Carb, Smart Carb 2, and EFI discussion

[Badland-F5 Pilot]

Yep, I really like boxer style engines and the F23 seemed to be a good choice, and still is a possibility. I'm not sure if an F23 will fit in under weight on the F1 through F4 series, but with a recovery chute that may be very possible, especially if you skip the electric start for a pull start. The Polini 303 seems to be a good option too. After talking with Chris and getting my build order on the calendar, Chris was telling me about three 4 stroke options I may have. I'm looking at all three. My planned flying will be long distance cross-country flights and back country off airport flights. Four strokes fit that bill a little better than a 2 stroke.

I think Chris mentioned he has 16 Badland aircraft in flying and in kits combined. I haven't been lucky enough to make it to AirVenture yet. I happened to see Peer's pictures on HomeBuiltAirplanes.com and found the UL I wanted. Nothing against the other types/designs of ultralights, I just want one that looks and flies like a full size personal airplane. After all, how can you not love an ultralight with doors!

The above is one of our member's Badland F3 Speed. Really a sharp looking aircraft. More pictures and information can be found in the following thread - viewtopic.php?p=940&hilit=Doors#p940

There's simply no other UL as complete like a Badland.

Again, welcome to the group, and please feel free to ask questions. I hope to have my F5 kit sometime in late December - keeping my fingers crossed. I have a lot going on until then, just retired, fixing up the house here in Texas to sell, moving to Florida to be near family, and trying to get my F5 kit down from Minnesota all before the end of the year. And I thought working for someone else kept me busy!

Take care,
Todd

[13brv3]

Hi Todd,

I think I've seen all of Peer's pictures, and he's answered some questions about whether I can fold my giraffe-like neck into one of these. I'd still need to find one of these to sit in before ordering.

I had an Airbike with an F-23, and it was a pretty impressive engine. I was going to put all the parts I've accumulated into a new Kolb Firefly, but I just can't bring myself to get another high engine pusher. I've had a couple Kolbs in the past, and they're nice, but I'm more of a traditional tractor engine guy. I'm all for a new lightweight 4-stroke, but honestly it will be a long time before I'd believe any new 4-stroke option is more reliable than the F-23. Fuel consumption wouldn't take long to believe though

It's really a shame part 103 has that restriction to prevent flying anything that previously had an airworthiness cert as an ultralight. That just makes no sense to me if you configure it to meet the ultralight weight and speeds. I could easily see a Badlands with the F-23, bigger tires, and 10 gal of fuel for now, then later convert to a lighter engine and less fuel if an ultralight was ever needed or desired.

So where in FL are you moving? I was born and raised in Pensacola, though that's not what most people call FL.

Cheers,
Rusty

[Badland-F5 Pilot]

Hi Todd,

I think I've seen all of Peer's pictures, and he's answered some questions about whether I can fold my giraffe-like neck into one of these. I'd still need to find one of these to sit in before ordering.

I had an Airbike with an F-23, and it was a pretty impressive engine. I was going to put all the parts I've accumulated into a new Kolb Firefly, but I just can't bring myself to get another high engine pusher. I've had a couple Kolbs in the past, and they're nice, but I'm more of a traditional tractor engine guy. I'm all for a new lightweight 4-stroke, but honestly it will be a long time before I'd believe any new 4-stroke option is more reliable than the F-23. Fuel consumption wouldn't take long to believe though

It's really a shame part 103 has that restriction to prevent flying anything that previously had an airworthiness cert as an ultralight. That just makes no sense to me if you configure it to meet the ultralight weight and speeds. I could easily see a Badlands with the F-23, bigger tires, and 10 gal of fuel for now, then later convert to a lighter engine and less fuel if an ultralight was ever needed or desired.

So where in FL are you moving? I was born and raised in Pensacola, though that's not what most people call FL.

Cheers,
Rusty

Fully understand the concern over height and sitting in one before ordering. Though low cost for an airplane, you don't want it to end up being a big paper weight because you can't sit in it comfortably.

