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Exploring FreeEMS for 50cc GY6 scooter 
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I have one of the very popular carburetor based 50cc GY6 Chinese scooter, made in 2012, itself a clone of the wildly successful Japanese Honda Elite GY6 engine from the early 1980s.

It's hard starting in especially in colder weather. It usually stalls out the first 5 or 10 starts before it'll stay running, IF it stays running. This is really annoying because the electric start battery usually runs down before the scooter can get running and stay running. This forces you to kick start it and try an infinite amount of times in the hopes it'll start and stay running.

The only adjustments on the carb are:
1. idle rpm throttle cable screw which apparently controls the idle - 1/4 throttle along with the idle jet's hole size.
2. the vacuum-operated, rubber diaphram-suspended, needle, with add-on rings which decide how far down into a metal hole air passageway it hangs and therefore how much air it blocks, this apparently controls the 1/4 - 3/4 throttle mixture.
3. air/fuel ratio mixture screw which apparently controls the 3/4 - wide open throttle mixture,
See more detail here: http://scootdawg.proboards.com/thread/2 ... e-gy6-carb

Anyway, I just want the thing to start up the first time and stay running, not fade and stall after 10 seconds, and no more instant stalling when I try to rev the engine past idle!

This is why I'm looking at FreeEMS.

1. Is there a parts list with a list of reliable suppliers and approximate prices for each part?
2. Has anyone ever added FreeEMS to a motorbike in order to get it to run EFI and make it perfectly reliable like a car?
3. Plenty of 50cc motorbike owners have added a bung to hold a wideband O2 sensor to their exhaust pipe in order to show the O2 level on their digital dashboard, this part is well known, tried out by thousands, relatively mainstream, no problem. What about:
a. small one cylinder throttle body with electrically controlled injector, to fit the tiny intake port,
b. sturdy injector pump that won't overheat and burn out,
c. return line,
d. temp sensor,
e. crank sensor - the bike sort of already has a sensor for crank because it has a fixed position dedicated coil on the stator plate for generating the primary voltage to send to the ignition coil which steps it up and sends to the spark plug,
f. intake MAF or MAP - mass air flow or mass air pressure - sensor?

Any idea of the approximate cost of the whole shebang?

Footnote, maybe an idea for turning this project into a sustainable business! Would be brilliant if there was an online e-shop, and once you got all the parts for your bike or car, you could plug them together like legos, because they have standard connectors. Then connect to 12v power, weld the O2 sensor bunk to your exhaust pipe, attach sensors, new intake manifold, fuel pump and return line, jelly splices to the spark plug primary wires, and you're good to go.


Wed Apr 05, 2017 8:46 pm
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FreeEMS found its way onto a 2 cylinder ride-on lawn mower, and a 4 cylinder CBR600RR engine in a race car, and nothing smaller AFAIK.

Challenges you will face:

1) Battery capacity and/or charging capacity to run the system sustainably
2) EFI fuel pump physically small enough and electrically efficient/lean enough to supply the engine and conform with 1)
3) Injectors with sufficiently small flow to not make tuning near-impossible
4) Instrumenting your engine sufficiently to monitor its behaviour and control it correctly
5) Coil sufficiently efficient to meet demands of 1)

Included in 4) is a reliable and sufficiently high resolution crank signal to handle starting without bad firing, and low enough to handle whatever RPM you can reach.

With those problems solved, it's a non-issue and as easy as any engine, more or less.

Hope that helps! :-)

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Thu Apr 06, 2017 4:30 am
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Quote:
1) Battery capacity and/or charging capacity to run the system sustainably
2) EFI fuel pump physically small enough and electrically efficient/lean enough to supply the engine and conform with 1)
3) Injectors with sufficiently small flow to not make tuning near-impossible
4) Instrumenting your engine sufficiently to monitor its behaviour and control it correctly
5) Coil sufficiently efficient to meet demands of 1)


Hi Fred, it's great to communicate with you directly!
I know it's possible to run EFI on the 50cc GY6 engine because many others have done it. An aftermarket EFI kit is available for the far too expensive cost of 500-800 US dollars. When you search youtube gy6 efi kit you'll find videos about it.

On the topic of power requirements, most users of aftermarket EFI kits on the 50cc motorbike engines, say you need to upgrade your stator from the stock 5 coil, to 7, or, ideally 11 coil. These are in fact 5 + 1 ignition coil primary trigger coil, 7+1 ignition primary trigger coil, and 11 + 1 ignition primary trigger coil. Others say the 18 coil is too large to fit the allocated space for a stator.

