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Old Feb 22, 2015, 03:24 PM
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Quote:
Originally Posted by ZAGNUT View Post
maybe that was true 15 years ago but today a CDI system with IBEC is only 2.5oz.
that means that on a .40 glow powered plane where you would normally use an 8oz tank with 10% nitro fuel you could switch to a 6oz tank of 0% nitro fuel and your power, flight time and weight would all stay the same. on smaller models the added weight would still be manageable while on larger model you would actually be saving weight.

and the perceived "hassle" of using CDI is also ancient history. one end of the IBEC plugs into the CDI and the other end plugs into the receiver....that's it, no switch, no battery, no soldering. the booster battery for glow plugs is actually more of a hassle....with CDI you just flip a switch on your Tx and then flip the prop.

the glow plug was a great advancement 65 years ago when the ignition systems of the day were really awful but it's time has passed. what is good is that along with the glow plug came came universal use of methanol based fuel.
What is a 'booster battery' ZAGNUT?
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Old Feb 22, 2015, 03:34 PM
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Originally Posted by ideas View Post
Are both engines the same, just the head ?
Yup, the only difference is the part number for the crankcase, and that's only because of the model number cast into the side of the crankcase.
Same crank, conrod, piston, liner and carby, so yes, they're the same engine.
Hobbico's pricing on this engine is nutz, in IMHO, they give you a $12.99 and leave out a 80 buck CDI and charge 50 bucks more than the GT15
Pete
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Old Feb 22, 2015, 05:53 PM
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Originally Posted by ideas View Post
Are both engines the same, just the head ?
Wouldnt the case be different for the ign. sensor ? Cheers the pope
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Old Feb 22, 2015, 07:28 PM
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Well, in the case of the EVO 15cc gas engine and its identical glow version, the glow version has the holes drilled and tapped for the ignition sensor.
Now, does OS drill the holes in the case for the sensor? If not, another reason to save 50 bucks and get the GT15. I wonder if there is a suitable adapter to fit a 1/4" spark plug in an head that takes a CM-6 plug.
Pete
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Old Feb 22, 2015, 08:38 PM
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Are we not talking about OS ?
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Old Feb 23, 2015, 12:56 AM
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Originally Posted by AA5BY View Post
I've tended to think that the shorter spark period of CDI is generally a good thing. With the higher voltage producing a higher heat spark with less current and less time interval, electrode wear is reduced.

With inductive discharge, the spark was generally in the red-yellow - orange heat range but CDI generally is blue and in my thinking capable of igniting a slightly wider mixture ratio.

Having offered that, it is a gut opinion and such have had been wrong many times.
Quote:
Originally Posted by Gary Cee View Post
Actually , the short spark has been a major drawback over the years and many corrections have been employed to make up for it . Generally the short duration CDI spark is less tolerant of mixture extremes than the longer duration sparks typical of the standard , non CDI systems .
Whatever the case, I cannot remember CDI ignitions (and I have never used or even SEEN systems with double spark or prolonged sparks or whatever) misfiring even the slightest bit, not in my bikes, nor in the CDI equiped models I own.
Apart from that... what is "standard" about a non-CDI ignition? To my knowledge, CDI has been the standard for most engines from the early '70's....
So in my opinion, this is a total non-issue....

If this is about the spark being momentary and the glow plug being lit continuously, the I take the constant (as in predetermined) timing of a spark over the variable (as in slightly random) timing of a glow plug any time....

Brgds, Bert
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Old Feb 23, 2015, 01:00 AM
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Originally Posted by Brutus1967 View Post
Whatever the case, I cannot remember CDI ignitions (and I have never used or even SEEN systems with double spark or prolonged sparks or whatever) misfiring even the slightest bit, not in my bikes, nor in the CDI equiped models I own.
Apart from that... what is "standard" about a non-CDI ignition? To my knowledge, CDI has been the standard for most engines from the early '70's....
So in my opinion, this is a total non-issue....

If this is about the spark being momentary and the glow plug being lit continuously, the I take the constant (as in predetermined) timing of a spark over the variable (as in slightly random) timing of a glow plug any time....

Brgds, Bert
Bert, it would therefore be interesting to see the progress of this project;

http://www.rcgroups.com/forums/showthread.php?t=2261048


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Old Feb 23, 2015, 11:49 AM
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Brutus ,

I am citing a well known shortcoming of short duration sparks from basic CDI systems . The longer duration sparks are more tolerant of mixture strength swings . This is why they work better with more precise fuel metering systems like electronic fuel injection . This is also why systems like multi-spark etc were developed . As a work around to the short duration spark issue . All part of the history of CDI systems .