I like the info about the F23. I've read some complaints about it, but I can't see having an engine with a 1000 hour TBO and it having problems on its own. Seems to me, it's more likely some have run into trouble because they failed to follow procedure(s). Having ridden dirt bikes in my youth, I'm familiar with what it takes to keep a two-stroke happy. I've got the time to wait on the new four strokes to prove themselves, but I like their low fuel burn rate. I've read plenty of posts about the F23 and how it loves to drink the fuel. I have been looking at Smart Carb 2 (https://smartcarbfuelsystems.com/). The reports are very good, including the 25% to 35% better fuel economy. The carb auto adjusts for altitude and temperature, and increases horsepower by 8% to 10%. They are very simple in design (isn't that the way things should be?). The only issue is that they are not cheap and the F23 of course takes two! Then I started looking at the 4 strokes when talking to Chris, and it's possible (on paper) to get 4 1/2 hours out of 5 gallons of fuel with an SC2 carb! Now that's plenty of flight time. As mentioned, I have time to see how things pan out as I build my F5.

I didn't know about any rule stopping a prior certified aircraft (if it can make 103 weight and other regulations) couldn't be flown as a UL. I agree, if that's that case, it doesn't make any sense. Chris will deliver an F5 or any of his planes above weight, and they can be registered as experimental. They do qualify under the 51% rule as a kit, so that's too bad that it can't be downgraded at a later date/time.

My sister and her husband, their kids and all live in Middelburg, FL. I've driven through (and broke down once) Pensacola several times. I love going through the tunnel. I have some rather large air horns on my Avalanche. When the little beep beeps start going off through the tunnel, and I hit the big horns, well, it gets quiet after that The plan is to find 5 acres, put a house and grass strip on it. That, hopefully will be sometime next year. For now, it's going to be park the travel trailer in their backyard and live in it until I find the property I'm looking for. Maybe some day you'll be back in Pensacola or further south at Sun-n-Fun and we'll bump into each other.

Todd

[13brv3]

I had read a few of your comments already about the smartcarb, and took a look at their site earlier today. The phrase that keeps going through my mind is- If it seems too good to be true, then it probably is." I don't think I'd believe their claims unless I saw them first hand. I'd go to fuel injection way before I'd try any other carb, and I really wish my F-23 was fuel injected. The Airbike was N numbered, and had 10 gal of fuel, so consumption was never a problem. 5 gal max is a different story.

Since I'd only fly it locally, I'd really love an electric motor, but the FAA has been unfriendly with their battery weight allowance. I've seen people claim equal weight in batteries to the weight of 5 gal of gas, and also equal volume in batteries to 5 gal gas. Sadly, I think the FAA gives no allowance at all to electric motor batteries from what I've read.

Realistically, a true ultralight is probably a future project for me, but the Badlands is at the top of the list.

Rusty

[LA F2 Flyer]

In regards to the Smart Carb, it wouldn't surprise me if they padded their numbers a bit (or maybe even more than a bit), but I think the appeal for me is the self-adjustment...I imagine it would be a big benefit not to have to re-jet for elevation, temps, humidity, you name it. Set it and forget it, so to speak.

[Badland-F5 Pilot]

I had read a few of your comments already about the smartcarb, and took a look at their site earlier today. The phrase that keeps going through my mind is- If it seems too good to be true, then it probably is." I don't think I'd believe their claims unless I saw them first hand. I'd go to fuel injection way before I'd try any other carb, and I really wish my F-23 was fuel injected. The Airbike was N numbered, and had 10 gal of fuel, so consumption was never a problem. 5 gal max is a different story.

Since I'd only fly it locally, I'd really love an electric motor, but the FAA has been unfriendly with their battery weight allowance. I've seen people claim equal weight in batteries to the weight of 5 gal of gas, and also equal volume in batteries to 5 gal gas. Sadly, I think the FAA gives no allowance at all to electric motor batteries from what I've read.

Realistically, a true ultralight is probably a future project for me, but the Badlands is at the top of the list.

Rusty

I can't tell you how many YT video's I've watched of dirt bike riders that have switched to SC2, but it's a lot and not one has given the SC2 a bad review. The same goes with the improvement on fuel use and increase in power. Remember, Smart Carb does give a range of improvement. I only quoted the possible maximum improvement, so there is some wiggle room. I was planning on going fuel injection with the F-23. The only problem I have with that is that the majority of complaints I've heard about the F-23's fuel injection is that the control module is not redundant and is prone to failure. When a carb starts acting up, most of the time limping home isn't an issue. When an electronic part like a fuel injection controller goes south, it typically ends your day instantly. That leads back to KISS, which is why I like the SC2. There are breakdowns of the SC2 design available, and the thing is very simple. The only complaints are that the metering rod used sometimes must be custom-made, which Smart Carb does, and once dialed in, the performance is outstanding (reported). I would like to see one in action, that's for sure but also have no issue trying one. The company has been in business for some time and metering rod carbs have also been around, clear back to the late 60's. In our last Badland Zoom Virtual Fly-In, one of the participants used a smart carb and had nothing but praise for it. The same issue though as mentioned above, he had them create a custom metering rod for him. He also said that he had great customer service, they were helpful throughout the process to get the SC2 to maximum performance for him. Since the FAA is unlikely going to grant us 8 to 10 gallons of fuel, I want to get every bit of energy out of what I am allowed to carry.