Besides the larger more power output stator, you also need to upgrade the bike charging system to use a full wave DC rectifier, instead of the stock which is half-wave DC, half-wave AC. The stock half wave DC charges the battery and runs the tail lights, while the stock half wave AC runs the bike's headlights, turn signals, which are incandescent bulbs, and can handle 12 V AC no problem. However using only half wave for the DC charging system is a needlessly huge sacrifice. Besides, the headlights and turn signals really ought to be converted to be powered off of 12V DC which allows you to save electrical power by running LED lights which use about 1/5 the power, for less heat wasted, longer life, and higher reliability.

Any idea how many Amps at 12 volts or 5 volts is required by:
a. the ECU? You run a special rugged embedded system board, this isn't a super low power arduino or the RPi is it?
b. fuel pump?
c. a typical small motorbike injector? These bikes when properly tuned, do about 60-100 miles (100 - 160 km ) per US gallon (3.5 liters) petrol.
d. o2 sensor?
e. map sensor?
f. engine temp sensor?
e. anything else?


Thu Apr 06, 2017 12:25 pm
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Yeah, I'm generally aware of stator and regulator upgrades - the FSAE cars need them, too. Most common cause of dead cars in the final lap session is: ran out of electrical juice! There's a compulsory stop, stop engine, swap driver, start engine, go, section. :-)

I'm not doubting the possibility, just pointing out which parts will be tricky to find/get/make. Even those kits may not use something that's really appropriate. It might just be the case that nothing appropriate actually exists :-)

Re juice:

ECU 1 ampere, or less, max 2 or less, but likely in the hundreds of mA region.
Fuel pump, 10A+ typically, some up to 50A, but smaller ones should draw less. Still need high pressure, though.
Injectors of a high-Z nature tend to burn about 1A each at full 100% duty use, progressively less at lower power levels, this is a function of impedance, not size/flow.
O2 is in the 2 to 5A range off the top of my head, I'd tune it with a battery pack on my back, and then not run a full time wideband.
MAP included in ECU draw, negligible.
temp sensors, ditto. TPS ditto. etc.

anything else? Not planning to run controlled ignition? Coils can draw up to about 50% duty 10A or there abouts, typically 25% of 10A including the ramp.

That seems like the bulk of it.

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DIYEFI.org - where Open Source means Open Source, and Free means Freedom
FreeEMS.org - the open source engine management system
FreeEMS dev diary and its comments thread and my turbo truck!
n00bs, do NOT PM or email tech questions! Use the forum!
The ever growing list of FreeEMS success stories!


Fri Apr 07, 2017 12:31 pm
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Thanks Fred.
Your estimate adds up to about 17.5 Amps at 12V electrical power needed just for the EFI system.
1. ECU 1 ampere, or less, max 2 or less, but likely in the hundreds of mA region.
2. Fuel pump, 10A+ typically, some up to 50A, but smaller ones should draw less. Still need high pressure, though.
2. Injectors of a high-Z nature tend to burn about 1A each at full 100% duty use, progressively less at lower power levels, this is a function of impedance, not size/flow.
4. O2 is in the 2 to 5A range off the top of my head, I'd tune it with a battery pack on my back, and then not run a full time wideband.
5. MAP included in ECU draw, negligible.
6. temp sensors, ditto. TPS ditto. etc.
7. anything else? Not planning to run controlled ignition? Coils can draw up to about 50% duty 10A or there abouts, typically 25% of 10A including the ramp.

Add the LED lights at around 2-5A total, worst case, and we're at 23.5 Amps needed at peak power demand.

The problem is, according to some documentation, I haven't tested the bike yet, the bike's stator and charging system supposedly produces about 3-5 Amps at idle 600 rpm, and about 15-16 Amps at the higher revs 3000-5000 rpm.

So we need a less power hungry EFI system for the bike!

I know such a thing is possible because it exists and is in use by several mainstream motorbike manufacturers who are selling new bikes on the market right now with EFI.

Also, you can buy an EFI retrofit kit, I won't name the brand because I'm not trying to promote them and have no affiliation whatsoever but the first three letters are eco I guess it's named that way because EFI helps to save fuel. That kit is for all size motorbikes, including those with the same size charging system as my bike, and they run fine, with no deficiencies in the charging system. You can see videos on youtube of people getting it running on a 150cc bike with 8 pole stator producing the usual 5-15 Amps of current.

Anyway, let's look at how could this be streamlined to save power.

What about a lower pressure fuel pump that needs only 1 Amp at 12 volts? I ask about this lower pressure pump because this 50cc bike uses such little fuel. The high pressure pump I found is made for big motorcycles, needs 10 Amps, and is able to do 100 psi and a volume of 190 liters per hour, which is absolutely 100 times more fuel volume than this bike needs. This 50cc bike uses about 2 liters per hour, when driven flat out max speed, which almost never happens. Could the EFI system be made to run the bike satisfactorily so that it gets by just fine with a lower pressure pump which does 20 liters per hour, at 4-6 psi? If yes, this would save us 9 Amps, and bring down our total power requirement to 14.5 Amps worst case!


