earlwb

I had bought this Evolution 58 GT gas engine at an estate sale and it looked great then. But later at home when I was checking it out more closely, I discovered that the power and LED cables or wires were missing. Somehow they got pulled out and off the ignition module. Of course a new ignition module would cost about $200, if I replace it with another one like it. Although I could probably go with a CH or RCexl ignition unit, I figured it is worth a shot to see if I can repair it or not. Thus I opened up the module to see what I have inside. Evolution is using a Valach ignition module rated at 4.8v for this engine.

Upon closer inspection, I can see what happened as the latex glue only partially covered the wires and thus didn't help protect the wires from being pulled on. So i cleaned off the glue and identified the pertinent PCB traces on the board inside. I'll have to solder the two ground wires to the metal case as it is too tricky to get inside to clear the solder off of the pad next to that small integrated circuit. But the LED wire pad and the +5V pad are doable though. The LED pad trace has a small resistor in series on it but the +5v pad on the top is more wide and it has a small thin trace on the bottom going to the small IC chip.

Anyway before I go tinkering with it, I wanted to see if anyone else agrees that those are where the wires go on the inside or not. I have provided pics of the top and bottom views of the board inside the ignition unit.

Thanks for looking.

skillet92

What the pics show look right but what is the worst that can happen. It does not work, like it does not right now? If it works great if not get an rcexl or ch. I got a replacement ignition for my 45gt from rcexl. Worked great.

earlwb

Amazingly enough, I was successful at getting it to work again. In looking at the manual for the engine, they mention a data line, but no LED was shown in the drawings. So I guess putting a LED on is a added bonus, at least it seems to work OK like that.  But it is generating sparks again, so all is well at home once again. I did order a CH ignition unit to use on the engine later though. I suppose I would not have been able to fix it if I didn't have a spare ignition unit on the way. A variation on Murphy's Law.

Anyway, it is firing off sparks on command. It is a little odd in that you have to rotate the crankshaft all the way around once before it generates a spark. Just waving the timing sensor across the magnet back and forth doesn't generate sparks like a RXexl unit does. So it is a little picky. But it seems to be working now OK once again.

Also the user manual for the Evolution 58 GX engine shows the CDI unit without a LED cable on it, and the third wire on the power cable is shown as a data line. Oh well, it does turn on the LED when I power up the unit and it is still generating sparks so I guess it isn't a problem. I don't know if it is a drawing illustration error or not. My other Evolution 26GX engine has a LED cable on it so I assumed that the 58 engine also needed a LED cable too. I might be in error about that.

Thanks everyone.

ZAGNUT

My Feedback: (1)

IIRC that ignition actually ADVANCES the timing as the RPM increases instead of just RETARDING it as the RPM decreases as is done with the CH and RCEXL units...IOW it has to "think ahead" to the next compression stroke. that might be why it won't spark just by moving the magnet under the sensor.

that circuit looks way over complicated for something that should be kept as simple as possible, no wonder they had problems.

AA5BY

If the led is hooked to the data line (tach line?) then it may be showing continuous glow due to hysteresis of human eye while it actually may be turning off and on with rpm. To illustrate what I'm saying, hook an led up to an AC transformer with the appropriate voltage drop resistor to properly wattage the led of course. Visually, the led will show continuous glow but one knows that it can only be rectifying half the AC cycle and therefore must be turning off and on. This can very easily be observed visually by moving the led across ones visual periphery where the led isn't positioned at the same spot to the eye where visual hysteresis comes into play. Now it will be clear it is blinking as is likely for the led on the data line.

ZAGNUT

My Feedback: (1)

regarding the LED: didn't someone make an ignition that would let you read an LED with a tach after landing to see what the max in-flight RPM was?

earlwb

Apparently they made two different early versions of the Valach CDI unit for the Evo gas engines. The one on the 58GX (first model) apparently didn't have a LED on it. But the unit on my Evo 26 GX engine has a LED on it. I show the pic below with the Evo 26GX engine's CDI unit and its LED cable that is built into it. I copied its layout as I didn't realize they made one without the LED cable. I have attached a screen shot of the hookup instructions for the CDI unit without the LED on it.

