Calibrating injectors

[antonch]

Today I finally had some time to install new injectors and tune it so the car is drivable. It was a bit frustrating because it felt that I didn't have the injectors properly modeled.



Before someone knocks on my VE table, this is whatever I was able to tune in the time given and I didn't have the time to copy/smooth some of the values out. You can tell where it was tuned and where it wasn't. Overall this table keeps my AFRs pretty much near their target throughout the map.

The first area of concern is idle. At idle speed of 1200rpm/50kpa Lambda is equal to 1. At 700rpm/40kpa Lambda is somewhere in the 0.8 range. If I decrease VE value at 700, the idle begins to fluctuate considerably because of what appears like a significant VE map change. If you look at the rest of the VE map, its right around 100; I believe that injector constants need some tweaks rather than the VE map. My idle PW is ~1.8ms which is awfully close to the injector open time of ~1.6 ms.

Rather than fudge the VE table, I rather have a proper injector table. If MAT is different than what I tuned for, the ECU will have no problem giving spot-on AFRs. Should I try to hunt down an oscilloscope? I'd prefer to be able to do some street tuning as its much easier.

My req_fuel is 4.7 ms. See this post for some injector data:
http://www.vems.co.uk/forum/index.php?topic=226.0

[rob@vems.co.uk]

If you're getting resolution issues at low rpm you can divide your req_fuel by 2 and multiply the VE values by two - this gives you twice the amount of resolution that you had before, and looking at your table will give you a maximum value of 208 (104 x 2)

This should clean up the idle a fair bit.

The next step is to sit and adjust the Inj effective rampup.  Some of the guys reckon that you can set this value to zero and tune the VE map accordingly, I've had some good results with increasing the number 100 at a time until the idle begins to sound better note this number, if you continue the idle quality may start to drop off again note the number and work out the midway point between the two noted values, then try smaller steps to get the optimum idle.  Its really handy to have a gas analyser with HC readings for this, but you'll get an ear for the note of the engine and the smoothness of the idle after a few goes.

Another thing to consider is your power - does the battery reading drop around idle?  If so you might need to tune the battfac value, this is the additional amount of opening time added to the injectors at 6v (IIRC) which is scaled according to Battery voltage

[antonch]

Hmm, I did notice the parking brake light flicker around idle. I'll check the voltage. I was under the impression that my alternator was good. Based on my VE table, would you say I have the TS diode installed?

[rob@vems.co.uk]

Its looking nice and flat, so its a high possability - there will be some sort of flyback, where did you get your ECU from?  It should be in the order spec.