during storage to prevent oil puudling on the spark plug.

Any inverted engine application, either GI or CDI, can be improved by canting the engine so that the exhaust valve is @ the bottom.

Sport_Pilot

..

I clearly said the latter is more complicated, that is multi cylinder engines. Read more carefully next time.

I was refering to oil on the glow plug not spark plug, I was refering to some 4 cylinder engines, especially before broken in. And the oil collects when idleing and especially when sitting when the engine is off and full of oil before the next start up.

SrTelemaster150

Well I guess you got there, but wy did you mention inverted in the same phrase in the 1st place?

But again you lack of knowledge about CDI sceaming for everone to notice.

There's nothing complicated about "multi cylinder" CDI systems either. And, you comment regarding CDI being somehow less stable on engines that are being broken in is ludecrous given the more stable ignition timing of CDI & how can the oil collecting on the (spark) plugs be more of an issue W/CDI when the engines are running 20% leaner?

Here's a single module, single pick up CDI system for 3 cylinder radials. 5 & 7 cylinder modules will soon be available too.

[youtube]http://www.youtube.com/watch?v=iERCMNum7XY[/youtube]

Here is a module for an even firing twin.



This works from a single hall sensor just like a single cylider unit. Real complcated huh?

Even a 4 cylinder boxer would only require 2 of the twin modules @ 2 hall sensors mounted 180° apart on the cam covers.

An uneven firing twin would only require 2 single modules W/the same 2 hall sensor set-up as the 4 cylinder.

Still not all that "complicated". Justb a little more "complex", but not "complcated".


Might as well convert to gas if you convert to CDI you say?

Here's the same Saito FA450R3D that was in the other video except it is now running on gas.

The prop is now a 22 X & it is turning just under 7K RPM.

[youtube]http://www.youtube.com/watch?v=GdZgxPjXLxQ[/youtube]

That's about 5.2 HP or 16% less than the CDI glow fuel burning version that put out 6.2 HP turning a 24 X 10 @ 6500 RPM.

The CDI/glow fuel engine will run cooler & internally cleaner than the gasoline conversion, but if fuel coast is a factor then the gasoline conversion makes almost as much HP as a GI FA450R3D does so it would be a good choice "if that's you cup of tea"..

Without exception, all of you naysayers have never had much experience W/CDI & therefore little knowledge.

Here's a quote from a smilar thread as this over on RCG. This respondent recently convert an engine from GI to CDI W/glow fuel.

Quote:

Originally Posted by Brutus1967

Just my two cents:

I have learned most of what I know about ignitions and their advantages from mr SrTelemaster and a few others here....

As to factual info, I can only agree with him/them, as everything stated here, turns out to be true.

Still, if I read this, and even with my firsthand experience in the back of my mind, the opening post seems a bit agressive, and I can see how people would just for the tone of that message, leave CDI where it is: on the shelf of the LHS....

And that is a bit of a shame, because, you know.... it is just all so true.

People saying a glow plug is cheaper to buy than a CDI.... well.... I typically use more $$ in glowplugs every two years, than a CDI would cost. Only the absence of a glowplug that can fail then invariably needs replacement, will earn back the money spent on a CDI, and a CDI you buy only once.....
I will typically save more $$$ in fuel every approx 6 months, than a CDI cost. And mind you, I was running "no nitro" allready before the conversion. Imagine the savings when going from for example, 15% Nitro to 0% Nitro....

Only the matter of installing such system, yep, that can be an issue. But luckily, most flying clubs have "go-to guys" that if asked friendly, will help you convert your first engine. After that, it is not black magic anymore....

Under .45 engines, it is likely that you do not have enough space to fit the system in your aircraft.
under .30 most likely even if the space is availlable, the added weight cancels out the performance gain.
Smaller engines also mean smaller fuel savings, so economically it is also not as interesting.

But anything over .60, no matter 2stroke or 4stroke, it is worth your wile.

