14 replies to this topic

[WilsonSteele]

I am in the midst of the AFR system install, and have read most of hte posts I could find on this topic.  I am putting in the Innovate LC-1 system, bought as a package from weekend-racer.com

 

I am debating:

 

-Weld on the bung, have a second O2 sensor right next to the stock one, leave all stock wiring and ECU signals alone

or

-Remove stock sensor, put wideband O2 sensor in the single stock hole, and run a line from the aftermarket gauge to the Mazda ECU.

 

I think that it is silly to have 2 O2 sensors on a car, but part of me remembers stories about people "cheating" by putting resistors in line with the O2 sensor, and running them through the heater controls or something to lean/richen at will.

    But at the smae time, if we can mechanically adjust rich/lean with our adjustable fuel pressure, is it really still considered illegal to adjust rich/lean electrically, with a programable signal from an aftermarket system?

 

    Or, are all the people correct about the ECU running in open loop mode during racing, and the stock O2 signal not being important.  But, and I overthink things here, part throttle performace (corner exit) would be a great place to improve power/response, even if full throttle power isn't changed by what the ECU does with the O2 reading.

 

So, keep stock O2 sensor, weld in the bung and have two, or ditch the stock one and feed the ECU off the aftermarket output?

 

 

[Caveman-kwebb99]

il-legal to run the inovate into the ecu, we all have a second O2 welded elswhere in the exhaust...

[Bench Racer]

Is there a rule that allows removal of the OEM 02 sensor?

[Caveman-kwebb99]

Is there a rule that allows removal of the OEM 02 sensor?

 

not that I know of, although we really dont need it...

[WilsonSteele]

I found 50/50 opinions on whether to have 2 O2 sensors or not in other threads.

I know that it would technically be illegal to remove the stock input to the ECU, but if I can mechanically tune AFR, with the adjustable fuel pressure, is it really illegal to electronically tune AFR?

I believe that it is well within the spirit of the rules to have one O2 sensor, and feed the ECU that adjustable signal.

 

Or, maybe I should ask, what could I do with the aftermarket / adjustable signal to the ECU, that I couldn't do with adjustable fuel pressure?

[SaulSpeedwell]

I am in the midst of the AFR system install, and have read most of hte posts I could find on this topic.  I am putting in the Innovate LC-1 system, bought as a package from weekend-racer.com

 

I am debating:

 

-Weld on the bung, have a second O2 sensor right next to the stock one, leave all stock wiring and ECU signals alone

or

-Remove stock sensor, put wideband O2 sensor in the single stock hole, and run a line from the aftermarket gauge to the Mazda ECU.

 

I think that it is silly to have 2 O2 sensors on a car, but part of me remembers stories about people "cheating" by putting resistors in line with the O2 sensor, and running them through the heater controls or something to lean/richen at will.

    But at the smae time, if we can mechanically adjust rich/lean with our adjustable fuel pressure, is it really still considered illegal to adjust rich/lean electrically, with a programable signal from an aftermarket system?

 

    Or, are all the people correct about the ECU running in open loop mode during racing, and the stock O2 signal not being important.  But, and I overthink things here, part throttle performace (corner exit) would be a great place to improve power/response, even if full throttle power isn't changed by what the ECU does with the O2 reading.

 

So, keep stock O2 sensor, weld in the bung and have two, or ditch the stock one and feed the ECU off the aftermarket output?

 

02 sensors (whether binary or wideband) degrade relatively quickly, are not very trustworthy from a controls engineer's standpoint, and are designed to fail by giving falsely LEAN readings (causing the ECU to run falsely rich).  Virtually every car from the 1980s through 2005 will use the 02s for little more than "cruise" mixture and throwing emissions codes.  I've had several cars that would give about 1 mpg back with a new O2, which made it worth replacing them semi-frequently.  (And thus, somewhere out there is a 1993 Supra TT hardtop that I rewired to accept Bosch aftermarket Taurus 02 sensors because they were the cheapest 4-wire sensors of correct heater wattage that you could buy with a connector already installed).

 

In any case, I can attest that the 02 is completely and entirely ignored on the 1990-2000 for any operating realm you care about.  All of those cars go open loop with almost any meaningful load, and there is NOTHING you can do (short of telling the ECU you are at a ridiculously low RPM) to make them not go open loop at high RPM.  I fully expect the same is true for the 2001-2005 cars, but I've never proven it to myself.

 

Although I believe it would be noncompliant at worst (and "look" suspicious and be protest bait at best), running the ECU from a wideband would work fine so long as you satisfy the factory ECU's 02 heater wattage expectations (if any) with a resistor.  

[WilsonSteele]

So, the consensus seems to be that, either:

A, it will do nothing bc it is ignored at race rpm/load, or
B, i couldn't trick the ECU in any way that isn't already accomplished with adjustable fuel pressure.

So, in essence, we've mandated the use of 2 sensors where 1 is really needed. This added cost was my point, which is why i think its in the spirit of the rules to run one O2 sensors.

