FTC RPM boundries
Thread Starter
Staging Lane
Joined: Aug 2002
Posts: 86
Likes: 0
From: Raleigh,NC
FTC RPM boundries Anyone change the rpm settings for the trim cells Stock is 2500--6500--6502.By changing the values to 2600---4600--6500 you can get more cell counts to fine tune the VE.What do you think??
In theory, if you dial in your VE table correctly this will not matter. For tuning many people turn off the LTRIMS and use the STRIMS to identify the VE for every MAP/RPM combination in the table. Once done, there is very little LTRIM variation
I find the FTC's helpfully because I have an A4 PCM & Harness in an M6 car and that I think is causing some unstable LTRIMs on Decel and low MAP tuning.
My stock FTC boundries were much lower, with the lower boundry at 900. I have changed them. 1100/1800/2700.
I'm not sure why you want FTC's above 6500.
I find the FTC's helpfully because I have an A4 PCM & Harness in an M6 car and that I think is causing some unstable LTRIMs on Decel and low MAP tuning.
My stock FTC boundries were much lower, with the lower boundry at 900. I have changed them. 1100/1800/2700.
I'm not sure why you want FTC's above 6500.
Thread Starter
Staging Lane
Joined: Aug 2002
Posts: 86
Likes: 0
From: Raleigh,NC
Yea i used to have 1800--3800--4600 and i'm thinking that maybe like this it is using so many cells that the transitions can't be a good thing and by raiising the upper one it might be easier to get a good zero at cell 15-wot.
The VCM learns in closed loop fuel mode. By keeping the engine in this mode, you can cover enough locations in the histogram to get an overall view of your engines tune. Make slow throttle changes and try and hit as many histogram table locations as possible.
Covering every single location is not needed, nor is it possible as the VE table covers areas the engine will never run in.
You do not want the engine to go into power enrichment mode, as this will turn off closed loop fuel.
The LTFT uses cells to “cover” the VE table. The current cell in use is called the Fuel Trim Cell (FTC). There are 16 cells (0 – 15). Cells 20,21,22 are used by the VCM when it does not want to make a permanent correction to the VE table values (examples would be Decel Fuel Cutoff, Power Enrich Fuel, Charcoal Canister Purge off).
By monitoring the current LTFT cell number (FTC) in the scanner, you can make a decision of when to ignore the LTFT correction. Do not use the histogram logged corrections for cells 20,21,22.
LTFT cells are “placed” on the VE table by using the LTFT Low, Mid High boundaries on the Closed Loop fuel tab.
The RPM boundaries on the sample are 1300 RPM, 2500 RPM, 3500 RPM
The Map boundaries on the sample are 32 kPa, 56 kPa, 80, kPa
A graphical representation of this layout is shown in the figure below.
The RPM Boundary values are shown in red, the MAP boundary values are shown in blue. The lines are for display purpose only and do not appear on the VE table.(figure 1)
LTFT cells are also “placed” on the Histogram LTFT table by using the LTFT Low, Mid High boundaries on the Closed Loop fuel tab. A graphical representation of this layout is shown in the figure below.
The RPM boundaries on the sample are 1300 RPM, 2500 RPM, 3500 RPM
The Map boundaries on the sample are 32 kPa, 56 kPa, 80, kPa
The RPM boundary values are shown in red, the MAP boundary values are shown in blue. The lines are for display purpose only and do not appear on the histogram.(Figure 2)
STFT: stands for Short Term Fuel Trim. This is the VCM’s ability to make needed corrections quickly to the Air Fuel Ratio by monitoring the vehicles stock O2 sensors.
The STFT corrections are instantaneous corrections and do not employ the use of cells, nor is it a permanent correction.
The STFT Histogram keeps track of these changes so you don’t have to. The corrections displayed in the scanner are a + - % correction to the values on the VE table, zero being no change. They are to be considered a “fine tune” for the LTFT cell adjustments. Seeing as the LTFT is cell based and covers a wide area on the VE table, the STFT corrects the conditions within those cells.
Covering every single location is not needed, nor is it possible as the VE table covers areas the engine will never run in.
You do not want the engine to go into power enrichment mode, as this will turn off closed loop fuel.
The LTFT uses cells to “cover” the VE table. The current cell in use is called the Fuel Trim Cell (FTC). There are 16 cells (0 – 15). Cells 20,21,22 are used by the VCM when it does not want to make a permanent correction to the VE table values (examples would be Decel Fuel Cutoff, Power Enrich Fuel, Charcoal Canister Purge off).
By monitoring the current LTFT cell number (FTC) in the scanner, you can make a decision of when to ignore the LTFT correction. Do not use the histogram logged corrections for cells 20,21,22.
LTFT cells are “placed” on the VE table by using the LTFT Low, Mid High boundaries on the Closed Loop fuel tab.
The RPM boundaries on the sample are 1300 RPM, 2500 RPM, 3500 RPM
The Map boundaries on the sample are 32 kPa, 56 kPa, 80, kPa
A graphical representation of this layout is shown in the figure below.
The RPM Boundary values are shown in red, the MAP boundary values are shown in blue. The lines are for display purpose only and do not appear on the VE table.(figure 1)
LTFT cells are also “placed” on the Histogram LTFT table by using the LTFT Low, Mid High boundaries on the Closed Loop fuel tab. A graphical representation of this layout is shown in the figure below.
The RPM boundaries on the sample are 1300 RPM, 2500 RPM, 3500 RPM
The Map boundaries on the sample are 32 kPa, 56 kPa, 80, kPa
The RPM boundary values are shown in red, the MAP boundary values are shown in blue. The lines are for display purpose only and do not appear on the histogram.(Figure 2)
STFT: stands for Short Term Fuel Trim. This is the VCM’s ability to make needed corrections quickly to the Air Fuel Ratio by monitoring the vehicles stock O2 sensors.
The STFT corrections are instantaneous corrections and do not employ the use of cells, nor is it a permanent correction.
The STFT Histogram keeps track of these changes so you don’t have to. The corrections displayed in the scanner are a + - % correction to the values on the VE table, zero being no change. They are to be considered a “fine tune” for the LTFT cell adjustments. Seeing as the LTFT is cell based and covers a wide area on the VE table, the STFT corrects the conditions within those cells.
Thread Starter
Staging Lane
Joined: Aug 2002
Posts: 86
Likes: 0
From: Raleigh,NC
well it sounds to me like my fear of transition problems from cell to cell is invalid since stft's cover this.I,m setting mine to 0-1000rpm(idle)--1000-2600rpms (casual driving)2600-4200rpms(spirited driving and 4200+ rpms(wot).what do you think?
I went with more focus down to fix my operating range where driving was a problem. With HPT/EFILive, this less on an issue. By the time I hit 4000 rpm I'm at WOT. I have thought about increasing my 1800 & 2700 boundries a bit more
