Wednesday, 1 March 2017

EGT Instrumentation & Dyno Calibration

EGT Instrumentation

To try and close out the base fuel & spark calibration once & for all, a deadline of mid February was imposed by booking a track day at Mallory Park. That provided some additional incentive to get the bike on a dyno in January to do the base calibration.

First, a few small loose ends on the electronics side needed to be tidied up. One of these was to try and implement EGT measurement to provide a second metric to determine optimum fuelling and make sure exhaust port temperatures were under control.

Initially the plan was to simply read EGT values and display them on a screen live and then keep an eye on them while running the bike on the dyno.

However, there would be several advantages to being able to feed the data into the ECU so that it could be logged with all other engine parameters. Unfortunately, due to the limited I/O capacity of the Microsquirt ECU, the only way of getting four additional data streams into the ECU would be via CAN-Bus. That meant using a microcontroller to read the EGT data from thermocouple amplifiers, arrange the data into a CAN message in a format that the Microsquirt could read and load the message onto the bus. 

To prove the concept, an Arduino Uno and CAN Shield were used to get the data processing & CAN code working together properly. The Megasquirt CAN-Bus protocol was the most difficult part of the task as it is quite different from the standard 11-bit or 29-bit header protocol that I am familiar with.

Once the hardware and code combination was proven, a single PCB was designed and manufactured which used an Arduino Micro as the controller and contained the thermocouple amplifiers, CAN controller, CAN transceiver and other peripherals that were required to make the board work on the bike. The finished board is quite large due to being conservative about component spacing to allow hand soldering of components and only used one side of the board for component placement. For future PCBs, component spacing could be tightened up, a dual layer PCB and a microcontroller with inbuilt CAN controller could be used to significantly reduce the board footprint. 
A protective case for the completed board was 3D printed.

EGT CAN-Bus Module Board
Cased Board

On the instrumentation side, 1.5mm K-Type thermocouples were installed as close to the exhaust ports as possible using compression fittings without interfering with the fitment of the radiator or making exhaust fitment difficult. The small diameter probes would allow shorter temperature stabilisation but at the expense of thermocouple life. This was determined to be a reasonable compromise as the main purpose of the thermocouples was to monitor temperatures during dyno runs and short road tests only. As they would not be used for long term control, durability was not deemed critical.

Thermocouple Tip Position In The Exhaust
Thermocouples & Flanges In Place


Exhaust Header Flange Upgrade

While the exhaust was removed for drilling & welding, the opportunity was grabbed to rectify the much annoying issue of the exhaust header flanges bending while the nuts were being torqued up on the studs.

The problem with the Honda design is that the flanges do not clamp between the nut and the cylinder head but rather the flange is designed to be clear of the cylinder head when fully torqued up so the flange has a tendency to bend around the header collar as the nuts are being torqued up. This may not be an issue if the specified torque was always adhered to but on both sets of headers I have owned (OEM & TSR), the flanges had been bent previously. Bent flanges mean that more preload on the stud is required to achieve the same torque which only amplifies the issue and risks stripping the threads in the cylinder head. The studs also bend as the nut tries to sit flush with the flange which can make removing the flanges difficult.

To try and combat this issue, a new set of flanges were laser cut from 316 stainless steel plate. Compared to the TSR exhaust flanges, the new design uses thicker material (8mm vs. 6mm) and also adds c.2mm of material around the outer profile. These changes have the effect of making the new flanges approx. 3 times more resistant to bending at their weakest point compared to the TSR flange.

Exhaust flange comparison, Redesign (left) vs. TSR (right)


Dyno Fuel Calibration

With the EGT instrumentation in place it was time to get the bike on the dyno and complete steady state fuel calibration.

The dyno was an eddy current braked dyno which allowed any speed and load to be held for a period of time to ensure engine conditions could stabilise at each calibration point. The only downside was that as it was a car dyno designed for much higher power vehicles, it was impossible to hold the engine at the lower speeds and throttle angles. Therefore only the area above 4,000rpm & 10% throttle angle could be successfully mapped. As this represents the area where the majority of riding is carried out then that was not much of a problem.

After the fuel mapping was carried out, an attempt was made to see if there was any additional power to be had in the ignition timing. The bike seemed to be very insensitive to part throttle, steady state ignition timing changes although this can be very difficult to judge on a chassis dyno, especially one with quite high inertia.

A few full throttle pulls from 8,000rpm to 16,000rpm were carried out with varying ignition timing to determine what effect it had on engine power. Baseline timing was the Bluefox ECU timing. It was found that a global timing offset of -2° produced a negligible change to engine power. Both +2° & -4° global ignition timing offset produced measurable power losses across the engine speed range. Given that the Bluefox ignition map is c.1.5° more advanced than the OEM Honda curve in that region, it suggests that Honda did a pretty good job of mapping the engine to MBT timing from the factory.

