LTFT Tuning and tuning below 1500 RPM
03-01-2005, 12:36 PM
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LTFT Tuning and tuning below 1500 RPM I'm working on getting my LTFTs dialed in to the -3 to +3 range so they will LTFTs will zero at WOT. These are my current LTFTs:
Cell 8 -0.8 to +2.3
Cell 9 +1.6
Cell 12 +3.9 to +5.5
Cell 13 +6.3 to +9.4
As far as cells 12 and 13, I would like to see these closer to zero. Question is, what area of the VE table should I adjust to get these values down? Looking at the log, cells 12 and 13 seem to reference KPAs in the ~ 75-83 range and RPMs in the 1400-3200 range. Is it logical to multiply the values in the VE table, 75-85 KPA, by 3-5% in either the 1400-3200 RPM range or the entire RPM range?
Another question regarding tuning in the lower RPMs. My car (LTs, lid, 233/239 cam) runs like crap below 1500 RPMs at part throttle. The car stumbles and doesn't want to accelerate. My thinking is this is caused by the overlap of the cam and the fact that some of the unburned intake charge is getting pulled out the exhaust port and causing a very lean reading for the O2s. When the car is stumbling like this, the O2 values will drop down as low as 30mv and fluctuate all over until it pulls above ~ 1500 RPMs. Is the solution to this adding more fuel down low (4-5%..?) and 1-2 more degrees of timing?
Looking for any feedback/help.
Thanks.
Cell 8 -0.8 to +2.3
Cell 9 +1.6
Cell 12 +3.9 to +5.5
Cell 13 +6.3 to +9.4
As far as cells 12 and 13, I would like to see these closer to zero. Question is, what area of the VE table should I adjust to get these values down? Looking at the log, cells 12 and 13 seem to reference KPAs in the ~ 75-83 range and RPMs in the 1400-3200 range. Is it logical to multiply the values in the VE table, 75-85 KPA, by 3-5% in either the 1400-3200 RPM range or the entire RPM range?
Another question regarding tuning in the lower RPMs. My car (LTs, lid, 233/239 cam) runs like crap below 1500 RPMs at part throttle. The car stumbles and doesn't want to accelerate. My thinking is this is caused by the overlap of the cam and the fact that some of the unburned intake charge is getting pulled out the exhaust port and causing a very lean reading for the O2s. When the car is stumbling like this, the O2 values will drop down as low as 30mv and fluctuate all over until it pulls above ~ 1500 RPMs. Is the solution to this adding more fuel down low (4-5%..?) and 1-2 more degrees of timing?
Looking for any feedback/help.
Thanks. 
03-01-2005, 02:08 PM
#2
I always set the maf fail freq to 0/set timing tables identical, get the LTFTs straightened out first with the VE table (in your case the secondary VE), then reenable the MAF and copy over and extrapolate the secondary VE to main VE on 98-00 vehicles and tweak the MAF table back to 0 LTFTs. This puts fueling and timing and everything in between in line. This is for starters and is just a general overview. 
