I want to make sure I'm doing everything right. I saw lots of post from the past where you want to drive around in 4th and about 2k rpm, and low or raise K constant until fuel trims are in line, then start fuel map tuning. Now I'm reading some new material that suggest fuel trims should be roughed in with TIM. What's the correct way before you dial in the fuel map for fine tuning? I'd really like to make sure I get K to the appropriate spot as it seems crucial for other aspects.
RB20DET
47 lb/hr injectors
Z32 MAF
K vs TIM - Fuel Trims
Moderator: Matt
Re: K vs TIM - Fuel Trims
TIM adjusts fuel injection time. So if you add 10% TIM then it adds 10% more fuel
K adjusts base load, which affects the load cursor access in all maps (TP). Also TP is a factor for total injection time. So if you increase K then it adds 10% more load, and 10% more fuel
So after doing the resize MAF (adjusts K) and resize injectors (adjusts K and TIM) if the car is running, then we get it warm and at cruise (around 2000rpm, quarter in the load table).
We should be sitting at stoich and if the O2 sensor is working properly, then it should be near 0%. If trims are say adding 5% more fuel, then pull TIM back 5% to keep trims near 0% and mixtures should still be stoich. This is your base mixture setup using TIM
Now back to K constant. The resize done on the MAF was for the maximum load that the Z32 can read (about 500-550rwhp). If your RB20 does say around 400rwhp, then you will not use the entire map
You might need to increase the load cursor (TP) to reach the end of the fuel/timing map on full boost. This part needs a proper dyno run to see how things are travelling. So you do a run, see how far TP goes. If not far enough (say it reaches 75% of the load scale) then you will need to increase K (to increase TP) about 25%
Once you adjust K to fix the load positioning, then it will add 25% more fuel and run too rich. We then scale back TIM by a similar percentage to get the cruise mixtures near stoich (and trims near 0% again)
The last two steps ^ you may need to repeat a few times until load is correct, and base mixtures are on track. Then you can adjust the rest of the fuel map to fine tune
K adjusts base load, which affects the load cursor access in all maps (TP). Also TP is a factor for total injection time. So if you increase K then it adds 10% more load, and 10% more fuel
So after doing the resize MAF (adjusts K) and resize injectors (adjusts K and TIM) if the car is running, then we get it warm and at cruise (around 2000rpm, quarter in the load table).
We should be sitting at stoich and if the O2 sensor is working properly, then it should be near 0%. If trims are say adding 5% more fuel, then pull TIM back 5% to keep trims near 0% and mixtures should still be stoich. This is your base mixture setup using TIM
Now back to K constant. The resize done on the MAF was for the maximum load that the Z32 can read (about 500-550rwhp). If your RB20 does say around 400rwhp, then you will not use the entire map
You might need to increase the load cursor (TP) to reach the end of the fuel/timing map on full boost. This part needs a proper dyno run to see how things are travelling. So you do a run, see how far TP goes. If not far enough (say it reaches 75% of the load scale) then you will need to increase K (to increase TP) about 25%
Once you adjust K to fix the load positioning, then it will add 25% more fuel and run too rich. We then scale back TIM by a similar percentage to get the cruise mixtures near stoich (and trims near 0% again)
The last two steps ^ you may need to repeat a few times until load is correct, and base mixtures are on track. Then you can adjust the rest of the fuel map to fine tune
Re: K vs TIM - Fuel Trims
Perfect explaintion. Thank you so much. I got some work to do now