| | | quote | Originally posted by darkhorizon:
no changes other than IFR need to be made.
When you add E85 in, set the IFR value to about 48.. tweak from there based on what you see afr wise. |
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Even for closedloop? One of the biggest and common issues when jumping from stock ~30 lb/hr fuel injectors to 60s and significantly larger injectors in general by adjusting the BPC only has been surging and an almost definate problem with maintaining a steady idle. Problem threads can be found regarding this issue across several popular forums (thirdgen to name one) attempting to address it.
I'm not running OBD II, E85 or iron heads and am not sure if it really makes a difference for the 3800 club, but I was not able to get my motor to idle reasonable enough to run closedloop idle until I did the following:
Calculate the appropriate BPC constant for my injector size change and displacement increase.
Adjust the battery volts offset table, which until I did made it impossible for me to lower my BPW enough to reach a 14.7:1 AFR at idle. Pulling idle VE points was having no effect and I couldn't figure out why until I went to this table and made an adjustment and noted an immediate change in AFR at idle along with immediate response in AFR with small idle VE changes.
Next I made changes to the BPW offset table. Theoretically significantly larger injectors open slower for the same time frame at low pulse widths and the lag time has to be offset so the lowest BPW values may need to be increased a click, or two.
My approach once I was near stoich at idle in openloop:
Scale the battery volts table by starting the initial adjustment with everything on; lights A/C etc, because these things will change your voltage and therefore your fuel delivery. The spec values are a good starting place, but in my case I had to improvise a little despite having set my fuel pressure to the factory test pressure for the injectors.
Once the AFR is fairly steady with the accessories on and off, I switched on closedloop and watched the Integrator and fine tuned with the idle VE table getting the best results by biasing the fuel slightly right of 128 on the Tunerpro dash gauge. I performed this step with the accessories off although unintended. I turned on the vent which is the best test because the vent motor load is not compensated by the IAC motor the way the A/C is (A/C related IAC step table). If the engine stalls, go to the BPW offset table and start making adjustments there one increment at a time which will usually be most prominent in the second cell near a BPW of 1 as the BPW will increase in an effort to counter the stall so more fuel there increases the fuel quicker to counter the engine load.
Tunerpro makes it possible to build history tables to log desired parameters and voltage is one that I chose to follow. At startup my alternator cranks out 14 volts in the log while cold. When the engine is hot, particularly on a hot day that voltage tapers down to about 13v. If I turn on the A/C it might go as low as 12.5v on a hot day so the battery offset table can't be ignored in my case because the fueling can change dramatically as a result. I also received the occasional rich code when trying to run closedloop before adjusting the above tables.
Again I'm running OBD I so it may not be as critical in OBD II. Hope this helps.
Here's my injector spec sheet:
[This message has been edited by Joseph Upson (edited 01-04-2013).]
