Fuel Trims - Long term and short term
 

Hi Forum Members,

I would like to ask help, inputs and opinions regarding our 86 stock ECU trims, air/fuel mixture and adaptation.

In my other cars, short term fuel trims greatly varies but long term stays put. In the 86, the long term varies a lot...why is this?

My car is stock with just an axle back greddy sp elite. Milage is 1,550kms, Manual. I checked and monitored the following data:

Idle 1,500rpm 2,500rpm
Short term fuel trims -1% to +3% -4% to +4% -6% to +3
Long term fuel trims -2% to +3% -4% to +6% -3% to +1
ignition advance +12 deg +18% +42 deg
Coolant temp 190'F-205'F

Octane is 100. Its called blaze here in the Philippines. Its without ethanol and uses organic additives as a substitute to ethanol. (i believe it sugar cane alcohol instead of corn?). Using this fuel is a good sign? as my ignition is on an increasing pace?

I think the car mostly runs on the rich side with light to moderate loads say -6% to +3% longterm and short term trims.

I will be installing a drop in HKS filter soon and I hope the ECU leans out a bit in order to generate more power =)

:search:

http://www.ft86club.com/forums/showt...ght=fuel+trims

http://www.ft86club.com/forums/showt...ght=fuel+trims

Which method is used to get the 100 Octane number? (R+M)/2 or RON?
BTW, sugar cane alcohol is mostly ethanol.

At any rate, based on the other threads it's looking like the twins may have a poor tune from the factory, much like older Subarus I've read about.

you running ecutek?

Ha Ha,

Yeah, I posted this thread a while ago. There are a few reasons.

1. There are 4 different long term trim bins that will be used depending on the maf reading so some of what you are seeing is the reading going from one long term trim bin to another

2. Stock Ecu holds closed loop for a relatively long time (so, slow transition to open loop)

3. Stock maf scaling seems to be crap for most cars crap

Its RON. I am only thinking they used sugar cane alcohol because it said 'no ethanol, with organic additives'

Lets see when I install the HKS drop in. hope to see improvements

Organic additives could be considered things like benzene, toluene, xylene, etc., which they pretty much have to be using if they aren't adding ethanol.

Good luck with the filter! You may need a custom tune to really have a smooth running car, though.