Question about Tuning SD, LTFT's
09-13-2006, 02:49 PM
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Question about Tuning SD, LTFT's When tuning in SD, what RPM range should you be logging to correct your VE tables? I've heard keep it out of PE and below 4,000 RPM...any input?
09-13-2006, 08:12 PM
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TTT
I was wondering this myself, went out on my first VE logging trip today and hit power reduction (trying to moderately get on the highway), limped to the side of the road, reflashed to the stock tune and went back to the garage for beer and more research
I was wondering this myself, went out on my first VE logging trip today and hit power reduction (trying to moderately get on the highway), limped to the side of the road, reflashed to the stock tune and went back to the garage for beer and more research
09-13-2006, 08:29 PM
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you want to stay in closed loop since your using trims.
if your in open loop (pe) your not gonna get trimming like you should hence the name open loop. The stock 02's are only accurate at 14.7 and its not commanding that when in open loop. I like to run safe timing and set pe at 90tps to tune the majority of the VE table then select second gear and tweak all rpms to about 4400 and then youll see where the graph is going and eyeball the WOT portion above that. If your ve table is correct than you PE divisor math will add up meaning 14.7/1.131=13:1 afr etc.....
if you have ltft timming in open loop(pe) the ve isnt correct at wot.
if your in open loop (pe) your not gonna get trimming like you should hence the name open loop. The stock 02's are only accurate at 14.7 and its not commanding that when in open loop. I like to run safe timing and set pe at 90tps to tune the majority of the VE table then select second gear and tweak all rpms to about 4400 and then youll see where the graph is going and eyeball the WOT portion above that. If your ve table is correct than you PE divisor math will add up meaning 14.7/1.131=13:1 afr etc.....
if you have ltft timming in open loop(pe) the ve isnt correct at wot.
09-14-2006, 01:13 PM
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So when you re-log your LTFT, are those values altered and not accurate to tune off of if your previous drive in the car maybe went into PE mode?(say 100% throttle 5K RPM). Should I re-load the .bin, or just continue logging and make change accordingly?
09-14-2006, 02:30 PM
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When tuning the VE with NBO2's, you shouldn't change Power Enrichment at all. It's there in the interest of providing your engine with enough fueling for the load placed on it. Moving or disabling PE can be potentially dangerous for the engine.
When tuning without a wideband, any data logged outside of closed loop (i.e. fuel trim cells greater than 19) should be filtered out. Once fueling is close enough (+/- 5% LTFTs), turn off LTFTs and tune based off of STFT averages.
There's usually 5 things I do to the tune before logging:
Then, go log. Don't start logging until the car is up to operating temps for 10~15 minutes. Remember, oil temps take longer to rise than coolant temps. Upon return, make your corrections to your VE table. Reflash the tune and reset the LTFTs (if still active). Repeat this process with a fresh log until you have a good VE. If repeating, try to do so in similar driving conditions. As IATs/ECTs change, fueling will change as well. See THIS THREAD for more info.
Once you're done with the VE, do the same with the MAF by making a map in your log to reflect the one you see in the tuning software. Restore the LTFTs, MAF, MAF MILS, and Low spark tables to stock. DFCO is the only thing that is still turned off. Log the learned LTFTs for each MAF frequency after some driving. Make the appropriate changes to the MAF table and turn off LTFTs. Dial in each MAF Freq. by using the STFT averages. Typically, the stock curve is close in shape. I like to see what the % increase is for a given range of the curve and make a general increase. In other words, if my logs/changes to my MAF leave me with a 2.5%~2.7% increase in the 3,000~3,500Hz range, I'll set those values to stock and multiply that entire range by 1.028. If it's too much fuel, the fuel trims will adjust. I do this for the entire curve that's hit under closed loop. Then to be safe, carry the adjustment in the highest range hit through the rest of the curve plus a little extra until I can get my wideband installed to dial in WOT.
When tuning without a wideband, any data logged outside of closed loop (i.e. fuel trim cells greater than 19) should be filtered out. Once fueling is close enough (+/- 5% LTFTs), turn off LTFTs and tune based off of STFT averages.
There's usually 5 things I do to the tune before logging:
- Copy High spark to Low
- Disable the MAF
- Disable the MAF MILS
- Disable DFCO
- Disable LTFTs (if close enough)
Then, go log. Don't start logging until the car is up to operating temps for 10~15 minutes. Remember, oil temps take longer to rise than coolant temps. Upon return, make your corrections to your VE table. Reflash the tune and reset the LTFTs (if still active). Repeat this process with a fresh log until you have a good VE. If repeating, try to do so in similar driving conditions. As IATs/ECTs change, fueling will change as well. See THIS THREAD for more info.
Once you're done with the VE, do the same with the MAF by making a map in your log to reflect the one you see in the tuning software. Restore the LTFTs, MAF, MAF MILS, and Low spark tables to stock. DFCO is the only thing that is still turned off. Log the learned LTFTs for each MAF frequency after some driving. Make the appropriate changes to the MAF table and turn off LTFTs. Dial in each MAF Freq. by using the STFT averages. Typically, the stock curve is close in shape. I like to see what the % increase is for a given range of the curve and make a general increase. In other words, if my logs/changes to my MAF leave me with a 2.5%~2.7% increase in the 3,000~3,500Hz range, I'll set those values to stock and multiply that entire range by 1.028. If it's too much fuel, the fuel trims will adjust. I do this for the entire curve that's hit under closed loop. Then to be safe, carry the adjustment in the highest range hit through the rest of the curve plus a little extra until I can get my wideband installed to dial in WOT.