I've been an alternative energy guy for a long time. I like the tech side of it a lot. I've been off grid with my travel trailer since 2013. Currently, I have 7 65Ah LiPo batteries in the trailer, complete with charge controllers, panels on the roof, and a 6000 watt 12v to 120v inverter. I owned a Chevy Volt that got me back and for from my home to work (60 mile round trip) for about five years. One of the cells went bad so, it went to a charity sale. Let's see, the car's market value was $2,300.00 and a refurbished battery was $7,000.00. That was a no-brainer, time to get rid of the car. I enjoyed it and it was very quiet. For a hop around the patch, an electric plane wouldn't be too bad, and yes the FAA certainly hasn't been friendly about it. I can kind of understand their position. Those 7 batteries in my travel trailer, that's 245Lbs all by themselves (7 35Lbs bombs if they let loose.

With Chris's backlog on orders, being a future project isn't an issue The guy works too much and needs an employee with the attention to detail he gives.

Todd

[13brv3]

This looks like a pretty good video description of how the Smart Carb 2 works.


They certainly sound good, but I haven't come across a good scientific test yet. I'd love to see dyno graphs for stock carb vs smart carb, and also fuel consumption for both measured at a typical high cruise power setting for aircraft. If they were more reasonably priced, I'd toss a pair on a 912 I have on a test stand.

Rusty (I hate carbs)

[Mountain Cat]

At $600-700 bucks it's almost twice the price of a Bing. But, if it does what they say, then it would be worth it for a Polini 303.

[Badland-F5 Pilot]

This looks like a pretty good video description of how the Smart Carb 2 works.


They certainly sound good, but I haven't come across a good scientific test yet. I'd love to see dyno graphs for stock carb vs smart carb, and also fuel consumption for both measured at a typical high cruise power setting for aircraft. If they were more reasonably priced, I'd toss a pair on a 912 I have on a test stand.

Rusty (I hate carbs)

Hahaha, I'm right there with you about carbs. Ever since I had to tune a Quadrajet AKA: Quadracrap way back when I was a teenager. I came from a small town in Northern California where we all were shadetree mechanics and went to the Triple M Raceway (dirt track) on Saturday nights.

I would also like to see some test results. There are a lot of people that have seat of the pants evaluations. Those are sometimes guided by the pain in the wallet and not wanting to admit in public that what they purchased was a waste of money

When Peer and I were discussing the SC2, and I was still firm on the F-23, I was thinking - these things better work or it's going to hurt the wallet big time since there's two!

Todd

[Badland-F5 Pilot]

At $600-700 bucks it's almost twice the price of a Bing. But, if it does what they say, then it would be worth it for a Polini 303.

Agreed, and of special interest is they auto adjust for altitude...big advantage if you're a pilot that want to fly low and slow as well as, well they are ultralights, so high and, uhm, slow

Todd

[13brv3]

The only way I see these improving efficiency is by more completely atomizing the fuel. Any liquid that isn't atomized will just sort of pass through the system without delivering it's full potential of energy. There are other non-carbs like the Ellison throttle body that make similar, but not so extreme claims for power and efficiency. Those use incredibly small holes in a metering tube to distribute fuel. I had an Ellison on an RV-8 with inverted oil and fuel, and that thing ran great. Of course the main feature I was interested in was being able to run the same in any attitude. Flying inverted gets old pretty fast though

I'd have to give thought to using a single carb (smart or dumb). The F-23 is really just a single cylinder split in two, and both carbs feed the crankcase, and not just the cylinder they're located on. Of course being an electronics guy, EFI rules

Rusty

[Badland-F5 Pilot]

