Hi all,
Im dealing with the catalyst heating spark table. I need to retard timing after cold start aggressively to get my converters heated for cold start emmissions test. I already achieved some promissing results, but Im struggeling with something I believe is a transient fuel issue.
Right after cranking, this means cranking mode is just over, the spak starts to drop massively as supposed in order to get some flames shooted to the converter. My issue is, that in the moment the retarding kicks in, the efficiency of the fuel mass burned naturally goes down dramatically. With other words, since more fuel is burned outside the chamber less energy is used to actualy turn the engine. In return this means a higher need of fuel to keep the idle stable.
The ECU does a pretty good job in quickly stabilising this within only a few seconds. The Abs. load goes up and inj cycle also gets to arround the doubled value. Then everything runs pretty straight slowly down the hill untill the heating cycle is ended.
What I want to do now is taking the strugle out of the first few seconds. I want to have the fueling corrected without relying on the ECU ability to recognize the added need and compensate it. By doing this I want flatten out the iny cycle curve and the load curve. Reason is, that during this condition also a pretty rich AFR is commanded, what I think is the ECU?s strategy to gain the needed fuel.
Has anyone expierience which tables or adders I could look at? I already have checked the warmup transient fuel correction and stomp compensation tables, but they seem not to do what Im looking for and effect later/other parts of the warmup phase.
Is there any kind of spark retard related fuel adder I can look for? In a perfect world this would also be related to ECT and ERT to make sure this adder is only considered for a cold start.
I will attach the log file of my last startup test. Looking realy close and slow you will also see a little strugle when cranking. This is due to leaning out the priming shot, since Im still under fine tuning of the priming fuel mass. So this should be possible to fix with my current "weapons". The issue is right between the first rpm peak and the time when falling back and passing 1000rpm. There you can see that inj timing goes low at first and spark retards. Both together will not gernate enough torque to turn the engine. So spark advanced again while load raises and inj cycle raises. Once a kind of stable status is reached, spark is retarded again.
What I want to see is a constantly retarded spark and, to compensate, a inj cycle which doenst fall down to 3ms as seen in second 15 of the log. Instead the inj cycle should stabilse at arround 6ms after cranking, which is the value seen from second 18 of the log and suitable for a stable idle.
Thanks in advance!
Soeren20210628_V0.58.hpl
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Originally Posted by cadillactech