Really....

If you want to buy now, fly in ten minutes, buy OBG. If you want sweet running engines with noticeably less "every-day-adjusting-to-the-weather" hassle, really low fuel cost (no nitro) and you do not mind a bit of initial tinkering, buy a CDI.

And I would say: ESPECIALLY those people that have trouble adjusting their engine every flying day, will GREATLY benefit from CDI over OBG, as adjustment is basically a one time, forget forever, affair.

Brgds, Bert

Here's a link to that thread if anyone carse to see the dialogue over there. The quote above is post #39 on page 3.

http://www.rcgroups.com/forums/showthread.php?t=1894329

Hobbsy

My Feedback: (102)

Dan, one thing you might consider adding to your recommendation is that, carefully setting the LS needle is of utmost importance since it controls the mixture for about 85% of the throttle range. An engine with a poorly set LS needle can actually get better fuel economy at full throttle than at, say, half throttle. I plan to set up my 1.50 with C&H Ignition and a Cline regulator, this should be the ideal combo as I will only need to run the engine 50 rpm rich of peak because leaning as the tank empties is no longer a concern. That should keep the spark plug cleaner as part of the bargain.

PS, I found another older C&H Ignition that has the wire set up for a Maloney 1.25, I'll get two of the 120 degree repair kits from Adrian. The Maloney had a special spark plug that Terry Grant used a special wire end on.

Here are a couple of pictures of the old C&H ignition, note it has a separate module for the SynchroSpark, this one is "all in" at 2,500 rpm, barely above idle. Maloney spark plug is visible.

Also note Deans connectors, a bit of history right there

SrTelemaster150

Yes , the LSN is important for fuel economy.

That's why I lean it out until it stalls on transition & then open it up just enough for smooth transition.

I especially like the FA300TTDP dual carb setup for setting the LSN.

I just lean outb the LSN @ idle until that individual cylinder drops out, then open it up until it just picks back up.

I love the dual carbs, For me they are easier to get balanced than the single carb 300s.
"
having lived through dual AMAL Monoblocs on my hopped up '65 BSA, setting up the dual Saito carbs is a "walk in the park".

I find the 50 RPM off peak unneccessary W/CDI, but I do back up to the rich side of peak RPM that can be 1/4 turn if leeway W/CDI.

That's some odd C&H unit you have there. I thought the earliest Snchrospark units were all metal cased.

I have 3 Mk I units from '97, some of the earliest SS units.

Hobbsy

My Feedback: (102)

That particular SS unit plugs in between the Hall effect sensor and the box. They came in 1,500 and 2,500, "all in" settings.

SrTelemaster150

I know how it works, but when was it made?

Was it pre'97? The plastic case makes me think otherwise.

The picture downloader isn't working again so here is a picture of the Mk I Synchrospark units circa 1997.

Note the delrin trigger magnet ring & primitive hall sensor bracket.



Here is the back of the case showing the manufacture month & year.



I bought that system last summer on RCG.

BTW, when are you guys going to get some 21st century sofware so PIX can be loaded directly. This software SUX!

Sport_Pilot

I should have said 4 cycle not 4 cylinder. And I did not say anything about CDI it was a reference to on board glow and oil in the glow plug not spark plug. The oil is a problem without onboard glow not with. Please stop trying to read between the lines.
Except there may be more pickups andor coils, depending on the method used for the CDI. Not a problem witha single pick up I suppose. But you still have to worry about the firing order, sometimeswith interferance. IMOinstalling the pickup is enough to go to on board glow. Especially when you plan on removing it when the engine is broken in.

Your 20% gain in fuel economy is only for those who use a glow plug too hot to begin with. I am sure the gain is considerably smaller after I have picked the glow plug with the highers RPM, and usually the leanest needle setting.

Having burned maybe 3 tankfulls of fuel last year, Idon't care if it saves 100% of fuel. I need to burn some fuel!

