Fuel trims & maf scale

Fuel trims & maf scale

Postby TJ4295 » Thu Jun 25, 2020 5:35 pm

I installed an intake on my 2010 tl and adjust the afm flow chart to match. My fuel trims are in safe range ant idle and when accelerating. But when I give it a small amount of throttle (like 7ish percent, just to keep the car at speed on a flat surface) the trims jump up to around 30%. I’m just wondering if this is something I need to stress or is that normal for such a light load?
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Re: Fuel trims & maf scale

Postby KTuner » Thu Jun 25, 2020 6:11 pm

You want the fuel trims to stay as close to zero as possible.
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Re: Fuel trims & maf scale

Postby TJ4295 » Thu Jun 25, 2020 8:35 pm

I would assume that means at all times then? Because like I stated before, the trims stay very close to zero under acceleration and idle. It’s only when I give it a tiny amount of throttle that it shows those Hugh trims. Figuring out the fix shouldn’t be a huge issue. I was more just wondering if I need to be hugely concerned with it. Thank you for the quick reply. This is my first time with a tuner and this thing has been an awesome to learning experience.
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Re: Fuel trims & maf scale

Postby KTuner » Thu Jun 25, 2020 8:38 pm

Glad you're enjoying the process so far. If it's adding 30% in a particular area of the MAF curve, you've neglected that section and you're running lean. STFT isn't generally applied at wide open throttle, so it will be zero when in open loop.
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Re: Fuel trims & maf scale

Postby TJ4295 » Thu Jun 25, 2020 8:53 pm

Yeah I haven’t worked on WOT much yet. I’m focusing on my fueling during casual driving right now. So when accelerating up to cruising speed the trims are almost spot on. So for example accelerating to 30mph everything is good, but say I’m on a flat surface, or slight incline. The tiny amount of throttle input in to keep it at 30 is where I see the STFT spike. I’ll look at my maf scale and fuel tables to see where I need to adjust. Thanks for the input.
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Re: Fuel trims & maf scale

Postby KTuner » Thu Jun 25, 2020 8:59 pm

No problem. I recommend using a scatter plot with MAF.v vs STFT.
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Re: Fuel trims & maf scale

Postby TJ4295 » Thu Jun 25, 2020 9:00 pm

Will do. Thanks
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