Now then I have observed my old Evo 26GX ignition unit would blink once when I turned it on, and then glow when the engine was running. But I don't remember it doing anything else though. I attached a screen shot of the LED blink patterns from the GX2 ignition instructions below.

Both of my ignition units use the spark plugs with their tops cut off and the odd spark plug cap where you use a set screw to lock it onto a inverted cover that is held on with a spark plug. It isn't a bad setup actually, the spark plug is lower down for a lower profile and it stays on pretty good and doesn't tend to come loose.

Yes I can agree that the LED may appear to be on all the time but the data rate may be to fast to see. There is a small four pin IC that may be a driver IC or a optoisolator IC that the LED trace on the ignition printed circuit board comes from and it has a small surface mount resistor on it too. So at the time it seemed reasonable that it was for a LED. But maybe the early Valach CDI units actually were designed to be hooked up to a computer running a program of some sort to communicate with the device. I don't know of course.

I can also agree that the CDI unit appears to be a lot more complicated that I would have thought it needed to be too.

First pic of my Evo 26GX engine with LED cable on it.
The second pic is a LED blink pattern for the GX2 engines using a different CDI unit.
The third pic is the CDI hookup drawing for a GX ignition unit from the instructions manual.

earlwb

Oh yeah, I forgot to include a pic showing the pads on the printed circuit board cleared ready for me to poke the wires through and solder them in again. I always feel anxious doing that as you don't know if the pads will lift up or come apart from the heat from the soldering iron or not. But the printed circiut board is a good quality one with plated through holes too. So it held up well to my cleaning the solder off and clearing out the holes in the pads. I used some solder braid to suck the solder off the pads with the sokdering iron. The large solder glob connecting the corner pad to the ground or common on the case cleared off a lot easier that I thought it would. I used a Weller soldering station with a fat tip for this, and a fine tip when I soldered the wires back in, and then switched to the fat tip when I put the solder back on to connect the corner pad back to the case again.

Now the case is thin sheet metal that was tinned. it is not alumimum. They may have slightly soldered the two covers on. On my unit, one cover was not soldered on and the other cover had one solder spot in the middle where the outer decal cover tape was wrapped around it. You may have to bend the covers a little to find where it is soldered on and if they over do it, you might wind up buggering up the cover a lot to get it off too.

earlwb

I just realized, stupid me for forgetting, but the old Evo 58 engine uses a dual magnet sensor setup for firing the spark plugs. I think one magnet is north pole oriented and the other magnet is south pole oriented. Anyway that explains why it had to have a complete rotation of the crank to get a spark whereas other brand CDI's only needed one magnet. Thus just waving the sensor past a magnet back and forth won't trigger a spark like it does with a different brand CDI unit.

Broken Wings

My Feedback: (20)

Good Job Earl!!!!

I probably would have chucked it....

earlwb

Thanks.

Yeah I had similar thoughts, but I couldn't fly that day, so I decided to have a go at it and try to fix it. Granted even though it is fixed, something else may fail on it, so it may be a short lived success. Apparently they had some problems with this type of CDI module. I need to get a propeller for the engine, so since it is a holiday, I won't be able to test run the engine to be sure yet.

Here is a crummy short video clip I made testing the ignition unit out by furiously rotating the crankshaft on the engine with the sensor unit mounted to it.

[youtube]http://www.youtube.com/watch?v=5fdvZJeib6Q[/youtube]

pe reivers

Earl, I have in my scrapbox a Vlach ignition, serial 25456, type EZM 1 Ti.
These ignitions do have a data output where you can read rpm and timing, as well as operating hours using a data terminal. No LED on these buggers.
The ignition is an advancer, that calculates when to fire due to engine "history", I believe last 10 rpm or so. For starting, the timing is late. The second magnet resets the ignition so it can fire again.
Since the serial number of yours is close to mine, I would suggest they are close in properties, though production for MVVS and Evolution may show large differences.
Do not try to run the engine without a resistor type spark plug. It won't work. It fires OK with a non-resistor plug, but the timing is all over the place; a sure way of getting a fire spitting, backfiring engine.
These ignitions were quite prone to different kinds of failures, though many still work okay by this day, even though discontinued since mid-2006, when they were replaced by MSR-ICU units.
I hope this information is of some help.