SrTelemaster150

Man, you are all over the map here.

Firing order is only relevant in our common modeling engines on radials.

On twins or even 4 cylinder engines the "firing order" is not relevant because the spark occurs @ everytime the piston passes over TDC.

It's called "waste spark". 1 of the spark cycles is "wasted" on the exhaust stroke just before TDC.

On radials, the new single module units from Saito, RCEXL & C&H have 1 more magnet than the # of cylinders. That reverse polarity magnet "sequences" the firing order.

A 3 cylinder radial fires 1-3-2-1, a 5 cylinder radial fires 1-3-5-2-4-1, a 7 cylinder radial 1-3-5-7-2-4-6-1. Every- other cylinder.

A reverse polarity magnet (the extra magnet) triggers the every-other cylinder firing order.

All you have to do is make sure than you are starting W/the #1 cylinder when the 1st magnet after the sequencing magnet is passing under the hall sensor.

Set that cylinder for whatever the appropriate timing advance is & the computer takes care of everything.

There are no external coils, they are contained in the module. The pickup is a small simple hall affect sensor & the most you would need on any model engine of 4 cylinders or less is 2. Radials only need 1.

It becomeing clear that this is over your head & that's OK & understandable.

For you GI is probably the best choice.

Sport_Pilot

Not over my head, I have dealt with complicated HVAC control systems. I just have not bothered to check it out, because I know that I won't bother with the extra weight, cost, and bother; no matter how simple it is. Many of my models are too small for the module. I would think it would have to be at least a 40 size.

iskandar taib

My Feedback: (5)

Hmmm.. Is it really all that complicated - or expensive, even?

http://www.hobbyking.com/hobbyking/s...r_1_5V_3A.html

Iskandar

SrTelemaster150

That's not the point.

A glow driver does not improve performance other than keeping the glow plug lit @ low RPM to prevent flameouts.

CDI is not really any more complicated & produces more power, 20% better fuel economy, easier starts & lower reliable idle speed.

CDI is not practical on engines much under 1.00 cu. in., but anything larger it has benefits & the larger the engine gets, the larger the benefits.

Sport_Pilot

Yes. Like the first thing Iwill do when getting back into the hobby is to buy a glow driver or electronic ignition!

Actually right now I am building a rubber powered free flight. So yes, for now it is too complicated and expensive.

You are assuming that I and others care. Till I am burning a lot of self mixed fuel, I won't care.

I am adding this because I now understand that I sound rather obnoxious. I am just explaining that many do not care. If they are getting good performance and reliability from their glow engine as is we won't bother with this and the glow driver looks a bit simpler and is a bit cheaper.

What you said has merit and I may consider this in the future.And BTW it doen't look much bigger than a glow driver and I have used a glow driver in a 60 sized plane before and probably not too large for a 40 sized. But I rarely have issues with power and reliability and have onlyhad periods where Iflew enough to be that concernerd about fuel economy. When it was an issue I simply started mixing my on fuel. Not much more expensive than gasoline fuel mix's then.

jfuller

My Feedback: (8)

Hi,

Let me throw in my .02 worth. I first used glow drivers about 20 years ago on ST 1.8 cu. in. engines. The carbs weren't the best and with inverted engines flameouts were commonplace. I used a micro switch epoxied to the motor servo that switched a Nicad on at anything less than 1/4 throttle. Easy install, low weight. No complexity, and it worked 100 percent. I later installed a C&H ignition system on a couple of ST's and a 120 4 stroke. Slightly more complex installation but nothing the average modeler would have any problems with. they all became one flip starters, idled at lower speeds, became totally reliable, and a pleasure to run. I switched to no nitro and still had lots of power. I don't think that spark ignition is as useful for anything smaller than .90 size engines decause of the added weight. Based on the above, I would think that plug heat or ignition systems add a lot of enjoyment to flying, a I agree that they save fuel costs.

JamesF