Larger Injectors - Minimum PW

[sigratton]

Hi, I have fitted some 640cc injectors to my NC1 mx5 and I am trying to reconfigure the ECU for the injectors. I have read a heap of information on injector scaling and believe I am taking the right approach.

The issue is, i can get the engine to start but then at idle the injector PW just goes to 800.000ms, the engine runs very rich, the short term trims go to -25%, but PW does not change as a result of the trims, it stays at 800.000ms. Is there a minimum PW setting somewhere, because it does not seem to matter what I change, the PW will become fixed at 800.000ms

Set up so far. 725cc
-- Injectors are Bosch 640cc EV14, they flow 651cc at 3 bar from the suppled data and 725cc at 4 bar according to this calculator https://app.calconic.com/public/calcula ... youts=true

-- Injectors have the following published dead times - https://goflowforce.com/pages/instructions , so I have re-scaled the 'Injector Opening Times' table using the values supplied in the zero column and maintained the percentage deltas to rescale each row. So should be in the right ball park.

-- I have changed the 'Injector Base PW' to 4.5 based on a calculation using the 725cc flow rate to achieve 14.7 fuel ratio at 6000rpm at engine load 1. Which seems reasonable based on the old injector size

-- I have rescaled the Injector cranking pulse width by 0.5 to compensate for the bigger injectors, which seems to work.

-- I have set the the Injector Global Scaling to 1

-- I have set the Injector Scaling Maybe 2 to 751, but it says that this should not matter.

From this starting point, I have tried reducing the Injector Global Scaling to as low as 0.5 but it has no impact. I have also tried reducing the Injector Base PW to as low as 2 and it has not effect. The result is the same, PW goes to 800.00ms and the engine is super rich.

I did set the Injector Global Scaling to 3 and the engine struggled to run, so it has an effect, which is why I am wondering if there is a min PW setting somewhere.

I have obviously looked through all the tables available and I cannot see it a min anywhere.

Thanks for you help.

[sigratton]

I think i am getting somewhere now, I have reverted back to the stock dead times and I am finding that the engine is lean now, which makes sense because the actual PW will not be long enough, so I thing it is a matter initially of dialing in the dead time. I will reach out the injector supplier and see if they have better data for MAP compensation, since they only supply data for what I assume is atmospheric pressure

Basically at 1.6x stock deadtimes I am running with 18% short term trim, so there I still have work to do and I realise this is only really working at the MAP for idle, so there is some work to do to tune the dead time table.

[sigratton]

I am guessing the 800ms seen is more a limitation of the logging with regards to the lower limit of log output and does not reflect what the ECU is using. Since I have things running reasonably well now and I am still seeing a 800ms flat line from time to time.