Evolution 35GT to RCexl ignition
06-07-2011, 09:37 AM
#1
Thread Starter
Evolution 35GT to RCexl ignition
I get a lot of Emails asking about using RCexl ignition on about all different brand of engines. The RCexl will work with just about any EI ignition engine, Some are plug and play and some you have to make modifications and relocate the hall sensor.
Had a customer to convert a Evolution 35GT and he also sent me a nice review of what he did and how the engine ran after the conversion. He elected to use the universal sensor clamp in place of drilling and threading for screws.
Below is a copy and past of his review and a couple pictures.
Hello Milton,
I picked up the 5/8" ignition kit at the Sharpsburg PO yesterday. Can you believe 24 hour service? The 5/8" cap fits the NGK plug perfectly. I really like the ignition test module. That is the cat's pajamas for sure.
Some photos of the engine running with the ignition you sent are attached. I also included a photo of the ignition it replaced.
Here is some info for you in case you get other inquiries about this engine series.
The engine is an Evolution 35GT, 35CC, sold by Horizon. They also sold a 26GT which is 26CC and uses the same ignition. Within a few months after I bought my engine in 2006, they discontinued the 35GT and started selling the 35GT2 with a smaller plug, possibly a CM-6 size, and a different ignition module. Hmmmm. They also did something similar with the 26GT.
When these engines are running good, they are outstanding. My 35GT will swing an APC 20x10 with plenty of gusto and haul a 22 pound P-51 around very impressively. Right now I have it in a 17 pound PT-19 I scratch built and fly for fun. It flies more like the full scale airplanes I used to like to fly and is just a downright pleasure to fly. It is propped down to a 20x8 wood prop which lets the 35GT loaf a little.
These engines were developed from the MVVS 2-stroke glow engines of the same displacement, and are manufactured by MVVS for Horizon under the Evolution brand name. MVVS replaced the piston, sleeve, and rod in the gas engines with new parts. They also machined the case to accept a Walbro carb adapter. If you look at the photos you will see the weak link in this engine. There is an external line running from a fitting on the crankcase to a port on the carb mount. This line delivers the pressure pulses to the carb and depends on 2 fittings and gaskets, a piece of fuel line, and several gaskets underneath the carb to make sure a good pulse reaches the carb. The Czechs must have had a rookie working on the project because that pressure hookup can cause you more grief with this engine than you can shake a stick at. The only thing I have found to work is a fresh piece of Tygon periodically, with a tight small strap around each end. It must be 1/8" ID Tygon. Although 3/32" ID will fit, it doesn't deliver enough "kick" at the right time!
These engines had a mounting boss that was cast and machined as part of the crankcase for mounting the 2-wire pickup you see in the photo of their ignition. It was positioned perfectly to fire at TDC. In order to position the new pickup so it would fire at 28 degrees BTDC, I had to either grind off the mounting boss and make the front end nice and round so the clamp would work, or machine a new groove in the prop hub, which is keyed to the crankshaft. Since I lack the precision equipment to machine a groove in the prop hub, I spent most of the morning carefully grinding and filing off the hall sensor mounting boss.
After checking and re-checking the TDC position and the locating the hall sensor at 28 degrees BTDC, I clamped it down and test ran the engine. Actually I made 3 runs with it. The battery I use for ignition is a NIMH 4.8V 2000mah pack. The idle is good and top end is good. Overall the engine starts and runs very easily. I did notice some operational differences: The throttle response is slow until the point where the ignition advances, then it accelerates rapidly. This is not a problem, just not as linear as before in the low end and mid range. Of course the Evolution ignition had a 16 bit microprocessor that was custom built for this engine, so I expected some differences using a generic ignition. On the other hand, the mid-range burble is gone that the engine always had before, and overall it seems to be more reliable and for the first time in 2 years it is back to running at the recommended high and low needle settings.
Thank you for providing this service to those of us who fly gassers. Now I am seriously considering one of these ignitions for my 3.2 with the stiff mechanical advance and CH ignition before I fly it in the Bates Bearcat. I hope the enclosed information will be helpful in case you get another inquiry about an Evolution 35GT or 26GT.
Second Email
Hi Milton,
Yesterday I forgot to mention that the idle is better with the new ignition than it ever was with the original "factory" ignition or the replacement "factory" ignition from Horizon. Top end is just as good, transition is good, and the old mid-range "burble" or "hunting" is gone. I notice this CDI unit is only rated at about 16k volts, but it must deliver more amperage than the factory ignition which is rated at 18k volts. You can visually see the difference between the two as well as hear it. This one is much stronger. I suspect the microprocessor in the factory ignition is "chasing its tail" in mid-range causing the advance to wander around. This one is much more solid at those settings.