The only way I see these improving efficiency is by more completely atomizing the fuel. Any liquid that isn't atomized will just sort of pass through the system without delivering it's full potential of energy. There are other non-carbs like the Ellison throttle body that make similar, but not so extreme claims for power and efficiency. Those use incredibly small holes in a metering tube to distribute fuel. I had an Ellison on an RV-8 with inverted oil and fuel, and that thing ran great. Of course the main feature I was interested in was being able to run the same in any attitude. Flying inverted gets old pretty fast though

I'd have to give thought to using a single carb (smart or dumb). The F-23 is really just a single cylinder split in two, and both carbs feed the crankcase, and not just the cylinder they're located on. Of course being an electronics guy, EFI rules

Rusty

You just needed to design and build a rotating cockpit so the planes wing surfaces would be inverted, but you'd be right side up! LOL

I also like EFI as long as the module running it is redundant. I was also considering a new intake manifold for the F-23 with a single carb. The first thing coming to mind as a potential issue is the length of the intake compared to the dual intake currently on the engine. Do you know if the EFI is a single unit or is their injection into two separate intake manifolds? Since both cylinders fire at the same time I would think the crankcase vacuum would be equal no matter how the crankcase is fed the fuel(?)

[Badland-F5 Pilot]

This looks like a pretty good video description of how the Smart Carb 2 works.


They certainly sound good, but I haven't come across a good scientific test yet. I'd love to see dyno graphs for stock carb vs smart carb, and also fuel consumption for both measured at a typical high cruise power setting for aircraft. If they were more reasonably priced, I'd toss a pair on a 912 I have on a test stand.

Rusty (I hate carbs)

Yep, that's one of the videos I found which helped a great deal into understanding the better atomizing of the fuel air mixture. The EFI is most likely the simplest and best method of fuel delivery since the fuel is atomized by high pressure, nozzle design, and not by semi-chaotic airflow. Then it's just about getting the timing of opening the valve and closing it set. Pretty simple really, if the electronics work. This is where the SC2 fits in well. It does a much better job atomizing the mixture while eliminating any possible electronic failure. There also is the advantage that the SC2 has that the fuel air mixture self adjusts for altitude. An EFI that would do this for a flight engine would have to be more complex. Do you know if the Hirth EFI adjusts, or am I wrong in thinking this is controlled by the EFI?

Todd

[Badland-F5 Pilot]

And two additional videos on the SC2 from the same guy who did the design/operation video above.

SC2 on his Enduro - basic seat of the pants performance.


SC2 Mileage


Something else to consider with mileage, this test is on a motorcycle, specifically an Enduro testing mostly off road. This means a lot of throttle changes. On an airplane the throttle is normally set at a single position for much of the flight. I believe that would increase the difference between a standard carburetor and the SC2.

I also like what he says at the end of the second video, basically, keeping his bike mechanically simple, part of this is with the use of the SC2. While I am an electronics nut, Keep It Simple Stupid (the KISS principal) with aircraft and flying is my preference.

[13brv3]

The enduro bike is about as far from our actual use as you can get. Maybe there's a test out there with a boat, or jet ski. I would actually guess that a high power cruise setting would make less of a difference, but I'd want to see that proven. A good test would be to run the same engine with each carb at a normal cruise power setting. Make sure they're both tuned to the same EGT temps so one isn't simply running leaner than the other.

Another dose of reality would be that it's hard to hide success. I've searched Rotax and Homebuilt forums to find any discussion of the smart carb, and there's almost nothing. With all the small engines in the aircraft world, I'd expect this to be front page news if it worked as well as they claim for our application. Maybe it's the best thing since sliced bread for enduro bikes, but that doesn't help us.

Not to divert from the SC2 discussion <g>, but how many Badlands planes are actually flying? It was mentioned that there are probably around 16 kits out there. On one hand, that doesn't seem like many, but if you had to weld all those frames, it would seem like a LOT more

Rusty

[Badland-F5 Pilot]

The enduro bike is about as far from our actual use as you can get. Maybe there's a test out there with a boat, or jet ski. I would actually guess that a high power cruise setting would make less of a difference, but I'd want to see that proven. A good test would be to run the same engine with each carb at a normal cruise power setting. Make sure they're both tuned to the same EGT temps so one isn't simply running leaner than the other.

This is true, but we only have what's currently available and someone will need the interest to do detailed and fine testing.

