Evolution 26GT hard to start/run
06-05-2014, 08:37 PM
#1
Evolution 26GT hard to start/run
I had a problem in that it would not draw fuel, so I sent it back to Horizon and they did what was necessary to get it running - but I noticed they replaced the blue drive washer (the one that has a magnet in it) with one that has two magnets! Will this effect the running of the engine? So far I have tried 2 times to get it running and she does 'run' but not well....I'll have to adjust the low/high screws as it wouldn't run right from the repair shop.
Your thoughts?
TIA
Your thoughts?
TIA
06-06-2014, 06:35 AM
#3
The two magnets should not affect the engine's ignition system. I would not think that it would be a problem. One magnet is north pole out and the other magnet is south pole out. The modern CDI units only use the one magnet to work. The timing magnet is the same on both the old and the new ignitions. The second magnet is for the old ignitions which used it for starting purposes.
In the past they used a ignition module made by Valach. It used the two magnets. The second magnet was for starting purposes and not used after that. It was basically telling the computer to retard the timing for starting. The Valach unit was pretty nice and did all sorts of things like having a nice advance curve to it. But it was too complicated and prone to failures. The Valach units used a inverted cap under the spack plug and you screwed down a set screw to lock on the spark plug cap to the engine.
I had a Evolution 58GT converted over to use a CH-Ignitions unit and it used only the timing magnet and ignores the other magnet. That worked great too. I am thinking about doing it to my Evo 26GT too. Mine has the Valach ignition unit on it.
You can check it easily enough. Unscrew the spark plug and holding the spark plug against the engine so it is grounded, you can rotate the crank so the magnets pass the sensor and it should only fire the spark on one of the magnets. You might need it to be fairly dark to see the spark though. Also do not try to see how big or long of a spark you can draw. You don't want the spark to be larger than the gap in the spark plug. Otherwise you risk damaging the ignition coil.
Now if it really does fire with both magnets, contact Horizon as they really screwed up then. But normally the hall effect sensor everyone uses only works with one orientation of the magnet not both.
I think that the low and high needles may be off on your engine, but it is hard to say without actually being there. I usually run all my engines on a test stand at first to see how they run and adjust them. That way if it ran good on the bench but doesn't run in the plane, then I know I have a problem with the fuel system up to the engine. Less to troubleshoot then.
My gas engines tend to be quite cold blooded and I have to warm them up before they'll run full throttle though. Since the chokes aren't a autochoke or enrichener system it tends to make3 them cold blooded in that respect.
I don't know if you have the old Valach ignition unit or the newer ignition units but here is information about how the older ones work.
The late Pe Reivers wrote this about how the older Valach Ignitions work:
In the past they used a ignition module made by Valach. It used the two magnets. The second magnet was for starting purposes and not used after that. It was basically telling the computer to retard the timing for starting. The Valach unit was pretty nice and did all sorts of things like having a nice advance curve to it. But it was too complicated and prone to failures. The Valach units used a inverted cap under the spack plug and you screwed down a set screw to lock on the spark plug cap to the engine.
I had a Evolution 58GT converted over to use a CH-Ignitions unit and it used only the timing magnet and ignores the other magnet. That worked great too. I am thinking about doing it to my Evo 26GT too. Mine has the Valach ignition unit on it.
You can check it easily enough. Unscrew the spark plug and holding the spark plug against the engine so it is grounded, you can rotate the crank so the magnets pass the sensor and it should only fire the spark on one of the magnets. You might need it to be fairly dark to see the spark though. Also do not try to see how big or long of a spark you can draw. You don't want the spark to be larger than the gap in the spark plug. Otherwise you risk damaging the ignition coil.
Now if it really does fire with both magnets, contact Horizon as they really screwed up then. But normally the hall effect sensor everyone uses only works with one orientation of the magnet not both.
I think that the low and high needles may be off on your engine, but it is hard to say without actually being there. I usually run all my engines on a test stand at first to see how they run and adjust them. That way if it ran good on the bench but doesn't run in the plane, then I know I have a problem with the fuel system up to the engine. Less to troubleshoot then.
My gas engines tend to be quite cold blooded and I have to warm them up before they'll run full throttle though. Since the chokes aren't a autochoke or enrichener system it tends to make3 them cold blooded in that respect.
I don't know if you have the old Valach ignition unit or the newer ignition units but here is information about how the older ones work.
The late Pe Reivers wrote this about how the older Valach Ignitions work:
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.
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.
Last edited by earlwb; 06-06-2014 at 07:15 AM. Reason: add more info
06-06-2014, 03:03 PM
#4
Thanks for the insight Earlwb! Yes this is one of their original run units.....and after a hour playing with the High and Low screws, it is now running - and I had one flight on my H9 P-47 - 150 ...... after a couple of minutes, the engine went dead, so a deadstick landing was in order. No damage (Thank goodness) and we then opened the front of the carb and noticed some (not a lot) black 'gunk' on the screen. Whereas it was now getting around 104 degrees in the shade, we decided to call it a day. I'll try again on Monday and this time I will change to an 18-6 prop and hope to get more RPM's out of her (she was close to 6K with the MA 18-8 - I thought it was a -6!!!).
Thanks again for the information and Ahicks, the magnets (and both ARE magnets) sit 180 degrees from each other.
Thanks again for the information and Ahicks, the magnets (and both ARE magnets) sit 180 degrees from each other.
06-08-2014, 05:13 PM
#5
My engine ran at about 8.100 RPMs with a Xoar 18x8 prop on it. But I had a tuned pipe on it as well.
You can see what other people were getting for RPMs when they ran their Evo/MVVS 26cc engines here:
ref http://www.rcuniverse.com/forum/tach...-evo-26-a.html
Yeah it is probably a good idea to use a fuel filter on the gas engines. The fine mesh screen in the carb can only filter out some of the larger bits of debris.
You can see what other people were getting for RPMs when they ran their Evo/MVVS 26cc engines here:
ref http://www.rcuniverse.com/forum/tach...-evo-26-a.html
Yeah it is probably a good idea to use a fuel filter on the gas engines. The fine mesh screen in the carb can only filter out some of the larger bits of debris.
Last edited by earlwb; 06-08-2014 at 05:15 PM. Reason: add more info
