I used my maf to create what I thought should be a valid 3d sd map. Long story short is there were spots that no matter how mush i adjusted VE they just would not change. Some of these spots were really lean and some were really rich. I then started messing with my fuel map in the areas where i was running lean by lowering the numbers and all the sudden my afr's are falling in line.

My understanding is that the fuel map has 0 effect on AFRs. This does not seem to be the case. What role does the fuel map play in 3D SD if any.....I am not sure which table I should be adjusting anymore. I feel like I must have overlooked some part of the setup or misread something.

FYI....I am running full open loop if that matters any.
ROM ID: 96534706 & GM IAT

 

The fuel map acts like normal. The ve map adjusts fueling aswell. Ve is not a linear adjustment sometimes it takes more ve change in some parts of the map to accomplish the same thing.

I've never encountered a stuck spot like that. I've been in full ol before too.

 

1. At what point should you adjust the fuel map?
2. How far past 100 is acceptable in a VE table? My thought is it should never past 100 but i heard some people
go well into the 120 range.


I haven't played with the rich spots as much yet. The leans sports received most of my attention thus far.

 

I've been 130ish. It's. maf curve table not really a ve table

Adjustment is up to you. There is no golden rule. I started logging load/kpa =ve and got 124% in some areas.

 

1. Both the VE table and the fuel table affect fueling, so in theory you could just leave the VE table alone and tune your fuel map to meet your afr, The VE table is setup so that you can use your original fuel map and set the VE so that afr matched your old tune. But either one will affect fueling.

2. It depends on how efficient your engine is, you can easily pass 100% in peak torque areas.

 

Be certain that your reading your KPA value when determing what to adjust in the VE table and not LOAD as they will be close but not exactly the same.

 

I used the Formula that Jamie from Dynotech said to use in some other thread to determine kpa. Then used that number to determine VE.

 

A better VE formula will be:

VE= Load/(MAP*(298/(273+MAT)))

So, it will vary as MAT changes. But using a simple load/map will be fine. As stated, you can tweak your tune with the tables. The formulas are just to get rough starting values.

Also, for load, keep in mind the notes from mrfred a while back:

spark advance lookup: For air temp below 77F, baro+airtemp compensated load is used for spark advance. For temps above 77F, then baro compensated load is used.

afr lookup: for closed loop conditions when load is < ~20, uncompensated load is used, otherwise, baro+airtemp compensated load is used. This means that baro+airtemp compensated load is used essentially all the time for AFR lookup.



Eric

 

Also, just for the records...some notes I posted a long time ago when I was testing SD. If you have the mass airflow patch that mrfred created, you can also do VE like this, as I tested (this was on my Evo 8 with minimal mods):

To get pounds of air: n (lbs/min) = P (psia) x V (CFM) x 29 / (10.73[ft3ˇpsiˇ °R-1ˇlb-mol-1] x T)
A(cfm)=Cid*VE*RPM/3456[PR]


VE=n(lb/min)*10.73*T(*R)*3456
__________________________
P(psia)*29*Cid*RPM



Data:

cutout open
lb/min RPM *R psia VE
6.9 2643 525.5 15.46 .930
14.9 3026 525.7 23.34 1.162
23.6 3503 526.3 38.2 .973
25.5 4020 526.1 36.65 .954
28 4520 526.5 36.64 .933
31.2 4989 527.4 36.56 .946
33.5 5490 529 36.27 .933
36.2 6029 530.9 35.94 .930
37.5 6506 533.1 36.33 .886
38.7 7038 538 34.76 .892

cutout closed
7.0 2784 525.4 16.22 .854
11.7 3003 525.5 20.79 1.032
21.8 3527 526.3 35.47 .961
25.5 4020 526.5 36.46 .960
27.9 4536 526.9 36.46 .931
30.3 5028 528 35.94 .928
32.9 5490 529.6 35.47 .938
34.7 6029 532.3 35.05 .916
36 6522 534.5 34.71 .891
36.2 6890 537.3 34.29 .863

Data just crusing (nearly closed throttle)
2027 .61
1.9 2502 525.5 7.06 .59

low RPM, but just after going full throttle (closed cutout)
7.0 2784 525.4 16.22 .854
open cutout
6.9 2643 525.5 15.46 .930

 

Can i use these formulas now that i have switched over or will it require me going back to the maft?

This maybe a silly question but does it make since you use the formula and fill out the table and then tweak the fuel map to hit your target values?

 

If you have switched over already, just keep it at that. No need to go back to get logs, etc. It just helps in getting rough values to start with.

Think of it this way maybe...use the SD tables for rough tuning, and use your fuel map for fine tuning. If you have to adjust your fuel map too much, then go back to your SD tables.

 

Thank you very much.

1 last question......what would you define as to much? 1 full point in either direction? Example is in the area i was having lean issues with i adjusted the numbers from 14.7 to 14.1 and that put me more in line with my target AFRs. Would that be considered too much?

 

I use half point as my ref.

 

What formula was that? Having a blonde moment and can't find it. I can't log lbs/min etc as I don't have a rom where that's been patched so I can't use l2r99's formula.

 

will this patch work with my rom? I have yet to find how to do this on my ROM. 95634706