For anyone who cares about these things, the final figure on that particular dyno was 37 bhp measured at the rear wheel at 14,700rpm. No gains over the standard bike were expected with EFI and given the engine is in an unknown state of repair, it was considered a reasonable result. The bike was never dynoed before the EFI conversion and even if it had been, the comparison wouldn’t have been possible on the same dyno and therefore not comparable.

It became apparent from studying the power & torque curves was that the original 18,000rpm rev limit is totally unnecessary as power drops off quite sharply after the peak. A graph of driving torque in each gear shows that there is no point in going faster than 16,000rpm in any gear as, above 16,000rpm, there will be more torque available in next gear up. As such, following the dyno testing, a soft limit at 16,500rpm and a hard limit at 16,700rpm was imposed with the aim to shift up at 16,000rpm.


Calibrating The Bike On The Dyno

The dyno run completed base fuelling & spark for a given barometric pressure and manifold air temperature. All other starts and runs from here on out will help to apply appropriate air temp & barometric pressure corrections and dial in the transient fuelling corrections.



 
Trackday

As planned, the bike was taken on a trackday at Mallory Park after dyno testing to see how it would manage. Unfortunately the chosen day turned out to be cold, wet & snowy but still proved to be a great test of the bike’s rideability with the EFI system.

It was also hoped to use the track day as an opportunity to get a lot of data logging done to help dial in the transient fuelling but as luck would have it, the brand new lambda sensor installed died within minutes of the bike being started so no fuelling data was recorded throughout the day.

Despite this setback, the bike rode really well on the track and throttle response & power were as good as could have hoped given the lack of any form of transient fuelling corrections.

Trackday

Tuesday, 21 February 2017

The Search For Electrical Overhead

Due to the additional electrical load being placed on the bike from the EFI system, the charging system needed some attention. It was suspected from the very beginning of the project that the original reg/rec may not able to cope with the constant drain on the system from a high pressure fuel pump and twin headlights. This became very apparent as the bike was being used more and more recently.
The battery could not be kept charged when either the dipped beams or main beams were switched on. There was a definite drop in battery voltage depending on whether the lights were switched on or not and it was noticed that the reg/rec was getting quite hot after night-time rides so it was likely that the reg/rec was going to fail sooner rather than later.

A new Shindengen FH020AA mosfet reg/rec had already been purchased for an upgrade further down the line but given the circumstances, the upgrade was moved to the top of the priority list. The installation of the new reg/rec was relatively straight-forward. The FH020AA is quite a bit bigger than the OEM reg/rec but still fits under the fairing in the same place. Just about. One additional hole had to be drilled in the mounting plate to accommodate the wider hole spacing of the FH020AA and the standard connector was chopped from the loom and replaced with the dual connectors required for the FH020AA.

FH020AA vs OEM mc22 reg/rec

An immediate improvement in voltage regulation and stability was observed with the FH020AA fitted and the reg/rec merely ran warm to the touch as opposed to hot. Although, since the reg/rec can only improve regulation efficiency and can not force the stator to provide any extra power, the bike was still a little short of electrical headroom. It was not bad enough to risk running the battery flat during a long night-time ride but rather meant that battery voltage with the lights on at idle tended to hover around 12V as opposed to the 14V which was observed at idle with no lights. When a current clamp was placed on the battery earth strap, it became apparent that with lights on, the predominant flow of current was out of the battery. As such, a way of either a) boosting the generated power or b) reducing the electrical load on the bike had to be found. Of the two, option b) was clearly the preferred route. Given the headlights represented the single largest current draw on the electrical system, they were the chosen target for modernisation.

After much deliberation, research and changing of mind back & forth, it was decided to install LED bulbs. The options were either HID or LED but eventually the LED won out due to being actually able to package the ballasts in the front of the bike, being more adjustable for beam pattern and having lower overall current draw although they were almost twice the cost of the HIDs for a quality set from a reputable manufacturer.

Each H4 LED bulb is rated at 20W compared to the 60W/55W rating of the standard halogen units so, in theory, a set of two should have freed up c.6A capacity which would be more than enough to cover the additional load the fuel pump, lambda heater & injectors placed on the system. Before installing the LEDs, a charge current of -7A (draining battery) at idle with dipped beam on and -6A at idle with main beam on was measured. With the LEDs installed, charging current was measured at +3A at idle with both dipped and main beams on, leaving ample headroom on the charging system.

