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.

1 comment:

  1. Stick with it Mate, I imagine Laslo the blown 250 will need your technology to solve it's uneven distribution to all four cylinders problem it has using the compromise draw through / carb system it uses

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