seanr

The difference between using cell 6-15 to get a average LTFT compared to using cell 1-19 is very small so does it really matter? I get a 0.2% difference. The same goes for WOT O2´s using 80% or 99.5% I get the same average O2's.

<img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

ChrisB

I would submit that you don't really need to know/care what fuel cell you are in if you are trying to tune for a certain l-trim range. Instead, as I believe was touched on above, you should scale your l-trims vs whatever you are using to correct them. If you are going to tweak them with the MAF transfer function then I would scale each l-trim vs. MAF frequency.

The fuel trim cells store the correction for the computer, yes, but I really don't see any way which they would be usefull in tuning - since all the changes you can effect are not scaled by fuel trim cells, etc. - but instead by rpm, g/cyl, map, whatever. The only reason I might worry about the fuel trim cells is if I was trying to shift their borders to make them more specific for a radical combination - but I really haven't experimented with that with ls1 edit.

Chris

wizkid

iTrader: (3)

I think I get it. FTC's are pretty much useless when trying to tune your car. I have never really used the FTC to do anything other than look at it and say, hmm, what confusing crap. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

Hence why everyone says to use the MAF freq.

ERic

TooManyIDs

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Team ZR-1:
<strong>....Since I do PCM tuning I use MAF freq as my guide marks for they tell me which cells were used. Each cell uses about 700 Hz. By having my template chart by MAF freq it shows me for each cell what the engine load was, knock count, delivered Tq and LTFT, thus I then go into about any tuning table and converting ( or recording MAF in grams) I can tune for how each cell is functioning. This way if I see cells 9 and 10 are lean, I know what freq that function in and then make the changes only to those MAF freq ranges....</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">John,
I want to make sure I understand this fully. Instead of basing the Excel template on fuel trim cell value, use AutoTap to capture the "Mass Air Flow Raw Input Frequency".

Since the MAF table in LS1Edit is aligned to Hz, modify the template to evaluate LTFT averages, around the same column break points used in LS1Edit. With that information, I would be able to scale my MAF table to the intake I'm using.

Did I get that right? If so, why would I care about Fuel Trim cells at all?

<small>[ September 19, 2002, 09:42 PM: Message edited by: TooManyIDs ]</small>

Team ZR-1

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by TooManyIDs:
John,
I want to make sure I understand this fully. Instead of basing the Excel template on fuel trim cell value, use AutoTap to capture the "Mass Air Flow Raw Input Frequency".

Since the MAF table in LS1Edit is aligned to Hz, modify the template to evaluate LTFT averages, around the same column break points used in LS1Edit. With that information, I would be able to scale my MAF table to the intake I'm using.

Did I get that right? If so, why would I care about Fuel Trim cells at all?[/QB]</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">By recording MAF as to freq and grams/sec we know that those values can be used to tune airflow and injector flow.

Let's assume you want to make changes to the injector flow and scale across the table.

Problem is that under certain loads LTFTs are lean and in another load range trims are too rich.
So now if a scale was done, it will help certain load ranges but hurt others.

Here is an example :

<img src="http://teamzr1.com/pcmecm/cellavg.gif" alt=" - " />

Now if you look at the cell #s at the bottom you see they are not smallest to largest cells but sorted by LTFT, load, MAF freq and torque.

As you can see at a certain load, a cell is used and its average MAF freq is used. That cell is always used then for that MAF freq and engine load.

Now if I want to solve the areas that are the leanest, I know what Maf freq range to tune or what the grams/sec is to tune voa the inector.
In fact to get a perfect tune I might tune injector flow for some cells and MAF to tweak other cells so in the end all cells show the same LTFT averages. Which I would use depends if there is knock, or misfire or both.
I might want in this above case want to richen up cell 11 ( a PE cell) only, well if I had no guide mark I would not know quickly where to make that change and not effect other engine loads.
This graph for this powertrain then is an index and I know exactly what Maf freq cell 11 uses and can tune just that cell.
Here you also can see that cell 22 is not the king of WOT, in fact cell 15 functions at a higher engine load and MAF volume.
I've seen much worse graphs from other powertain makeups where some cells are way rich and others are too lean and reason you have to be able to use some guidestick and that is MAF freq and engine load.

BTW, People tune, assume WOT is when TPS is 99% or greater, when in fact EPA defines WOT as only when engine load is at 100% and if you look at the raw scanner data, 100% engine load can be reached long before getting to the upper trim cells, thus PE is more important to tune then true WOT is.

<small>[ September 19, 2002, 11:13 PM: Message edited by: Team ZR-1 ]</small>