All that said, i have my own machine shop and welder at work, so i installed the second bung, and now have 2 sensors on the car. I just chafe at redundancy and extra expense, in dollars and man hours...

[FTodaro]

Dave wheeler where are you. Dave normally will say, if its not in the rules then you can't do it. The rules are silent on removal of the 02 sesnsor, i do not see it as clearly legal.

 

Having said that, I have a mig welder and it took me about 20 min. to weld in a second bung. Also you can keep the tip of the sensor above the air flow so it does not cause a restriction.

[Jim Drago]

So, the consensus seems to be that, either:

A, it will do nothing bc it is ignored at race rpm/load, or
B, i couldn't trick the ECU in any way that isn't already accomplished with adjustable fuel pressure.

So, in essence, we've mandated the use of 2 sensors where 1 is really needed. This added cost was my point, which is why i think its in the spirit of the rules to run one O2 sensors.

All that said, i have my own machine shop and welder at work, so i installed the second bung, and now have 2 sensors on the car. I just chafe at redundancy and extra expense, in dollars and man hours...

 

Actually none are needed?  Car will run just fine with none installed. We dyno with main O2 out of the pipe all the time

 

 

On the second O2, I run mine to ground in the trunk.  I never understood why you wouldn't at least hook it up so you keep the CEL off. 

I often ask people why the CEL is on.. They say, rear O2. Not sure how they always assume it is just rear O2. I like have a functioning CEL, so when it is on, I actually look into it and not assume it is rear O2

[davew]

I'm here Frank !!!!

 

If I had a nickel for every time I ........

 

Listen to Jim, he has all the nickels

 

Dave

[WilsonSteele]

Drago,
Then, to clarify, it sounds like you run one O2 in the stock location, and one "to ground in the trunk".

And no O2 signal to the ECU. Which, even if not in the rules, offers no performance benefit.

Which i applaud, because it keeps cost down.

Or maybe it doesn't, as it seems we can all run the old, used, dead O2 sensors out of our street cars to feed the ECUs desire for data, to keep our CELs off. As there seems to be agreement that while racing, the O2 signal is completely ignored by the ECU.

No matter what, 2 O2 sensors in a 94 seems silly to me.

Am i understanding comments correctly?

[Rob Burgoon]

Drago,
Then, to clarify, it sounds like you run one O2 in the stock location, and one "to ground in the trunk".

And no O2 signal to the ECU. Which, even if not in the rules, offers no performance benefit.

Which i applaud, because it keeps cost down.

Or maybe it doesn't, as it seems we can all run the old, used, dead O2 sensors out of our street cars to feed the ECUs desire for data, to keep our CELs off. As there seems to be agreement that while racing, the O2 signal is completely ignored by the ECU.

No matter what, 2 O2 sensors in a 94 seems silly to me.

Am i understanding comments correctly?

 

 

Maybe the NB cars have multiple O2 sensors stock?

[Jim Drago]

Drago,
Then, to clarify, it sounds like you run one O2 in the stock location, and one "to ground in the trunk".

And no O2 signal to the ECU. Which, even if not in the rules, offers no performance benefit.

Which i applaud, because it keeps cost down.

Or maybe it doesn't, as it seems we can all run the old, used, dead O2 sensors out of our street cars to feed the ECUs desire for data, to keep our CELs off. As there seems to be agreement that while racing, the O2 signal is completely ignored by the ECU.

No matter what, 2 O2 sensors in a 94 seems silly to me.

Am i understanding comments correctly?

 

 

Not sure I am understanding you?

 

In 99 miatas there are two O2 sensors, one pre cat and one post cat.  We leave the Pre cat in the header as I believe is required by the rules.  The ost cat O2 sensor is in a part of the exhaust we are allowed to change and remove. I ground this O2 sensor in the trunk and leave it hooked up. If you do not hook it up, you will get a CEL. If you run  neither sensor at all, throw them in the garbage, you will not lose any performance.

 

Does that make sense?

 

Jim 

[WilsonSteele]

Right, it sounds like we are confusing the issue.
My '94 came with 1 pre-cat O2 sensor installed in the first ~4 inches of the down pipe, next to the 3 bolt flange from the header.
Sounds like your '99 has a pre and post cat O2 sensors.

If you run an AFR gauge, you take your input from the post cat bung?

And leave the stock pre-cat O2 to feed the ECU?

My car only had one stock bung, pre-cat, which i wanted to use to feed my AFR gauge, thus deleting the ECU signal.

Though its good to have the discussion in the forums for public consumption for posterity, it's a moot point for me now, as i welded in a second bung for my wideband O2, right next to the stock location on the down pipe.

The big names seem to agree that, on a 94, we must run the aftermarket gauges off aftermarket O2 sensors that are in parrallel to all stock equipment.

Thanks for all the input everyone...

[Todd Green]

Everyone agrees that any SM must run the aftermarket gauges off aftermarket O2 sensors that are in parrallel (sic) to all stock equipment.

 

Fixed.  You don't get to interpret the rules as you'd like them to be.  Even if they don't make sense (to you).  If you want something changed, write in and request a rule change.