The physical installation of the bulbs was reasonably straight-forward. The heatsinks on the back of the bulb made it all a bit bulkier than the standard setup but the heat sinks are well hidden given they are black in colour. The two small ballasts found a nice place to sit either side of the clock stay bracket where they do not interfere with anything else. Getting the beam pattern right took the most time but the adjustment in the bulb housings worked a treat. There is also the advantage that the LED headlamps are quite a bit brighter than the halogens which makes night-time riding quite a bit more enjoyable.

Friday, 9 September 2016

ECU Modifications

There were two further modifications I wanted to make to the control system before getting the bike back on the road for a decent period of time and collecting data.

  1. Bluetooth connectivity
  2. Barometric Pressure Sensor


Bluetooth Connectivity

I had been looking at incorporating Bluetooth connectivity on the Microsquirt for quite a while and had purchased an RS232 to Bluetooth module for the purpose. I never got around to installing it permanently though as I needed to add a separate power connection for the module.
When I was building the new ECU harness recently I added a switched 12V power & ground connector with the intention of using this connector to power a Bluetooth module.

However, getting into the detail, I became less happy with the RS232 to Bluetooth module option. This option meant I would still need to use a 2.5mm jack to RS232 cable between the ECU harness & the Bluetooth module which not only made the setup bulky but also introduced more connectors than required  with the potential for connection issues.
I researched alternative serial-Bluetooth modules and came across the HC-05 & HC-06 modules which are commonly used in Arduino projects and can be easily reprogrammed using an Arduino. I decided upon using a HC-06 module as I did not have the requirement to switch between master/slave modes. The physical size of the module was a large part of the attraction. The plan was to use a linear voltage regulator to drop the switched 12V supply down to an acceptable level for the HC-06 and enclose the module in a small case with a flying lead terminating in a 2.5mm jack to communicate with the ECU. However when this setup was tested, the software would recognise a Bluetooth device was connected but it could not read the firmware signature. The signature appeared as though the baud rate was incorrect even though it wasn’t. After much frustration & further research, it was found that the HC-06 works with straight serial data and cannot deal with RS232 serial as it was receiving via the 2.5mm jack in the ECU harness.

Then I discovered an article online that described installing a HC-06 Bluetooth module inside the Microsquirt case. 5V power & ground connections were taken from the development header on the main board and Tx & Rx were soldered directly onto the main board prior to the RS232 chip. This installation had the immediate attraction of being extremely tidy as everything would be hidden inside the ECU case with no external wiring. I added a toggle switch to the 5V power connection so that the Bluetooth module could be switched on & off from outside the ECU, allowing the choice of connecting to the ECU via Bluetooth or via direct RS232 serial cable.

The internal installation worked great the first time and has made datalogging and loading calibrations onto the ECU significantly easier given that every ride can now be datalogged using a smart-phone in the pocket without requiring a laptop with wired connection to the ECU to be carried around in a backpack. It will significantly increase the rate of data collection and usability of the bike.

HC-06 Bluetooth Module

Barometric Pressure Sensor

Given the location of the lambda sensor on the TSR exhaust system, it is impractical to run closed loop lambda correction during daily use and so the intention was to dial in the fuelling as best possible and run open loop fuelling. In order to correct fuelling for varying atmospheric pressure and riding at altitude, the preference was to add a separate barometric pressure sensor which would allow constant fuelling corrections with pressure/altitude.

The simplest option was to add a second MAP sensor which would be dedicated to atmospheric pressure measurement. However, MAP sensors tend to be able to measure across a larger range of pressures than required so accuracy would be compromised. I also had not added the external wiring necessary when I renewed the ECU harness.

I had seen some examples of Microsquirt ECUs modified to include an internal MAP & Barometric pressure sensor such as the DIYAutotune MAPDaddy board. This particular solution did not appeal to me though as it is relatively expensive, includes 2 pressure sensors when only one was needed and the sensors are 4 Bar sensors which are likely to be quite inaccurate when trying to measure in such a small range of the sensor’s capability. This did however open up the idea of using a board mount pressure sensor located within the ECU case.

I looked at using a Bosch BMP sensor but as the output is digital I would need additional electronics to convert the signal back to analogue 0-5V so that the ECU could read it. A Honeywell pressure sensor was also an option as it gave an analogue output and being a through-hole package, it could easily be mounted on standard stripboard. However the cost was prohibitive being over half the cost of the dual sensor MAPDaddy board and the physical size and measurement range was still larger than I would have liked.

In the end I have chosen an Infineon KP235 Barometric pressure sensor as it is low cost, designed for use in automotive applications, narrow useable measurement range & small package size. The one disadvantage was that the surface mount package and small size meant I had to design and make a PCB to mount it and allow it to be connected to the ECU but this was a small price to pay for the size and cost of the unit.

