MichaelR32GTR Posted March 12, 2023 Report Share Posted March 12, 2023 I’ve been collecting some logs and my on boost afrs are going super rich on boost on a rb26 - 2.8 stroker with 76mm precision, E85 on about 38psi boost, starts off fine around 0.78/0.77 lambda, then from 7000rpm onwards it starts going 0.75 lambda, then 0.74, 0.73, 0.72 by 8500rpm i have made some adjustments via afr target table but that didn’t change anything I’m assuming next thing to do is adjust via VE table, question is, how sensitive is the table, will removing a value of 1 say instead of 101 to 100 be a big enough change to see it slightly leaning out ? Quote Link to comment Share on other sites More sharing options...
Adamw Posted March 12, 2023 Report Share Posted March 12, 2023 Im assuming it is still ITB's with TP Vs RPM on the main fuel table? Typically for this type of set up you would enable a 4D fuel table with MGP Vs RPM on it's axes, most of it will be zeros with some fuel pulled out in the high boost/high RPM corner. Quote Link to comment Share on other sites More sharing options...
MichaelR32GTR Posted March 12, 2023 Author Report Share Posted March 12, 2023 Main Fuel table is TP vs RPM yes, In FUEL—> FUEL CORRECTIONS—> 4D fuel table is ON On its axis is MAP (KPA) and RPM yes your correct, table is mostly zeros except for around 6500rpm and 280, 320, 360kpa which has 1.0 in that row then 7000rpm to 9000rpm and 280,320,360kpa has 2.0 im not familiar with this table sorry, is it basically adding fuel in the rows with 1.0 and 2.0 ? Quote Link to comment Share on other sites More sharing options...
MichaelR32GTR Posted March 12, 2023 Author Report Share Posted March 12, 2023 I should add that as I lower boost to say 33/34psi (or so) that it’s target afrs are perfect, as I raise boost from there to high 30’s it starts going super rich Quote Link to comment Share on other sites More sharing options...
rrob Posted March 12, 2023 Report Share Posted March 12, 2023 The 4d table should be removing fuel as the turbine back pressure rises. MichaelR32GTR 1 Quote Link to comment Share on other sites More sharing options...
MichaelR32GTR Posted March 12, 2023 Author Report Share Posted March 12, 2023 So I should have values in the minus at the desired areas Quote Link to comment Share on other sites More sharing options...
Adamw Posted March 12, 2023 Report Share Posted March 12, 2023 Yes, negative values in the 4D table. "-5" in the table would remove 5% fuel. MichaelR32GTR 1 Quote Link to comment Share on other sites More sharing options...
MichaelR32GTR Posted March 13, 2023 Author Report Share Posted March 13, 2023 Thankyou !! Quote Link to comment Share on other sites More sharing options...
MichaelR32GTR Posted March 13, 2023 Author Report Share Posted March 13, 2023 Working out some calculations for how much fuel I should add just a question in regards to existing values in the 4D table if in one box it currently has a value of “2.0” and I need to remove 4% of fuel, would that value now be “-2.0” which is taking away the existing 2.0 value and then another minus 2 to give -4% ? thanks !! Quote Link to comment Share on other sites More sharing options...
Vaughan Posted March 13, 2023 Report Share Posted March 13, 2023 1.02 * 0.96 = 0.9792 so to remove exactly 4% you would use a value of -2.08 (would have to be -2.1 for the 1dp available in the table) but yes -2.0 would be around a 4% reduction from +2.0 MichaelR32GTR 1 Quote Link to comment Share on other sites More sharing options...
MichaelR32GTR Posted March 19, 2023 Author Report Share Posted March 19, 2023 Now that I have taken some fuel out using the 4D table and it’s targeting 0.77 lambda nicely should I change my afr target table to match the 0.77 afrs on boost? afr target table on boost is currently on 0.85 lambda or won’t matter and won’t make a difference and just leave as is Quote Link to comment Share on other sites More sharing options...
Adamw Posted March 19, 2023 Report Share Posted March 19, 2023 If open loop lambda table is on then you are meant to tune to the target that is in the table, you if you change the target later the AFR will change automatically without retuning. If you change the target now it will go very rich. But it would be best to change the target then retune so the measured lambda does match the target. MichaelR32GTR 1 Quote Link to comment Share on other sites More sharing options...
MichaelR32GTR Posted May 1, 2023 Author Report Share Posted May 1, 2023 I haven’t had much time to finalize tweaking afrs, but I’m headed in the right direction with the help I was given can I ask, if 4D fuel is enabled, what would happen if all the boxes are 0 and boost is increased instead of removing fuel with minus (-) values Quote Link to comment Share on other sites More sharing options...
Electredge Posted May 1, 2023 Report Share Posted May 1, 2023 21 minutes ago, MichaelR32GTR said: I haven’t had much time to finalize tweaking afrs, but I’m headed in the right direction with the help I was given can I ask, if 4D fuel is enabled, what would happen if all the boxes are 0 and boost is increased instead of removing fuel with minus (-) values If 4d fuel is enabled and the table has only zero's then it will be doing nothing to change the fueling. It will basically be multiplying the final fuel value by 1 Quote Link to comment Share on other sites More sharing options...
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