Idle Tables, Tuning Modes and Correct AFR

[Clockwise]

This forum has been informative but confusing at times. Just like everything else on the web you have to filter. I appreciate the information.

I would like some confirmation/clarification on the following. I'm getting conflicting information from paid people. The only hardware modification to my engine is a BTR Torque/Truck Cam and different from factory air intake.

1. From My understanding research and experience, when adjusting idle tables specifically Base and P/N, they intersect and must be zero differences at those intersects. The factory tables are set up that way and it makes logical sense.

2. Tune in Open Loop is the predominate advice all over the web, MAF and VE specifically. Recently discovered from individuals that charge for their tuning services, that is not true, they tune in Closed Loop with a WB. Confirming weather I was chasing my tail for days because of the Open Loop advice, because it sure seems that way?

3. AFR at idle, cruising and WOT. If you read the advice on the web, 14.6 is the target at idle and cruise, if anything slightly rich. 12.5 at WOT. After a Tuners Rev's my AFR at Idle bounces from 14.6 to 15.3. Not seeing what's advised on the Web. One tuner told me its the quality of my WB, its not the best. New AEM 30-0334. If my AEM's WB are not within 1 % accuracy then I guess the consumer is being scammed. All Over the Web, AEM, AEM, I even watched the Episode of Engine Masters Comparison. Also during a log 3rd rev., I'm seeing RED all over AFR table, majority is RED.

Thank You in Advance for the advice.

[RobZL1]

I think almost everyone tunes part throttle in closed loop with the factory narrowbands. Those are what the car uses to set the fuel trims anyway, so it doesn't really matter what the wideband says. Perhaps in the GEN 3 and early GEN 4 days open loop might have been the ticket, but not anymore. You don't even have to "set" open loop for WOT tuning. It's going to go to open loop all by itself.

AFR at idle and part throttle is controlled by the narrowbands, so again, it doesn't really matter what the wideband says in those areas. The 30-0334 wideband is perfectly fine. There is no use in fine-tuning around a tenth of a point between the WB and the NB's if you are in closed loop. You can affect a small change by moving the NB switching voltage, but no real need in my opinion.

AFR at WOT depends on the car. Yes, you can generalize that a DI GM Gen 5 N/A motor could start around 12.5 (0.85 lambda) and go from there. If it's forced induction, it going to be a richer target starting point. Some like as rich as 0.80 or 0.81, others target 0.82-0.83, others push it to 0.84 or even 0.85. Regardless, the real target AFR is what each car likes on a dyno in a controlled environment. That said, it's not going to make a huge difference if you are a little richer than peak power AFR- better that way than the other.

Sde note, if you are going to start tuning, calibrate yourself now to start thinking in lambda instead of AFR.

[96GS007]

I agree with RobZL1 and with the tools from Cringer for MAF & VVE, it's a relatively quick process

1) I found the easiest way to adjust the idle tables was to go into each one and then make a universal change. For instance, if you want to raise the rpm by 100, highlight all the cells and then add 100. It keeps them all aligned. Do this in the tables you mentioned. I know that on a percentage basis it's different across cells but the absolute value approach has worked for me. Where ever your new idle rpm is, you can shift the axis in the External Load table as well....or log it a few times and use the logged values. I was skeptical that would work with my fairly large cam, but it worked well

2) With Cringer's tools....or hunting and pecking, your choice...you tune both at the same time in Closed Loop. The tools make it easier though.

3) I shoot for ~5% rich on the combined LTFT+STFT. I logged a factory stock car and holy smokes....having the occasional cell that's -10% or +5% in my tune at part throttle no longer bothers me :lol:

As a sanity check I look at fuel trims vs VVE, MAF, and Dynamic Air. When all three are telling me the same thing...I feel life is good.

It's like everything else in life...There's "exactly correct" and then you balance that with "good enough". I suppose if I was more than a hobbyist and I was tuning for a professional race team with an unlimited budget I'd feel differently.

I'll also recommend to not chase data. Sometimes "perfect data" yields less than satisfactory engine performance. I have that on mine with my Zero Pedal torque. MAF, VE, and Dynamic Air all line up. 15*-18* of timing at idle. Fuel trims at my target of 0% to -5%. No torque management when driving. Virtually no cam surge at 1200rpm in any gear, and on and on. Yet my Zero Pedal at idle averages -14. I've made changes to VTT and a bunch of other stuff and whether I do a series of incremental changes or singular incremental changes, I can get Zero Pedal to -5 or even 0 or 5....and the drive-ability goes in the dump. -14 it is!