Still learning the in's and out's of tuning. Decide to adjust the timing alil. Did an overall trim decrease of 4% so if it was 35° its dropped to 32.8°. I was under the impression that less timing would lead to a richer combustion. AFRs increased in the cruise range (light load 3k ish rpm) stayed about the same every where else. Whats the deal the deal?

Also with stock injectors and 8.5 psi of boost, whats the staging you guys would recommend? Primary or common mode. How much boost can the primaries typically handle?

This is a Jspec s5 motor. Everything stock.

 

Now you see why an O2 sensor is not the absolute answer for tuning. Your AFR by mass has not changed only the reading on the gauge. Since the sensor is only looking for unused oxygen, when it reads leaner, without an actual change to AFR by mass, its telling you there is more oxygen left in the exhaust stream. This means fewer fuel molecules have combined with oxygen molecules to be burned and generally means less efficient combustion. At what load and rpm was the reading taken?

Probably try to stage them around 3 PSI or so. Don't want staging so low that you hit it under normal cruising speeds and loads. With stock injectors I would be tempted to fire all four of them all the time and eliminate the need to stage them. Just a thought.

Common mode allows you to extract max duty cycle from the primaries with less thought going into the setup. Primary hold is generally easier to get clean staging transition. Imo neither is head and shoulders better. Only different.

 

Readings were taken primarliy in light load between -5.0 and .5 psi around 3k-3.3k. I found that area had the biggest change. Pretty much the whole map was less efficient. I lost about 1.1 psi of vacuum at idle.

I might try that all 4 injector thing. The throttle transition thing is a big pain in the butt to tune. Any time I blip the throttle it drops rpm either from leaning out or over enrichment.

Also I noticed in my NA motor that if the secondaries weren't used much over a period of time(several months) they would become sticky. Granted they were never professionally cleaned, just used Gumout(which works surprisingly well).

 

so when you change timeing it can change the reading that the wideband gets but the afr isnt actuly changing?

 

Yes. The wideband only reads oxygen. It doesn't actually read air mass/fuel mass.

 

hence why its called an O2 or (oxygen) sensor.

 

how much can it change?

 

It depends. Mine changed by a full unit. It drove like it too. Less power and sputtering all over the place.

 

i would not mess with a timing map unless you know what you are doing. a fuel map is a little more forgiving.