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Go Back   E46Fanatics > Tuning & Tech > Driveline, Engine & DME Tuning

Driveline, Engine & DME Tuning
Talk about driveline improvements, NA tuning and DME tuning your E46 BMW here. This includes diffs, intakes, exhausts, chips, software and OBD tuning.

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Old 01-07-2009, 08:51 PM   #1
iaknown
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Oxygen Sensor Simulator Question

Hey guys, me and a friend are currently working on developing a post-cat oxygen sensor simulator for use on cars with race catalytic converters or no cats at all and had a question. The current gerbil car is my 2001 330i, we figure if it can fool that ECU, it'll fool pretty much any other car out there. We're aware there are already O2 simulators out there but we are trying to make a complete package with provisions for the O2 heaters so the sensors can be completely eliminated w/no check engine lights. Here be my question...what is the average voltage and fluctuation of an operating post-cat O2? I have read between .1-.3 volts is common but what about on our cars? I had already taken mine out a while ago when installing headers and never checked any of the readings. Right now I have the module set to switch between .1-.3 volts and am getting a voltage deviation code. Can any of you guys do a quick scan while your car is running? Thanks in advance....
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Old 01-08-2009, 04:29 AM   #2
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ohh. sounds interesting.

so you want us to splice into our o2 sensors and use a multimeter to find the volts?
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Old 01-08-2009, 11:31 AM   #3
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Yup and I guess there are two options and neither should require unplugging the O2. Either backprobe the wire at the plug that sends the voltage signal back to the computer, with the other lead on ground (plugs are right on top of the motor near the fuel rail, grey or black wire-I forget)OR read the value with a scanner. Either should be pretty easy.

Last edited by iaknown; 01-08-2009 at 11:34 AM.
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Old 01-08-2009, 11:36 AM   #4
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damn there was a thread on here were a tech posted the voltage of his 02 sensors but i cant find it
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Old 01-12-2009, 07:32 AM   #5
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maybe post 18 might help?

http://forum.e46fanatics.com/showthr...hlight=carsoft
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Old 01-12-2009, 01:32 PM   #6
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Nah, that's for a pre-cat O2 voltage...Pre-cat voltage will switch back and forth depending on rich/lean mixture whereas the post-cat O2 should remain steady and lean, I just need to get a typical voltage of one.
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Old 01-12-2009, 01:43 PM   #7
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Well, shouldnt you be measuring resistance and not voltage?
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Old 01-12-2009, 10:54 PM   #8
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No, I need voltage as in the O2 signal that goes back to the computer. The O2 sensors produce a signal somewhere between 0 and 1 volt....
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Old 01-16-2009, 12:41 AM   #9
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Had it set below .4 volts and got an engine light....looks like the computer is looking for a near steady .45 volts in case anyone is curious.
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Old 01-16-2009, 11:09 PM   #10
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Innovate technologies LC-1, 2 programmable analog outputs. I have the e-bay headers with no cats and as a kicker I blocked off the secondary air port in the head and removed the pump and check valve. And noooo check engine light.
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Old 01-17-2009, 01:05 AM   #11
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huh? what about my original question?
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Old 01-18-2009, 11:34 PM   #12
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huh? what about my original question?
Good timing, i'll be doing headers next week and before i pull them off i'll be measuring that voltage. I had something similar in mind. I'll get back with you next week, if i forget, pm me on wednesday or later and i'll share my results.

I was thinking of seeing if other obd2 mil eliminators would work from domestic or jap vehicles, but just in case i need to make some i wanted the original values.
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Old 01-19-2009, 12:30 AM   #13
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Sounds good, maybe I can help you out with what I've found out so far too....
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Old 01-19-2009, 09:22 PM   #14
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Hey guys, I hate to tell you but those simulators don't work. Eventually your DME is gonna run the mixture way lean to test the catalytic converters, the simulators don't go that low on voltage to simulate that condition. The Innovate LC-1 takes care of all the hardware you just need to program the voltage and delay to mimic a cat.
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Old 01-20-2009, 09:29 PM   #15
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Quote:
Originally Posted by F1004fun View Post
Hey guys, I hate to tell you but those simulators don't work. Eventually your DME is gonna run the mixture way lean to test the catalytic converters, the simulators don't go that low on voltage to simulate that condition. The Innovate LC-1 takes care of all the hardware you just need to program the voltage and delay to mimic a cat.
so the Innovate technologies LC-1 just keeps the oem ratio from the pre:post cat sensors?
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Old 01-25-2009, 07:30 PM   #16
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The pre-cat sensors are cool they do there job in the header just fine, the innovate LC-1 makes and analog output that you can adjust based on a wide band input. You then splice this into both the rear cat signal lines, ground the sensor ground lines to the same ground as the LC-1 and put a 50-ohm 10-watt resistor in line with each of the bank 1 and 2 heater wires and your good to go. You now have you own adjustable rear 02 sensor.
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Old 01-26-2009, 12:09 AM   #17
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Is this what you are running now? I find it hard to believe a 10-watt resistor will hold up and if it does it probably won't last...
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Old 01-29-2009, 10:21 PM   #18
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Dude... don't be so negative. I did the math for a 5 watt limit, at 13.85 Volts 38.36 ohm's gives you .361 amps and about 5 watts. This is a 50 ohm at 10 watts, it's hell of a lot higher then the 2.7 ohms that the stock O2 sensor heater is, but the DME seems to be happy cause the light has been off and the OBD-II monitors have even passed. If you wanna split hairs it's less amperage draw then the stock sensors, that's less draw on the alternator, you know where I'm going that's more power!

Last edited by F1004fun; 01-29-2009 at 10:24 PM.
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Old 01-30-2009, 01:20 AM   #19
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Umm, ok not being negative just wondering how that's working for you cause I've run lower wattage resistors like that and they glow they get so hot. I will certainly give it a try though if you say its working for you. One thing you mentioned though, I don't know what O2's you have but mine measure 10ohms, where did you come up with 2.7ohms? You're just measuring the heater circuit unplugged right?
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Old 01-30-2009, 03:41 PM   #20
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That's strange, I think we both have the same engine managment MS43, but either way the bypass resistor will work, Radio Shack 50 ohm 10 watt cerammic block resistor.
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