50cc Power efficiency project (GY6/139QMB)

[gab]

Basic info: 49ccscoot.proboards.com/thread/32384/greetings-quebec-canada

Jul 30, 2024 19:09:27 GMT -5 gab said:

Hi all! I am Gab. A 17 year old that has a very large thirst for anything that has to do with engines.

I will soon get a scooter equipped with the classic GY6/139QMB, though I want to spoil myself with only the best, so what crosses my mind is a few upgrades that that I think will improve the overall performance of my machine, without having a big bore install or anything blatantly modded.

For those curious;

-changing the carb to an indirect EFI system (specifically from ECOTRONS)
ecotrons.com/small_engine_fuel_injection_kit/

-changing the variator if stock is limited

-promoting airflow in and out of the engine

-changing the spark plug for an iridium spark plug

My goal with those upgrades is to make my engine slightly more powerful, also making it more efficient, while keeping the scooter looking stock.

Before I make a mistake by installing something I completely wouldn't need. I am asking if I am doing something wrong and if anything could be improved to make the smoothest GY6 there could be.

I am not here to break any record, I just want something that'll stay good!

Any help is super welcome!
You can also ask questions, I will answer them!

Estimated time: 1 year

Will ask for tips: yes

Goal: More powerful engine while being more efficient without having a big bore



Feel free to ask questions!

[sinfull]

Welcome and looking forward to seeing what you come up with 😃

[90GTVert]

I edited your first post to add a quote from your other thread and the link to the ecotrons kit, just to make it easier to follow.

Jul 30, 2024 19:09:27 GMT -5 gab said:

-changing the carb to an indirect EFI system (specifically from ECOTRONS)

This may not be the best plan, IMO. It depends on your goals. If you are on a mission to find out what kind of fuel economy and power you can get out of the stock displacement, maybe. If you want to create the best scooter to ride, probably not.

Fuel injection is a great thing in some respects and I'll tell you upfront that I have no experience with these EFI conversions. My thought is that you may overcomplicate it with EFI. There's the immediate issues like placing more demand on the charging system and hoping it delivers proper voltage, having to get it all installed and setup, and making sure it's in a good state of tune for example. What makes me a bit nervous with these kits, and even the stock injection on some newer Chinese scooters, is troubleshooting in the future. It's likely more difficult than the carburetor to figure out and you can replace an entire carburetor for a small amount of money if need be. A decent carb in a good state of tune works pretty well most of the time. When you add more components, you have more potential failure points.

I'm 300 pounds and when trying specifically for fuel economy, I got over 100MPG on a stock TaoTao 50. Normal riding, which is wide open most of the time cruising and some in town, I would get around 80-85MPG. Most people that are smaller and lighter than me should be able to do better than those numbers, so you've already got something that sips fuel. Let's say you can increase fuel economy by 10%. With my high number at 85MPG average, that's an extra 8.5MPG or 93.5MPG. That would be great, but is it worth the cost and potential troubleshooting issues later? It would take a lot of miles to save the money that the kit costs.

As far as power is concerned; I don't think you're looking at huge potential here. If it can keep the fueling just right and improve mixture quality through better atomization, maybe there's a small gain. I'd be a bit surprised if it were significant vs a carburetor in a good state of tune. The big potential here would be changing riding conditions. If you ride in the mountains and elevation changes a lot, then the carburetor is not likely to be at it's best throughout your rides. Sometimes it could be in a great state of tune and if you change 2000ft it may be rich or lean. Weather swings do the same, with hot humid air needing a different tune than cold dry air for example, but usually less drastic than very large elevation changes. I think EFI, assuming it controls the mixture well, could increase average horsepower/efficiency in those conditions compared to a carburetor left to deal with a range of variables with it's original tune.

The other advantage that I think could be noticeable is ease of starting. It shouldn't be a big issue with a carb, but EFI is usually easier to start in any conditions. Again, assuming the EFI system works well.

The question that someone else would have to answer is; how well do these aftermarket EFIs actually work? Not just does it run OK and start easily, but are they managing the mixture well with changing conditions?

Jul 30, 2024 19:09:27 GMT -5 gab said:

-promoting airflow in and out of the engine

You can certainly open it up and find port mismatches and poorly machined bowls in the head and things like that. Spend a day cleaning this stuff up well and you'll probably feel better about your improved flow paths... but I don't think it's going to be a significant change. A pro-porter can probably find some power and efficiency, but I think most of us would make minimal change. Stock exhaust seems to work well on stock bores, and maybe even big bores, but you can probably try to build a tuned exhaust and get something out of it for a lot of effort.

