I used Datamaster to datalog and I tuned my ecm BLM's to 128 using Tunercat.. I attempted to smog my car and it failed idle HC's .. max ppm is 100 and I measured 186ppm. I was flowing 9g/s of air at an idle of 950rpm, I increased my MAF settings at and around the 9g/s cell to get all of my BLMs down below their max of 160.. I then increased fuel injector pulse too all the injectors at idle until I obtained 128.. I thought an idle with 128 BLM's would make my car pass emissions without a problem but my HC's are still high..

WTH!!

Isn't running 128 BLM as close to perfect A/F ratio of 14.7:1 ?



I am running a Golen 383 with edelbrock performer heads and a CC503 cam.. stock TB , 30lb SVO inj., Granatelli MAF, MSD opti and coil, Stock air box with a K&N filter, 1.5rr, SLP shorty headers, two cats to a 3" Magnaflow catback.. M6tranny..

Are the Bosch O2 sensors giving me bad readings?
Is the Granatelli MAF only calibrated for more flow for a stock 350?
How do I tune the motor to drop the HCs when I have a Perfect BLM count?


Thanks.. I am new to tuning and having a great time doing it, I hope you guys can help me..

 

128 is correct, ASSUMING your O2 sensors are providing the correct data, there are no exhaust leaks before the O2 sensors, no misfires, no wiring problem, valves are adjusted correctly, cam overlap is not excessive, etc. If you had BLM's near 160 the first step should have been to determine why. Not starting changing the MAF calibration and the injector constant (ASSUMING the correct data was in the program when you were seeing the high BLM's).

 

thank you for your help.. I was thinking about what I had done and I guess I did bandaid my idle and not figure out why my BLM's were high.. I am going to do a spark plug and wire replacement today because I believe I have a missfire going on.. I will keep my progress posted..

 

Yes. So is a steady state BLM of 150, or 110.

As said above, _if_ all sensors are working, no leaks, etc.

 

The BLM's were 160, which was the maximum.. I guess there was my indicator that Houston has a problem..

 

If its an idle problem, start working on the individual cylinder fuel trims. That will even work for values up to 14% throttle. The problem with your plan of getting the 128 blm or any blm inside the limits is that the AVERAGE air fuel ratio is stoich. The issue with that is some cylinders can be rich and others can be lean, and actually either of those conditions can drive up HC%. It can also be a timing issue as well and getting an incomplete burn as a result.

This is of course after you get whatever issue it is worked out, if a HC problem remains.