Not knocking CDI , just relating the developmental history and basic characteristics of CDI systems . Not all electronic ignition systems are CDI . As in other than CDI systems that generate a loger duration spark . Or multi spark systems both CDI and non CDI . There are some profound differences between AC and DC CDI as well .

News Flash ! Not all ignition systems rely on solid state switching .

Still , for the record , as I originally worded , pre strawman spin , Basic CDI is a sort duration spark that generally requires tighter control of mixture strength for reliable firing .

Get over your glow plug problem , I made absolutely no mention of GLOW PLUGS .
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Old Feb 23, 2015, 12:20 PM
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for small engines, both two and four stroke, CDI has been the standard for decades....scooters, motorcycles, chainsaws, trimmers...seems to work fine even with the crappy carbs most of those have. main drawback in automotive use was emissions related but that's been fixed with better EFI systems and CDI is now the norm there as well.


TF, "booster battery" to light the glow plug....
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Old Feb 23, 2015, 12:23 PM
I convince things to work
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I never said that you were not telling the truth, Gary, and I even never mentioned that I have a glow plug issue (I only stated that I preferred spraks)

The only thing I said, was that short duration Sparks are a non-issue.
If for example my 1978 Honda CB 400T, with carbs having leaking membranes and all, never missed a beat, if my trusty old Ducati Paso with its very crude Weber Carb never missed a beat, then this "intolerance to mixture extremes" is a non-issue. Both bikes have (if not, the manufacturer is lying) a bogstandard CDI.

That is what I said, no more, no less.

Don't make anything else out of it...

Brgds, Bert
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Old Feb 23, 2015, 12:24 PM
I convince things to work
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I never said that you were not telling the truth, Gary, and I even never mentioned that I have a glow plug issue (I only stated that I preferred sparks)

The only thing I said, was that short duration Sparks are a non-issue.
If for example my 1978 Honda CB 400T, with carbs having leaking membranes and all, never missed a beat, if my trusty old Ducati Paso with its very crude Weber Carb never missed a beat, then this "intolerance to mixture extremes" is a non-issue. Both bikes have (if not, the manufacturer is lying) a bogstandard CDI.

That is what I said, no more, no less.

Don't make anything else out of it...

I would like to say: get over it, that some people prefer sparks

Brgds, Bert
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Old Feb 23, 2015, 12:27 PM
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Bert, that's why I wrote:

Quote:
Originally Posted by Taurus Flyer View Post
Bert, it would therefore be interesting to see the progress of this project;

http://www.rcgroups.com/forums/showthread.php?t=2261048


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Because a crankshaft in a crankcase isn't a mixing stirrer in a vessel!

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Old Feb 23, 2015, 02:37 PM
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Bert ,

I have no problem with sparks nor glow plugs . It was never an either - or issue with me . For most small to medium size applications; In most cases personally prefer the light weight and simplicity of glow . I base that on considerable experience with both .
I also realize the basic differences and characteristics of a myriad of ignition systems as related to mixture strength , cylinder pressure etc . During my tenure at Sun Electric Company we developed engine test systems , dynos and emissions testing equipment and we took all elements in to consideration .
I also had a 1947 Velocette KSS with Amal Standard carbs and Lucas rotating coil magneto that never missed a beat . In fact over 20 Moto Guzzis with Magneti Marelli and Bosch systems Kettering type inductive ignition that did as well with DellOrto carbs . Simple anecdotes , so what ?

The reality of the short spark drawback remains . I never said it was a reason to rule out CDI . Not by a long shot .

Yes , flywheel / AC CDI are very common on today's small garden type engines . This is a bit different from the total loss DC primary , battery totters that some folks stick into airplanes .

This thread however is about the fairly new or at least re-discovered and fine functioning glow system for gasoline fueled model engines . Clearly they are coming of age and a very viable alternative . Anyone who dislikes the high cost of nitromethane (at least where they live) may find gasoline a welcome alternative . Surely they often cite the ability to run a smaller tank for alky fuel with spark rather than glow . In this case , they can run an even smaller still tank and leave the CDI box and battery behind as well .

All about trade offs and personal preferences . Your choices may be fine for you but they may not come close to meeting my standards and vice - versa .

I like a little variety .
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