Timing and fuel trim

[Pavetim]

If he's getting good number of cell counts it will average it out and 13.5 is rich at cruise, you only really need richer afr when in PE mode. You can safely go to 15 at a cruise then when you hit PE mode use 13.1, and 12.7 at WOT. Best bet is to tune using your stock O2 sensors and then you will need a Wide band to tune your PE/WOT. You want your LTFT's in the -5 to 0 range, if your in the + that means your lean and it will carry over the correction into PE so will throw off your tune. But tuning using LTFT is actually pretty easy, and pretty accurate using stock Narrowbands.

[George C]

id rather have a +1 or + 2 then having a rich condition of -3

in cruise mode timing should be high 40s to low 50s with no load, slight load timing decreases but should still be high 30s to low 40s

keep working at it till the MAF is next to zero for error and fuel trims are around 0 thru +3

this is where your mpg will come around at. not enough timing will also increase EGTs!!!!!!!!!!!

[Pavetim]

If you have negative LTFT when you hit PE mode your O2's will lock and it will not correct. You will be going strictly off your commanded, VE table and MAF if your using it. If you have positive LTFT when you hit PE mode it will carry over into PE mode and sometimes can be tricky nailing it down because you will get corrections in PE mode if your positive on your ltft. You can have negative LTFT thats no biggie, don't mean your rich because it will correct to what you have set for stoich anyways. But you tune it the way you want everybody is different. Thats why you work your VE table to get between 0 and -5 but as close to 0 is ideal. All mine are between 0 and -2.

[farmtruc]

Quik +1 on what Pavetim said, you want your ltrims slightly negative during cruising and anything not in PE mode, so that when your foot goes wot, ltrims go to zero, then you can nail down the a/f ratio and make commanded = actual.
If they are positive, you can't do that.
Having the ltrims positive just to richen up wot is more work and you won't always have what you're commanding in the end.

Pavetim, I completely understand what you're saying, the only statement that I... Is that you have to scale your MAF table to get ltrims negative and positive as well during non PE cruising. The VE table is mostly used in open loop and cold startup, then you scale the maf after the engine warms up.

There's a little more to it, but maf is used to scale ltrims during operating temps, ve is used for open and cold startup.

[Pavetim]

Oh yeah I do the MAF at the same time as the VE table too, forgot to mention that. You want the MAF freq correction factor as close to 1.0 as possible too. Sorry thought we were just talkin about trims. But yeah for people keeping the MAF you can tune your VE table using LTFT, PE using WB, and MAF all at the same time if you've got the right calculations.

[Frenchy]

But yeah for people keeping the MAF you can tune your VE table using LTFT, PE using WB, and MAF all at the same time if you've got the right calculations.

Details? First I've heard of that, but I'm still new to this.