(LS1Edit) Ltrims by RPM, sudden change from + to -
09-14-2004, 08:29 AM
#1
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(LS1Edit) Ltrims by RPM, sudden change from + to - Basicly while lightly accelorating at low rpm the Ltrims are +3 through +7 and then at a certain RPM that changes to -1 through -4 ish. During this change, I get a large amount of knock 3-4 degrees and a stumble along with the occasional exhaust pop.
Do i need to add fuel in the + LTRIM range?
If so, what table and where should I be doing it?
Do i need to add fuel in the + LTRIM range?
If so, what table and where should I be doing it?
09-14-2004, 10:20 AM
#2
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On an F-body you may have the same whacked fuel trim cell
(FTC) RPM boundaries I did - 2500, 6502, 6503 - meaning that
your Cell 0/4 have to model everything from the bottom of idle to
highway cruise. A tough job especially if you have headers
making the idle trim process a bit flaky. Further, my stock MAP
boundaries were set so that Cell 0 top is right about in the
middle of my idle MAP.
I rejustified all of the boundaries so that I have all cells
active, cell 0 is <1000RPM and 40 MAP. Also the "top line"
is 4000RPM which is where the SD-MAF cutover lies. In
the stock scheme, Cell 1/5/9/13 have to cover 2500RPM
and up, but the mixture calculation mode is changing within
that space so I think it's going to cause a bit of contention
and driving-based trim drift (did you spend more time below
or above 4000RPM, lately?). If you partition the trim space
more finely you can perhaps get a better handle on the
nonlinearities, with a less discontinuous result and better-
fitting trims within each cell.
Attached a couple of screen shots for illustration, stock vs
current.
(FTC) RPM boundaries I did - 2500, 6502, 6503 - meaning that
your Cell 0/4 have to model everything from the bottom of idle to
highway cruise. A tough job especially if you have headers
making the idle trim process a bit flaky. Further, my stock MAP
boundaries were set so that Cell 0 top is right about in the
middle of my idle MAP.
I rejustified all of the boundaries so that I have all cells
active, cell 0 is <1000RPM and 40 MAP. Also the "top line"
is 4000RPM which is where the SD-MAF cutover lies. In
the stock scheme, Cell 1/5/9/13 have to cover 2500RPM
and up, but the mixture calculation mode is changing within
that space so I think it's going to cause a bit of contention
and driving-based trim drift (did you spend more time below
or above 4000RPM, lately?). If you partition the trim space
more finely you can perhaps get a better handle on the
nonlinearities, with a less discontinuous result and better-
fitting trims within each cell.
Attached a couple of screen shots for illustration, stock vs
current.
10-27-2004, 01:16 PM
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Originally Posted by jimmyblue
On an F-body you may have the same whacked fuel trim cell
(FTC) RPM boundaries I did - 2500, 6502, 6503 - meaning that
your Cell 0/4 have to model everything from the bottom of idle to
highway cruise. A tough job especially if you have headers
making the idle trim process a bit flaky. Further, my stock MAP
boundaries were set so that Cell 0 top is right about in the
middle of my idle MAP.
I rejustified all of the boundaries so that I have all cells
active, cell 0 is <1000RPM and 40 MAP. Also the "top line"
is 4000RPM which is where the SD-MAF cutover lies. In
the stock scheme, Cell 1/5/9/13 have to cover 2500RPM
and up, but the mixture calculation mode is changing within
that space so I think it's going to cause a bit of contention
and driving-based trim drift (did you spend more time below
or above 4000RPM, lately?). If you partition the trim space
more finely you can perhaps get a better handle on the
nonlinearities, with a less discontinuous result and better-
fitting trims within each cell.
Attached a couple of screen shots for illustration, stock vs
current.
(FTC) RPM boundaries I did - 2500, 6502, 6503 - meaning that
your Cell 0/4 have to model everything from the bottom of idle to
highway cruise. A tough job especially if you have headers
making the idle trim process a bit flaky. Further, my stock MAP
boundaries were set so that Cell 0 top is right about in the
middle of my idle MAP.
