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Old 02-12-2005, 12:17 AM   #1
ride5000
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Default tuner/tuner pro users: easy free air cal.

just get a good head of speed on (hwy prefered, 4th or 5th gear), lift off the throttle completely. injectors will shut off. before rpms reach 1k, go into your tuner menu and select free air cal. it will take a few seconds to make sure the afr and sensor temp are up to snuff, then it will complete the test.

after around 10k miles on the tuner pro (w/bosch sensor) my FAC went from 283 to 280, fwiw.

i didn't come up with the idea, but i did test it on our cars with the tuner/bosch and it works well, and avoids having to crawl around under the car to do the FAC.

ken
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Old 02-12-2005, 03:30 PM   #2
happasaiyan
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thanks for the tip! i just unplug the sensor, then unscrew it out of the bung (mine is on the top of the downpipe, right after the turbo) and then plug it in and calibrate it.
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Old 02-12-2005, 03:36 PM   #3
kenlee
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happasaiyan,
Do you think you could get me a pic or idea as to where you placed the o2 on your downpipe? I have to do this next week and it might save me some time. Thanks
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Old 02-12-2005, 04:46 PM   #4
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Not to be sceptical, but doesn't the sensor need to be in free air to do a free air cal? I don't get it.

peace
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Old 02-12-2005, 07:46 PM   #5
happasaiyan
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Quote:
Originally Posted by hippy
Not to be sceptical, but doesn't the sensor need to be in free air to do a free air cal? I don't get it.

peace
i was thinking that too...but if your pistons are just going up and down with no fuel being injected, then there isnt a problem, really. youre pumping fresh air.
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Old 02-12-2005, 11:19 PM   #6
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Quote:
Originally Posted by happasaiyan
i was thinking that too...but if your pistons are just going up and down with no fuel being injected, then there isnt a problem, really. youre pumping fresh air.

I don't think so you're still gonna get some fuel in the exhaust and the WB02 will pick up that fuel when it calibrates won't it? Wouldn't that throw the cal off?
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Old 02-12-2005, 11:31 PM   #7
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Quote:
Originally Posted by antimullet
I don't think so you're still gonna get some fuel in the exhaust and the WB02 will pick up that fuel when it calibrates won't it? Wouldn't that throw the cal off?

Where is the fuel going to come from? Unless you have a leaky injector. The injectors are off during decel.

TMS
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Old 02-13-2005, 09:46 AM   #8
ride5000
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i thought about the effect of pulling the free air through the engine.

my conclusion was that IF there are any residual vapors left over, i would WANT that to be compensated for in the calibration of the wideband sensor. ie, if i'm not injecting ANY fuel, then i want the sensor to read "free air," despite the fact that there may be trace amounts of oil/gasoline molecules in the airflow. i think we can all agree that there's certainly no combustion taking place, so the concentration of oxygen will not change. that is after all what the sensor is reading.

i got the idea from a pointer on wrxhackers.com, and it came originally from innovate. they've got some experience with widebands.

ken
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Old 02-14-2005, 03:33 PM   #9
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This technique is mentioned in the manual for the LM-1 wideband unit. It only works for Manual transmission cars, as automatics don't engine brake.

And yes, it works just fine and is WAY easier than taking the O2 sensor out of the pipe. The inj. shut down completely, and the engine is just pumping air, allowing for on the fly 'free-air' calib.

-jason
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Old 03-29-2005, 08:00 PM   #10
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Back from the dead..... Saw someone about to perform this, so I figured I'd put my 2 cents in again. Here are some quotes from the tuner manual which I thought were interesting(especially the bold parts).

Quote:
....The calibration is performed with the sensor warmed up in Free Air that has a known quantity of oxygen under normal atmospheric conditions......

....For best results with a free air calibration, the sensor must be removed from any exhaust and be completely in free air and at operating temperature. It is important that the surrounding air is not contaminated with exhaust air such as in a workshop with running engines.....

