Newbie - Two Stroke Project

[daveyb]

Hi All,

I am investigating the best method to convert my bike's two stroke engine from running on carbs to efi. I have looked at firms such as Ecotrons. But I don't believe these systems meets my needs.

I have a 1992 Honda NSR 250 MC21. This is a crank case reed valve induction, 90 degree V-twin two stroke and it is used primarily for the track. At the moment is produces 67 rear wheel brake horsepower and it is running the zeeltronic ecu that controls the ignition, power jets, air jets and exhaust power valves. It uses information from the gear position sensor, tps, cdi timing and rpm to control these functions. It does not use inlet air pressure/temp to work out engine control timings. I am currently looking at the MS3X to replace the Zeeltronic in not only running the efi but also the ignition and the powervalves to start with.

I have seen a number of success stories on the forum, but their method is a bit vague. I would like to use four injectors per cyclinder firing in batched pairs through the transfer ports i.e. Cylinder 1, 1st pair feeeding the B ports at low load/rpm followed by the 2nd pair feeding the A ports at high load/rpm. This I believe would give a better fuel control instead of using the usual method of injecting in front of the reed valve in to the crankcase! What I'm worried about is placement of the air pressure sensor. I know the signal strength of air signal (MAF or MAP) in the inlet is quite low therefore can it differentiate between the engine being in or out of the power band?

To get around this problem, I was hoping on installing on to each expansion chamber's (exhaust) upper belly portion a EGT and Pressure sensor, as I believe this would really be the best point to determine if the engine is in the power band or not. But looking at the manual it seems the MS3X can only use one pressure sensor for mapping, is this correct? I was even thinking of installing a lamda sensor in the pipe's belly as well to aid set up.

I am looking to weld a trigger wheel on to the generator. As the current method used for timing is a pair of long teeth on the exterior of the generator, which I believe will not be accurate enough.

Could I set up the MS3X to run as a piggy back data logging system whilst still running on the Zeeltronic?

If any one has any hints or tips on how should start this project, it would be greatly appreciated.

Many Regards
Dave

[LAV1000]

Did you also look at the MSpro ?

I think the biggest issues are controlling current CDI ignition and exhaust port valves.
Make a list for yourself of what you have/ need on inputs and outputs.
And what type output you need to drive, injector, ignition type, solenoid, pwm, stepper.


Does the gear position sensor alter the ignition, like a wheely control ?

[elutionsdesign]

It can use two pressure sensors for fueling, possibly running %baro would be appropriate? It can certainly log many pressure sensors.

[Matt Cramer]

I have seen a number of success stories on the forum, but their method is a bit vague. I would like to use four injectors per cyclinder firing in batched pairs through the transfer ports i.e. Cylinder 1, 1st pair feeeding the B ports at low load/rpm followed by the 2nd pair feeding the A ports at high load/rpm. This I believe would give a better fuel control instead of using the usual method of injecting in front of the reed valve in to the crankcase!

This can be done with the staged injection code on MS3. I would treat each pair of injectors as a single injector with double the flow rate, so you'd use four outputs.

What I'm worried about is placement of the air pressure sensor. I know the signal strength of air signal (MAF or MAP) in the inlet is quite low therefore can it differentiate between the engine being in or out of the power band?

A number of two stroke fans, like Whittlebeast here, favor using a MAF sensor on two strokes. If using a MAP sensor, there is an option to sample the sensor reading only at a certain crank angle, which can also help with reversion issues. Usually the "in or out of the power band" part can be determined by RPM and the sensor reading unless there is a region where there is a small change in MAP that produces a huge change in air flow; if that is the case, I would either use a MAF or possibly ITB load mode.

To get around this problem, I was hoping on installing on to each expansion chamber's (exhaust) upper belly portion a EGT and Pressure sensor, as I believe this would really be the best point to determine if the engine is in the power band or not. But looking at the manual it seems the MS3X can only use one pressure sensor for mapping, is this correct?

You could use the exhaust pressure sensor to command the MS3 to blend between two separate fuel tables.

While the code allows using an EGT sensor for table blending as well, but I'm concerned it would not react fast enough.

I was even thinking of installing a lamda sensor in the pipe's belly as well to aid set up.

The lambda sensor itself is easy to use for closed loop correction.

Could I set up the MS3X to run as a piggy back data logging system whilst still running on the Zeeltronic?

It could record some data but would not be able to capture the ignition timing or pulse width. I wouldn't bother.

[daveyb]

Wow, so many responses.

Hi LAV100.
The Gear Position Sensor, does alter the ignition curve, basically it retards it slightly in 1st and 2nd then progressively gets on to the full fat curve from 3rd to 6th. I use it this was on the Zeeltronic for smoother gear changes initially as well as trying to keep the front wheel below the horizon (works up to a point). I have made a spread sheet of all the inputs and outputs that I think will be needed, I am hoping some will be used later on once I get a good foundation to work from and the project starts progressing.

Hi Elutiondesign.
The two throttle bodies will be in a sealed airbox, that 1% is all important on a 250. I take it the baro input will need to be fed from the inside of the airbox?

Hi Matt.
If I am running a ram airbox and using a throttle body per cylinder would I require two MAF sensors or could I get away with one i.e. using one cyclinder as a master cyclinder for example?
What is ITB load mode?
I nknow I have a radical exhaust temperature change when the engine is in the power band. Out of the power band the EGT is usually around 495C and when in the band is around 580C. I'm not sure how fast this happens as I'm running an analogue guage, about a second visually, although the guage probably has some form of damping.

Many thanks guys, its a lot to consider
Dave

[Matt Cramer]

If I am running a ram airbox and using a throttle body per cylinder would I require two MAF sensors or could I get away with one i.e. using one cyclinder as a master cyclinder for example?
What is ITB load mode?
I nknow I have a radical exhaust temperature change when the engine is in the power band. Out of the power band the EGT is usually around 495C and when in the band is around 580C. I'm not sure how fast this happens as I'm running an analogue guage, about a second visually, although the guage probably has some form of damping.

Currently there is no dual-MAF support; you could use an airbox with just one inlet and put the MAF there.

ITB mode blends between a MAP sensor at low load with a TPS reading at high load.