Another dose of reality would be that it's hard to hide success. I've searched Rotax and Homebuilt forums to find any discussion of the smart carb, and there's almost nothing.

The premise that the SC2 has not been used on aircraft engines because few are talking about it is missing the important reason why this may be so. The SC2 was originally and only marketed to motorcycle (and specifically off-road) enthusiasts. I had never heard of the Lectron or STIC Keihin carbs which are direct competitors to the SC2 before hearing about it. Yet both exist and are very popular alternative carbs.

The use of the SC2 has only recently entered the PPG market (displayed on the SC2 website). A quick search on YT shows a few PPG pilots testing the SC2 - https://www.youtube.com/results?search_ ... martCarb+2 I've not viewed any yet, so I have no idea what the results are.

Even more recent, only the last year or two have UL pilots been looking at the SC2 to see if they can get more flight time and other benefits. I mentioned one pilot on our forum that uses the SC2 and is very happy with the performance. That is only one, so of course if/when I get the SC2 carb(s), I'll do extensive testing long before the plane gets off the ground. This may be another reason there's not much out about using the SC2 for PPG or UL. Changing a carb on a bike may leave the rider stranded in the woods. Changing a carb on an aircraft may leave the pilot dead. There is bound to be a reluctance in changing out a proven part for a 3rd party part even when the proven part "may" not be as good as the 3rd party part.

With all the small engines in the aircraft world, I'd expect this to be front page news if it worked as well as they claim for our application. Maybe it's the best thing since sliced bread for enduro bikes, but that doesn't help us.

Most people are accustom to name brands. PWK, Mikuni, and others are well known. That being said, it could be like Microsoft Windows, well known, but is it the best? There's the economics about the SC2 to also consider. It's an $800.00 carburetor. That's a lot of green to lay down to "hope" it pays off as a good deal. Even with a lot of dirt bikers using it, and some PPG pilots using it, I'm still hesitant of forking out that kind of money. The desire to fly longer and the automatic compensation for altitude density is a strong draw for me. Also, there has to be some that are willing to work with products that are new to that market. I'm willing to do that, but only after much more research, especially with the team at SC2.

Not to divert from the SC2 discussion <g>, but how many Badlands planes are actually flying? It was mentioned that there are probably around 16 kits out there. On one hand, that doesn't seem like many, but if you had to weld all those frames, it would seem like a LOT more

Rusty

Not 16 kits, it's a mix of completely built and kits. I'll have to check with Chris on this question. He of course can only tell us how many he's delivered fully built. I'm sure some kits haven't made it to flying, and there's always a few that never will. I can tell you that Chris works on up to 3 planes at a time and (I may have this wrong) a full kit takes 3 months for him to build. That may be with 3 at a time, I'm not sure. Peer's kit was I think the second plane (Peer chime in if that's correct or not). The first one is the blue and white naked one on the Badland Aircraft website (https://www.badlandaircraft.com/gallery/). Chris is a one-man shop, so he can only work on so many at a time. Last I spoke with him, he said he's possibly got someone in line to come in and give him a hand. The issue I'm sure is finding someone as detailed as he is. One sure thing is that "it's good enough" for his customers is not acceptable to him. He is a very detailed manufacturer, and master welder on top of that. I told him that he needed to move to Florida (where I'll be moving soon – retired) and I'd be happy to help. I think we might end up slowing down production instead of speeding it up. My sister keeps telling me "perfection is an illusion". On some things she insists I'm a bit too detailed. I think Peer might agree with her.

Todd

[Badland-F5 Pilot]

In our desire to get the best out of our engines and flight, I've found two interesting videos.

The first is from Tucker Gott (PPG pilot and major YouTuber). Tucker was contacted by Vittorazi, a popular Italian PPG engine builder. Vittorazi contacted Tucker to see if he's like to fly Vittorazi engine with fuel injection. The design is in testing and not available to the public at the time of the video. In Tucker's video, the smoothness of the EFI fed engine over his past video's with a carburetor fed engine are obvious. The engine is very smooth in all throttle positions and changes. The engine sounds fantastic. I agree with Tucker in that this is the future of even small flight types, including UL's.



