simple tune questions

[keypunch]

Have been using efilive scan for several months and purchased tune 2 months ago. Understand most of it but the VE , AFR stuff has me very confused so here goes my position. I’m running a Magnacharger on an Ls1.During several long scans hitting all cells my average LTFT's are1.7 to 2.3.During several steady pulls in 4th gear at throttle positions of 25% to 35% my trims are always steady at 0. 0 to0 .8 and go to zero at WOT. From what I understand, these areas of my tune are excellent. Should mention here that my commanded AFR (B3606) is set at 11.7.

My questions( hypothetical changes to help me understand…I will be installing a wide band)

1. What would happen if I change the AFR(B3606) say to 11.9? Does it change VE? Does it really lean out the ratio?

2.I will be adding headers, what will happen to VE and AFR? From what I understand these changes will cause the AFR to go rich, correct? So do I run auto VE to correct any change in LTFT’S and then set AFR(B3606) via wide band readings at WOT .back to say 11.9?

I understand the ect,iat correction stuff,just cant get into my head,adjusting the AFR stuff.In other words if trims are proper how do I set AFR?

Yes Im an old carb guy new to injection and forced induction.Gave cars up for years but retired and bought an 04 GTO to play with.

[dc_justin]

B3606 does not define your commanded AFR. It just defines what the richest AFR would be allowed to be.

To determine your WOT commanded AFR, look at table B3618 as the primary table. B3617 and B3641 are adder tables to B3618 and then there are a couple of other parameters that can play into it as well.
The PCM will look at all of these parameters that define commanded AFR and take the richest of those as it's basis for fueling.

Fuel trimming takes place during closed loop only and the fuel trims you see are what the PCM has determined to be the average amount of fuel correction needed to keep the mixture as close to stoich (~14.7:1) as possible. Once you go heavy into the throttle, PE mode kicks in and you drop out of closed loop into open loop fueling.

A few months back, someone came up with a flowchart that contained the majority, if not all of the tables and parameters that contributed to the final commanded EQ ratio. If I can find it, I'll post it up here.

Justin

[joecar]

Keypunch,
Welcome to the forum. :cheers:

If you follow the AutoVE procedure to dial in your B0101 VE table, and if your B4001 IFR table is correct for your injectors and fuel pressure, this is what happens:

Open Loop:
the AFR is determined by the richer of B3605 (OL AFR) and B3618 (PE AFR)... now if your B0101 VE table has been dialed in using a WBO2, then what you put in these tables is what you will see with the WBO2;

Note: Cat-Over-Temp-Protection will also influence the AFR unless you leave COTP disabled (as done in the AutoVE tutorial).

Closed Loop:
the AFR will be closely around 14.63 (from NBO2 feedback), and when going WOT, OL applies (see above).


Answering your questions:
1) B3606 is Maximum enrichment in hot mode (you don't need to change this)
B3605 is the open loop fuel-air table
B3618 is the power enrichment vs rpm table

Changing those will not change the VE, but will change the AFR;

If your B0101 VE table is dialed in, then what ever AFR you put in B3605 and B3618 will show up on the wideband (i.e. actual AFR will follow commanded AFR); of course, the richer of those two tables determines the AFR.

2) Headers may change your actual VE some amount;
the wideband would tell you whether the result is rich or lean...
AutoVE can then be used to adjust the B0101 VE table for those headers, and you do not have to adjust any other table (except possibly the B5001 MAF table if you're running the MAF).

If you have a wideband O2 sensor, don't always necessarily trust your trims (LTFT's) which are derived from the NBO2, especially at WOT.

Cheers
Joe
:cheers:

[Tordne]

This is the flowchart I think is being referred to..

http://forum.efilive.com/showthread.php?t=3537

[dc_justin]

Keypunch,
Welcome to the forum. :cheers:

If you follow the AutoVE procedure to dial in your B0101 VE table, and if your B4001 IFR table is correct for your injectors and fuel pressure, this is what happens:

Open Loop:
the AFR is determined by the richer of B3605 (OL AFR) and B3618 (PE AFR)... now if your B0101 VE table has been dialed in using a WBO2, then what you put in these tables is what you will see with the WBO2;

Note: Cat-Over-Temp-Protection will also influence the AFR unless you leave COTP disabled (as done in the AutoVE tutorial).

Closed Loop:
the AFR will be closely around 14.63 (from NBO2 feedback), and when going WOT, OL applies (see above).


Answering your questions:
1) B3606 is Maximum enrichment in hot mode (you don't need to change this)
B3605 is the open loop fuel-air table
B3618 is the power enrichment vs rpm table

Changing those will not change the VE, but will change the AFR;

If your B0101 VE table is dialed in, then what ever AFR you put in B3605 and B3618 will show up on the wideband (i.e. actual AFR will follow commanded AFR); of course, the richer of those two tables determines the AFR.

2) Headers may change your actual VE some amount;
the wideband would tell you whether the result is rich or lean...
AutoVE can then be used to adjust the B0101 VE table for those headers, and you do not have to adjust any other table (except possibly the B5001 MAF table if you're running the MAF).

If you have a wideband O2 sensor, don't always necessarily trust your trims (LTFT's) which are derived from the NBO2, especially at WOT.

Cheers
Joe
:cheers:

Way to show me up Joe, with your color highlighting, italics, et al. :D


One thing to note, Keypunch. Don't do the AutoVE with your setup unless you're going to run a 2-bar MAP sensor. AutoVE with the 1 bar sensor and your supercharger would not work out very well...

[joecar]

Way to show me up Joe, with your color highlighting, italics, et al. :D
...Justin,

:D lol... didn't mean to show you up... :D ... and you beat me by mere minutes....

The colouring helps me weed out serious typos :bash: on key words/phrases when I preview my post...

lol, typos fit me like a glove...

Edit: see the word richer ... I actually had typed leaner... lol.

[keypunch]

Many thanks for the responses to my inquiry, they really helped. Just a couple of other things I want to be sure I understand.

1.I said in my first post that I thought my fuel trims were ok in that they go to zero at WOT. My question is, looking at my scan logs they show zero LTFT”s at 100 percent throttle but is that the data I should be looking at?Do they freeze and add fuel to the AFR at some other throttle position? How do I tell where they freeze and add fuel?

1.If the trims freeze at say 5.8 positive, how do you compute the AFR adjustments. Ex. my afr map says at 4,000 rpm AFR is 11.7, how much does the 5.8 adjust that ratio?

Thanks again…I plan on heavily modding my GTO but only after I understand the tune stuff

[joecar]

The 5.8 positive trim adjusts the fueling to produce a commanded 11.7 (in your example).

But you can't tell the actual AFR until you hook up a wideband.

[keypunch]

Thanks,any other comments/help?How do you tell what your trims freeze at?Also,was of the opinion from reading on this board that trims add to afr when they are positive but will not subtract if negative.Also was recommended earlier not to use auto ve with a blower so I would need to alter ve on a manual basis so I would need to know how to compensate for the trims if positive,correct?