Fuel Trim?

[LinuxRacr]

Ok, can someone explain what Fuel Trim is and what the purpose of it in modern Fuel Injection is?

 

[DBR]

i surf several sites and found this post. i assume "fuel trim" refers to the ECU marginally adjusting the amount of fuel to keep the air/fuel ratio where it should be:

http://www.hyundaiaftermarket.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=16;t=001559

 

[LinuxRacr]

That was very informative. Thanks!

 

[70]

I think the Protege has short term and long term fuel trim...

I'm trying to remember what all I was looking while I went on that ride with Ken at FM in the Miata they were setting up with the Link.

Oh well.

 

[LinuxRacr]

I think the Protege has short term and long term fuel trim...

I'm trying to remember what all I was looking while I went on that ride with Ken at FM in the Miata they were setting up with the Link.

Oh well.

This is correct! Both are measured on on my PDA Dyno.

 

[nobody]

basically u want to have close to zero fuel trim, both long & short term. When there's fuel trim, the ECU is trimming or adding fuel....a few % is fine..no more than 5%...

 

[Keith@FP]

When the ECU is in closed-loop operation, it's adjusting the fuel delivery according to what's being returned from the sensors. Short term trim is just that - short term adjustments. I believe the range is -30% to +25% on the Protege. That's what causes headaches for people trying to throw more fuel in to compensate for forced induction. The changes are not stored, but are transient.

Long-term trim is done over, well, a long term. If the signals from the sensors show consistent correction is necessary, the ECU will add a certain amount of trim to its starting point. This can be removed by resetting the ECU.

Keith