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Garage Queen
 
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Why to monitor your AFR!

Gents,

When I added my LM-1, I felt it was more an item of curiosity than a critical item. I have since changed my mind. Look at the two session below. They were taken on the same drive and 1 hour apart. The first shows my AFR at 13ish while cruising and just around 10 on boost. This is how most of my drives are.

The second session shows a dangerously high AFR and how these cars change. I watched my AFR creep from 13.2 to 14.2 while cruising after an hour. This was odd to me, so I decided to record it a short session for record. I'm glad I did. I couldn't watch my gauge, but the recording shows that my car was in a range that could have caused damage.

Fortunately, my LM-1 keep me aware of the changes and I drove cautiously home. I have now learned that my car, after extended drives, leans out and loses its ability to maintain a predictable AFR.

My next project is an adjustable WUR to see if I can fix this problem. Also, I now log boost and RPM.






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Old 09-13-2010, 05:56 PM
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Sorry, flip the graphs.
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Old 09-13-2010, 05:58 PM
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AFR monitors and wide band sensors IMO are the best tools we have now a days to tune engines, monitor engines and be aware of whats really going on inside that motor.
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Old 09-13-2010, 06:02 PM
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Crotchety Old Bastard
 
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You don't have a problem. The AFR will creep from the mid-13's when cool to low 14's when fully warm. As the engine fully warms the bimetalic strip in the WUR will lean out the mixture. Optimum cruising mixure is in the low 14's. At idle it will pop back down to mid-13's.
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Old 09-13-2010, 06:25 PM
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Brian,

I would think my car would be fully warm before going over an hour of driving at 75 MPH or higher, Also, is my AFR jumping to over 20 normal? Even though it is for only a short period prior to boost.
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Old 09-13-2010, 06:35 PM
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You have to consider the driving conditions and the precision of the system itself. The WUR is located on top the engine and is influenced by the ambient temperatures. An extreme example of this is winter driving. On a sub-freezing day my engine will operate normally while idling or driving slowly, then after a burst of high speed it will idle hunt upon coming to a stop, which indicates and overly rich condition. Simply put, the WUR got so cold it knocked down the fuel pressure in response to the temperature. A stock engine would be much less prone to do this but you get the idea.
I see the same spikes in my graphs as you have. I am not certain exactly what phenomenon is being read by the O2 sensor at that time but I do know that if it is indeed real that it must not be harmful as I see it commonly on healthy engines such as my own that have been operating that way for decades.
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Old 09-13-2010, 06:48 PM
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Brian,


Well, I'm glad to know it is normal. Can the "phenomenon" increase in intensity? Say AFR jumping to 30?
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Old 09-13-2010, 07:15 PM
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great post, ive got an LM-1 also but have plans to build an LC-1 into my 911 so i can use the LM-1 for other projects w/ out removing it from the 911 each time i want to do something.
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Old 09-13-2010, 07:34 PM
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does the LM1 have an RPM line? Or maybe boost input. Would be good to know.

I don't have a turbo, but a good AFR instrument on my 1973 2.7 MFI have really helped me adjust the MFI setting to get the car really running well.

I have not used the Innovate product, but like the Daytona Sensors Wego IV that our host sells a lot more. I feel it is much more advanced product and more features for less money and hassle as the Innovate line.
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Old 09-13-2010, 07:58 PM
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Quote:
Originally Posted by dicklague View Post
does the LM1 have an RPM line? Or maybe boost input. Would be good to know.

I don't have a turbo, but a good AFR instrument on my 1973 2.7 MFI have really helped me adjust the MFI setting to get the car really running well.