Wed Apr 12, 2017 4:24 am
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Can't do injection, or at least good injection, with much less than 30psi. The pump
you mention draws lots of current because of the volume it moves AT that pressure.
Moving less volume at the same pressure will reduce current demand. 4-6psi sounds
like a carby pump, which only has to deliver volume to fill a bowl, not pressure
through a tiny hole that's opened for a few milli seconds at a time.

Ecotrons is a bad, evil, dishonest, and low-quality company based out of China
trying to play North American tricks. You can mention them all you like, a quick
search on this forum would put most off buying anything from them.

I make out current to be about 1.5A + fuel pump draw, at full power. At idle it'd
be around 0.5A + fuel pump draw. Fuel pump could be PWMed with RPM to limit
regulator non-linearity and current draw. But you should find a small pump to
start off with, anyway. Maybe source one from the OEM that does a bike like
this with a factory setup?

Running a wideband full time is a bad idea in such a small light low power vehicle.

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DIYEFI.org - where Open Source means Open Source, and Free means Freedom
FreeEMS.org - the open source engine management system
FreeEMS dev diary and its comments thread and my turbo truck!
n00bs, do NOT PM or email tech questions! Use the forum!
The ever growing list of FreeEMS success stories!


Wed Apr 12, 2017 12:31 pm
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Good idea Fred, to find out which pump is being used by the smaller bike manufacturers. The one I mentioned was for use on a Ducati 1100, two or four cylinder not sure. The current draw numbers you mention, 2 Amps or so, that's totally doable on this bike

Crossing off the eco company's products from consideration, how would you recommend going about getting the following up and running. Thinking it would be good to start with a basic DIY O2 sensor setup, to gather data on why it's stalling out, then add other bits to get full EFI moving forward. It's straightforward to first weld a bung on the exhaust pipe, nearby the exhaust port for the the heat, thread in a Bosch 17014 5 wire O2 sensor, power it thru a relay operated by the keyswitch, and strap on a dvm multimeter semi permanently, to measure the voltage or current, for the purposes of seeing where it goes wrong when it stalls out, so that then we're no longer flying blind, and can do an informed manual tuning of the air fuel ratio on the carb. Would the sensor be putting out 20 milliamps or so of positive or negative current, based on how far off from the perfect 14.7 : 1 air fuel ratio ? Should I stick a fixed resistor across the O2 sensor output and just measure the voltage drop to make it easier? I've seen wideband O2 sensor kits in action on youtube, they display things like 040 when it's ideal and 821 when it's rich, this is a different scale of numbers than the positive and negative current which supposedly comes off the wideband O2. Suggestions, warnings, shortcuts?


Thu Apr 13, 2017 12:38 am
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Does FreeEMS support communicating through a standard automotive ODB-II port ? I believe it's just a serial port running at a range of possible baud rates...?

Does FreeEMS support logging faults or most/all data to some type of network connection to a tablet or pc ? I guess rsyslog or something of that type. It'd be great to be able to let the tablet or pc scan the log data then upload interesting data to an internet server for further review. For example, maybe when a cylinder misses, or timing slips for an unknown reason, or fuel injection fails. Then, you know something needs fixing, and you can get parts ready to repair the car/vehicle when it gets back.?

Dynamic tuning - any plans to let FreeEMS dynamically tune the timing and quantity based on variations of sensor inputs, and/or just to improve the engine efficiency, performance, etc. Maybe the manually tuned values, achieved over five manual tunings in succession, were a good starting point, yet FreeEMS would then make use of its artificial intelligence smarts to constantly fine-tune up the engine better.?


Tue May 16, 2017 1:16 am
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The MCU includes CAN hardware, however little implementation has been done, and no OBD2 work, AFAIK. Serial only, for now.

No real fault detection at this point, however all useful data is logged in the standard packet structure. More can be added, or fat can be trimmed - it's fully programmable. Putting into a network connection is trivial however interpreting it into usable data has to be done one one side of that link or the other.

Auto trimming is certainly possible, however I don't think I'd like to have it on my vehicle(s). This is useful for unmeasured things like humidity, fuel temperature at the injector tip, etc.

_________________
DIYEFI.org - where Open Source means Open Source, and Free means Freedom
FreeEMS.org - the open source engine management system
FreeEMS dev diary and its comments thread and my turbo truck!
n00bs, do NOT PM or email tech questions! Use the forum!
The ever growing list of FreeEMS success stories!


Sat May 20, 2017 11:13 am
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