I'd consider examining the compression ratio as well if you're going for it. You may be able to change squish and compression and improve the engine if you use premium pump gas.

Put ignition timing in there too. There are gains to be had with some timing fiddling... and if the EFI system can use it's sensors to make a more detailed map, then it may show gains from that as well.

Jul 30, 2024 19:09:27 GMT -5 gab said:

-changing the spark plug for an iridium spark plug

Not a bad mod. Cheap and easy compared to many other things. Not likely to be noticed in the real world. I think the most common change is potentially easier starting. Possibly longer plug life, though regular plugs last a long time and they're again cheap and easy to replace.

Jul 30, 2024 19:09:27 GMT -5 gab said:

-changing the variator if stock is limited

There are definitely gains with CVT tuning. I'm not sure that you'll see much difference at the gas station, but you can certainly pick up some acceleration and maybe a small amount of speed. Speed, at least for me, is often horsepower limited. You can only do so much with the power that these little engines are putting out. That said, if you can keep RPM where you want it then you can see improvements.



With all of that said, if you asked me what to do to have a quicker/faster ride that was pretty similar in reliability and appearance to stock... I'd definitely put a 47mm (72cc) big bore kit on the top of the list. A big bore accompanied with carb and CVT tuning to work well with it makes a much more powerful scooter. Acceleration improves greatly and speed goes up as well. If you still want to ride at 30MPH and accelerate gently, you use less throttle to do it and it shouldn't guzzle gas. If you ride around wide open going quicker and faster than ever before, then yes it will certainly use more fuel. With a stock pipe and air filter, it looks and sounds essentially the same as stock. Reliability should be very similar. I'd choose a Taiwan made kit vs the cheapest kit I could find on amazon.

A BBK doesn't work if you really want or need to stay at 49cc, but if you just want a scooter that's more fun to ride and more capable, that's what I'd do. Example below.

youtu.be/PoK6ofGjeZA?si=YBzXv2UACs_k2avz

[gab]

Aug 1, 2024 8:34:04 GMT -5 90GTVert said:

This may not be the best plan, IMO. It depends on your goals. If you are on a mission to find out what kind of fuel economy and power you can get out of the stock displacement, maybe. If you want to create the best scooter to ride, probably not.

Fuel injection is a great thing in some respects and I'll tell you upfront that I have no experience with these EFI conversions. My thought is that you may overcomplicate it with EFI. There's the immediate issues like placing more demand on the charging system and hoping it delivers proper voltage, having to get it all installed and setup, and making sure it's in a good state of tune for example. What makes me a bit nervous with these kits, and even the stock injection on some newer Chinese scooters, is troubleshooting in the future. It's likely more difficult than the carburetor to figure out and you can replace an entire carburetor for a small amount of money if need be. A decent carb in a good state of tune works pretty well most of the time. When you add more components, you have more potential failure points.

[...] That would be great, but is it worth the cost and potential troubleshooting issues later? It would take a lot of miles to save the money that the kit costs.

As far as power is concerned; I don't think you're looking at huge potential here. If it can keep the fueling just right and improve mixture quality through better atomization, maybe there's a small gain. I'd be a bit surprised if it were significant vs a carburetor in a good state of tune. The big potential here would be changing riding conditions. If you ride in the mountains and elevation changes a lot, then the carburetor is not likely to be at it's best throughout your rides. Sometimes it could be in a great state of tune and if you change 2000ft it may be rich or lean. Weather swings do the same, with hot humid air needing a different tune than cold dry air for example, but usually less drastic than very large elevation changes. I think EFI, assuming it controls the mixture well, could increase average horsepower/efficiency in those conditions compared to a carburetor left to deal with a range of variables with it's original tune.

The other advantage that I think could be noticeable is ease of starting. It shouldn't be a big issue with a carb, but EFI is usually easier to start in any conditions. Again, assuming the EFI system works well.

The question that someone else would have to answer is; how well do these aftermarket EFIs actually work? Not just does it run OK and start easily, but are they managing the mixture well with changing conditions?

You addressed very much and many of my concerns with everything about this and i have to thank you for it. I am not worried about the fact of fiddling around with the ECU since i knew very well that i was to be doing that one way or another, where it'd be for power gain, power curve adjustments or whatever.

Bringing up power issues is now a kind of dealbreaker for me since it is just adding many things on the battery and might just end up sucking the life out of the engine instead of making some. I will continue looking into this though since i have a very profound love for technology in engines.