This second video is of a Moto X rider demonstrating the difference between the stock carb on his bike and the switch to an SC2 carb. In this video notice the difference in the sound of the engine when the carbs are switched. The SC2 sounds very similar to Tucker's test of the EFI Vittorazi. The acceleration from low RPM to high is very smooth. The Moto X rider mentioned the low end torque with the SC2 carb is excellent. This goes back to something Rusty observed and commented on - that the SC2 may show much more promise at the low end, so fuel consumption at higher RPM may not be as high as we'd like to see. Rusty, correct me if I'm wrong if this wasn't what you were pointing out. One thing I noticed with the Moto X rider is when he showed his riding with the stock carb, the engine wasn't nearly as smooth as with he rode with the SC2. The engine seemed to jump to it's power band instead of revving p to it smoothly.



One of the things of interest to me is, if the SC2 does create more torque at lower RPM, could we run a prop at a higher angle of attach and lower RPM so the plane doesn't sound like a chainsaw? And, if that would work without issue, wouldn't there be an increase in fuel economy?

Todd

[Badland-F5 Pilot]

Another plug for Smart Carb. This is an interview with Corey Dyess from SmartCarb. This is a detailed history of Smart Carb and answers many questions about it. Note this is on 2 stroke dirt bikes, not aircraft engines. The video interview is long, but excellent because it comes directly from the actual guy that makes the carburetor. Enjoy.



Todd

[Kaveman]

I've been watching the SC2 for some time, and I think it's very promising. I have yet to come across one in the wild, so there's that. However, I did purchase my first fuel injected 2 stroke last year, and all I can say is WOW!

To be fair, I do tree work, so my EFI 2 stroke is a chainsaw, the Stihl 500i. Also to be fair, it has several hundred hours on it, and I can say with absolute certainty that it is the finest chainsaw I've ever run. That engine has never stumbled, spit, sputtered, or anything but run perfectly. And when I say it's smooth, remember it's not in a frame between my legs, or on a firewall in front of me, it's literally in my hands. It's handled elevation changes flawlessly, from the desert at 3300' to the Doug Fir around Green's Peak at 9500'.

But enough about my favorite saw, half the reason I bought it is because I hate fiddling with carbs! I can do it, and quite well too, but I'd rather be running said engine, not twisting a screwdriver. With the variance in altitude, the SC2 is super appealing. My fear is just all the tinkering that may come before everything is dialed in. I'm sure not afraid of trying it, on whatever engine I choose to hang of my future F series for three reasons.

1) I'm looking at the F5, pretty close to fully built out, that's a pile of money. Plus I've got to learn to fly, another pile of money. Then I must purchase certain miscellaneous items such as a good radio, PLB, another shipping container to store said plane in, etc. Somewhere in there the SC2 won't even be noticed.
2) I don't like to leave anything on the table, and there's a lot of range improvement to be had. What's the point of having a tiny bush plane if you can't take little trips to the back country? With only five gallons I've got to squeeze every drop! There's no way I'm spending the aforementioned piles of money to fly circles around some dusty, disused airstrip!
3) For all the praise I showered on my EFI chainsaw, I'm not qualified to work on a large portion of it, most people aren't. I don't necessarily want electro-gizmo-wizardry on my plane, at least not that part of it. The box of wizard wires got mad and my windmaker has stopped, is not what I want going through my mind as I transition to glider pilot.
I understand the black magic of the carbutater, and isn't part of the attraction to ULs the fact that you can do things yourself?

[Badland-F5 Pilot]

1) I'm looking at the F5, pretty close to fully built out, that's a pile of money. Plus I've got to learn to fly, another pile of money. Then I must purchase certain miscellaneous items such as a good radio, PLB, another shipping container to store said plane in, etc. Somewhere in there the SC2 won't even be noticed.
2) I don't like to leave anything on the table, and there's a lot of range improvement to be had. What's the point of having a tiny bush plane if you can't take little trips to the back country? With only five gallons I've got to squeeze every drop! There's no way I'm spending the aforementioned piles of money to fly circles around some dusty, disused airstrip!
3) For all the praise I showered on my EFI chainsaw, I'm not qualified to work on a large portion of it, most people aren't. I don't necessarily want electro-gizmo-wizardry on my plane, at least not that part of it. The box of wizard wires got mad and my windmaker has stopped, is not what I want going through my mind as I transition to glider pilot.
I understand the black magic of the carbutater, and isn't part of the attraction to ULs the fact that you can do things yourself?

