HELP! have a problem! IAT Question
09-16-2009, 10:45 AM
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HELP! have a problem! IAT Question Ok, so last night i got my car tuned, and the whole time we were tunning my IAT sensor was not plugged in. I just saw it this morning, by plugging this back in, what will happen? Im also on a SD tune.
Last edited by bongva; 09-16-2009 at 10:51 AM.
09-16-2009, 11:38 AM
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Wow, that could be a problem.
I wonder what temperature (minus the IAT sensor) was used to orginally determine the density of the airmass and then the correct fueling?
Anyway, as has been debated many times..a good SD tune will compensate for changes in temperature, so the plug-in of your IAT sensor should not be the issue.
It would be interesting to know the 'default' temperature that was used, and whether if that temperature was not correct how that effect your tune.
We might need a 'real' expert to figure this one out.
..WeathermanShawn..
I wonder what temperature (minus the IAT sensor) was used to orginally determine the density of the airmass and then the correct fueling?
Anyway, as has been debated many times..a good SD tune will compensate for changes in temperature, so the plug-in of your IAT sensor should not be the issue.
It would be interesting to know the 'default' temperature that was used, and whether if that temperature was not correct how that effect your tune.
We might need a 'real' expert to figure this one out.
..WeathermanShawn..
09-16-2009, 12:45 PM
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good question, was changing out some stuff on the TB and totally forgot to plug it in....
so what about timing??? will it advanced it? will i be getting knock from this as well??
09-16-2009, 02:45 PM
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Well, your airmass calculation would have been computed using the air density that is normally found when the IAT is -40C.
First question is, how did it start? If it was really computing the airmass at -40C, obviously that would be a very dense air mass. So you would get a lot of fueling. It would seem odd that with a wideband, you would not notice that. It would be extremely rich.
Second question is, did you tune it open-loop SD or closed? I guess theoretically, a SD tune would compute the new IAT and adjust the fueling accordingly. It is just that -40C is a long way from 'standard atmosphere' or standard temperature, so any small measurement error would tend to be greatly exaggerated.
If it was tuned SD closed-loop, your Trims will tell the story. I guess you could hook up your wideband and see how the AFR's are. Your timing will be based off the computed airflow. At -40C, it would be a lot of g/cy for every Rpm range, so your spark would be close to the WOT spark values (lower spark values than say 10c for every Rpm).
Either redo the tune, or hook up your wideband and start logging.
Good luck.
..WeathermanShawn..
First question is, how did it start? If it was really computing the airmass at -40C, obviously that would be a very dense air mass. So you would get a lot of fueling. It would seem odd that with a wideband, you would not notice that. It would be extremely rich.
Second question is, did you tune it open-loop SD or closed? I guess theoretically, a SD tune would compute the new IAT and adjust the fueling accordingly. It is just that -40C is a long way from 'standard atmosphere' or standard temperature, so any small measurement error would tend to be greatly exaggerated.
If it was tuned SD closed-loop, your Trims will tell the story. I guess you could hook up your wideband and see how the AFR's are. Your timing will be based off the computed airflow. At -40C, it would be a lot of g/cy for every Rpm range, so your spark would be close to the WOT spark values (lower spark values than say 10c for every Rpm).
Either redo the tune, or hook up your wideband and start logging.
Good luck.
..WeathermanShawn..
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09-16-2009, 05:31 PM
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If you plug it back in now you will dangerously leen !!
Get it retuned sorry...
mate forgot to put his back on the other day after doing some welding on his intake pipe (turbo setup with 60# injectors) and car was that rich it would hardly run.
Get it retuned sorry...
mate forgot to put his back on the other day after doing some welding on his intake pipe (turbo setup with 60# injectors) and car was that rich it would hardly run.
09-16-2009, 08:58 PM
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Ok so a few more questions, will having the IAT un plugged affect my gas mileage on partial throttle?
and if i plug it back in just to drive it around, and i want to floor my car, can i just unplug it and get the same afrs as i had on the dyno?
and if i plug it back in just to drive it around, and i want to floor my car, can i just unplug it and get the same afrs as i had on the dyno?
09-16-2009, 09:43 PM
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Well, you will get the fueling as if the outside temperature is -40C. The problem is in Oklahoma, it is a whole lot warmer. So, the air entering the intake manifold will be far less dense than your tune.
Why not just enable Trims and try it? Chances are you will be very rich, gas mileage will be poor, and your spark will be low (reference the g/cy vs spark).
There is an outside chance that just replugging in your IAT sensor and letting the computer figure out the new airmass/fueling might work. The people with the experience that have posted in this thread think it is unwise. I think with Trims enabled it would be interesting to see if you can get at least get it to idle. You will know within 5 minutes if you can drive it. Note that approach could leave you very lean, so proceed with caution if at all.
Otherwise, car and tuner need to get together before driving.
Good luck.
..WeathermanShawn..
Why not just enable Trims and try it? Chances are you will be very rich, gas mileage will be poor, and your spark will be low (reference the g/cy vs spark).
There is an outside chance that just replugging in your IAT sensor and letting the computer figure out the new airmass/fueling might work. The people with the experience that have posted in this thread think it is unwise. I think with Trims enabled it would be interesting to see if you can get at least get it to idle. You will know within 5 minutes if you can drive it. Note that approach could leave you very lean, so proceed with caution if at all.
Otherwise, car and tuner need to get together before driving.
Good luck.
..WeathermanShawn..
09-16-2009, 10:03 PM
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im just gonna leave it unplugged like the way it was tuned, until i can get a better tune. tune is scheduled for next week. i will be sure to double check everything this time.