Questions on VE/MAP tuning

[cscott]

I'm fairly new to tuning, and have been following a document referenced in several places (forums, etc.) to get started. The first part of the procedure basically includes disabling MAF, and LT fuel trim. From there, the ST fuel trims are used to make updates to the primary VE v. MAP v. RPM table. Assuming that's a valid procedure, my issue is that I spent an hour chasing my tail. I'd copy the ST values, and use them in a 'paste special -> multiply %' function in the editor. After several iterations of that, I'm still pretty much seeing the same ST values in the same places (yes, I flashed tune updates)!? What gives?


I've installed a wideband o2 sensor right across the header from the primary o2 sensor. The wideband indicates lean (~15..16 afr) while the PCM is generally pulling fuel (negative) trims. The basically means there's a big mismatch there right? WB thinks lean and primaries think rich?

I can post my tune and scan logs when I get home tonight. At this point, I'm mostly looking for some validation that my approach and understanding is sound.

TIA

[NKBALLR]

I would recommend using the LTFT instead. the STFT change so rapidly its hard to get good data, and with your wideband issue have you set it up correctly in hp tuners

[cscott]

Thanks for the LTFT suggestion. Yes, as far as I know my WB is configured correctly. I used Innovative Motorsports instructions to configure HPT which included determining the voltage offset from a spreadsheet.

[SultanHassanMasTuning]

you can setup the histogram to adjust everything in the VE map

[jimmyblue]

Depending on how you are set up, LTFT (and to some extent
STFT) may "bundle" too much data from too broad a range of
load-points, to give you good point-specific feedback. The
stock FTC boundaries on my platform, stock, are gross in span.
What can you tell from a LTFT whose cell covers 2500-6000RPM?
Which VE table cell can you say this pertains to? That range is
like 9 columns. And probably dominated by a couple of the lower
ones, but you'll apply it to anything it touches, just because
you have a number to work with? Uhh...

Using the trims is for people without proper gear. Don't place
more faith or hope in it, than maybe a rough (very) guide
unless you can hold a single load-point and wait for trims to
settle in, to where other history has been scrubbed away.

[Nastruck]

I found a post a while back about setting a Histogram up for LTFT+STFT together and it made better changes or me. Instead of tuning all LTFT to Zero then going back and doing STFT to zero. Both together Multiply % half seem to make my truck pretty happy