I rejustified all of the boundaries so that I have all cells
active, cell 0 is <1000RPM and 40 MAP. Also the "top line"
is 4000RPM which is where the SD-MAF cutover lies. In
the stock scheme, Cell 1/5/9/13 have to cover 2500RPM
and up, but the mixture calculation mode is changing within
that space so I think it's going to cause a bit of contention
and driving-based trim drift (did you spend more time below
or above 4000RPM, lately?). If you partition the trim space
more finely you can perhaps get a better handle on the
nonlinearities, with a less discontinuous result and better-
fitting trims within each cell.
Attached a couple of screen shots for illustration, stock vs
current.
..... just a little fine tuning needed but was thinking of starting with the boundry change ... any thoughts on your new boundry numbers? Last edited by J&JsTA; 10-27-2004 at 02:19 PM.
10-27-2004, 02:34 PM
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They caused me no trouble and made it easier to
true up my idle trims. There is no downside I can
see.
I drew up a little graphic (probably just going to
make for more questions, but anyway....)
The left side of the cartoon is my stock settings
and the right, my current; the attempt is to make
things stop stepping all over each other and give
more resolution to the areas where closed loop
operation has any likelihood of occurring.
Depending on your car you may want somewhat
different boundaries. Some cars are just more sane,
to begin with. But in general you would want your
lowest MAP boundary to be above idle MAP; though
big-cam cars might be "throwing away" too much
here, and would want the lower MAP boundary
slightly above low cruise MAP, etc. The lower
RPM should be above idle, barely; upper RPM at
the all-MAF cutover of 4000RPM, the center one
probably just below highway cruise RPM. Segment
it so your most normal "operating modes" look like
they have a cell all to themselves, sorta. In fact I
really ought to bring down the MAP boundaries so
the upper coincides with PE enable (which in stock
is set to a silly 15kPa, my current is 60). There is
very little point in wasting trim cells on MAP higher
than where you will disable trimming.
true up my idle trims. There is no downside I can
see.
I drew up a little graphic (probably just going to
make for more questions, but anyway....)
The left side of the cartoon is my stock settings
and the right, my current; the attempt is to make
things stop stepping all over each other and give
more resolution to the areas where closed loop
operation has any likelihood of occurring.
Depending on your car you may want somewhat
different boundaries. Some cars are just more sane,
to begin with. But in general you would want your
lowest MAP boundary to be above idle MAP; though
big-cam cars might be "throwing away" too much
here, and would want the lower MAP boundary
slightly above low cruise MAP, etc. The lower
RPM should be above idle, barely; upper RPM at
the all-MAF cutover of 4000RPM, the center one
probably just below highway cruise RPM. Segment
it so your most normal "operating modes" look like
they have a cell all to themselves, sorta. In fact I
really ought to bring down the MAP boundaries so
the upper coincides with PE enable (which in stock
is set to a silly 15kPa, my current is 60). There is
very little point in wasting trim cells on MAP higher
than where you will disable trimming.
10-27-2004, 03:27 PM
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Thx Jimmyblue, I haven't had much luck tuning my LTFTs in and I think I have just been adding "fuel" to the fire trying VE adjustments on top of previously altered IFR tables so I figure I might as well start back with a stock IFR table,stock VE table, then adjust the boundries and proceed to log and see where I am and go from there ... a fresh start with all the reading and knowledge I have gained in the last 18 months not to mention the methods are better then they were 2 years ago..... it should be a breeze
Below is what my FTC map looks like right now with the wacky boundries
.....
to the fire trying VE adjustments on top of previously altered IFR tables so I figure I might as well start back with a stock IFR table,stock VE table, then adjust the boundries and proceed to log and see where I am and go from there ... a fresh start with all the reading and knowledge I have gained in the last 18 months not to mention the methods are better then they were 2 years ago..... it should be a breeze Below is what my FTC map looks like right now with the wacky boundries
..... Last edited by J&JsTA; 10-27-2004 at 05:54 PM.