I have not used the Innovate product, but like the Daytona Sensors Wego IV that our host sells a lot more. I feel it is much more advanced product and more features for less money and hassle as the Innovate line.
i have the added sensor for my LM-1 to record RPM and a few other sensors. right out of the box the LM-1 only records A/F ratio.
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Old 09-13-2010, 08:35 PM
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Quote:
Originally Posted by carslutt View Post
great post, ive got an LM-1 also but have plans to build an LC-1 into my 911 so i can use the LM-1 for other projects w/ out removing it from the 911 each time i want to do something.
I run with an LC-1 as well, simply because I wanted a permanently installed AFR gauge so I can watch what's going on at any time. The only thing I don't like about these things is that it tends to draw your eye constantly just to "make sure" everything is allright. Too much information is sometimes just too much and can become an obsession if you're not careful.
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Old 09-13-2010, 08:48 PM
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A good add on tothe LC-1 controller is a SSI-4 from Innovate. You can monitor other sensors..ie tps, boost sensor,rpm and even vehicle speed. i had one installed on my other turbo car and its very easy to set up..it also has 5v outputs for additional sensors if say you want to install a IAT sensor in the intake plumbing. I beleive they are about 120.00 bucks and they are a daisychain install
to the LC-1 and also the LM-1. As for irratic sensor readings I would look at doing a free air calibration once and a while. Decel will give you over 20 afr readings but not sure with CIS because of the possible fuel dump on decel

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Old 09-14-2010, 07:32 AM
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If you start seeing leaner mixtures under load, I'd definitely be concerned.

I buy what Brian B is suggesting. At light throttle and cruise, you want to see a lean mixture. No reason to burn the gas if you're not trying to make power!
Old 09-14-2010, 07:52 AM
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Just to be clear, with the Daytona Sensors Wego IV you get AFR, RPM, and one 0-5 volt sensor input. The latter could be Vacuum/boost, TPS, CHT, or any 0-5 volt dc input.

You get a bright digital readout and 2 hours of data logging all in one package, and it costs less than $440.00. The kit includes all cables, Bosch wideband sensor, software USB cable, bung and the main unit.

Quite simple to wire and one box.
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Old 09-14-2010, 02:03 PM
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Quote:
Originally Posted by dicklague View Post
does the LM1 have an RPM line? Or maybe boost input. Would be good to know.

I don't have a turbo, but a good AFR instrument on my 1973 2.7 MFI have really helped me adjust the MFI setting to get the car really running well.

I have not used the Innovate product, but like the Daytona Sensors Wego IV that our host sells a lot more. I feel it is much more advanced product and more features for less money and hassle as the Innovate line.
As mentioned above, the LM-1 can log RPM. I just added an LMA-2 and just hooked up the sensor for RPM. Boost is next. Still working on how to configure the RPM on the graph. I'm just a Noobie at this.

Thanks to everyone for their input my lean AFR readings after extended trips. It is just scary to see such a jump.

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Old 09-14-2010, 05:22 PM
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If your AFR's are moving around after 10 min or so, you need to check the voltage to the WUR. It should be a solid 12v or a bit better, depending on your elect system. As you know, the bi-metallic strip reacts to temp - whether from the engine (heat soak) or the 12v source (for cold starts or cold days). The idle should not hunt (or system pressure) if the WUR gets 12v even at very low temps - the system was designed in Germany for all types of injected cars for all types of weather.
Old 09-14-2010, 08:04 PM
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It won't hunt on a stock engine Don, or I should say it should not hunt. Mine did because of the mods done. I just used that as an extreme example. Good point about checking your voltage. I'm sure and old worn out WUR will flake out as well.
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Old 09-14-2010, 09:30 PM
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GAL,

I'm glad you brought this up. I've been staring at my recorded sessions with my LM-2 (right now only logging rpm and afr). I have the opposite "phenomenon" going on where I go rich after letting off the throttle (makes sense if it's the fuel dump DonE refers to). I get a cabin full of exhaust when letting off throttle after hard accel, so i started to monitor...

So here is another graph to compare to:

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Old 09-14-2010, 10:16 PM
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Pat, do you vent your BOV to atmosphere?
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Old 09-15-2010, 05:07 AM
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Am I the only one, or does that look a bit lean across the board?

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00 Saab 95 Aero wagon stick
01 Saab 95 Aero wagon auto
03 Boxster
90 Chevy PU Prerunner....1990
Old 09-15-2010, 07:04 AM
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