earlwb

Thanks for the information Pe Reivers,  I appreciate it.

earlwb

I found out that quite a few people had problems with the Valach CDI unit on these engines and that they may have been yanking the input wires out of the units in frustration. So I decided to have the engine converted over to use a CH-Ignition system instead. The CH-Ignition guy made a timer adapter for the engine and set it up for me. I can't wait to run it, but I can't seem to find my drill guide at the moment. As soon as I can drill the propeller, I will be bench running the engine. After that it will go on a Great Planes Giant Aeromaster Biplane I happen to have too.

I can use the Brisk UR17 spark plugs without having to cut the tops off of the spark plugs too.

The timing sensor only senses the one magnet, as the magnets are setup in a north pole and south pole configuration, thus the sensor only works with the one magnet. So one could swap out the timing sensor and bracket quite easily then.

pe reivers

Nice sensor adapter. You may have to file a bit off the hub boss to get the timing late enough (rat tail)
Using the prop disks as drill guide is very easy to do if you have a drill press.

earlwb

Thanks.
Yes I have thought about that too. But I think it might need to slide some the other way if it needs adjusting and in that direction it has a lot of room to move to advance the timing more. I still need to break out my degree wheel and see where it is set now for a reference before I do anything. But I won't know for sure about the timing until I get it mounted and test run.

pe reivers

Set the engine timing between 24° (long mufflers) and 28° (short mufflers)
Long mufflers are tuned pipes and canisters and other low flow resistance devices
short mufflers are low flow rate side dump mufflers

earlwb

Thanks for the heads up on static timing settings, I appreciate it.

earlwb

I thought I would follow up and state that I tested out the engine with the repaired Valach two magnet ignition module and it works OK. The engine fired up and ran pretty good actually.  Using a Top Flite 24x10 propeller with the Bisson muffler, I was getting around 5750 to 5775 RPMs out of the engine which is around 6.5 horsepower.



Here is a boring video of me playing around with the engine.
[youtube]http://www.youtube.com/watch?v=rWHvsunrVTo[/youtube]

pe reivers

Tuned waaaay too rich.

earlwb

Yes you are correct. It sucked the fuel tank dry pretty quickly. But I'll be tweaking it some more.
I have been a bit afraid of the thing, so I have been approaching the needle adjustments with a lot of caution.

pe reivers

Afraid? You should have operated the 116, 152, or 175.
I treat the 116 in my giant tow plane with utmost respect. It's on tuned pipes and delivers 15hp on a 27x12x3 propeller. Would not mess with that destructive potential.

earlwb

Yeah I have seen the guys with the bigger engines before and they require a lot of respect or else. For me the largest engine I messed with was around a  80cc size engine a number of years ago. But I didn't have anything that I could get that could fit into my car to transport to and from the flying field. So I eventually sold the engine.  Normally for me something larger than a 30cc or so plane won't fit so I pretty much flew planes of that size or smaller. But a while back I came into possession of a large biplane that just fits in my car, and then later this big 58cc Evo engine showed up on my doorstep, so I adopted it. So it has been quite a while since I messed around with a bigger model airplane  engine. But those big props are getting scary big in size. I am still getting over the urge to stay like six feet away from the prop when the engine is running.  It is great we have electronic ignition systems nowadays versus the old magneto ignition systems that had a tendency to kick back viciously on you.

TimBle

respect for a propeller or large capacity engine is not a bad thing. recently a fellow had the skin and muscle torn from his four fingers after a disagreement with a DLE55.

apalsson

My Feedback: (1)

I run one of those (the standard MVVS58) in my Top-Flite Giant P47 on a stock Pitts muffler and spin a 3-blade Xoar 24x10 prop
When tuned well, it spins that prop with great authority
These engines are very user friendly, both to tune and operate