Firebird 3.1 ECM tuning with Tunerpro

Note to self: add TunerPro installer, EPROM bin file and XDF for .bin definition file.

Firebird 1991 with 3.1 engine uses 1227730 ECM. Origally this engine uses pintle style fuel injectors with GM p/n 17084888. They should flow about 160 cc/min, which converts as 15,23 lbs/min. If you buy new injectors, like GB Remanufacturing 83211116 / 832-11116, they seems to be disk style fuel injector. Disk style injectors will open significally faster than pintle injectors, even when their flow rate is equal. Manufacturer claims they are drop-in replacements.

In my case, ECM was able to compensate injector opening time difference with enough engine load. Basically every time the throttle was open more than 5 %. However, compensation limit was reached at idle - BLM hit 100. In my research, injector control pulse was about 2,5 ms at idle, in room temperature and with hot engine.

1227730, ARPM memcal and 88$ mask

Injector size compensation

At first I thought injectors were just bigger than original and it needed to be re-programmed. TunerPRO has constant "Injector Flow Rate", that had value of 16.71. According to mask file this value should be located at address 0x6BC. I made six different EPROM's with different values but none of them made any change. I do not know if this is a bug in XDF file or ECM related issue. There is also parameter "Injector Flow Rate (display)" whitch should compensate driver's diplay (this care does not have that), but that did not have any affect also.

I found by search engine that someone had used "Base Pulse Constant Vs. Desired % EGR" table to compensate injector size. Tried it and... it worked! Just calculate difference in injector sizes (19 lbs / 16,7 lbs = 1,138) and divide this whole table with that. But as I mentioned, there was no issue with flow rate in this case.

Ensimmäinen kokeilu Web-hallinta Web-hallinta

Injector opening time and idle issues

So, it was obvious that injector were different type than original. There are two tables that can be used to define injector opening time.

"BPW Offset Vs. Battery Voltage" has quite large numbers and this is what I used. In total I needed to remove about 0,74 ms @ 12,8 V. This is just a guess, as I did not want to remove injectors again and do intensive research. Close is enough is sometimes good enough and ECM has capability to adjust the rest. If we make an assumption that disk type injectors opens at 0,5 ms, I just cut fuel at idle about 60 %! The final values I used were: 

		19,2: 213,62 --> 30
		17,6: 274,66 --> 61
		16,0: 396,73 --> 61
		14,4: 579,83 --> 61
		12,8: 793,46 --> 61
		11,2: 1037,60 --> 213
		9,6:  1525,88 --> 400
		8,0:  2380,37 --> 1000
		6,4:  5432,13 --> 2990

"Low BPW Correction Vs. Pulse Width" sounds more correct table, but only had maximum compensation capability of 0,49 ms. I did not even try this, but it could be used to get quite close.

Mastoon Mastoon Mastoon