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Help with building your Speeduino, installing it, getting it to run etc.
By kettlekev
I have a 750cc 3 cylinder water cooled 2 stroke I would like to EFI.

I have seen a couple of posts on 2 stroke work (TZ350?) but cant find much detail.

I have some Arduino experience and wondered if anyone had a working system? Guidance?

While I would like to do fuel and ignition I am happy to start with fuel first....I think that will be a big enough challenge :D

I believe the sensor suite I need is;

TPS sensor to run Alpha-N (no MAP sensor).
IAT (Inlet Air Temperature).
CLT (Coolant Temperature)
MAF (mass air flow)
Wideband O2 sensor and controller (optional), to check for optimal combustion. Oil will be an issue.....
Rev counter
Crank sensor


By kettlekev
Apologies, confused between MAP and MAF.

So inputs;
MAP (where is this placed on a two stroke?)
Crank sensor. I have timing at 120 degree intervals so what is the optimal teeth number given 36-1 is max for the system? Missing tooth on crank wheel to provide RPM info
CLT and IAT sensors (presume IAT is in throttle body or just exposed to ambient?)
Lambda (will need eternal controller). As oiling may be an issue, will the system work without? Closed loop maps?

3 channels of fuel and ignition (sequential, 120 degree apart, 1,2,3)
Injectors must be high impedance. One per cylinder I assume assuming the age can be covered (100 bhp @ 10k revs)
Thermo fan
Fuel pump (3 bar approx with regulator)
My CDI inputs are a low power input from the three hall sensors so it looks like the Speeduino can drive the CDI

Mega with V3.0 Speeduino look OK?. What is the interface between Arduino and Speeduino - serial?

Clearly new to this and the Wiki didn't answer all my questions as far as I could see.
By dazq
I'm sorry but you need to re-read the wiki !
The speeduino board is a kind of shield in effect for the Arduino just like the many that the Arduino system has had developed over the years.
36-1 is not the limit but is a common and popular wheel type to use.
The missing tooth is a reference not to calc the rpm itself.

Iat is inlet air not Ambient.
V3 are really meant for experimental work but some use them for permanent installs.

Your CDI may not work , more research needs to be made to confirm how it operates
By kettlekev
I understand the Speeduino is a shield but again I am not sure what the interface/link is? Via serial? I looked at the speeduino PCB layout and couldnt see how a Mega just plugged it?

I know IAT is inlet air temperature. Sorry my question was meant to ask if the inlet air temperature is taken from inside the inlet manifold or outside (ambient). Therefore where is the sensor positioned?

On the crank sensor, thanks for clarifying, 36-1 seemed like the ax tested value in the Wiki, I guess my question was can the missing tooth be used to interpret RPM and is that available in the firmware or does that need another sensor?

Thinking about the CDI I agree, it has its own timing plan so will need to bypass that.

Please bear with a newbie, I am reading but clearly not fully understanding yet and 2 strokes seem to have more issues than 4 strokes!!

With a few of my questions answered I am sure I can make progress.

Summary is;

Where are MAP and IAT positioned on a 2 stroke?
What decides how may teeth I need on the crank sensor, given my 2 stroke application?
Hows does Mega and Speedino interface together (serial?, I2C, SPI?)
V3.0 still looks OK especially for development?

By dazq
Map needs to be In the manifold, iat as I stated is inlet not Ambient so position it where it will get a good reading .
Choose a trigger wheel that suits your application, the type etc of engine has no bearing on the number of teeth.
The whole trigger wheel not just the missing tooth enables angular calculation as well as rpm rpmdot and much more
The mega plugs into the back of the speeduino board, it drives direct pins no SPI ,i2c etc.

As I said beforeboard choice is a personal one ,how much space you have, cost and finally your capabilities to build one.

Lastly there are several build threads with two strokes so have a good search and read.
By LAV1000
I see you did find the posts of T350, it is a lot to read.
To start, find a way to make or use a trigger wheel for the CPS, it doesn't have to be an 36-1.
12-1, 18-1 or 24-1 wil also work.

You could run Alpha-N , no need to use the MAP sensor then.
You can always use it later on.
Just keep the MAP sensor option open.
Alpha-N uses the TPS (Throttle Position Sensor), IAT, CLT, CPS (Crank Position Senor)
If youre sure that the current CDI uses HAL sensors then there should be a way for Speeduino to trigger it.
Can you post some schematics on your current CDI ?
Is it stil the OEM one or an aftermarket type ?

My idea is to start with ignition it is the basic part that needs to be spot on.
If ignition works like it should then adding injection isn't difficult any more.

When switching to injection check output of alternator.
It might not up to the extra power the fuel pump needs, don't ask how I know this....... ;)

V3.0 is a development type it has screw connections, which tend to run loose when used in or on a vehicle.
V4.0 type has crimp connections better suited for the job.
They both have the same functions.
By kettlekev
Thanks guys. Great info. and yes a lot to read in TZ350.

Quick question on the crank sensor. I can see how any number of teeth will give me TDC and RPM but as fire is a few degrees before TDC, is that just maths in the code (offset from TDC) as the wheel increments wont be fine enough for every timing point in the spark table?

I will post some CDI stuff but is basically a fixed curve aftermarket system now so not very useful. I assume the speeduino can replace it if I get the hardware coil drive right?
By LAV1000
On ignition timing.
As far as I understand it.
Speeduino calculates the time between the tooth and then exactly knows at which position the crank is and where to ignite each of your 3 cilinders.

Speeduino only needs a trigger wheel and one sensor to know when to set your 3 ignition signals (channels).
Same for the injection channels.

If you want to know if speeduino can control your CDI unit.
Then you need to share more specific information on the CDI unit.
Like schematic, what is inside the CDI unit or how it is wired to your bike ( bike electric schematic).
Do you know the difference between HALL and VR sensor ?

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