View Full Version : Tune question

07-27-2013, 11:58 PM
Am getting everything needed to get my car tune pretty soon but my question is
Do I have to run the stock twin o2 oxygen sensors ( motor is a Rb26 with a single turbo conversion) or I can I just purchase a aem Wideband
Tuning car with apexi l jetro

If anyone can help out with some info

07-28-2013, 12:33 AM
You can wire the AEM wideband to be used as a regular o2 sensor. But regardless buy the wideband.

07-28-2013, 10:22 AM
You can wire the AEM wideband to be used as a regular o2 sensor. But regardless buy the wideband.

not on a pfc

07-28-2013, 07:13 PM
You can turn off the o2 feedback in the PFC so you don't need the stock o2 sensor.

07-28-2013, 09:26 PM
Cool man thanks

So in the pfc I can just turn of the o2 sensors and run off my aem Wideband what else do you recommend bro

Got Insulin?
07-28-2013, 09:52 PM
Does the PFC allow you to simulate the stock o2s in not running them?

07-28-2013, 10:44 PM
I don't think you can run the aem wideband off the power fc. You can run an Innovate wideband but you need the datalogit box. Your aem wideband is just for reference for you to look at and see your afr's it doesn't connect and give information to the power fc. Your stock o2 sensor is what will "talk" with the pfc and adjust afr's. You can turn o2 feedback on and off. With it on, when cruising at light throttle/load your air fuel ratio is controlled by the o2 sensor; so when going uphill at low rpm but lots of load or full throttle it doesn't do anything. You don't need an o2 sensor, but your gas mileage will suffer. Most people get tuned for max, safe power so the o2 sensor helps increase mileage. You could spend alot of time tuning for cruising and low throttle scenarios so you could do without the o2 sensor and turn feedback off. This way your going completely off the values in the fuel map.

This is basically what I understand about all of it from my researching. I just added an o2 sensor and turned feedback on, I can see my afrs around 14.7 at cruising where before they were a bit lower.

07-28-2013, 10:53 PM
To turn feedback on and off select ETC then FUNCTION SELECT, on and off are japanese characters, the one that looks like it has a plus sign (+) is off. Check out "Basic Hand Controller functions and use - Checking Functions" here for more info: Apexi PowerFC FAQ (http://www.paulr33.com/powerfc-faq/powerfc-faq.htm#40b)

This whole page is pretty useful for power fc information

07-29-2013, 10:41 PM
I'm pretty sure AEM has a 5v narrow band output. So theoretically, you can splice that 5v signal into o2 sensor signal into the ECU.

But at the same time, when you tune with a PFC, most tuners usually kill the stock o2 feedback and basically tune with just the wideband. Only reason you'd turn it back on so you can get better gas mileage for your partial throttle.

Or you can leave it off, lean out your light throttle AFRs using your wideband.

(Just read JMAX's reply...same thing).

08-04-2013, 05:46 PM
I have an AEM wideband plugged into my datalogit for my power FC. It logs air fuels into the laptop so I can see and adjust after I am done driving and safe in sitting down.

If you know how to tune an engine, you do not need a narrowband for most cars. You dont even want one most of the time. Your high vacuum situations may benefit from 15:1 air fuels for best fuel economy. If the engine is capable of removing heat easily (high quality cooling system and cold spark plugs) I will shoot for 15.3:1 during open loop cruise. Timing is usually between 31-35*. I find SR20 do not enjoy high timing until after 3000rpm and the peak during cruise is usually best around 32*. Recently I have been trying different things and have found no increase in fuel economy when using more than 32* total advance on a truly built up SR20 with lightweight internals. The weight of the rotating assembly will affect your timing numbers.


The power FC (with datalogit) has the ability to decide when to use the narrowband, if you so desire. You can set up the INJ map to only use the narrowband during certain situations, such as very high RPM cruising when the transient delay is low for O2 feedback and you do not want to risk a high Air fuel ratio, but at the same time, do not want it to be too rich. Something like a 110MPH cruise for instance. Most SR20s will be in a low vacuum situation and open loop; however, going down hill, decelerating, you might hit 15-18" vacuum. It would be safe at 4400rpm and 17" of vacuum to enable closed loop off your narrowband with 28-30* of ignition timing in most SR20 cars that weight 3000lbs or less. And it might help keep the engine from getting a lean tip in during part throttle acceleration if the driver decides to get back into boost, since most people do not tune the acceleration enrichment at those RPMS any if at all. However, If the spark plug gap is poor (small for no good reason other than "they told me to") then the air fuel cannot be trusted coming off the wideband during many situations anyways and tuning should be done based on recorded injector on-times from lower RPMs at similar volumetric efficiencies where complete burning is expected to occur. To verify, use plugs with a wide gap that are brand new after you are finished tuning your part throttle situations and check to see that the air fuel does not move. Also manipulate the engine load using the E-brake and A/C clutch to get a better understanding of what the engine seems to want.