A PCB was designed to accept the KP235 sensor and include smoothing capacitors on the input & output voltages as recommended by the manufacturer. Surface mount 0805 package capacitors were used to help keep the size of the board down and the interface with the ECU would be through standard size header pins and DuPont connectors. This way the board size was kept down to 25mm x 12mm.

Copper board was painted to mask the copper layer. Then a negative of the PCB layout was etched in the mask to expose all the unwanted copper. The exposed copper was then removed using an acid solution before removing the paint mask and protecting the remaining copper with a liquid tin solution. The header pin holes were then drilled and the components soldered in place. For additional protection and isolation from vibration, the completed board was coated in a layer of silicone rubber.

Completed Sensor & Board

Protected Sensor Board

5V power & ground were taken from the header pins on the main board as with the Bluetooth module and the output signal wire was soldered to the SPAREADC2 pin on the Ampseal connector between the connector and the ECU board. A 1.5mm hole was also drilled in the ECU case to allow pressure inside the case to equalise to atmospheric pressure.

Sensor Installed In The ECU

Both the Bluetooth module and barometric pressure sensor are held in place using hot glue. The Bluetooth module is located underneath the topside of the Ampseal connector and the barometric pressure is located underneath the lower side of the Ampseal connector. The Bluetooth switch is located on the RHS of the ECU and is easily reachable when it is installed on the bike.


Following these two upgrades to the ECU, the physical install is considered as good as complete. The bike is now back together again and on the road where the goal over the next few months is to collect as much data as possible and continue to refine the calibration.


Friday, 19 August 2016

Idle Control Valve & More Wiring

Idle Control Valve

One of the things that was bugging me about the whole install was the fact that because I had converted the carburetors to throttle bodies and disabled the choke, cold starting was still a bit of an issue. There was a fine line between setting the throttle stop such that the engine would run when cold and still not idle massively high. I had got it to a point where it would idle at c.2,000 rpm when hot but when cold it would struggle to life & I couldn’t touch the throttle until a reasonable amount of heat had built up in the engine. It was OK for the short term but it wasn’t good enough for a road engine so I started looking into getting some form of idle control implemented.

As most idle control valves are based on a stepper motor driving open the throttles when cold I began to look at these. I contemplated mounting a stepper motor to the throttle bodies to drive the throttle stop screw in and out so that I could vary the closed position depending on coolant temperature. The issues with this were the placement of the stepper motor & also the stepper motor drive. The Microsquirt does not have a stepper motor output so I would need an external unit to convert the PWM output of the Microsquirt into something that could be fed into a stepper motor. Space constraints won out in the end. The thermostat housing is located pretty much exactly there the motor would need to be mounted and I had already moved the thermostat housing as much as possible just to get the fuel rail to fit.

I also considered a mechanical system with a thermostat that would retract a plunger as coolant temp rose and close the throttle more but the same space constraints also killed that idea.

I then thought that I could bleed air past the butterflies by using the carb sync nipples that I was already using to measure MAP from. Having air leaking in here results in rough running on a carbureted system but with the FI system I would have the ability to add fuel to compensate and make use of the additional air being drawn in. A solenoid valve could be driven by PWM directly from the Microsquirt to regulate the flow of air past the butterflies and the MAP sensor could be T’d in between the solenoid & the split to all the ports so that MAP could still be sampled in the same way as before.

After a little research I purchased a Bosch canister purge valve used in many cars and a selection of silicone hose & T pieces to plumb in the system. The diagram below shows a schematic of the plumbing I ended up with.


The idle control valve so far has only been tested for a very short time on the bike but so far it is looking very promising. When the engine is warm, the difference in engine speed between valve closed & valve open is 1,000 rpm and I can also use the valve to control to a target idle speed in closed loop mode. It certainly needs more running to dial in the settings but it is a big step in the right direction.



Wiring Harness Issue 02

Given the addition of an idle air valve, I needed to run the signal wire from the ECU to the injector harness to drive the valve so that required a small change to the ECU harness. Small changes spiral quickly with me though and this was no exception.

Even though I had spent some time this time last year tidying up the wiring harness, I had become pretty unhappy with it as time went on. In diagnosing a faulty main relay some months back I became sceptical about the quality of connections I had made in the harness. Since most of these connections were made at the very beginning of the project when I had little experience and were added on a “when needed” and “where is accessible” basis, I did not have a clear idea about how reliable they were and where the connections were physically located within the harness. The harness was also far bulkier than I cared for and was generally not up to my current standards.

