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Old 05-27-2005, 01:32 PM   #1
ptaaty
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Default warmer weather=rich running?

Since I am not an EM guru, I wanted to confirm my thoughts.

Western Washington weather has taken a marked turn for the warmer recently, up to 85 yesterday....it appears that this has caused my stage 2 wrx to run a bit richer than before.

When cooler the light backfires/pops were almost non-existant but have started happening far more often with more burbling during engine braking.

I suspect as the warmer air is less dense the amount of air has gone down, causing a richer condition.

Does this make sense? I thought that the ECU was able to adjust by using the MAF sensor, but maybe it just isn't quite as good as I thought.

Anyone else with a similar situation? Sorry this is my first summer with a WRX
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Old 05-27-2005, 01:34 PM   #2
Uncle Scotty
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yeah...warmer = richer.

ya may want to try resetting the ECU on a warm day and see wassupwidat
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Old 05-27-2005, 01:40 PM   #3
scoobyracing
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Listen to your Uncle Scotty.
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Old 05-27-2005, 02:21 PM   #4
jblaine
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Quote:
Originally Posted by ptaaty
I suspect as the warmer air is less dense the amount of OXYGEN has gone down, causing a richer condition.
^^^^ See edit.
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Old 05-27-2005, 02:28 PM   #5
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And yes, it should be handling the fueling for the temperature change...
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Old 05-27-2005, 02:37 PM   #6
ptaaty
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well yeah...air mass per volume (density) has gone down, meaning that oxygen has gone down, along with nitrogen, and the trace gases O2 is always exactly 20.95% of the gas content of air...everest, sea level, hot cold...no matter.

I may try a reset and see how it works, it really isn't this horrible rich pig, just richer than it was, and I thought the ECU would adjust because it is basing fuel amount on the air mass flow amount. I suppose this means that the MAF sensor isn't linear?
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Old 05-27-2005, 04:18 PM   #7
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what is EM?
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Old 05-27-2005, 04:51 PM   #8
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EM - Engine Management
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Old 05-27-2005, 04:58 PM   #9
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I know there's a air temp sensor pre turbo, does the ECU use this sensor in manipulating fuel for temp changes?
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Old 05-27-2005, 05:10 PM   #10
ptaaty
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Quote:
Originally Posted by hondaeater69
I know there's a air temp sensor pre turbo, does the ECU use this sensor in manipulating fuel for temp changes?
I am not sure if it is related? I always thought the MAF (mass air flow) sensor was measuring the actual amount of air being used, but if the MAF functions by measureing air speed alone, a temp component would be needed and a lookup table to find the actual air mass.

*edit* if it wasn't measuring air mass and needed the temp probe it would need a pressure probe as well to take into account altitude so it must not....


Maybe what is happening the the MAF sensor isn't as accurate because the density of the air at the different temperatures causes a different flow pattern that it was calibrated to in the factory? They assume a certain type of flow to be accurate I guess.
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Old 05-27-2005, 05:53 PM   #11
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know that i thought about it, i bet the temp sensor is for coldness on startup. It takes collant temp into consideration for high idle, but our cars will also run very rich on startup (around 10:1!) for about 1-2 minutes under extrememly cold situations, that's probably what the temp sensor is for

I don't believe it uses the temp sensor for fueling beyond start up.

Measuring the air "mass" takes temp into account.
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