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Bosch LSU 4.9 A/F Sensor

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#1
Chris D.

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Sorry for the repeat topic.    Does anyone know if they sell this sensor in bulk like at Costco?   I could use a ten pack.   I really tried to baby this last one that died on me.   By that I mean I added a relay that applies power to the sensor only when the engine is switched on.   I read a lengthy article that said that you don't want the thing heated up prior to engine start or condensation in the exhaust could kill it.  If anyone has had decent luck keeping these alive, please share.   These same sensors live long lives in OEM applications.   But, the OEM applications can control the sensor much more tightly based on input from several vehicle readings.  I should also add that I am using the AEM UEGO controller.  


Chris Dilluvio

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#2
BNaumann

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My third one has survived an entire three weekends so far since I put it on a separate switch to eliminate any Key On Engine Off time. Fingers crossed.
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#3
Tom Hampton

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I have an AEM UEGO.  I just replaced the first Bosch sensor...simply due to age (3 years old), it never failed---I just didn't know if it was still accurate or not.  I put the old one in a box as a spare. 

 

That said, I DO have it on a switch.  Not for the purpose you mention....just because I put all of the race systems on switches (gages, cool, camera, data) with separate fused power straight from the kill switch.  I generally only turn on the gages after the engine is running...just as a habit. 

 

The only other thing I know I did was carefully mount the bung according to the instructions---tip pointing down at a 45 degree angle or something like that.  I marked the downtube while it was in the car....and then removed the downtube and drilled / welded the bung in place.  I recall the instructions making reference to this improving sensor life.  At $100 a pop, seemed worth the hassle. 


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#4
Steve Scheifler

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I own and like some of the AEM products, but their wideband seems to be a common PIA. I certainly don’t need the extra aggravation at the track of worrying about how I switch things on or start/restart the endine. Rubbish. I would cut my losses and do something else.

BTW, all O2 sensors should be installed at least a few degrees above horizontal to avoid condensation and contaminates from flowing back into them, but other than that there is no special angle.
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#5
Steve Scheifler

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And FWIW, I’ve had a lot of people show up to use the dyno with dead or very inaccurate widebands, most commonly AEM and Innovate (perhaps because they are most common) but we have never had a sensor just flat fail on our cars or the dyno. Drift a bit with age and abuse (too rich is hard on them, so is leaded fiel) but never fail.
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#6
Tom Hampton

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I don't recall exactly what the instructions said, it was about 4 years ago...may have just said "above horizontal".  I know mine is installed so that I could conveniently reach it with a wrench through the wheel-well.  Thus, it is fairly high on the down tube and points more up than horizontal. 

 

I have literally never thought about the sensor, or the gages being switched.  I put mine on independent circuits (and switches) because I didn't want to break into the stock harness:

 

1.  Simply to avoid introducing a failure point in a 25 year old harness.

2.  I didn't like the really fine guage of wire used in the stock harness.  

3.  If I need to swap the main harness (or retub), there's no rework because its bone stock.

 

So, my switching is simply a consequence of that.  I never read any of these other recommendations until today.  I turn on the key and fire the engine, and then flip the switches.  When I get back, I'm not sure which order I do things in.  But, since the gages are on straight battery power....they get turned off. 

 

I'm on my 3rd O2 sensor, which so far I've replaced every 2 calendar years, or 18 months of usage.  I baseline my O2 against the dyno O2---when they drift far enough apart...I replace.  However, the most recent replacement was simply preventative because I didn't have time to get over to the dyno. 


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#7
Steve Scheifler

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Tom, the 4.9s have been around quite awhile now but AEM had built 4.2s. Not sure when they switched but are you certain yours is 4.9? Even if so, how many miles are you getting from one?

Look at it this way. Automobile manufacturers need to warrant most emissions related parts for what, 100k miles regardless of owner? I got several new injectors in my (bought at auction) diesel at 97k, no charge without even asking. Anyway, they’ve moved to something that responds a little faster and stays accurate longer FOR THEM. They figure out exactly where in the pipe for the right temperatures, strictly control fuel mixture which is almost always far leaner than we run, and control it however works best for them, probably starting with a genuine Bosch chip. Even enthusiastically driven sports cars don’t get the abuse we give ours. Heat, vibration, mostly rich (12.5-13 rather that 14.7-16+) all make for very different conditions along with a possibly less optimized controller.

Plug the AEM into a stock street car connected to the ignition switch circuit and it will probably last for years at a typical 12-15k/year. Yet people are getting what, a few hundred miles from one in an SM with1000 or more being noteworthy? What does that tell is? I don’t NEED something that is a bit faster and theoretically lasts 100k miles but is fragile and finicky, I need something reliable, reasonably accurate and cheap to replace as a wear item.
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#8
Chris D.