Aug 1, 2024 8:34:04 GMT -5 90GTVert said:

You can certainly open it up and find port mismatches and poorly machined bowls in the head and things like that. Spend a day cleaning this stuff up well and you'll probably feel better about your improved flow paths... [...] Stock exhaust seems to work well on stock bores, and maybe even big bores, but you can probably try to build a tuned exhaust and get something out of it for a lot of effort.

I'd consider examining the compression ratio as well if you're going for it. You may be able to change squish and compression and improve the engine if you use premium pump gas.

Put ignition timing in there too. There are gains to be had with some timing fiddling... and if the EFI system can use it's sensors to make a more detailed map, then it may show gains from that as well.

Most of what i mean by opening up and making airflow whatever is mostly out of a slight paranoia that the stock exhaust would include airflow restrictors and that the airbox would have a tab that i could just pull out to have at least 1% more airflow.

About the gas i'm stuck between getting ordinary or premium gas even though premium would be better (I will or will not just be listening to the engine) but will defo be looking into it!

I very much thought about ignition timing and with the EFI it would be a breeze since the CDI is connected to the ECU and it will surely map out everything. I will once again look further into the documentation of the ecotrons pnp system.

Aug 1, 2024 8:34:04 GMT -5 90GTVert said:

Not a bad mod. Cheap and easy compared to many other things. Not likely to be noticed in the real world. I think the most common change is potentially easier starting. Possibly longer plug life, though regular plugs last a long time and they're again cheap and easy to replace.

Pretty much added this because some dude on youtube tested and compared spark plugs and with surprising results the IX series of NGK spark plugs came out top, looked at the comments just to see that people got efficiency and power gains with said plug, so i'm really just hopping on a hypetrain. Once again it's not much about power but overall just to have a better combustion.

Aug 1, 2024 8:34:04 GMT -5 90GTVert said:

There are definitely gains with CVT tuning. I'm not sure that you'll see much difference at the gas station, but you can certainly pick up some acceleration and maybe a small amount of speed. Speed, at least for me, is often horsepower limited. You can only do so much with the power that these little engines are putting out. That said, if you can keep RPM where you want it then you can see improvements.

What i meant here is that i once saw that some scooters have a backplate on the variator that limits the speed and i just want some speed, so i don't want said speed to be limited. I didn't mention it and that's my fault, but the whole goal of changing out the variator if the stock one is limited is to just get a better top speed other than 55km/h. (34mi/h)

Aug 1, 2024 8:34:04 GMT -5 90GTVert said:

With all of that said, if you asked me what to do to have a quicker/faster ride that was pretty similar in reliability and appearance to stock... I'd definitely put a 47mm (72cc) big bore kit on the top of the list. A big bore accompanied with carb and CVT tuning to work well with it makes a much more powerful scooter. Acceleration improves greatly and speed goes up as well. If you still want to ride at 30MPH and accelerate gently, you use less throttle to do it and it shouldn't guzzle gas. If you ride around wide open going quicker and faster than ever before, then yes it will certainly use more fuel. With a stock pipe and air filter, it looks and sounds essentially the same as stock. Reliability should be very similar. I'd choose a Taiwan made kit vs the cheapest kit I could find on amazon.

A BBK doesn't work if you really want or need to stay at 49cc, but if you just want a scooter that's more fun to ride and more capable, that's what I'd do.

The reason why i overall don't wish to do a bbk is because
1. I don't really trust myself to do this
2. I do not have the tools to decently do this

Coming back on the CDI thing, if the EFI doesn't work out i will probably get me a variable CDI.
If EFI doesn't work i saw an alternative, but it unfortunately costs as much as a budget pair of loudspeakers, or like 17/72rd the price of my scooter. (The alternative in question)

Thank you so much for the second opinion! I appreciate it so much!

[90GTVert]

Aug 1, 2024 9:45:22 GMT -5 gab said:

Most of what i mean by opening up and making airflow whatever is mostly out of a slight paranoia that the stock exhaust would include airflow restrictors and that the airbox would have a tab that i could just pull out to have at least 1% more airflow.

What i meant here is that i once saw that some scooters have a backplate on the variator that limits the speed and i just want some speed, so i don't want said speed to be limited. I didn't mention it and that's my fault, but the whole goal of changing out the variator if the stock one is limited is to just get a better top speed other than 55km/h. (34mi/h)

Basically you just want to make sure it's not restricted from the sound of it. 30-35MPH is very common full throttle cruise speed on flat ground for GY6 50s. Tucked down and/or with a tailwind you may see 40 or above. If you list the make/model/year here, someone may know if you're likely to have restrictions.

