What are LTFT's?
04-02-2009, 12:08 PM
#1
TECH Resident
Thread Starter
iTrader: (2)
Join Date: Mar 2007
Posts: 751
Likes: 0
Received 0 Likes
on
0 Posts
What are LTFT's? I know they are long term fuel trims, but what do the % numbers i see on my scanner mean? and what should they be?
I have an 02 trans am ls1 in my el camino, and its still all stock except free flowing dual exhaust. My LTFT's are 8.xxx% and 9.xxx%, is this ok?
I ask because i have recently been getting 15 mpg, my daily route has changed from highway to big city downtown stop and go, i realize this is a major factor.
Thanks guys.
I have an 02 trans am ls1 in my el camino, and its still all stock except free flowing dual exhaust. My LTFT's are 8.xxx% and 9.xxx%, is this ok?
I ask because i have recently been getting 15 mpg, my daily route has changed from highway to big city downtown stop and go, i realize this is a major factor.
Thanks guys.
04-02-2009, 04:56 PM
#2
TECH Regular
The %'s are how much fueling your car is adjusting for so 8% means it's getting that 8% more fueling for that bank. Idealy you want them to be 0's but it's not possible so you aim for the + or - 5 range. Keep in mind though when you have positive numbers that gets added to your PE fueling tables so it may make you rich at WOT. I aim for negative values in that 5 range.
04-02-2009, 05:53 PM
#3
LS1Tech Sponsor
those ltft's are high... you want to get your fueling adjusted so that they are in the 0 to -2 range, then you'll be golden...
__________________
06MonteSS / DiabLew Tune
2014 Camaro 2SS/RS - LS3, 6-speed manual, short-throw performance shifter, NPP dual-mode performance exhaust, 1LE front splitter, ZL1 rockers, Z28 Rear Spoiler, all paint-matched Red Rock Metallic, BMR strut tower brace, Cold Air Inductions cold air intake, Apex Motorsports, Inc. catch-can, Custom DiabLew Tune
www.diablewtune.com -- www.diablocustomtune.com -- www.diablocustomtunegm.com
06MonteSS / DiabLew Tune
2014 Camaro 2SS/RS - LS3, 6-speed manual, short-throw performance shifter, NPP dual-mode performance exhaust, 1LE front splitter, ZL1 rockers, Z28 Rear Spoiler, all paint-matched Red Rock Metallic, BMR strut tower brace, Cold Air Inductions cold air intake, Apex Motorsports, Inc. catch-can, Custom DiabLew Tune
www.diablewtune.com -- www.diablocustomtune.com -- www.diablocustomtunegm.com
04-02-2009, 08:55 PM
#4
TECH Resident
Thread Starter
iTrader: (2)
Join Date: Mar 2007
Posts: 751
Likes: 0
Received 0 Likes
on
0 Posts
I dont have access to any tuning tools, so other than tuning it, is there any reason stock ltft's would be high?
It was tuned by wait4me for the swap, but could vacum leaks or other problems cause this?
It was tuned by wait4me for the swap, but could vacum leaks or other problems cause this?
04-02-2009, 09:11 PM
#5
LS1Tech Sponsor
yes... vacuum leak, intake leak, exhaust leak...
if it was tuned by Wait4Me, it should be good as gold and all dialed in... so those LTFT numbers tell me that there's an air leak somewhere now...
if it was tuned by Wait4Me, it should be good as gold and all dialed in... so those LTFT numbers tell me that there's an air leak somewhere now...
__________________
06MonteSS / DiabLew Tune
2014 Camaro 2SS/RS - LS3, 6-speed manual, short-throw performance shifter, NPP dual-mode performance exhaust, 1LE front splitter, ZL1 rockers, Z28 Rear Spoiler, all paint-matched Red Rock Metallic, BMR strut tower brace, Cold Air Inductions cold air intake, Apex Motorsports, Inc. catch-can, Custom DiabLew Tune
www.diablewtune.com -- www.diablocustomtune.com -- www.diablocustomtunegm.com
06MonteSS / DiabLew Tune
2014 Camaro 2SS/RS - LS3, 6-speed manual, short-throw performance shifter, NPP dual-mode performance exhaust, 1LE front splitter, ZL1 rockers, Z28 Rear Spoiler, all paint-matched Red Rock Metallic, BMR strut tower brace, Cold Air Inductions cold air intake, Apex Motorsports, Inc. catch-can, Custom DiabLew Tune
www.diablewtune.com -- www.diablocustomtune.com -- www.diablocustomtunegm.com
04-02-2009, 11:02 PM
#7
TECH Regular
It doesn't mean for sure there is a air leak. 8-9% isn't a huge deal IMO. You will notice normal fluxuations of about 3-4%. Thats why you try for + or - 5 because those values change constantly. I think your fine, your tuner can only do so much with the time he has it, the only way to get the LTFT's completely dialed in is multipule runs in different conditions.
There are too many things other then an vacuum leak to consider, dirty air filter, car running a little hotter, ect. You would get a code if you had a decent size leak in your intake.
I take logs in my car and they are different every time, you have to have some kind of error range, your pcm has formulas to compensate for weather and pressure changes but it isn't perfect hence the changes in LTFT's.
There are too many things other then an vacuum leak to consider, dirty air filter, car running a little hotter, ect. You would get a code if you had a decent size leak in your intake.
I take logs in my car and they are different every time, you have to have some kind of error range, your pcm has formulas to compensate for weather and pressure changes but it isn't perfect hence the changes in LTFT's.