At the time I started to doubt the harness I had decided that I would build a completely new main bike harness incorporating the ECU harness and dash and a few other upgrades that would make the bike a bit more modern so I thought the old ECU harness would do the job until I got the main harness built.

However, having to run a single wire along the harness presented the perfect opportunity to tear it all apart and start again to make the ECU harness tidier and more reliable until the upgraded bike harness would be ready to drop in. The main aims for the new ECU harness were:

  1. Remove all unused wires from the harness. Previously I had just chopped the unused wires back but they still ran within the harness up until the front of the pillion seat.
  2. Replace any wires within the harness which were deemed overkill for the level of current they are expected to carry.
  3. Replace all previously spliced wires with new more reliable spliced connections.
  4. Tidy up the power connections around the fuse box & add proper relay connectors to make removing and replacing components more foolproof & straightforward
  5. Tidy up how the external coil driver box interfaced with the harness
  6. Mainly use the process to create a complete & up to date harness drawing and pinout chart including connector specs, wire routing, wire sizes, splices & splice locations and harness lengths. All this would take more time now but would really help with any fault diagnosis and harness alterations in the future. It would also get me one step closer to a full set of documentation to capture all the alterations & modifications I have made to the bike throughout this project.

While drawing up the new ECU harness I decided to change the way injector power was being delivered to enable me to fit in the idle valve wiring in the same connector that was already in the harness. Previously, each injector bank (2off) had its own fused power supply so I merged these two supplies into one which also provided power to the idle valve and allowed me to use a 4-way connector between the ECU & Injector harness. That change did however force a rebuild of the injector harness even though I was reasonably happy with that. At the same time it was a good excuse to make a few nice changes and make it altogether more robust.

First was to remove all the wires from the ECU Ampseal connector that were not being used. Also any signal wires which had been cut and spliced previously were removed and replaced with fresh wire. The harness was then laid out and laced together with the branches coming off the main trunk at the correct locations. Then connectors were added and the whole lot wrapped. Installed on the bike it is now far easier to install & remove the harness and it looks much tidier also.

Laced ECU Harness

Installed ECU Harness
While that all looked good, I felt that wrapping the harness tended to twist the bundle a little when wrapping and the wrap was also a little untidy around the areas where the branches broke away from the main bundle so for the Injector harness I took a slightly different approach. I sleeved the wire bundles with DR-25 and then covered the joints with adhesive lined heatshrink to provide some rigidity. I also redesigned the harness so that the main bundle would be tied to the throttle bodies just below the airbox rather than onto the fuel rail where it was previously.

Completed Injector Harness

Installed Injector Harness

Installed Idle Valve

Thursday, 18 August 2016

Back To Basics

I realise it is close to a year since I updated this but better late than never. Not much has happened in the way of real engine calibration since the last update but still some reasonable progress in terms of fine tuning settings. The bike got MOT’d right after the last blog entry and had a few outings afterwards but hasn’t really moved since Christmas.

I wanted to check a few things that were bothering me about the Microsquirt control and so ended up carrying out quite a lot of bench testing on the ignition side of things over several months.

I actually don’t remember where it all started but at some point during the last year I started to question the accuracy of ignition timing provided by the Microsquirt ECU. I carried out some tests using a crude trigger wheel simulator on the bench & then on a running engine which confirmed my suspicions; ignition timing appeared to drift as much as 5 degrees at 18,000rpm. On top of this I noticed two further uncertainties while testing.

  1. Battery voltage as read by the ECU did not track actual battery voltage. There appeared to be some hysteresis in the measurement as the ECU recorded a different offset depending on whether the battery voltage was rising or falling. This was obviously an issue as it would result in incorrect coil dwell times & injector dead times.
  2. During ignition coil testing using the ECU’s output test mode, coil dwell times measured did not match what was demanded by the ECU even with battery voltage compensation disabled.

When I first noticed the timing accuracy issue I figured I could simply get a new, higher resolution trigger wheel made to replace the standard 12-3 wheel. However I hadn’t reckoned with the fact that the Microsquirt doesn’t have the processing power to cope with a higher resolution wheel at the kind of engine speeds seen on the CBR250. The Megasquirt developers have stated that even with the low resolution wheel on the CBR250, 18,000rpm is pushing the boundaries of the Microsquirt hardware capability and that an MS3Pro ECU would do a far better job at controlling the engine at these speeds. Coming out of this, I will most likely be upgrading to an MS3Pro ECU sometime in the future but given the expense and the fact the wiring harness would need to be redesigned to work with the new ECU I tried to find a way to make the Microsquirt work acceptably until I was ready for the upgrade and so I continued with reasonably extensive bench testing in order to measure and understand how the ECU controlled the ignition side of things.


