Stop bad fuel economy, eliminate idle and off-idle surging, regain that stock feel

[mike01z]

yeah I did, thanks for this thread also btw, there was no other way to get my cam to idle and keep closed loop, I am starting to feel as though the car is streetable again.

[mike01z]

and why is this not a sticky? Seriously this can help anybody with idle issues IMO cause you can fine tune the a/f this way without worrying about trims and proportional fueling.

[405HP_Z06]

TTT for an excellent idle tuning thread.

[Ben Charles]

Bringing this back with a few questions

My car starts up in Open Loop anyways and after it warms up goes into Closed Loop desiring the 14.7 AFR. My thinking is that I want a leaner idle, I don't see a need for 14.7. My cam is not that large considering a 383 (sig), but if I can get a little better idle then thats a plus too.

So this is what I need to do

Set PE enrichment to Desried AFR (14.7/.967=15.2) from 0RPM to 1200RPM inclusive. I have seen some people 16.X at idle, so this may be something I can play with?

Set the OFLA table in the MAP idle cells to the same AFR above (Above Ex .967) covering idle temps.

Set PE enable cold TPS to 0 from 0-1200rpm. My thinking says 400-1200 though since I want a richer AFR at initial cold start, and based off the PE and OLFA table the PCM takes the richer value. But if thats the case 0-1200 would work since the OLFA table will have a richer value at cold start Ex 1.24vs .967 (answered my own question)

These two things below is where I get confused on why I have to do this? Car will not be using 02 sensors anyways since its in Open Loop.
1.) Raise all O2 rich/lean vs. airflow switchpoints by 40%. I set mine all to 541, as I wont be using Airflow modes 0-6 since I will be in open loop.

2.) Set Closed loop proportional O2 error to:
0.06250 0.06250 0.06250 0.06250 0.06250 0.06250 0.06250 0.15479 0.18750 0.21484 0.24023 0.27002 0.27979

Save and flash to car


Anything else I need to add or any help?

[MNR-0]

Just set your target PE AFR from 0-1200 to what you want and ensure your OLFA is set to the same at idle MAP, then your PE enable TPS to 0 from 0-1200

done

[Wnts2Go10O]

Set PE enable cold TPS to 0 from 0-1200rpm. My thinking says 400-1200 though since I want a richer AFR at initial cold start, and based off the PE and OLFA table the PCM takes the richer value. But if thats the case 0-1200 would work since the OLFA table will have a richer value at cold start Ex 1.24vs .967 (answered my own question)

<snip>

even if it didnt, you could delay the activation of idle pe by making the cold tps something like 5% or 10% throttle at 0-1200

[Ben Charles]

ok guys thanks, I will try this soon. I read somewhere that this would not work with the Fbody PCMs then I have seen some that say it does? I guess as time has went by this works for ECU's?

Mine being an 02 411 ECU

[Jamz]

does this work on gen 4 e38 pcms?

[SSUte01]

Yes. It's not always as straightforward to arrive at your calculated lambda at any given point, but yes it does work.

[Jamz]

Oh great news. Now do you know where I can find the formulae to calculate the IVT gain table on the gen4.

Or would you just leave it as 1.00 in all the idle areas and .95 in the open loop fueling area to command .95 lambda afr?

[SSUte01]

Log all the variables for the various tables so you'll be able to figure which OL tables at which area you are looking to change ie IVT, MAP, ECT, and so on if you're trying to do that. By zeroing the TPS, you'll end up in PE, so that table will allow you to enrichen or stay at 1.0 or whatever, if that's what you're after since you said 0.95 lambda.

If you're trying to lean out at low rpms leaner than lambda of 1.0 (ie larger, but EQ less than 1), there are enough tables in the editor to allow that, but for some reason we must be missing a table or two (or I missed it) as when the MAF is failed ie SD, I cannot achieve leaner than 1.0 for more than a few seconds. It will remain in OL, but return to lambda of 1.0 for some reason. Turn off key and same will happen, all criteria met, achieve lean out and straight back to 1.0. Same tune with MAF, leans as commanded. It's odd. I've put it down to some sort of table (that I cannot access) that says the Min EQ Ratio when MAF fails (P0101/2/3 most likely) is 1.0..... maybe. Dunno for certain, not too worried at this point. It does take a bit of effort initially to achieve this though and more tables than you'd expect to get it to work properly.

I guess I'm not entirely sure what you're trying to achieve, if it's simply OL idle based on TPS, then yep, works on E38s as per PE OL Commanded EQ unless some other richer OL wins out. Lean is a slightly different story thus far.