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Discussion Starter · #1 ·
So many of you have used turbos on your OBDI systems. (Am I correct in assuming the 91-96's are OBDI) So there isn't a post cat O2 sensor. After speaking with an engine specialist about my setup and showing him the turbo he voiced 2 concerns:

1) The VJ-11 has a very small exhaust port as compared to the diameter of the Manifold and the post cat piping. He is concerned this will be very restrictive and that the car won't run well

2) The ECU uses the post cat 02 sensor to calibrate the fuel system. If running a turbo even with a CAT he said that it will immediately sense that the system is running way off and will default into a "limp home" state where the engine will be running in a very basic non optimal way. How did you guys get around this?

Anyone have any feel on these topics, also there are 2 power and 2 o2 sensor wires. Which one of the o2 wires do you hook to for your A/F guage? Does it matter?

Thanks,
Tim
 

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couple options:
option one:put a o2 sensor after the cat or just place another o2 sensor..
option two:wire the sensors together?
option three: standalone(megasquirt)


2 of the wires are for the heater core(heated o2 sensor HEGO)
the other 2... one is pwer and one is signal. im not sure which is which but you could splice both of them and find out... i think its the gray wire coming off the actual sensor
 

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tokstad said:
1) The VJ-11 has a very small exhaust port as compared to the diameter of the Manifold and the post cat piping. He is concerned this will be very restrictive and that the car won't run well

2) The ECU uses the post cat 02 sensor to calibrate the fuel system. If running a turbo even with a CAT he said that it will immediately sense that the system is running way off and will default into a "limp home" state where the engine will be running in a very basic non optimal way. How did you guys get around this?

Anyone have any feel on these topics, also there are 2 power and 2 o2 sensor wires. Which one of the o2 wires do you hook to for your A/F guage? Does it matter?

Thanks,
Tim
1) What manifold are you talking about?
Ask him this: if a 2.2 150hp Mazda motor run's just fine with that turbo, then why wont a 2.0 110hp motor?

2) The first main O2 sensor is used to trim the AFR (air fuel ratios) in closed loop mode. The second O2 sensor is just there to make sure the cat is there, if it senses a problem it will trip the CEL, but there is no reason for limp mode with the 2nd bank O2 reading being off, maybe the first bank main, but not the second. On my 96lx (OBD2) I have removed the Cat, and just reinstalled the #2 sensor back in the pipe, so far it does'nt seen to care and it's been over a year.
As long as you dont change the injector size to drasticly, and make up for the added injector flow by decreasing the fuel pressure, the computer wont know the difference.
If all that fail's just get a custom chip or SCT package.
 

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Discussion Starter · #5 ·
Mine is an ODBII so I will have one after the cat, that isn't the concern, the concern is that the reading that it will give back to the ECU from both sensors will send the system into "limp home" mode.

Is anyone out there running a 3rd gen turbo? What did you do if anything to get the ECU to run correctly, I was thinking that with a cat and both 02 sensors the system would run correctly but the engine/FI specialist seems to think otherwise?
 

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tokstad said:
Mine is an ODBII so I will have one after the cat, that isn't the concern, the concern is that the reading that it will give back to the ECU from both sensors will send the system into "limp home" mode.

Is anyone out there running a 3rd gen turbo? What did you do if anything to get the ECU to run correctly, I was thinking that with a cat and both 02 sensors the system would run correctly but the engine/FI specialist seems to think otherwise?
Like I said, my OBD2 is fine with out a cat, it's been that way for over a year.
There are no turbo OBD2's, well there has been 2 that I can think of, but one is from a very long time ago and I never spoke to him, and the other never made it out of the drive way.

I think your "FI specialist" is making you worry too much. Just how many OBD2 Ford's has he turbo'd?
I would think, that with a good tune, and a cat with the #2 sensor behind it just like stock, you'll be fine.
Worst case is you''ll need a cutstom chip.
 
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