Megasquirt Support Forum (MSEXTRA)

This is my first post since long time. I am (not very actively) fighting with all small issues at the final stage of my Citroen DS21 EFI conversion. The easiest of which seem to be the correct measurement and setting of the injectors stats.

I am trying to calculate the stats of Bosch 0280150151 injectors. The injectors are new and have flow rate of 240.7cc@2bar, 304.8@3bar according to http://users.erols.com/srweiss/tableifc.htm. Fuel pressure is reduced to 2.1bar, because the injectors are rather big for this engine (for this I will be asking later).

I have set up a test bench around my car using an adjustable power supply for the mega and the injectors and a second, external battery for the fuel pump.
I used the method from youtube: https://www.youtube.com/watch?v=lJgi8l-2XG4
I have measured the volume of the fuel with 2,4,6,8 and 10ms pulse width at 12.2, 13.2 and 14.2. The graphics are nice and straight.
The calculated flow rate is close to the one mentioned at http://users.erols.com/srweiss/tableifc.htm - 260cc@2.1 bar.
The calculated dead time is: 0.181@14.2v, 0.325@13.2v, 0.590@12.2v
The calculated voltage correction 14.2-13.2v = 0.144v, 13.2-12.2v = 0.265v

What I find surprising is that the voltage correction is not linear between 14.2 - 13.2v and 13.2 - 12.2v
Also the calculated dead time @13.2v seems very low. Therefore I have tried testing it by increasing the PW starting at 0.35ms with step of 0.1ms, while waiting for the injector to start dripping. The first drops are seen at a pulse of ~0.9ms

Any advises how I can calculate correctly the stats are more than welcome.

I am not sure if your adjustable power supply is up to the current need/speed of your injector.
I would also run the injector from a battery, battery delivers instant current, your power supply needs time to control the current.
So maybe your power supply is boosting the voltage to deliver the wanted current, you can't measure this whit a DMM they are to slow.

Thanks for the advise.
I tested it without involving the power supply and the results are similar:
- with a single battery, powering both the mega and the fuel pump (voltage is around 11.8-12v and drops rather fast)
- with a dedicated battery for the fuel pump (voltage that the mega sees is stable and around 12.4v)
- as above, but with a charger, connected to the battery which is connected to the mega

That 0.9msec seems like normal value.
Otherwise measure again and also add 1.5 msec and drop the next ones whit 0.1 so you get 1.4, 1.3, 1.2. to 0,6, or til it stops spraying.
It is possible that injectors are not linear in the last part.

if you want to make a voltage for the injectors , put a diode in series.

If they are big for idle use you certainly need this figures spot on.

I am running injectors and fuelrail/regulator from a GTI Turbo II on my DS23. Runs perfect!

krum wrote:Therefore I have tried testing it by increasing the PW starting at 0.35ms with step of 0.1ms, while waiting for the injector to start dripping. The first drops are seen at a pulse of ~0.9ms

The injector dripping is not useful for determining dead time. It might perhaps estimate opening time, but it ignores closing time. Do not do that.

The accurate method for measuring deadtime is measuring fluid flow and plotting a graph.

James