As an FYI if you fiddle with one of these series engines, when you order the head gaskets you get a set of 3 ea metal gaskets that are .010". That is so you can "tune" the engine as many of these are run on pipes for 3D. In my case, I use all 3 gaskets for a total of .030" and my fuel mix is 100 low lead avgas mixed 32:1 with Mobil1 2T - 2 cycle motorcycle racing oil. This oil has been discontinued in the USA (more EPA nonsense?) but I manage to find an auto parts store with a case so I bought it and split it with a buddy. I run this fuel mix on all my gas engines.
I ran it again this morning while it was cool just to make sure it is ready to fly next week. Yesterday it was well into the 90's when I ran it and I see no changes with temps in the high 70's. Carb settings on the Evolution 35 are 1.75 turns open for both needles when everything is working like it should.
All is well - many thanks!
Milton
Had a customer to convert a Evolution 35GT and he also sent me a nice review of what he did and how the engine ran after the conversion. He elected to use the universal sensor clamp in place of drilling and threading for screws.
Below is a copy and past of his review and a couple pictures.
Hello Milton,
I picked up the 5/8" ignition kit at the Sharpsburg PO yesterday. Can you believe 24 hour service? The 5/8" cap fits the NGK plug perfectly. I really like the ignition test module. That is the cat's pajamas for sure.
Some photos of the engine running with the ignition you sent are attached. I also included a photo of the ignition it replaced.
Here is some info for you in case you get other inquiries about this engine series.
The engine is an Evolution 35GT, 35CC, sold by Horizon. They also sold a 26GT which is 26CC and uses the same ignition. Within a few months after I bought my engine in 2006, they discontinued the 35GT and started selling the 35GT2 with a smaller plug, possibly a CM-6 size, and a different ignition module. Hmmmm. They also did something similar with the 26GT.
When these engines are running good, they are outstanding. My 35GT will swing an APC 20x10 with plenty of gusto and haul a 22 pound P-51 around very impressively. Right now I have it in a 17 pound PT-19 I scratch built and fly for fun. It flies more like the full scale airplanes I used to like to fly and is just a downright pleasure to fly. It is propped down to a 20x8 wood prop which lets the 35GT loaf a little.
These engines were developed from the MVVS 2-stroke glow engines of the same displacement, and are manufactured by MVVS for Horizon under the Evolution brand name. MVVS replaced the piston, sleeve, and rod in the gas engines with new parts. They also machined the case to accept a Walbro carb adapter. If you look at the photos you will see the weak link in this engine. There is an external line running from a fitting on the crankcase to a port on the carb mount. This line delivers the pressure pulses to the carb and depends on 2 fittings and gaskets, a piece of fuel line, and several gaskets underneath the carb to make sure a good pulse reaches the carb. The Czechs must have had a rookie working on the project because that pressure hookup can cause you more grief with this engine than you can shake a stick at. The only thing I have found to work is a fresh piece of Tygon periodically, with a tight small strap around each end. It must be 1/8" ID Tygon. Although 3/32" ID will fit, it doesn't deliver enough "kick" at the right time!
These engines had a mounting boss that was cast and machined as part of the crankcase for mounting the 2-wire pickup you see in the photo of their ignition. It was positioned perfectly to fire at TDC. In order to position the new pickup so it would fire at 28 degrees BTDC, I had to either grind off the mounting boss and make the front end nice and round so the clamp would work, or machine a new groove in the prop hub, which is keyed to the crankshaft. Since I lack the precision equipment to machine a groove in the prop hub, I spent most of the morning carefully grinding and filing off the hall sensor mounting boss.
After checking and re-checking the TDC position and the locating the hall sensor at 28 degrees BTDC, I clamped it down and test ran the engine. Actually I made 3 runs with it. The battery I use for ignition is a NIMH 4.8V 2000mah pack. The idle is good and top end is good. Overall the engine starts and runs very easily. I did notice some operational differences: The throttle response is slow until the point where the ignition advances, then it accelerates rapidly. This is not a problem, just not as linear as before in the low end and mid range. Of course the Evolution ignition had a 16 bit microprocessor that was custom built for this engine, so I expected some differences using a generic ignition. On the other hand, the mid-range burble is gone that the engine always had before, and overall it seems to be more reliable and for the first time in 2 years it is back to running at the recommended high and low needle settings.
Thank you for providing this service to those of us who fly gassers. Now I am seriously considering one of these ignitions for my 3.2 with the stiff mechanical advance and CH ignition before I fly it in the Bates Bearcat. I hope the enclosed information will be helpful in case you get another inquiry about an Evolution 35GT or 26GT.