Ignition Timing Accuracy
Firstly I wanted to spend some more time bench testing the ignition control both to understand the issues better and to be able to present the issue properly to the Megasquirt developers which would help find out if the MS3Pro would actually fix the issues. That meant making sure that all other variables were as accurate as I could make them. The most important of these was the trigger wheel offset relative to TDC. I had determined this value early in the project using a timing light so it was potentially not as accurate as it could be.

To determine this properly with the oscilloscope, I needed to compare it directly with the output of the standard MC22 ECU at a known engine speed and spark advance. I wanted to have a way of accurately simulating the crank trigger signal as would be seen by the ECU in a running engine. There are lots of ways available to simulate hall effect trigger signals but I specifically wanted to simulate the VR type of signal that creates a zero crossing. After some research & trial & error I settled on using an Arduino board to create the signals using a modified version of the Ardustim code.

The Ardustim code normally generates a hall type signal by asking a single pin to go high at specific times. With some modification to the Ardustim code I ended up creating a VR type signal by switching two separate pins & merging them into a single channel. The voltage output from the merged channel would depend on the combined state of the two Arduino pins.

Both pins high = 5V; Both pins low = 0V; 1 pin high + 1 pin low = 2.5V.

The output is fed through a transformer to create the needed zero voltage crossing. The simulated VR signal could then be used to determine the 1st tooth angle offset to TDC from the standard MC22 ECU.

As I had a CBR250RR(R) ECU, the benchmark from the manual is spark demand at 20°BTDC at 1,500rpm. Measuring the time delay on the oscilloscope between the 1st tooth trigger & coil firing signal and converting to degrees at 1,500rpm gave me a 1st tooth angle of 70.5°BTDC. 0.5° closer than I had measured with the timing light.

1st Tooth Offset Determination. Note The Simulated VR Signal
With the foundation settings correct in the Microsquirt I then proceeded to map the ignition angle error across the engine speed range to build up some data and understand what the exact nature of the error was. It was only when I actually wrote the error values down that I discovered that the errors were consistent in terms of time throughout the engine speed range. This led me to wonder if this was something that could simply be corrected for in the calibration by adjusting the spark hardware latency offset setting. I had not used this previously as I had understood that it was to be used to correct for any delays which might exist within external hardware and since the errors I had been seeing were from within the Microsquirt itself, I ignored this feature.

I made some small adjustments to the latency offset and rechecked ignition timing across the speed range each time until I was happy that the measured ignition timing was consistent with what was being demanded.


Voltage Reading
It was actually quite straightforward to fix the battery voltage reading error within the calibration. I used a digital benchtop power supply to vary the voltage supply to the ECU & noted the voltage readings within the ECU. I quickly found that the different voltage readings depending on if the voltage was increasing or decreasing was being caused by the smoothing function which I had set quite high initially. Once the smoothing was removed, the ECU voltage readings tracked consistently all the time but were offset slightly from the supplied voltage.
I used the measured error to determine new values for voltage at max & min ADC to change the voltage reading calibration which brought the voltage readings in line with the supplied voltage.


Coil Dwell Time
While testing and characterising the ignition coils using the controller’s output test mode to drive the coils, I found that the measured coil dwell tended to be longer than what was being demanded from the ECU by a factor of c.1.14. This did became a little worry at the time but I have since noticed that the error appears only when controlling the coils in the output test mode. When the engine is running (or simulated) the measured dwell time matches what is being demanded by the controller and so this became a non-issue.


Ignition Coil Characterisation
A major unknown in the ignition system was the dwell time required for the ignition coils.

First, the standard MC22 RR(R) ECU was mapped in order to determine what dwell times it was requesting at different engine speeds and then compared against how the Microsquirt code handles dwell.
Looking at the dwell times that were being requested by the standard ECU and how they changed as engine speed increases gave the impression that the coils may be performance limited at high speed as the dwell time at 17,000rpm is significantly shorter than at 5,000rpm for example and if the dwell being provided at lower engine speeds is necessary for good coil performance then it would mean that the coil is not getting fully charged at higher engine speeds and ignition performance may be compromised.

This observation prompted an investigation into trying to fit some higher performing pencil coils from a more modern machine to try and get consistent ignition performance throughout the speed range. The biggest issue was and still is finding coils which will physically fit in the MC22 plug bores.

All TCI coils found are too high and protrude quite a lot above the cam cover and foul the radiator fan.

