Electronic solutions to modifying glow engines of all sizes to gasoline
08-24-2024, 04:02 PM
#2151
What you need, is an equivalent to your current carb Stihl M-tronic carb, or one at least compatible to your engine.
Since Stihl uses a different bolt pattern from Walbro, you will need to do some modding here and there.............
Since Stihl uses a different bolt pattern from Walbro, you will need to do some modding here and there.............
Mind you, you still need a TX with good curve programming functions, and you still need to determine those curves yourself.
Thanks for the good replies.
Jim.
08-25-2024, 10:49 AM
#2153
Like the others have stated, it is NOT possible (at least not without great effort) to modify an existing Walbro carb for use with the solenoid.
What you need, is an equivalent to your current carb Stihl M-tronic carb, or one at least compatible to your engine.
Since Stihl uses a different bolt pattern from Walbro, you will need to do some modding here and there.
But once fitted, indeed the electronics as discussed in this thread and the RCGroups thread, should be fully able to do the job for an engine in airplane configuration.
Mind you, you still need a TX with good curve programming functions, and you still need to determine those curves yourself.
What you need, is an equivalent to your current carb Stihl M-tronic carb, or one at least compatible to your engine.
Since Stihl uses a different bolt pattern from Walbro, you will need to do some modding here and there.
But once fitted, indeed the electronics as discussed in this thread and the RCGroups thread, should be fully able to do the job for an engine in airplane configuration.
Mind you, you still need a TX with good curve programming functions, and you still need to determine those curves yourself.
[In reply to the bold]
It's definitely not easy to modify the wt to accept the solenoid valve. I've screwed up two carb bodies in the process of figuring out where all the fuel passages are.
I have one bored out to the correct depth to fit the solinoid, and the fuel passages at the bottom of where the hi/lo needle seats are, once you bore down to the seat tappers, the fuel passages that feed the main jet, and idle / intermediate jets are large enough for the solenoid to modulate fuel delivery correctly, just like the m-carb does.
The issue is plugging the original fuel passages under the welch plug in the metering chamber that feed both needles, and then drilling a new passage from the welch chamber to feed the solenoid valve chamber. Once that is done the carb will operate just as the m-carbs do.
The other thing I would like to achieve, is to relocate the hi/lo needles to the side of the carb body to intersect the main and idle/ intermediate fuel passages to fine/trim the fuel delivery from the solenoid as needed (if needed?). After ruining one carb body, I know where those passages are, so relocating the needles is not as difficult as milling the solenoid chamber and relocating the fuel feed passages.
It's not easy to do for sure, and you need an endmill, or a decent drill press and a solid means to hold the carb body to the mill table. It's not something anyone can do.
Fitting an original m-carb to the engine would be the way to go, but for me, the m-carb is too big to fit in the location inside the cowl without having to move the engine forward, and that's not something I really want to do. So for now, I'm going to just persist and try to finish modifying the walbro.
Last edited by John_M_; 08-25-2024 at 12:22 PM.
08-25-2024, 01:21 PM
#2154
Senior Member
Thread Starter
The other thing I would like to achieve, is to relocate the hi/lo needles to the side of the carb body to intersect the main and idle/ intermediate fuel passages to fine/trim the fuel delivery from the solenoid as needed (if needed?). After ruining one carb body, I know where those passages are, so relocating the needles is not as difficult as milling the solenoid chamber and relocating the fuel feed passages.
Which means that in ordr to modulate the fuel for, say, a 3 hp engine, the solenoid has to operate in the lower 10% of its dutycycle. In itself not too bad but it would require custom calibrated electronics or it would go at the cost of resolution in the curves.
Fitting an original m-carb to the engine would be the way to go, but for me, the m-carb is too big to fit in the location inside the cowl without having to move the engine forward, and that's not something I really want to do. So for now, I'm going to just persist and try to finish modifying the walbro.
I was not aware that the M-tronic carb is that much larger than the equivalent Walbro. But I would think that building a suitable header between engine block and carb would allow for relocation to any more suitable location?
08-25-2024, 08:54 PM
#2155
It is imperative to have at least SOME form of "calibrated orifice", adjustable or not, because the solenoid itself has a full flow capacity sufficient to feed (estimated) a 30 hp engine.
Which means that in ordr to modulate the fuel for, say, a 3 hp engine, the solenoid has to operate in the lower 10% of its dutycycle. In itself not too bad but it would require custom calibrated electronics or it would go at the cost of resolution in the curves.
Which means that in ordr to modulate the fuel for, say, a 3 hp engine, the solenoid has to operate in the lower 10% of its dutycycle. In itself not too bad but it would require custom calibrated electronics or it would go at the cost of resolution in the curves.
I'd expect the original M-tronic carbs to have a fuel orifice tailored to the engine range it is intended for.
I was not aware that the M-tronic carb is that much larger than the equivalent Walbro. But I would think that building a suitable header between engine block and carb would allow for relocation to any more suitable location?
I was not aware that the M-tronic carb is that much larger than the equivalent Walbro. But I would think that building a suitable header between engine block and carb would allow for relocation to any more suitable location?
The m-carb body is quite a bit bulkier than a walbro wt series carb, even after removing the choke lockout mechanism, and the choke position switch. I don't have an image available to show you the gaui f50r installation in the Super cub, it's a shoe horn fit to begin with, with the wt carb. To fit the m-carb I would have to move the engine forward about 3/4" (19mm). I like scale apperence, and moving the engine that much forward, would make the cub way too long in the nose. I'll get something sorted out.
Anyway how you doing mate? I haven't seen much activity from you for a while. Hope things are going well with you.
I had a bad experience with the J3, one of the receivers failed, just shut down, and left me with half the control surfaces working, shut down making a left turn. The right aileron, and elevator half were stuck in a downwards position, about 20% of their travel. Rudder and throttle still active. Ended up forcing a landing with a bad approach, stalled and bellied in on the gear, caught the right wing tip on the edge of the rwy. Fortunately minor damage to the wing tip and collapsed the gear. She's good as new, but I switch over to jeti for the J3, still using the 18sz for the SC.
Last edited by John_M_; 08-25-2024 at 09:13 PM.
08-28-2024, 05:44 PM
#2156
Here are some videos of the 30CC Gasser conversion fitted with the stock M tonic carb - the carb bore is slightly big for the 30cc but I got it to work by keeping the choke fitted even though its unused or by using a 3D printed "restrictor"
The discussion starts around page 350 of the "other" forum mentioned above and goes for many pages.
The discussion starts around page 350 of the "other" forum mentioned above and goes for many pages.
08-30-2024, 01:25 PM
#2158
I've seen those videos back when you first posted them, it's what made me look into adding it to the 50cc. The 201 m-tronics carb is designed for their 35cc chsinsaw, it's does have a larger venturi, but there is a black plastic restrictor, a turbulator of sorts behind the throttle plate.
09-06-2024, 01:36 PM
#2159
Senior Member
Thread Starter
For now, I'm again sold out. 4 kits went to 3 different buyers in France, one kit reserved for one of my own to be commissioned planes, the remaining 5 kits went to 3 dutch buyers.
Just requested 10 new controllers to be made, and tomorrow I'll ordeer 10 solenoids.
Still 13 housings in stock, so before the end of the year I'll have to ask my buddy to fire up the CNC once more...
Just requested 10 new controllers to be made, and tomorrow I'll ordeer 10 solenoids.
Still 13 housings in stock, so before the end of the year I'll have to ask my buddy to fire up the CNC once more...
