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Old 02-28-2007, 12:33 PM   #1
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Default Test Pipes and fooling the computer?

So I have been searching for a way to fool the computer on my 1.8 96 miata. Basically I need to replace the cat, but I don't have the money and figure I will be buying a whole new exhaust for the new motor thats in the works. That being said, if I pull the cat I should get a check engine light. So is there a gismo out there for the miata that will get rid of the secondary 02 sensor? In the BMW world there are 02 sensor simulators that just fool the car, but I don't know about the miata world.

They don't test emissions in Florida because its just a bullshit tax and means nothing but a way to tax you for being poor and having an old car. So I don't really care at this point. My 1970 cutlass polutes a hell of a lot more, so I figure if I drive the miata I am saving the atmosphere a little every day.

So how do I install a test pipe and not get a check engine light?
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Old 02-28-2007, 12:35 PM   #2
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Pull the light bulb is one solution. I to am interested in O2 simulators because my rear O2 sensor is still connected but just taped under the car, pretty sure it's the source of my current CEL.
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Old 02-28-2007, 12:38 PM   #3
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I drilled out a spark plug fouler and screwed that into the not so good cat of my Sister's 1996 GS-R and screwed the 02 into that. No check engine lights. I have seen the s2k crowd do the same with no issues.
Might want to do a google search for those links.


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Old 02-28-2007, 12:42 PM   #4
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The ecu compares the voltage produced by the first and second sensors. The second sensor is supposed to output less voltage. I don't know if it's a percentage less, or a fixed amount less, but there has to be area for fudge factor because the cat degrades over time. You could probably parallel the output of the first sensor to the second sensor input, diode isolate it and add a very small amount of resistance in the form of a multi turn potentiometer. Tweak the pot to increase/decrease the voltage drop until the ecu is happy.

I've never attempted such a thing, but it would probably work, and it's not difficult.
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Old 02-28-2007, 12:45 PM   #5
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Think i might try that then, i have a POT at home that should work fine.
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Old 02-28-2007, 12:50 PM   #6
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The hardest part will be getting the pot set correctly. If you get it to work, measure the resistance that was needed. We can then build an o2 replacement kit to sell to the m.netters. Let's see, a diode, some resitors, 6" of wire, and some crimp connectors. How does $149.99 sound? Too cheap? :gay:
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Old 02-28-2007, 12:52 PM   #7
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Sounds good to me. I'll get back to you on that later.
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Old 02-28-2007, 01:17 PM   #8
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Lord it is nice to having to worry about this

or emissions testing.
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Old 02-28-2007, 01:51 PM   #9
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I have a 96 that I put a test pipe in and I get no check engine light. I've had it on the car for about 10,000 miles.
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Old 02-28-2007, 03:26 PM   #10
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Quote:
Originally Posted by FSTASNTZ View Post
I drilled out a spark plug fouler and screwed that into the not so good cat of my Sister's 1996 GS-R and screwed the 02 into that. No check engine lights. I have seen the s2k crowd do the same with no issues.
Might want to do a google search for those links.


Jason
That's the Subaru WRX/STI/FXT way too. Actually two anti-foulers to get the rear 02 out of the exhaust stream.

Or a 2.2kw resistor in the ECU side of the rear O2 harness.

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Old 03-01-2007, 06:50 PM   #11
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FWIW I have no cat and both of my o2 sensors are connected and I have no cel light. '99 OBDII stock ecu + EMU.
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Old 03-08-2007, 10:23 PM   #12
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Well, this is very informative. I guess I should just buy a new engine management computer and chuck the stock ecu. But until I have lots of money, I guess I will try that other way around. Now what the hell is an exhaust fouler thing?
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Old 03-08-2007, 10:40 PM   #13
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http://forums.clubrsx.com/showthread...91#post6186391

Follow this link, it describes the process of using defoulers and includes pictures of what a defouler is. Defoulers are available at nearly all chain autoparts stores such as advanced, autozone, o'reilly.
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Old 03-08-2007, 11:06 PM   #14
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simple fix dude....just get a OBD1 motor...either 1.6 or 1.8 and never worry lol
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Old 03-09-2007, 10:49 AM   #15
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The spark plug fouler fix did not work for me. So I just pulled the Bulb.
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Old 03-12-2007, 10:03 AM   #16
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Well, doesn't pulling the bulb ultimately not solve the problem? The system changes the way the motor runs to optimize emissions. If you dont fool it, its always running in limp home mode.
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Old 03-12-2007, 10:19 AM   #17
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The rear o2 just monitors the health of the CAT. I don't think it has any input as far as fueling goes.
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Old 03-12-2007, 10:38 AM   #18
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Quote:
Originally Posted by Ben View Post
The rear o2 just monitors the health of the CAT. I don't think it has any input as far as fueling goes.
I have found the same thing. The rear O2 has no effect. Other then the light.
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Old 03-18-2007, 09:51 PM   #19
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Take a look at the Baker Electronix O2 sim I'm selling.
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Old 03-19-2007, 10:37 AM   #20
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Quote:
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Take a look at the Baker Electronix O2 sim I'm selling.
I have one of these in my glove box. I never installed it. Did it work?
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