CDI coils such as installed in ’97-‘99 Suzuki GSXR600/750s & 2009 Yamaha YZF250 seem to be the smallest coils physically and could be made work but even these are c.10mm longer than ideal for the MC22. The issue with the CDI coils then is that while they can be made work with a TCI ignition system, the charging current is far higher and the dwell times are far shorter than a normal TCI coil and the ECU and coil drivers would need to be capable of controlling them very accurately.
The charging current can be dealt with using an appropriate ignition IGBT specced for the high current & fly-back voltage. I did purchase a number of appropriate transistors which were capable of driving the CDI coils successfully during bench testing.

However it was found during testing that the Microsquirt firmware did not have the dwell demand resolution needed to accurately control the GSXR CDI coils. The Megasquirt firmware can only control dwell to the nearest 0.1ms but the GSXR coil nominal dwell is c.0.3ms so accurate control of the dwell is impossible with the Microsquirt controller. Due to this control limitation, the coil upgrade idea has been parked for the foreseeable future.

Given no alternative ignition coil solution was on the horizon, the standard MC22 wasted spark coils were tested to characterise them and ensure they were being driven properly by the ECU. The coils are nothing special for the MC22 as one might expect for an engine that was being asked to rev higher than most other engines at the time. They are TEC MP08 coils which seem to have been the standard Honda wasted spark coil of choice during the 1990s.

A current clamp was connected to the oscilloscope to observe how the charging current increased with dwell time & determine the optimum dwell time for a range of battery voltages to provide consistent performance. Observing the way that current draw increased with time it was decided to limit the charging current to 2.75A. The standard ECU does not correct for battery voltage and dwells the coils for 6ms at idle and up to 4,000rpm. As can be seen in the current trace below, this level of dwell overcharges the coil and dwell times could be significantly reduced without too much of an effect on ignition performance. Reducing dwell times would also ensure the coils are performing consistently across as wide an engine speed range as possible. At 12V, the dwell time to 2.75A is 2.5ms and even at 10V there is no sense in dwelling the coils for more than 4ms although it does not reach 2.75A.

TEC MP08 Primary Current at 12V Supply, 6ms dwell
This investigation showed that as long as battery voltage is kept above 12V there would be no reduction in ignition performance across the full engine speed range. Another benefit is that by keeping the dwell as low as possible at lower engine speeds, this would reduce the load on the charging system compared to the standard settings. Also the old adage, “leave well enough alone” holds true as there is no point in chasing the COP coils option when there is nothing suitable on the market at the moment for reasonable money. For a bigger engine it would be worth it purely to free up some space and provide the option for sequential ignition at a later date.


While getting all this information took a lot of time and investment in new equipment, it is worth it to ensure that the basics of the system are working correctly otherwise it would make future calibration more difficult.

Tuesday, 10 November 2015

Re-Calibration

First off, the new fuel fittings have been installed and are a success. The install looks quite tidy now and I have adequate clearance between the frame and the banjo bolt. The 90degree fitting also directs the hose in the right way so that the quick release fitting is lined up with the pump spout. Installing and removing the fuel tank is now very straightforward.

Fuel Hose
As well as re-testing the injectors, I also took the opportunity to properly calibrate the Suzuki MAP sensor using a Druck calibrator I had available to use. This corrected any errors in the calibration at the start of the project which was done using a mechanics analogue vacuum gauge. The MAP sensor now tracks barometric pressure to +/-1mBar.


Due to the change in injector characterisation within the ECU software, I needed to revisit the calibration which had been carried out during road tests at the end of 2014. The estimated dead time previously had been too large which then meant that I ran into issues running the engine using the same fuel table & warmup settings as previously determined.

I had originally planned to go the route of timed semi-sequential injection as that has the potential to give more repeatable results and better fuelling control at idle and part throttle, low speed than untimed batch fire injection. This is how the ECU was programmed up until a few weeks ago and I had managed to get a relatively good idle and had a decent fuel table. However, as the previous calibration was based on incorrect injector dead-time, the fuel table values were skewed.

When I started the bike again a few weeks ago with corrected injector characteristics & a good MAP sensor calibration, engine idle was erratic and not very well controlled. Lambda readings were as high as 1.35 despite using the same fuel table as before and the idle bins needed a lot more fuel added in order to get the engine to idle at a sensible lambda. Even then readings were swinging constantly between 0.9-1.1. The issue was that the correct dead-time was quite a bit lower than the estimated value used previously and so that meant injector pulsewidths were now low enough to demand pulsewidths at the lower end of the non-linear flow region such that little to no fuel was actually being injected each time and leading to high lambda idle and lean misfire. This was compounded by the fact that the semi-sequential control required each injector to fire twice per cycle, halving the demanded pulsewidth for a given quantity of fuel.

