Disabled O2 sensor in functions (PFC) - affects fuel economy?
 

I have removed the Air Control Valve (ACV) and Airpump on my Mazda RX-7 FD (1992).

My engine is newly overhauled and streetported, I did all of the R&R myself and got a local rotary specialist to do the overhaul and porting.

So, the first time I got the car running I had issues with the idle. I found a few pointers online and reset and got it improved by disabling IDLE-IG CONTROL and O2 F/B CONTROL and tuning the Air Bleed Valve.

The F.C values in Rev/Idle settings where set to 1500 RPM and A.E = 850, E/L set to 900 and A/C set to 1000.

I did not do the 3x10 minutes procedure and want to reset the PFC and try again.

Here is my issues/questions:

From the Apexi PowerFC FAQ website:
"If you have 0/2 Feedback turned off the PowerFC will not enter its closed loop feedback mode and will waste fuel and be very un-economical. Expect bad fuel economy"

1. Is this true for the RX-7? Suggestions I found elsewhere was that the O/2 Feedback should be disabled if you have removed the airpump.

2. Turning on the A/C button (I have removed the A/C from the car) forces the fans on and makes the car keep a steady 84 degrees (celcius) which is pretty good. But when I do this, the idle RMP goes up towards 1500 RPM. When I don't have the A/C button on, the engine reaches 95 degrees and the fans turns on.
The FC-Datalogit is shipping to me now and I will configure it to turn the fans on at 87 degrees. Is there anything else that happens when I turn the A/C button on?

3. A.E, E/L and A/C idle, does A/C that mean AirCon RPM? What does the other two mean?

4. I'm currently driving in the new engine and using the basemap (as I don't have the Datalogit yet), should I continue to do this when I receive the Datalogit?
Should I try to get a finished map that is close to my setup? Where can I get/generate one?

My setup:
JDM 1992 FD
Streetported (one new rotorhouse + rotor)
Modifications: A/C Removed, Airpump Removed, Emission Removal, Seq. Turbos Simplification.
Parts: HKS 3" downpipe, Greddy FMIC, Aluminium AST, APEXi Super Intake, Efini Y-Pipe Tube Kit, PLX AFR Wideband sensor

(The Y-pipe and AFR should arrive soon)

Thanks in advance,
Sondre

you need to do the 3x10 mins idle tune... seriously.
do all the adj prior to doing that tune

and yes, no o2 will give u "bad" fuel economy

slpin, thanks for the response. I'm receiving PLX AFR, Efini Y-Pipe Tube Kit and APEXi Super Intake and FC-Datalogit tomorrow and will install these mods before I do another idle tune.

Configured idle revs to be 3x1500 and 3x1100 which seems to be required due to the streetport.

Might wait with all of these until the engine is fully driven in, I've completed 555km so far and need another 445 km before I can start driving it like it should be driven.

disabling o2 will not give you "bad" fuel economy if you go in and tune the cruise areas...in fact, you will end up with better fuel econ and smoother operation by doing this.

(1) +1, you can actually tune and get better mileage than stock ever got.
14.7 stoich AFR is only optimum for emissions. About 16.5 AFR is best for mileage.
(2) If using the ISC, the revs should increase to the higher idle setuped for A/C.
(3) no load, electrical load, A/C load: these are the three for you to figure out.
(4) any map is good for brake-in and low boost. Contact Steve Kan.

notice the quotes when i said bad.....

When it comes to science, slang is not appropriate as it's meaning is not guaranteed

Actually, you'll get identical fuel economy with the O2 feedback on or off. I have been running my car with the O2 feedback disabled for quite some time now - I get about 18-19 city, 21ish highway, just the same I got with the O2 sensor enabled.

This is one of those things that's easy to test - prove it to yourself.

BTW, this is on the base map, no tuning done in the cruise areas or anything.

Dale

Even with O2 feedback on, mine doesn't seem to ever enter closed loop (watching the wide band AF meter).

Mark