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Old Feb 23, 2004 | 07:09 PM
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From: Oak Creek, WI
Wideband question

I was wondering if any of you people had pics of your install on the interior and where you mounted the sensor in the exhaust. I am planning on doing this in the next week or so since the car will be down for a few weeks. I will be using the AEM UEGO with the gauge, and PDA datalogger also.
Old Feb 23, 2004 | 07:28 PM
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From: Agrestic
Yeah, I was wondering about this too. AEM recommends that the sensor be placed at least 36" downstream of the turbo. Does that make sense? Does the AEM EMS with WB require a new sensor location?
Old Feb 23, 2004 | 07:31 PM
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36"??? Thats about the lenght of the down pipe.
Old Feb 23, 2004 | 07:36 PM
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Wow, that's pretty far downstream. I have my TechEdge sensor about 12" from the bottom of the o2 housing. I mounted the control unit behind the passenger side kick panel, and only use the display when I tinker, the laptop when I tune. The display/laptop connection (cat5) is mounted in the glovebox so it's out of sight.
Old Feb 23, 2004 | 07:40 PM
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From: Agrestic
Yeah, I thought it was far too so I went back and reread the sensor manual. To be more precise, in the manual AEM recommends 36" from the "exhaust port".
Old Feb 23, 2004 | 08:26 PM
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I made my downpipe with a special O2 sensor location so that you can use your factory O2 bung for your wideband. I believe it is 36 inches away from turbo. NOt sure why they need that far though. I put my O2 bung within 5 inches of the turbo outlet on my personal car and works great.
Old Feb 23, 2004 | 09:44 PM
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Originally posted by propellerhead
... AEM recommends that the sensor be placed at least 36" downstream of the turbo. Does that make sense?...
The reason we recommend at least 36" downstream is because we found that on turbo cars, if the sensor was placed too close to the turbo the sensor was getting too hot and the sensor life was greatly reduced.
Old Feb 24, 2004 | 11:44 AM
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Originally posted by JR From AEM


The reason we recommend at least 36" downstream is because we found that on turbo cars, if the sensor was placed too close to the turbo the sensor was getting too hot and the sensor life was greatly reduced.
That makes perfect sense. When you say "greatly reduced", how much do you mean? I think I read that the normal lifespan is projected to be 50,000km (31,000mi).

I wonder if people who use the AEM EMS with UEGO relocate the sensor on the O2 housing to a position further downstream. Not that it's a big deal but I've never heard mention of it by any of the vendors who are developing kits based on the 30-1313.
Old Feb 24, 2004 | 12:06 PM
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Bosch recommends 18" for an OEM application. We extended that to 36" based on a few UEGO sensors that failed from what appeared to be excessive heat at the sensor tip. These had failed with between 1,000 and 10,000 miles. Further investigation by AEM revealed that a major contributing factor in short life UEGO sensors was the EGT at the sensor tip. Bosch says they can go to over 1,000C, but should not exceed 800C for long periods of time.

I don't think the OEM's push the production cars half as hard as you guys do so we thought it the right thing to do. Going to 36" downstream eliminated this problem and really has no downsides. We include a weld in bung for this reason.
Old Feb 24, 2004 | 06:58 PM
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I also understand that there is no such thing as a "too cold" EGT for the sensor.
If you aren't running a cat, use the rear bung for temp install/tuning. Just let the stock O2 sensor hang, (and not touch anything, it get hot).
Old Feb 27, 2004 | 07:59 AM
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The further down stream it is the more "gas transport time" you run into. In other words, if the gauge says you are running lean at 4000 RPM on a wide open pull you probably actually nead to richen up the A/F ratio at 3,500 RPM.... those are the exhaust gases that are reaching the sensor as your tach needle passes through 4,000 RPM.

This is just an example though, I don't have enough real world testing to tell you how many feet down streem = how many RPM lag in the readout.

Keith
Old Feb 27, 2004 | 10:23 AM
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Originally posted by Fourdoor
The further down stream it is the more "gas transport time" you run into. In other words, if the gauge says you are running lean at 4000 RPM on a wide open pull you probably actually nead to richen up the A/F ratio at 3,500 RPM.... those are the exhaust gases that are reaching the sensor as your tach needle passes through 4,000 RPM.

This is just an example though, I don't have enough real world testing to tell you how many feet down streem = how many RPM lag in the readout.

Keith
Yes, you are correct about the increased transport time but in practice, it's very small and IMO can be safely disregarded.

[ENGINEER BS]
Assuming a 3" exhaust, 18 inches long, after a turbo, the volume is 127 cubic inches at atm pressure, which is roughly = 64 cubic inches at 15psi. Thats about the displacement of 2 cylinders which is exhausted by the motor each 1 engine revolution (1/2 engine cycle). So the sensor delay due to moving the sensor 18" further downstream would be about equal to the time of 1 engine revolution. So at 3,000 rpm it would be about 1/50 of a second, or about 20 milliseconds. At 6,000 RPM, it would be about 10mS. At idle, it would be about 60mS.

Very rough calculations but accurate enough to determine that it can be disregarded in all but the most exacting environments.

However, putting one in the tailpipe is a different thing all together. Assume an exhaust length of 12 feet (144 inches) will give a delay of 160ms, which is starting to be large enough to be worried about. Assume 2nd gear run, 5 seconds over 6,000 rpm change gives an acceleration of 1,200 RPM/sec so the delay would manifest itself as an offset of about 200 rpm. Not the end of the world. It would be worse in lower gears and better in higher gears.

Same example but with the 20mS delay would give only a 25 RPM offset.

Smaller exhaust diameters and/or increased boost reduce the transport delay.
[/ENGINEER BS]

Last edited by JR From AEM; Feb 27, 2004 at 10:30 AM.
Old Feb 27, 2004 | 08:35 PM
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Originally posted by JR From AEM


Yes, you are correct about the increased transport time but in practice, it's very small and IMO can be safely disregarded.

[ENGINEER BS]
Lots of good info deleted to save space[/ENGINEER BS]
Can you tell I am used to dealing with a lot longer tubes and pipes than the length of the exhaust system?

Keith
Old Feb 28, 2004 | 01:21 PM
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I have the Aem Ems with the wide band setup, and we intalled the O2 sensor in the fatory location. It works great there, very accurate, even on the dyno. It was easy to do, the bungs are the same size, unscrew one, screw in the other.




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