General Fuel Trims

[xdime00]

Ok, i just started tuning with my logger and SAFC and am kinda confused. I have a 1g, using the pocketlogger software. My fuel trims are 139% across the board. From what ive gathered im quite lean, but im not getting knock. Ive been tuning for knock and timing, is it ok to have these fuel trims as long as knock and timing is ok? (mods: 2g maft, 550's, 3" tubro back, 16psi on 14b)

 

[tpi_roc]

"Ok" is relative. What it means is the ECU has "learned" your condition and is compensating, however now that you're pretty far into the positive fuel trims you have less resolution for correction on a cold day etc. Not to mention when you reset your ECU it will have to relearn again, those are the downfalls of not having correct trims.

So technically its currently "ok" but it might not be tomorrow given any condition changes. Thats why EFI tuning aims for fuel trims closer to home.


Hope that helps

 

[DSMtuned]

Ok, i just started tuning with my logger and SAFC and am kinda confused. I have a 1g, using the pocketlogger software. My fuel trims are 139% across the board. From what ive gathered im quite lean, but im not getting knock. Ive been tuning for knock and timing, is it ok to have these fuel trims as long as knock and timing is ok? (mods: 2g maft, 550's, 3" tubro back, 16psi on 14b)

Fuel trims are for part throttle tuning and will have nothing to do with knock. I try to keep mine around 110% for the best fuel mileage. Set-up your logger so that you can read O2 trim, Hi, low fuel trims, and airflow hz.

Low= 0-125hz of airflow
Mid= 125-175hz
Hi= 175-300hz

Drive around in like 2nd and 3rd and try to keep your air flow in each of those ranges. You can then look at your O2 trims, which are basically the current reading of the fuel trims. The longer the O2 trim is centered around 139% at like 200hz, the more likey it is that your Hi fuel trim will go up toward 139% You got me?

Since it doesn't sound like you have an SAFC, you can't adjust fuel at certain RPM ranges. You will want to do an intake leak test and check all of your vaccuum lines to make sure they are connected. Also if your MAS is hacked, your fuel trims will reflect that.

Good luck!

 

[ITSME4G63]

I have the same fuel trims as you do 139%, cant figure the shit out.

 

[KeltonDSMer]

Add fuel across the board and then drive around for a while and keep the car in those airflow ranges for a while, (1G ECUs take a while to change the fuel trims). The longer you drive around at those airflows, the better the ECU will re-adjust the fuel trims.

Try to get them to 100% which means the computer doesn't have to add or take away fuel to reach the desired conditions.

 

[kpt4321]

My fuel trims are 139% across the board...is it ok to have these fuel trims as long as knock and timing is ok? (mods: 2g maft, 550's, 3" tubro back, 16psi on 14b)

When you tune, you use fuel trims to get the car working properly at idle and cruise, an you use knock and timing at full throttle.

Use the fuel trims to set up the low throttle map on the SAFC.

Read this:

http://www.dsmtuners.com/forums/showthread.php?t=111005

(and you will end up here: http://www.dsmtuners.com/forums/showthread.php?s=&threadid=58403)