The F5 is certainly a chunk of change. I have mine half paid for and waiting for the build to be done, so I can pay the other half. This is taking into consideration that the F5 has almost doubled in price since I first looked at it over two years ago. I'm also looking at squeezing every drop out of whatever engine I finally hang off the front end. When some of these UL's state they have great flight time of 1.5 to 2 hours....uh, no, that's not long enough. The goal is to get at least 3.5 hours, if not more. We'll see if I can get there. I want to fly some distance. I like the SC2 because it's a very simple carb (very simple is always best, less possibility of issues) and I'm not a fan of EFI for flight after seeing Tucker Gott try an EFI on his para motor. Tucker showed that the EFI was run by a battery, and once the battery was dead, so was the EFI - no more engine! So would that same happen on a UL? Most likely not, since we can have external power. However, I've heard of issues with the EFI on the Hirth F23. I do like the Hirth, so don't misunderstand, but I don't care for the idea that the engine would just stop because of an EFI issue. To me the SC2 gives the reliability and simplicity needed for putting my life on the line in the air. Getting regular carbs tuned is too much of a pain. Most regular carbs don't have auto altitude adjustment, and for me, altitude is life. And yet the SC2 performs (from what I can tell) almost as good as EFI's do.

Todd

[Stormin]

Extremely interested in this smart carb concept with auto altitude adjustment, I guess a real test would be on an F23 because of the fact that you have to sync the carbs, and watch egts on both cylinders to see if burn rates are the same on the ground and at altitude. As far as cost if i just spent 50K on a plane i don't think id scoff at 1400 for a set of carbs that do "as advertised". HA.... They do sound like a great alternative.

[Badland-F5 Pilot]

I don't think you'd have any trouble with syncing the carbs. There's only one control on the carb that would need adjustment (as best I can tell), and that's to make sure both throttle cables pull the same. As long as you did the same turns on the only fuel mixture adjustment, then they should be the same. By the way, that adjustment, does not require the carb to be pulled apart! You can adjust it while it's on the engine and within seconds. Another possibility is to find out what the F23 uses for carb size. If there's a single Smart Carb that is large enough to handle both cylinders, then get a shop to make a single intake manifold and use one large Smart Carb. Since both cylinders pull intake at the exact same time, that should work perfectly. That would cut your costs in half and ensure exact same feed of the gas/oil mixture into the engine.

Todd

[Bill in MN]

I put a SC 28 on my Polini 250 a couple of years ago and to my knowledge was the first to do so. Out of the box it was horrible and I figured I wasted a lot of money. It ran lean at the bottom end/fat on top, rpm fluctuated and throttle response was poor and no matter what metering rod was in there or how many clicks were dialed in it never got better.

I worked with the guys at Smart Carb for several weeks trying this, that and the other thing and I can't say enough about their customer service. They really went the extra mile. In the end we determined that vibration was causing fuel to foam up inside the bowl and the solution was a stiffer durometer intake boot as well as supporting the daylights out of the carb directly to the engine via brackets. Once we figured that out it worked as advertised. I flew it in the winter in Minnesota and it worked fine even in temps approaching 0.

I don't recall what rod is in there but I can pull it the next time I'm in the shop and report back. As for the stiffer intake boot, I went with SC's suggestion and IIRC it was off a Honda 80 dirt bike. It's very possible Polini has superseded the boot with something stiffer. My 250 is a very early production version and quality control was not exactly their strong suit......about on par with Polini's legendary customer service

[Bill in MN]

They are now using an ek27 on the 303 and an ek26 on the 250.

[LA F2 Flyer]

Wait....does Polini actually HAVE customer service??? haha

[Badland-F5 Pilot]

I worked with the guys at Smart Carb for several weeks trying this, that and the other thing and I can't say enough about their customer service. They really went the extra mile. In the end we determined that vibration was causing fuel to foam up inside the bowl and the solution was a stiffer durometer intake boot as well as supporting the daylights out of the carb directly to the engine via brackets. Once we figured that out it worked as advertised. I flew it in the winter in Minnesota and it worked fine even in temps approaching 0.

I've read and watched on YT of people that have worked with SC customer support. All say the same as you did above. This is great news that someone uses an SC2 on a UL. How is fuel consumption? Did you notice any difference? Also, yes please, when you have time, post what rod you eventually used.

Thanks Bill! Your post is going to help me tune the ThumpAir once I get it purchased and installed....oh wait, I think I'm ahead of the game....still in line waiting for Chris to get to me and build my kit

Todd