Ls7 black smoke at wot? Help
09-22-2017, 05:05 PM
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Ls7 black smoke at wot? Help So we are working on my buddy's 1970 chevelle that we put a ls7 into, it's 11.8 cr with a ls7r cam (248/256 .658"/.658" 114+3 (with 1.8 rockers) 1 7/8 header with duel 3in exhaust, trans is 4l60e with yank ss4k. It seems to be down a bit on power and we keep getting puffs of black smoke out the tail pipe at wot. Here's a run down of where its at and what I have checked so far..
-A/f is 13.0 across the curve
-timing is 24 degrees (checked with a timing light)
-lower timing and adding race fuel did not help
-tryed 2 different sets of injectors
-tryed a hole different set of coils
-lifter pre load is .060
-plugs are tr6 at 45 gap
-tryed tigher plug gap
-plugs look clean and all the same - no detonation either
-new Taylor plug wires
I think that's it's, im kind of stumped here, dont know what else to try. The car is 3650lbs with driver and it ran 118mph, 3.73 gear with yank ss4000, that comes out to 465 ish rwhp and it should be up 60 or more from that imo, car has no hesitation or missfire you can hear or feel, only thing we can tell that's off is these random puff of black smoke out of the tail pipes..anyone have any idea here?
-A/f is 13.0 across the curve
-timing is 24 degrees (checked with a timing light)
-lower timing and adding race fuel did not help
-tryed 2 different sets of injectors
-tryed a hole different set of coils
-lifter pre load is .060
-plugs are tr6 at 45 gap
-tryed tigher plug gap
-plugs look clean and all the same - no detonation either
-new Taylor plug wires
I think that's it's, im kind of stumped here, dont know what else to try. The car is 3650lbs with driver and it ran 118mph, 3.73 gear with yank ss4000, that comes out to 465 ish rwhp and it should be up 60 or more from that imo, car has no hesitation or missfire you can hear or feel, only thing we can tell that's off is these random puff of black smoke out of the tail pipes..anyone have any idea here?
09-22-2017, 08:12 PM
#2
What is your End of Injection Settings (EOIT tables)? Sometimes unburnt fuel will leave the chamber if your EOIT is too late (retarded), but the wideband will still report a leaner AFR because it responds to oxygen content but doesnt compensate well for excessive unburnt hydrocarbons. If you have changed this a lot in your tune, try moving your EOIT tables back to stock, or at least advance them closer to stock and do a WOT pull...If the EOIT is moved back to a more appropriate location, your reported/measured AFR will richen up (according to the wideband) with the same amount of fuel being injected.
the quickest way to make the change is to numerically LOWER the values in the "Boundary" tables. Grab the whole table and multiply it by say 0.9, try it, then 0.8, try it, etc.
On the other hand, if you haven't touched the EOIT tables with that cam you are running, then you really need to adjust them appropriately to make up for that increased duration. You would be leaving a lot on the table otherwise and that could be the issue as well. This would be the opposite of what I just described. You retard the tables by the amount of the duration difference between new cam and stock cam as a starting point, then dial them in.
the quickest way to make the change is to numerically LOWER the values in the "Boundary" tables. Grab the whole table and multiply it by say 0.9, try it, then 0.8, try it, etc.
On the other hand, if you haven't touched the EOIT tables with that cam you are running, then you really need to adjust them appropriately to make up for that increased duration. You would be leaving a lot on the table otherwise and that could be the issue as well. This would be the opposite of what I just described. You retard the tables by the amount of the duration difference between new cam and stock cam as a starting point, then dial them in.
09-23-2017, 09:35 AM
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What is your End of Injection Settings (EOIT tables)? Sometimes unburnt fuel will leave the chamber if your EOIT is too late (retarded), but the wideband will still report a leaner AFR because it responds to oxygen content but doesnt compensate well for excessive unburnt hydrocarbons. If you have changed this a lot in your tune, try moving your EOIT tables back to stock, or at least advance them closer to stock and do a WOT pull...If the EOIT is moved back to a more appropriate location, your reported/measured AFR will richen up (according to the wideband) with the same amount of fuel being injected.
the quickest way to make the change is to numerically LOWER the values in the "Boundary" tables. Grab the whole table and multiply it by say 0.9, try it, then 0.8, try it, etc.
On the other hand, if you haven't touched the EOIT tables with that cam you are running, then you really need to adjust them appropriately to make up for that increased duration. You would be leaving a lot on the table otherwise and that could be the issue as well. This would be the opposite of what I just described. You retard the tables by the amount of the duration difference between new cam and stock cam as a starting point, then dial them in.
the quickest way to make the change is to numerically LOWER the values in the "Boundary" tables. Grab the whole table and multiply it by say 0.9, try it, then 0.8, try it, etc.
On the other hand, if you haven't touched the EOIT tables with that cam you are running, then you really need to adjust them appropriately to make up for that increased duration. You would be leaving a lot on the table otherwise and that could be the issue as well. This would be the opposite of what I just described. You retard the tables by the amount of the duration difference between new cam and stock cam as a starting point, then dial them in.