Following this development I abandoned semi-sequential injection in favour of batch fire. While it is a more crude method of fuel delivery and does not usually yield as fine control as lower loads & speeds, the tradeoff in favour of longer, more predictable pulsewidths as idle and low load are worth it for my application

In the past two weeks I believe I have managed a much smoother, controlled idle than I had with the earlier 2014 calibration. So far I have not had any issues with repeatability on the batch fire sequencing and off-idle throttle response is far better than ever before.

I need to finish some other non-EFI conversion related work on the bike before I will be able to get the bike on the road and continue calibration work.

Thursday, 27 August 2015

Permanentisation!

The project came to a bit of a halt over the winter and spring due to the unexpected rebuild of another bike. Now though it is slowly coming back into line.

While I have not started the bike in months and progress would appear to be slow from looking at the semi-naked bike in the garage, some good and very important steps have been taken towards making sure the EFI system is fully integrated into the bike.

Firstly is wiring. During the early calibration and testing stages, I still had not fully finalised the wiring loom. While the EFI side of the loom is good and did not need to be touched, the auxiliary loom which forms part of the Koso dash installation had not been finalised. I pulled out the dash loom again and split it into two definitive sections which allows the dash to sit much better when the nose fairing is installed. One section feeds into the original loom via one of the original clock connector and the other which routes down the RHS of the bike taking the constant power source & fuel level signal to the dash. CLT & speed sensor wiring was also plugged into this side of the loom and I integrated the Eclipze headlight upgrade wiring into the auxiliary loom also.
That bit of tidying has fixed some items which I was not 100% happy with.


Revised Dash Harness Routing


The second and most important thing was to permanently turn the carburetors into throttle bodies. When I first fitted the throttle bodies I was unsure if removing the slides completely would cause issues with response & rideability at low throttle openings given that the throttle bores are so large in comparison to the inlet ports. In order to verify this, the slides were simply held in their fully open position using silicone sealant to test the rideability. During testing, no adverse characteristics were noted so the original plan to bond the slides in place permanently was carried out.

The slides were each filled with reinforced epoxy resin and bonded in the fully closed position with the same epoxy. The main slide area was then cut out using a dremel tool and cut back to meet the throttle bore wall. A brake cylinder hone was then used to grind any imperfections down and ensure bore roundness was maintained. After initial honing, epoxy resin was reapplied on any low spots and the honing procedure repeated. Once a good finish was achieved with the hone, the bores were finished by working up to 800grit emery paper. Right now, the gas path is smooth all the way through the throttle body with none of the imperfections of the carburetor left to disturb the air.

Epoxy Infill After Roughing

Finished Throttle Bore


I was not 100% happy with the injector testing which I had carried out before. Only one injector had been tested, the flow rate was a little approximate and the dead time calculations had been inconclusive so that my current calibration still contained the default figures. Getting the injector dead times right is crucial to a good idle, especially as the injectors are still a little on the large side for the mc22 so I opted to retest all four injectors using better equipment.

Short lengths of flexible tubing were slipped on over the end of the injectors to direct the flow and also to minimise vapour spray. The injector being tested was fired into a plastic container which was placed on a scales. Weighing the fuel injected was far more accurate than measuring it from a graduated cylinder as larger quantities of fuel could be used for the test and thereby minimise the effects of any errors in readings.

A variable bench power supply was used to power the ECU & injectors which allowed dead time tests to be conducted at 3 different voltage points and measure dead time variation with voltage. The fuel pump was still driven by the battery as the power supply did not have the current rating to support the fuel pump power demand.
Each injector was tested at 100% duty cycle for several periods of 1-2mins to get an average flow rate. Dead time tests were conducted using 10 different pulsewidths at 3 different voltage settings, with each data point test timed to last 2mins. This resulted in long test times although confidence in the results is very high.

Measuring Injector Discharge

Test Bench

Test Results


The fuel line fittings are also being upgraded. The initial testing was carried out with a standard steel banjo fitting feeding into the end of the fuel rail. A fibre reinforced fuel line had to be used due to space restrictions not allowing an aeroquip hose to bend around to meet the fuel pump. Space was also so limited that the banjo bolt fouled on the frame with the throttle bodies fitted. It was good enough for early testing but certainly not good enough to stay that way.

One solution was to cut 2-3mm from the end of the fuel rail and to shorten it. However, an alternative banjo fitting had to be found anyway to route the fuel pipe to the pump so modification of the fuel rail was held off until suitable fittings could be found.

Luckily enough, the good people at ATEC Autotechnic make a selection of quality motorsport grade fittings and will supply CAD models of everything on request. That allowed the packaging to be determined before buying and it was found that by using these quality fittings, the banjo stack height could be reduced by over 3mm meaning that no fuel rail modification was needed.

New Fuel Fittings

Old vs. New