Second Email
Hi Milton,
Yesterday I forgot to mention that the idle is better with the new ignition than it ever was with the original "factory" ignition or the replacement "factory" ignition from Horizon. Top end is just as good, transition is good, and the old mid-range "burble" or "hunting" is gone. I notice this CDI unit is only rated at about 16k volts, but it must deliver more amperage than the factory ignition which is rated at 18k volts. You can visually see the difference between the two as well as hear it. This one is much stronger. I suspect the microprocessor in the factory ignition is "chasing its tail" in mid-range causing the advance to wander around. This one is much more solid at those settings.
As an FYI if you fiddle with one of these series engines, when you order the head gaskets you get a set of 3 ea metal gaskets that are .010". That is so you can "tune" the engine as many of these are run on pipes for 3D. In my case, I use all 3 gaskets for a total of .030" and my fuel mix is 100 low lead avgas mixed 32:1 with Mobil1 2T - 2 cycle motorcycle racing oil. This oil has been discontinued in the USA (more EPA nonsense?) but I manage to find an auto parts store with a case so I bought it and split it with a buddy. I run this fuel mix on all my gas engines.
I ran it again this morning while it was cool just to make sure it is ready to fly next week. Yesterday it was well into the 90's when I ran it and I see no changes with temps in the high 70's. Carb settings on the Evolution 35 are 1.75 turns open for both needles when everything is working like it should.
All is well - many thanks!
Milton
06-07-2011, 12:14 PM
#2
Senior Member
Join Date: Jan 2002
Location: Arcen, , NETHERLANDS
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RE: Evolution 35GT to RCexl ignition
Some tips for evolution GX and MVVS engine users.
The original ignitions for GX are Vlach ignitions, special made for MVVS deliveries to Horizon
The GX2 ignitions are by MSR, to Horizon spec's, also supplied by MVVS.
All other parts in the engine are identical to MVVS parts, except the anodize colour. Horizon has the Glow-blue of MVVS.
The carb pulse line nipples can be fitted using loctite. This will avoid all air leaks and will hold for as long as the engine lives. A 3mm Tygon line is sufficient. ( 3/32" is only 2.4mm).
Use a small piece of the same tygon line over the line ends. No more clamping is needed. (see image)
With a good Vlach ignition, I could get stable idle rpm as low as 900 rpm. This also is achievable with the MSR ignition. Some of the Vlach ignitions indeed did sometimes have "mapping" instability. That is why MVVS changed to MSR.
To fit the RCexl ignition, the south pole can be used, and no boss filing is needed if the long nose sensor is used, fastened with a nylon zip-tie. This setup is easy to adjust, and will be trouble free. I have used this system since 2002 to experiment with all kinds of setups.
The original ignitions for GX are Vlach ignitions, special made for MVVS deliveries to Horizon
The GX2 ignitions are by MSR, to Horizon spec's, also supplied by MVVS.
All other parts in the engine are identical to MVVS parts, except the anodize colour. Horizon has the Glow-blue of MVVS.
The carb pulse line nipples can be fitted using loctite. This will avoid all air leaks and will hold for as long as the engine lives. A 3mm Tygon line is sufficient. ( 3/32" is only 2.4mm).
Use a small piece of the same tygon line over the line ends. No more clamping is needed. (see image)
With a good Vlach ignition, I could get stable idle rpm as low as 900 rpm. This also is achievable with the MSR ignition. Some of the Vlach ignitions indeed did sometimes have "mapping" instability. That is why MVVS changed to MSR.
To fit the RCexl ignition, the south pole can be used, and no boss filing is needed if the long nose sensor is used, fastened with a nylon zip-tie. This setup is easy to adjust, and will be trouble free. I have used this system since 2002 to experiment with all kinds of setups.
06-08-2011, 08:03 AM
#3
Thread Starter
RE: Evolution 35GT to RCexl ignition
Good idea Pe.
Nice quick fix and if all of them time in the same position the RCexl ignition bracket could still be installed with screws without having to file off the raised part on the crankcase.
Nice quick fix and if all of them time in the same position the RCexl ignition bracket could still be installed with screws without having to file off the raised part on the crankcase.
06-08-2011, 01:07 PM
#4
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Join Date: Jan 2002
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RE: Evolution 35GT to RCexl ignition
In the perfect world that is. The first generation Vlach equipped engines had only one single magnet.
The mounting bosses however are so small, and contain so little material, that a few deft strokes with a good file will remove them. It takes me 5 minutes at most to get it perfectly round.
The mounting bosses however are so small, and contain so little material, that a few deft strokes with a good file will remove them. It takes me 5 minutes at most to get it perfectly round.
