Krambo Posted March 25, 2009 Report Share Posted March 25, 2009 (edited) Krambo, I am not sure if I read your post correctly but it sounds like you have it backwards. A richer A/F is numerically lower than stoich ie. if you are runing an A/F of 10:1 then you are rich and thus numerically lower than 14.68(stoich). A leaner A/F is numerically higher than stoich ie. if you are runing an A/F of 17:1 then you are lean and thus numerically higher than 14.68(stoich). You are correct in your statements and I apologise for an ambigous statement. That is what happens when you start typing faster than you are thinking... without proofreading. I went back and edited that post. Good catch...someone is reading Edited March 25, 2009 by Krambo (see edit history) Quote Link to comment Share on other sites More sharing options...
SRT10KLLR Posted March 25, 2009 Report Share Posted March 25, 2009 As SRT10KLLR stated, monitoring your Fuel Trims is a way to see if your PCM is adding or subtracting fuel to get you to your commanded STOICH (14.68 for typical pump gas) during cruise and part throttle (non Pe mode). If your fuel trims are "+" your PCM is adding fuel to correct for a lean condition and if the fuel trims are "-" the PCM is pulling fuel to compensate for a rich condition. (Rich = numarically HIGHER than Stoich, >14.68) (Lean = numarically LOWER than Stoich, <14.68) Typical trims on a stock tune will vary and it isn't a cause for alarm unless they are way out. Varying weather conditions, altitude, ethanol content in your fuel, bolt-on mods etc. will all impact your trims. The way to correct wide ranging LTFT's is tuning your Ve table of which you will probably hear tuners talking about. A well dialed in Ve table will show 0 to -3 for the LTFT's and takes time to get there. I have seen stock brand new trucks with +/- 7 on the LTFT's. Now if your fuel trims are "+", your PCM will dump that extra number (understood by the PCM as a %) on top of your WOT (Pe) commanded AFR. So if your LTFT's are +7 and you command say a 12.0 in WOT, the PCM will add 7% on top of that 12.0 to richen up the mixture. It is kind of a safety thing that is programmed into the logic of the PCM when using the stock Operating System. I prefer to tune my trims on the negative side (rich). Monitoring your Fuel Trims is also a good way to diagnose post MAF air leaks or Exhaust leaks (pre front O2 sensors). Way positive fuel trims indicate that the PCM is dumping alot of fuel to compensate for a perceived lean condition. So if your LTFT's are say +22...start looking for air / exhaust leaks. There are also STFT (short term fuel trims) but for all case in purpose, ignore them or you will go nuts. I still think it may be wrong because you have the following: (Rich = numarically HIGHER than Stoich, >14.68) (Lean = numarically LOWER than Stoich, <14.68) And I think it should be: (Rich = numerically LOWER than Stoich, <14.68) (Lean = numerically HIGHER than Stoich, >14.68) Rich = 10:1, Stoich = 14.68:1 and 10 is numerically lower than 14.68 so since 10 < 14.68 then rich is numerically lower then stoich correct? Quote Link to comment Share on other sites More sharing options...
Krambo Posted March 25, 2009 Report Share Posted March 25, 2009 YES! What the &$^* I swear I typed it correct. Good lord! Is someone messing with me??? Other Mods??? Quote Link to comment Share on other sites More sharing options...
SRT10KLLR Posted March 25, 2009 Report Share Posted March 25, 2009 Stop drinking during the day unless of course you are going to share, lol. :cheers: :cheers: Quote Link to comment Share on other sites More sharing options...
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