$DA2 on 93 lt1 vette, stoichiometric AFR - can this be modif

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dizwiz24
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Joined: Mon Jun 29, 2009 6:15 pm

$DA2 on 93 lt1 vette, stoichiometric AFR - can this be modif

Post by dizwiz24 » Fri Aug 10, 2012 4:04 am

I have a 93 lt1 corvette w/ speed density original equipment ECM. Im using $DA2 definition file.

I noticed a 'stoichiometic AFR' value. Currently, its set to 14.7:1. If I put wide band O2 sensors in place of the stock narrow band sensors, Can I change this for other fuels?

ALso,
I noticed a table (actually 4 tableS) for left (and right) and fast (and slow) O2 rich/lean vs. air flow.

What is this for? I dont have a MAF. Im totally speed density. So is this table irrelevant for me, or do they do something.

Finally, one last thing.

I ntoiced a Fast O2 rich/lean threshold currently set to 0 mV ( I got the tune from a vendor specializing in the mods I have). Does this sound correct for this to be set at 0 mV?

Any help is appreciated!

robertisaar
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Post by robertisaar » Fri Aug 10, 2012 8:38 am

you can use the narrowband O2 for different fuels. you'll obviously want to change the stoich AFR around to match whatever fuel you're running, regardless of narrowband or wideband O2.

narrowband and wideband O2 sensors measure lambda, so they're compatible with any fuel(assuming it doesn't contain lead, silicone or a couple of other substances that will cause degradation/failure), it's just that one has a really steep response near lambda 1.0, the other is considerably more linear.

airflow is calcluated with the speed-density system as well, those tables as used to tell the ECM where to consider the system rich and to lean out the fuel or where the system is lean and to richen up the fueling. obviously, only used in closed loop.

that last table.... it might be for a hysteresis of 0mV, since if it was raw rich/lean, then any O2 sensor reading above 0mV would be considered rich and the ECM would always be pulling fuel.

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EagleMark
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Re: $DA2 on 93 lt1 vette, stoichiometric AFR - can this be m

Post by EagleMark » Sat Aug 11, 2012 3:45 pm

dizwiz24 wrote:
I ntoiced a Fast O2 rich/lean threshold currently set to 0 mV ( I got the tune from a vendor specializing in the mods I have). Does this sound correct for this to be set at 0 mV?

Any help is appreciated!
Stock bins are not. Sounds like a way to run open loop, while in closed loop... that would be intresting data to watch.
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dizwiz24
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Joined: Mon Jun 29, 2009 6:15 pm

Re: $DA2 on 93 lt1 vette, stoichiometric AFR - can this be m

Post by dizwiz24 » Fri Aug 17, 2012 4:53 am

dizwiz24 wrote:
I ntoiced a Fast O2 rich/lean threshold currently set to 0 mV ( I got the tune from a vendor specializing in the mods I have). Does this sound correct for this to be set at 0 mV?

Any help is appreciated!
Stock bins are not. Sounds like a way to run open loop, while in closed loop... that would be intresting data to watch.[/quote]

OK. robertisaar is correct.

The correct name of the table is:
Fast O2 Rich/Lean Threshold Hysteresis.

cousinit99
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Post by cousinit99 » Wed Dec 24, 2014 1:36 pm

robertisaar wrote:you can use the narrowband O2 for different fuels. you'll obviously want to change the stoich AFR around to match whatever fuel you're running, regardless of narrowband or wideband O2.

narrowband and wideband O2 sensors measure lambda, so they're compatible with any fuel(assuming it doesn't contain lead, silicone or a couple of other substances that will cause degradation/failure), it's just that one has a really steep response near lambda 1.0, the other is considerably more linear.

airflow is calcluated with the speed-density system as well, those tables as used to tell the ECM where to consider the system rich and to lean out the fuel or where the system is lean and to richen up the fueling. obviously, only used in closed loop.

that last table.... it might be for a hysteresis of 0mV, since if it was raw rich/lean, then any O2 sensor reading above 0mV would be considered rich and the ECM would always be pulling fuel.
The ECM supplies a 450mV reference to the o2 sensor circuits on these vehicles. The Hysteresis constant specifies a mV value above or below the supplied 450mV that, essentially, the ECM ignores when determining whether to increase or decrease injector pulsewidth in its effort to maintain lambda (14.7:1 for gasoline). That still leaves me with one question, though..

Robert, do you by chance know how the ECM utilizes this parameter when a value over 0mV is specified? Specifically, if I specified 50mV of hysteresis, would that effectively be 425mV to 475mV, or 400mV to 500mV? If anyone knows, it's gotta be you.. :D

robertisaar
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Post by robertisaar » Thu Dec 25, 2014 12:19 pm

i'll have to reinstall IDA and find out... I still haven't gotten everything organized/dealt with since a fresh OS re-install.

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