EFIDynoTuning Forum

Been working on getting fuel dialed in on the 98 cobra which is pretty close up to about 400 AD counts but I noticed at the 200 AD count range, I am getting about a 3% variance between the -1 and 0 columns in the histogram. I have about 250 samples in the -1 and 250 in the 0 column so I would assume they should be close to each other. There are a few other ranges that show the same thing but there are only a few samples in either column depending on the location many in the other column so in that scenario, I just trust the column with significantly more samples.
Second question, ive noticed while idling, the car seems to overshoot stoich when switching back and forth from lean to rich but it only seems to happen at idle. While driving, it seems to respond much faster and I never see it drop into the low 14s or into the 16s. The car seems to over correct AFR when switching back and forth. Example, The car is at 14.3 and switches to calling for lean and it will jump to 15.2, then ill see 14.1, then 15.5, 13.9to16.3, then it seems to settle down and fall right back to around stoich then repeat. When it does this, the car sounds like its got a very slight surge that gets more noticeable as the AFR swings are larger. Is there a way to minimize the swings?

a few percent is normal

you can reduce the hego amplitude and increase the hego delay

Is this checking long term fuel trims of both banks to each maf voltage step?

Yes. There are 3 histograms for this, There is one for each bank and then a bank 1+2 average. You want to use the Running Sample count which takes all samples into account and then averages them out. Makes it extremely easy to dial in fuel within a few percent of perfect.

@Decipha. In my scenario would I just take the average of the 2 as where its actually falling? in this case the average is 1.034.

you can just most ideal to keep the corrections positive and never negative

better to add 3% fuel rather than pull 1%

So youre saying It should be ~.97 in the histogram?

no. .97 is removing 3

better to be 1.03 rather than .99

That's what i thought. I normally aim for 1.03. As you can see in the previous screen shot, its pretty close. I sneak up on it as I get close

Also, I found the Hego amplitude setting and changed it to .035 and im gonna see how that works out. I wasnt able to find a hego delay setting. Can you tell me which FN it is?

Is there a reason both the low and high speed fan off temps are higher than the on temps?

8x10

someone probably did that to either be lazy or remove the hysteresis