JonGTR

You may cause the fuel trims to adjust without an O2 sensor, but I would think the timing would retard, therefore negating any gains from fuel.



If you could do both with a good ECU, I could see gaining 20whp using race fuel and aggressive timing.

i8acobra

The fuel trims shouldn't adjust without an O2 sensor. The ECM only adjusts fuel trims in closed loop, which requires an O2 or AFR sensor. Usually, the ECM will simply fault to open-loop and refer to the standard tables.



I agree though that a 10% gain with a proper ECM and fuel isn't out of the ordinary.

2000J25SP

Thanks for the info and advice, I really appreciate it.



I'm picking up the Apexi this weekend. It'd be cool if I find a good deal on a better setup, but until then I'll make do with what I have.



I wasn't really planning on tuning closed loop fuel trims for this reason. But since were all here, I guess I'll ask you this:



Forgive my noobishness. But what kind of time frame/run time/mileage did it take before the ecu started adjusting the fuel trim? Or was it almost immediately? The reason I ask is because my work commute is less than 5 miles and 95% of the time I drive less than 10 miles/minutes at a time. (have a Buick for a road trip car) I'm wondering about installing an interior mounted ecu reset switch and resetting it before or after every drive. That way I could tune it and drive it while the ECU is always in the same state of mind. ?

i8acobra

I considered it as a temporary workaround but decided against it because doing that would reset everything, not just the fuel trims. Emissions drive cycles, timing tables, etc... Plus, from the moment you start the car, the ECM is trying to compensate. Any time the car is in closed loop, it would see your AFR as rich or lean and adjust the trims.

Juanra

On a 2.0L Beta swapped X3 with 1.8L pistons, two exhaust cams and all other basic NA mods. I used a 1997 1.8L ECU, out any O2 sensors and a Apex NEO, I gained 7 HP and a about 6 of MPG when cruising.

2000J25SP

Awesome, what kind of peak power did it make?

2000J25SP

Installed it today. It took two hours, half of that was trying to figure out why it wouldn't turn on. Turns out the wiring harness connector just came loose from the circuit board inside the device. It also turned out to be an safc-1 not safc-2, it's probably almost as old as the car lol.

blitz

Brother, don't waste your time with it ! Save money for SMT-8 , cause for N/A project it's more than enough.



I know that you are curious to see what you can achieve with it , but some of us have already been there.



Here is my dyno sheet and you can see the difference before and after we played with the Apexi Neo

Tibbi

At the price he's getting it it'd be better to just buy it then sell on ebay at a profit.

2000J25SP

I installed the SAFC and AEM wideband. Did a baseline pull today, no safc adjustments. The 1.8 ecu runs leaner than I thought it would. This is with the stock head and bolt-ons. Still need to get the Beta2 head shaved and put it back together.



4000 13.6

4250 13.4

4500 13.4

4750 13.3

5000 13.1

5250 12.9

5500 12.7

5750 12.3

6000 11.6

6250 11.3

6500 11.3



Next week I will probably install the 2.0 ecu so I can compare the AFR vs RPM graph with the 1.8 ecu, just for the hell of it. I made a couple runs, they were both within .2 of each other at the same rpm.