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I considered adding a switch, but I just know that I'll forget to flip it on at some point.   I read that another sure way to fry these things is to subject it to hot exhaust without it being powered up.  I've attached a link to what I thought was a very good article on the subject.

 

http://www.nzefi.com...e-applications/


Chris Dilluvio

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#9
Tom Hampton

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Steve-

 

I just checked my most recent order.  You are correct, mine is a 4.2, not a 4.9.  As far as the rest goes, I'm not sure what you are trying to say...short version seems to be:

 

They use it differently, they manage it differently, and they are nicer to it than we are.  So, they get different life from it than we do. 

 

The same thing is true of almost everything else on the car.  A full weekend with test day is about 200 miles.  So, I would say 2000+ miles or so in the racecar.  


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#10
Steve Scheifler

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Ah, so first let me repeat in case it was missed, your seemingly better luck than Chris with an AEM unit is not apples & apples, you have the older 4.2 AEM version (also not my favorite but at least less inclined to fail).

So back to my points regarding the 4.9, exactly what you say, which is why for our purposes I much prefer the earlier 4.2s which are hardier and otherwise perfectly adequate. As I mentioned, we’ve never had an outright failure. They may not respond quite as fast, but we don’t have them connected to a mini super computer trying to tweak all manor of trims at countless times per second. They may be slightly more accurate in an absolute sense, but we tune for power then note what our in-car guage shows so we can try to keep it close to that as conditions change using the crudest of adjustments (FPR), and keep an eye on it for indications of issues like a failing fuel pump or significantly different fuel. They may (under ideal conditions) last a lot longer, but we don’t have ideal conditions and surely won’t ever put 100k miles on a single race car. Even Mark Webber (no, not the former F1 driver) hasn’t approached that.

So my point is, from my experience and what I know, and I’ve been using these since the original Motec PLM of which I own two, and I reviewed patent docs for Innovate before they first went to market with their genuinely radical approach to controlling and “interpreting” wideband sensors, anyone having repeated issues with a 4.9 should consider selling it or moving it to their street car and purchase a good 4.2.

By all means if you have a 4.9 and the sensor lasts multiple busy seasons, keep using it. But someone like Chris or BNaumann surely must have better things to spend his time and money on than sourcing a bulk purchase of over-priced 4.9 sensors and replacing them like cheap Christmas tree bulbs.
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#11
Tom Hampton

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Ah, so first let me repeat in case it was missed, your seemingly better luck than Chris with an AEM unit is not apples & apples, you have the older 4.2 AEM version (also not my favorite but at least less inclined to fail).

...

So my point is, from my experience and what I know, and I’ve been using these since the original Motec PLM of which I own two, and I reviewed patent docs for Innovate before they first went to market with their genuinely radical approach to controlling and “interpreting” wideband sensors, anyone having repeated issues with a 4.9 should consider selling it or moving it to their street car and purchase a good 4.2.

By all means if you have a 4.9 and the sensor lasts multiple busy seasons, keep using it. But someone like Chris or BNaumann surely must have better things to spend his time and money on than sourcing a bulk purchase of over-priced 4.9 sensors and replacing them like cheap Christmas tree bulbs.


Fair enough. When I made my original post I was unaware that I had the 4.2 vs. the 4.9.

I'll revise my statements to say: I've had zero problems with the Bosh 4.2 sensor, and associated AEM gage, under the usage model I listed above (manually switched on/off concurrent with engine power). I don't know why I would "upgrade", as upgrades aren't always...
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#12
Steve Scheifler

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Now we are on the same page!
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#13
Jeff Wasilko

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I've got a 4.2 sensor in my car, and a 4.9 sensor in my wife's car (both with AEM gauges). The 4.9 had 1 failure after 2 years and the 4.2 hasn't failed in 5 years.



#14
Chris D.

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Thanks for the feedback.   I have two more 4.9s on order.   If I have similar issues (no reason to believe I won't), then I'll probably switch over to the 4.2 along with a corresponding controller.  For whatever reason, maybe the 4.2 is more reliable in our application than the 4.9.   I'd like others to chime in on their experience as well (4.2 vs. 4.9)


Chris Dilluvio

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#15
FTodaro

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I must be lucky, on my innovate, i have only changed one in 5 to 6 years. Mounted at at the 12 o'clock position. wired on the switched power so it is only on when the motor is running. No reliability issues.


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#16
Steve Scheifler

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Frank, do you know whether you have the 4.2 or 4.9? Innovate has made controllers for both and even offer one which can use either with software and cable updates.

You’ve had it long enough I’m guessing it is a 4.2 controller & sensor, in which case you aren’t so much lucky as further evidence of the relative reliability. If it is a 4.9 then I’d agree, you seem to be beating the odds. When did you last do a free-air recalibration?
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