Aug 1, 2024 9:45:22 GMT -5 gab said:

About the gas i'm stuck between getting ordinary or premium gas even though premium would be better (I will or will not just be listening to the engine) but will defo be looking into it!

Use what the manufacturer recommends if it's stock. If it runs well on regular without detonation, premium won't make it any faster. Premium won't really make it any slower either, so if you like "insurance" it's an option and at scooter economy it's really not a huge difference in spending. Definitely use premium if adjusting ignition timing or changing compression (big bore as well).

Aug 1, 2024 9:45:22 GMT -5 gab said:

Pretty much added this because some dude on youtube tested and compared spark plugs and with surprising results the IX series of NGK spark plugs came out top, looked at the comments just to see that people got efficiency and power gains with said plug, so i'm really just hopping on a hypetrain. Once again it's not much about power but overall just to have a better combustion.

Absolutely try it because it's cheap and easy and won't make you any slower or less efficient. That said, I've got a spreadsheet of about 700 1/8 mile runs over the last 2.5 years with a 14,000RPM 25-30HP 94cc two-stroke. Not a 139QMB... but with the inefficiencies of a two-stroke, burning oil in the mix, being prone to fouling, high revs... it's more sensitive to plug selection than the average 139QMB. I'd bet no one could look through the list of runs and tell which had iridium plugs and which were standard. I can't tell the difference. A dyno would tell more detail, but if you can't see it in real world tests then does it really matter?

Aug 1, 2024 9:45:22 GMT -5 gab said:

The reason why i overall don't wish to do a bbk is because
1. I don't really trust myself to do this
2. I do not have the tools to decently do this

EFI will be a much more complicated process. I've got a full how-to on big bore kit installation with all of the details and there are probable tons of YouTube videos of the process. Not a lot of fancy tools are required. A torque wrench is really the only thing that anyone with an average tool kit may not have.

Aug 1, 2024 9:45:22 GMT -5 gab said:

If EFI doesn't work i saw an alternative, but it unfortunately costs as much as a budget pair of loudspeakers, or like 17/72rd the price of my scooter. (The alternative in question)

TBH I think you're overcomplicating this in some ways. No offense intended, just offering my take to save you some headaches and cash. Specifically, fueling. You really don't need a fancy carb or EFI to have a well performing and reliable scooter. I bought a different expensive miracle carburetor once and spent a lot of time and money to finally decide that it was no good for me and go back to the much more standard carburetor that I was using beforehand. I'm not saying they're all bad. Smartcarb has a big following and lots of happy customers. I don't really believe you'll ever make up for that price in fuel savings or that you're going to see much of a gain. To me, that stuff is for people chasing every fraction of a horsepower on a dyno or every tenth of a second in a race or again potentially someone suffering from riding issues due to severe elevation changes.


If you haven't seen it, I'd suggest checking out my Project TaoTao vids. They're old and the production isn't great, but the info is useful IMO.
youtube.com/playlist?list=PLm3-Rt5jsoltCeQHjl-SJPKGpxk1sVq92&si=xspZTNE0SIt9FIpB

[gab]

Aug 1, 2024 11:53:25 GMT -5 90GTVert said:

TBH I think you're overcomplicating this in some ways. No offense intended,

Definitely

I just have to wait and see, i have many things before even getting the project scooter, some things in my head may change. Though i like complicated stuff, I just wanna do what's right.

[gab]

Project plans update
from sure to unsure

• Iridium Spark plug
• CDI change
• EFI kit

[gab]

Aug 1, 2024 12:13:15 GMT -5 gab said:

Project plans update
from sure to unsure

• Iridium Spark plug
• CDI change
• EFI kit

Damn. I don't know what to think about this after further research. The concept of an EFI kit just grows more and more appealing and a CDI just seems like a downright waste of cash after seeing what Admin and a guy with a dyno did.

Thank you Admin

The reason why I love the concept of fuel injection so much is how versatile and modifiable it is, i could just be outside just looking at a chart and improving my scooter instead of rotting in my room playing games. Other than the complexity, I do not see many flaws with this. Though i will not put this kit before putting a decent chunk of miles on the thing, the price isn't even shown!

I will therefore stick to a carb and just think more and more about it.


