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I data loged today and noticed the air fuel would rise to 14.73 then hold. When I drive it hard to afr goes down to 12, when I let up it goes back to 14.7. On tunerpro is there a way to adjust so it will show above 14.7? Will changing the stoich on tune to say 17. do anything or is this the wrong idea?
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14.73 is the stoichiometric ratio, and when in closed loop, it will show that, and actually achieve nearly that (it will achieve stoichiometric in closed loop, but that may be slightly different depending on the fuel, but don't worry about it). When you tromp it, it's going into PE mode (power enrichment), and should target something in the 12:1 AFR area, as you're seeing. What you're seeing is perfectly normal and correct. But what you're seeing is the "commanded AFR" not the actual output AFR. The actual AFR can be seen with a wideband. If in closed loop, you'll only see the actual AFR near 14.7 +/- ~.3, going up and down and up and down = normal closed loop. When full throttle, it goes to PE mode (which is not technically closed loop), and the AFR will be steady at near 12:1-13:1 (and it ignores the oxygen sensor). If the VE table or MAF tables are wrong, the commanded AFR won't match the actual AFR on the wideband. This is what half of the "tuning" is all about - getting the actual to match the commanded.
__________________ -Jeremy- EFI Calibration Engineer, Director of R&D, Software Designer (Fuel Injection Technologies - dianpen.com) - still in China since Nov '04!!!
86 Z28 - rusty, tired, and in storage - 89 GTA with plans, but - also in storage now needs paint - badly, 79 Malibu classic with 91 L98, 4L60, 3.73
Next question. Am I able to test this with a dvm? Don't have the cash for the wide band. Also Ihave read obout tuning in open loop by raising the temp of closed loop mode. I have the 730 ecm speed density running rich at idle, runs good a wot. I have tested for vac leak, no leak. I have adjust the tune alittle (lower the ve table) and did not help. I am still new to tuning so I may be missing something. I have posted many times, Is the stock aujp tune good for the holley stealth ram or is it way off and need alot of tuning. I also found AFR tune v1.0 in chapter 2 in the stickies, it is used to change the AFR, could I use this to correct my problem?
When I first started tuning I did not have a WB. I just datalogged to get the closed loop tables close. the PE is calculated off those tables being accurrate. Under 128 adding fuel it uses that BLM. Above 128 BLM it pulls fuel and uses 128 for calc. On dyno with WB monitor it turned out fine. I was commanded to 12.3 and WB showed 11.9 on first run and 12.0 on second. Having underlying tables accurate should bring the PE where you want it. AE no so for me.
I have read threads of some using the NB data to determine if rich lean for PE. The volts change so fast makes it difficult I think. the WB controller I recall averages the "hits" so as to have meaningful A/F display. OBTW I believe you can build a controller. search. then the Bosch WB sensor is like $50?
I data loged today and noticed the air fuel would rise to 14.73 then hold. When I drive it hard to afr goes down to 12, when I let up it goes back to 14.7. On tunerpro is there a way to adjust so it will show above 14.7?
The 02 sensor acts as a switch, correcting fuel at part throttle. As mentioned above, WOT = PE (power enrichment mode), which is why your afr goes down to 12.0 (rich), completely ignoring the O2 sensor, but once you ease up on the throttle, the 02 is immediately enabled again, and headed for the commanded afr, 14.7....
Quote:
Originally Posted by runningagain
Will changing the stoich on tune to say 17. do anything or is this the wrong idea?
That's way too lean, why would you want to do that....?
The 02 sensor acts as a switch, correcting fuel at part throttle. As mentioned above, WOT = PE (power enrichment mode), which is why your afr goes down to 12.0 (rich), completely ignoring the O2 sensor, but once you ease up on the throttle, the 02 is immediately enabled again, and headed for the commanded afr, 14.7....
That's way too lean, why would you want to do that....?
I got the wrong idea that the AFR went to 12, why does'nt go past 14.73. The PE and the disregard of the o2. Just thought I missed something.
You are looking at the AFR that the ECM is commanding. IOW, it is commanding stoich (14.73) while in closed loop, and 12:1 in PE mode. What this does is change the injector PW. This in turn changes the volume of fuel added to the incoming air, thereby changing the AFR in the combustion chamber.
now needs paint - badly, 79 Malibu classic with 91 L98, 4L60, 3.73 