.....6. If the temperature stabilizes, but the sensor gives a reading less than 200, then the calibration will fail with Er2. This is typically because the sensor is not in pure free air, such as the case if it is left in an exhaust, even if the engine is not running. Breathing on the sensor will alter its reading, so free air calibration is quite sensitive......
peace
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Old 03-29-2005, 08:16 PM   #11
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Quote:
Originally Posted by hippy
Back from the dead..... Saw someone about to perform this, so I figured I'd put my 2 cents in again. Here are some quotes from the tuner manual which I thought were interesting(especially the bold parts).



peace
Fair enough, but turning off the car is very different from coasting. Watch the wideband some time - my car reads 16:1 or so for at least an hour after shutting off, just from the leftover exhaust gas in the, well, exhaust.

Coasting on the other hand allows the exhaust pipes to be continuously flushed with fresh air.
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Old 03-29-2005, 08:26 PM   #12
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Quote:
....under normal atmospheric conditions........Breathing on the sensor will alter its reading...
blahblahblah
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Old 03-29-2005, 09:31 PM   #13
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I will test this tonight.

I JUST did a free-air-calibration (273) 20 minutes ago.

In theory, using this method, I should be right at 273+/-
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Old 03-29-2005, 11:58 PM   #14
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I'm back.
273 was my original value. (I did FAC 6 time and threw out the high and low, 273 came up more times then others)

Now I just did the method using 5th gear, and a couple 4th gears... Each time I got a value between 275-278.
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Old 03-30-2005, 08:41 AM   #15
ride5000
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aaron, i'd say for the reduction in pain in the ass factor, it's worth it...

maybe we should all do this a couple of times (in pipe vs. true free air cal) and post the delta. there is probably a highly repeatable shift.

i don't really know how much difference it makes. maybe i'll try changing the calibration number by +10 and -10 with the car off and see how much the indicated afr changes.

thanks for the data.
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Old 03-30-2005, 10:02 AM   #16
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I'll stick to pulling the sensor. Mine is in a slightly harder to reach location than happsaiyan's, but still accesible in under 3 minutes of labor from above the car.

I did the deceleration trick when I had the LM-1 but that's because it had a huge Calibration button on it. I don't like fiddling with the laptop when I'm driving and the dip switches on my tuner are hidden in the dash it is DIN mounted into.

So for safety and accuracy's sake. I'll remove.
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Old 03-30-2005, 10:49 AM   #17
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Quote:
Originally Posted by ride5000
aaron, i'd say for the reduction in pain in the ass factor, it's worth it...

maybe we should all do this a couple of times (in pipe vs. true free air cal) and post the delta. there is probably a highly repeatable shift.

i don't really know how much difference it makes. maybe i'll try changing the calibration number by +10 and -10 with the car off and see how much the indicated afr changes.

thanks for the data.
I'm right there with you. I have to drive up on homemade ramps, jack up the car, clip a zip tie, unscrew the wb02,... blah blah blah...

so everybody do the in pipe vs. true free air cal test and let us know how it went.
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Old 04-08-2005, 06:30 PM   #18
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Bump... come on slackers... do the test!
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Old 04-08-2005, 11:17 PM   #19
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i still don't know if this method would work, from what i've heard, even breathing on it (c02 from lungs) will make it off. BTW, the place mine is right after the turbo, before the DP curves down, just like happasaiyan's most likely is, right on top, easy access.
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Old 04-08-2005, 11:39 PM   #20
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^good, then doing this test and reporting back your findings should be very easy.
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Old 04-22-2005, 01:32 PM   #21
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bump.
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Old 04-23-2005, 11:46 AM   #22
DarthChicken
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I do this to calibrate the sensor on my hydra - or to make sure its still calibrated. Its easiest and most accurate if you have a hill you can go down while engine braking - it keeps the RPMs up so you have more time to pump out all the fuel.

When I do it this way, the numbers are identical to pulling it out of the downpipe, with the added benefit of being able to run the car and keep maximum power going to the sensor (instead of just battery power).
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Old 10-21-2005, 05:48 PM   #23
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taps fingers... somebody else please try this.
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