About my research. Admin tried CDIs on project TaoTao with no absolutely major difference to stock and showed alternative. Another guy tried many CDI's on a kitted out 2 stroke and the variation in horsepower in those tests were of about ±0.5 hp

In conclusion, i will not swap the CDI, EFI is for a near future and the spark plug i will stay loyal to. I will be careful to not run the scooter too hard first run to just give it a break-in period, despite my excitement.

[aeroxbud]

It's good to share information. That's what forums do so well. Doing detailed research before committing to a plan is always best.
Enjoy your scooter while looking into future plans.

[gab]

Unfortunate News

The project will be postponed about 2 months.

I'm quite deeply saddened right now, won't have the project scooter in a while (failed theoretical exam). Will attempt to keep you all updated on this because school is coming up, I have work and i need to study HARD to finally be able to get a scooter.

More Fortunate news though is that i have pretty much ripped the concept of EFI out of my head, ofc will be looking into more things and may change my mind, but keeping it simple will be my way to go. Will be walking you all through this micro project while getting ideas to just have a good scooter for a while.

See you all later!

[gab]

Now that my "depression period" is over...


Let me tell you about my choices
My choices are quite abundant, but when it comes to Chinese scooters, we have a good selection.
The main 3 potential brands are Scootterre, TaoTao, and ADLY


The first choice i have and long for is the Scootterre AR-50, a Minibike, it has a GY6 and the main reason why i made this build thread.
I recently have worried about the weight as it is about 20kg heavier, consumes more gas and has a worse top speed compared to other models.

Here's pics of it:

The specs are also listed on the website;

My second choice is from the same brand and also contains a GY6 (all scootterre have a GY6) the Scootterre Bistro
Lighter and has a bigger fuel tank, better fuel economy like listed compared to the AR-50
Here's it;



Specs for comparison sake;

You might ask:
Why does one love the AR-50 so much?

The short answer is purely the looks, it's something that i do not see often and really stands out from other scooters (because it's pretty much a bike)

Long answer; By the looks of it i can have the liberty of having potentially more space in the compartment than a regular scooter, In my way of seeing things, i am guessing that i could improve upon the design by maybe getting rid of unnecessary weight and "remodel" the thing. I am definitely worried about what this whole thing could be in terms of drivability and in terms of mods that could be done, but i can rest assured that i have good alternatives from other models (especially the bistro). Will dedicate my spare time into doing my research, If new info comes, i will be sure to transfer it to you all just in case anyone spots something i shouldn't do or if i want to ask for help on something i am unsure of.

Later!

[aeroxbud]

It's a bit heavier, but the 12" wheels are a good upgrade. A lot less prone to get unsettled by road imperfections .

[gab]

Any update on the project I will do as an unlisted or public youtube video if some wish to see everything come together. Will also add text in every post, but the overall of what has been done will be low effort landscape phone recordings.

I really want everyone to see what is happening in the best way possible. You can't hear an image haha!

[90GTVert]

If you have the opportunity, walk into a dealer and check out similar models. Both of those have many like them by other companies. Get a feel for each style. I would absolutely take the form and fit of the one I liked best over worrying about 22kg/48lb difference. Yes, the lighter bike should be better for acceleration and fuel economy, but it won't be a game changer IMO unless you are really after hypermiling it or plan to time your acceleration runs or race someone. The step-through is easier to get on, has more storage options, and probably has an aero advantage with your legs tucked in behind it rather than alongside the bike. Both will have a different riding feel. Pick what you like and what you think will work best for you rather than stressing over the specs too much. Chinese specs are also notoriously terrible, though the ones shown actually seem realistic.


Oh, and regarding CDIs and timing... Ignition timing can absolutely improve power and rideability. The main issue with many aftermarket CDIs is that I think they focus more on making money with the idea of going quicker/faster than trying to provide a quality product. Especially true with cheap CDIs, which is the majority of the market. I got one for a pitbike that I think should work on the 139QMB and I've meant to try it but haven't touched my little four-stroke in a long time now. Anyway, the CDI has low advance at cranking RPM to allow for easier starting, but lots of advance otherwise that I think may provide more noticeable gains. Either that or it's too much timing and it causes detonation. LOL Anyway, timing works and is nice if it can be tweaked, but most of the time you don't even know what you're getting with CDIs.

[gab]

I might've done one too many verifications to realise that the bike is as big as a scooter, so i know that i'm able to not tip toe a standstill lol

Both of the models shown are available locally and i will visit the shop to gain more knowledge about both models, other than the engine.

About the CDIs, i would rather not risk having something that i just buy without much noticeable difference and potentially worse experience. I know there's good and bad, but rather not for now.