Shrinking the LV8 scalar - something beneficial?

BJM

Senior Member
I have been wondering about this for a while. LV8 is an indicator of engine load and is used to index many tables. One thing that has always bothered me is the fact that LV8 maxes out at 255 at around 4-5 psi. The LV8 scalar is set to 1.04 from some reason but as far as I can tell there is no real magic to that value and is perhaps a hold over from other non-turbo applications. The main spark table is reduced from being a 3D surface to being a 2D line with the engine being jammed at one end of the table. If one were to cut the scalar down to say .5 you would have meaningful timing control out much further to maybe 12-15 psi.

Currently I have a boost sensing harness and use it to adjust timing so that I have some timing control when LV8 is pegged but maybe I don't really need it.

Any thoughts?
 

BradB

New Member
I also use a form of boost feedback to control timing and after reading this I took a quick look at my chip. The last boost/temp point I use is 11-12 lbs/ 92 Deg. So if changing the scaler would buy me control to 12-15 lbs it would be time to re-evaluate how to use the boost feedback. Very interesting.

Brad
 

bruce

Rest In Peace
Originally posted by BJM
I have been wondering about this for a while. LV8 is an indicator of engine load and is used to index many tables. One thing that has always bothered me is the fact that LV8 maxes out at 255 at around 4-5 psi. The LV8 scalar is set to 1.04 from some reason but as far as I can tell there is no real magic to that value and is perhaps a hold over from other non-turbo applications. The main spark table is reduced from being a 3D surface to being a 2D line with the engine being jammed at one end of the table. If one were to cut the scalar down to say .5 you would have meaningful timing control out much further to maybe 12-15 psi.

Any thoughts?

I dun played with it <cough> some........

The LV8 is just used in the timing, and is an guessimatation <my new word> of engine load, can stretch it out, but then you lose alot of granularity. ie it's more difficult to ramp the timing out coming off light cruise to WOT.

IMO, they'd have done better with a Gm/Sec vs RPM look up table for timing instead of trying to save so much space, code wise.

IMO, the best set-up for the 148, is using a Translator, and the big reason for that is that it has it's own temp compensation for the MAF input to the ecm. Then use a Boost sensing harness and populate the IAT tables with entries that actually do something.
Better yet, is expanding those tables, and really getting serious about getting it right.

The ultimate bad boy, EFI, IMO, is going to be what GM's doing now. ie MAP for transistional areas, and MAF for WOT.
And do away with the LV8 calculation all together.

Just as a FWIW, this is what I consider having enough granularity for getting the timing right.
And you ain't gonna be able to do this with the 148. This is what I'm playing with in the 749 experiment, it has er, can be made to have the room do to these tables.


; TABLE Main Spark Advance
FCB 0 ; F1_NTRPMP F1 - R Min 0
FCB 0 ; F1_NMAPLD F1 - Q Min 0
FCB 17 ; F1_NUM F1 - R Num 17
* 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 kPa
FCB 77,77,77,77,77,77,77,77,77,68,68,68,57,57,57,57,57 ; 600 RPM
FCB 77,77,77,77,77,77,77,77,77,68,68,68,57,57,57,57,57 ; 800
FCB 77,77,77,77,77,77,77,77,71,57,57,57,57,57,57,57,57 ; 1000
FCB 32,32,32,32,32,58,81,81,68,63,57,57,57,57,57,57,57 ; 1200
FCB 32,32,32,32,32,58,84,81,74,68,68,63,63,68,57,57,57 ; 1400
FCB 32,32,32,32,32,84,87,87,87,81,74,71,68,68,63,63,63 ; 1600
FCB 32,32,32,32,32,81,87,87,87,87,84,74,71,68,68,68,68 ; 2000
FCB 32,32,32,32,32,77,84,87,87,87,84,74,71,68,68,68,68 ; 2400
FCB 32,32,32,32,48,74,90,90,90,84,81,71,68,68,68,68,68 ; 2800
FCB 32,32,32,32,68,80,80,74,74,71,71,71,68,68,68,68,68 ; 3200
FCB 32,32,32,32,68,74,74,74,71,71,71,68,68,68,68,68,68 ; 3600
FCB 32,32,32,32,68,71,71,71,71,71,68,68,68,68,68,68,68 ; 4000
FCB 32,32,32,32,68,68,68,68,68,68,68,68,68,68,68,68,68 ; 4400
FCB 32,32,32,32,68,68,68,68,68,68,68,68,68,68,68,68,68 ; 4800

BoostTimingTbl
FCB $20,$00,$11
* 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 kPa
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6
* 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
*
FCB 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57 ; 800 RPM
FCB 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57 ; 1200
FCB 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57 ; 1600
FCB 63, 63, 63, 63, 63, 63, 63, 63, 63, 63, 57, 57, 57, 57, 57, 57, 57 ; 2000
FCB 68, 68, 68, 68, 63, 63, 57, 54, 51, 48, 45, 45, 45, 45, 45, 45, 45 ; 2400
FCB 68, 68, 68, 68, 63, 63, 57, 54, 51, 48, 45, 42, 42, 42, 42, 42, 42 ; 2800
FCB 68, 68, 68, 68, 63, 63, 57, 54, 51, 48, 45, 42, 42, 39, 39, 38, 38 ; 3200
FCB 68, 68, 68, 63, 63, 63, 57, 54, 51, 48, 45, 42, 42, 39, 36, 38, 32 ; 3600
FCB 68, 68, 68, 63, 63, 63, 57, 54, 51, 48, 45, 42, 42, 39, 36, 32, 32 ; 4000
FCB 68, 68, 68, 63, 63, 57, 57, 54, 48, 48, 45, 39, 39, 36, 36, 32, 32 ; 4800
FCB 68, 68, 68, 63, 63, 57, 57, 51, 45, 42, 42, 39, 39, 36, 36, 32, 32 ; 5200
FCB 68, 68, 68, 63, 63, 57, 57, 51, 45, 42, 42, 42, 39, 36, 36, 32, 32 ; 5600
FCB 68, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 36, 36, 32, 32 ; 6000
FCB 68, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 36, 36, 32, 32 ; 6400

; Spark Advance Adjustment vs ADMAT1K
FCB 0
FCB 0
FCB 9
; .0 12 25 37 50 62 75 87 100
FCB 62,62,62,62,56,56,56,56,56 ; COLD
FCB 62,62,62,56,56,56,56,56,56 ; 22dC
FCB 62,62,62,56,56,50,50,50,50 ; 49
FCB 62,62,56,56,56,46,46,46,46 ; 80
FCB 62,62,56,52,52,46,46,46,40 ; HOT
 
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