We dont check emissions here (yet) and I am thinking about grounding the O2 input to the DME and putting in the coding plug to use the ROW fuel maps. If I do this and adj the AFM mixture(screw and spring) to read about .8v at the O2 sensor and by reading the plugs(like us old school tuners do) do you think the Cat would be OK. As long as I just run a hair rich.
BTW...anyone done this and pass emissions?

 

Uh, what are you trying to accomplish?

"adj the AFM mixture(screw and spring) to read about .8v at the O2 sensor"

You need more accuracy than that. A reading of 0.8_v on the O2-sensor could be anything from 9.0:1 to 14.0:1 air-fuel ratios depending upon exhaust temperature. Aim for 0.86-0.88v under full-throttle conditions. Anything outside of this range will not be optimal and you need to maintain this value across the entire RPM-range.

"As long as I just run a hair rich."

When dealing with these types of adjustments, it's best not to use black&white, all-or-nothing qualitative statements, but rather rely on shades-of-grey quantitative values (meaning numbers). Only with numbers can you answer the following important questions which will really determine the safety of your mod:

- Exactly how much richer will you be running percentage-wise?
- And is this across all RPM ranges?
- If not, what does the shape of the air-fuel ratio look like?

Here are some more numbers to review:

<img src="http://www.gururacing.net/ImagesMisc/TurboPartThrotFuelCompare.gif" alt=" - " />

As you can see, the ROW fuel-map is pretty much 5% leaner under ALL operating conditions compared to the USA map (except at the very high-end). At the fully WOT operating range, all the fuel-maps are identical:

<img src="http://www.gururacing.net/ImagesMisc/TurboWOTfuelCompare.gif" alt=" - " />

Now the assumption that the fuel mixture will be rich just because you remove the O2-sensor is not correct. It will just remove O2-sensor feedback from making corrections in your last-used fuel-value. The straight pre-programmed values will be used off the chips. Whether or not this results in a rich or lean mixture depends upon the chip maps. If you are using the USA map, you'll probably be rich. If you're using the ROW or Sweden/Swiss maps, you'll most likely be very close to a stochio. misture. If you've made air-flow increasing mods like increasing boost, intakes & exhaust, then you'll be lean using ANY of the maps.

That's why keeping the O2-sensor feedback is critical to obtaining an optimal air-fuel mixture. The fuel-value is computed on a running-total basis, like the DOW-average. The last value is compared to the O2-sensor feedback. If it's rich, a certain percentage is removed. If it's lean, a little more fuel is added. Then with the next O2-sensor sampling, this fuel-value is adjusted once again.

A lot of the newer EFI systems (aftermarket and stock) are using closed-loop operation with O2-sensor feedback 100% of the time! Rather than having esoteric millisecond pulse-widths or correction-percentages in their fuel-maps, they use an air-fuel ratio target map. At some operating ranges such as low-throttle/freeway crusing, the target may be a 16:1 air-fuel ratio. In the mid-range, it may be 14:1. Anything with positive manifold pressure will be 12:1 and full-throttle will increase fuel to 11:1. The feedback is so fast, with adjustments made instantly, that the LED air-fuel displays never dithers! You see it move from 16:1 to 14:1 to 12:1 to 11:1 and stays rock steady the whole time. That's because the dithering range is smaller than the resolution of a single LED!

 

Thanks Danno...You will see in my other posts that I have a part throttle hesitation issue that I cant seem to nail down. I just pressurised my intake and found a slight leak at the cycling valve and I also backflushed my injectors and replaced the seals. Ive replaced the TPS,BOV,O2 sensor, cleaned the AFM, cleaned all grounds and connections. The hesitation is less pronounced with the O2 sensor disconnected.
I'm just trying other things until I pull the intake and replace the hoses.
I noticed with the DVM exactly what you said. I drove around with a DVM connected to the O2 sensor and the ROW maps read .75 v but would drop as I slightly lift the throttle, while the USA map, with no O2 sensor would read .82 volts and pretty steady except at WFO (.84v) or closed throttle (0v)
I also noticed, when reading plugs, that my 2 inner cyl are running leaner than the outer 2. I switched injectors to see if the leaness goes with the injectors.

 

" when reading plugs, that my 2 inner cyl are running leaner than the outer 2. I switched injectors to see if the leaness goes with the injectors."

If this is the symptom that you're trying to diagnose, then a flow test of the injectors is what you want to do.

 

No one around here will flow check injectors, but swapping from once cyl to another and looking for the symptom to follow the injector is a viable troubleshooting technique. Anyway, it does look like it stayed with the inner cyl. The inner cyls are running a touch leaner than the outer 2. I read where you had stated that the injectors all use the same driver. Is there any way that the inner 2 injectors could be recieving a lower duty cycle than the outer 2?

 

All the injectors are fired simultaneously using the same driver-transistor. Even though their wires are paired 1&2 and 3&4. If it was a DME or wiring problem, you would see symptoms with that pairing, not the 2&3 that you're seeing.

Could it be something else that you're seeing? With modern electronics plug-reading is almost worthless because the fuel-control is so consistent. Could it be oil-fouling that you're picking up? Try some brand-new plugs. Also do a compression & leakdown test.

RC-Engineering can do injector cleaning, flow-testing and balancing with a 2-day turnaround.

 

Thanks Danno,
The plugs look great as far as oil fouling. I'm a pretty good motorcycle tuner, tuning MX 2 strokes and multi carb sportbikes. I can jet a set of carbs by plug chop readings and seat of the pants 'feel' so the dyno will barely show a needle/jetting transition at all with no flat spots <img border="0" title="" alt="[Wink]" src="wink.gif" /> This may just be a vac leak I have yet to find. Or perhaps, the leak at the Cycling valve is causing the problem. Its funny...the hesitation always shows up with over 60% throttle and as it reaches about .2 bar boost...right where the cycling valve is suppose to be energised...It will be interesting to see what happens if I plumb the ReliaBoost directly to the wastegate and disconnect the cycling valve.