Tuesday, 10 November 2015


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


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