OLSD - Hptuners guys, iat fueling fix?
02-06-2014, 07:47 AM
#21
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hmmm, I will have to take a closer look to where my afr goes while driving and sitting at the lights. I have essentially blamed the 80lb injectors for an inconsistent idle. It will idle deadly at one stop light, low at the next and high at the next lol.
02-06-2014, 11:41 AM
#24
The actual sensor element itself, hangs in the air inside the little plastic cage. I'm assuming you have the screw in IAT and cut the bung down so the cage is fully in the air stream.
I would think that if installed correctly, and the engine is running, heat soak would not be an issue?
Of course it will depend on the response time of the sensor itself. I remember reading that you can change the thermistor itself to a faster responding part, I'm trying to find that info. You have to be good with a soldering iron though.
I'm just puzzled about the heat soak given the construction of the sensor itself.
I would think that if installed correctly, and the engine is running, heat soak would not be an issue?
Of course it will depend on the response time of the sensor itself. I remember reading that you can change the thermistor itself to a faster responding part, I'm trying to find that info. You have to be good with a soldering iron though.
I'm just puzzled about the heat soak given the construction of the sensor itself.
02-06-2014, 11:55 AM
#25
The actual sensor element itself, hangs in the air inside the little plastic cage. I'm assuming you have the screw in IAT and cut the bung down so the cage is fully in the air stream.
I would think that if installed correctly, and the engine is running, heat soak would not be an issue?
Of course it will depend on the response time of the sensor itself. I remember reading that you can change the thermistor itself to a faster responding part, I'm trying to find that info. You have to be good with a soldering iron though.
I'm just puzzled about the heat soak given the construction of the sensor itself.
I would think that if installed correctly, and the engine is running, heat soak would not be an issue?
Of course it will depend on the response time of the sensor itself. I remember reading that you can change the thermistor itself to a faster responding part, I'm trying to find that info. You have to be good with a soldering iron though.
I'm just puzzled about the heat soak given the construction of the sensor itself.
the sensor responds great when it has air constantly moving across it...
but at low air speeds, it is compromised by its own casing transferring heat to the thermistor....
there is no way around it with such a confined space and budget sensors.
you could make one that doesnt transfer heat...but nobody wants a $500 IAT sensor
heat soak is all in the sensors....causing them to read incorrectly...
the air itself doesnt actually heat soak...its moving far too quickly to gain any heat from "heat soak" in that short of a time
02-06-2014, 12:20 PM
#27
but it is made of metal...and it does heat soak just the same.
its better because of the faster responding thermistor...but it still has heatsoak issues
02-06-2014, 02:08 PM
#29
Aren't the GM based tables basically going off ambient temps? There shouldn't be rapid changes in ambient temps. I can see why changing locations to charge piping would drive the tune all over the place.
Wouldn't your tables be alot closer if you mounted the IAT right at the turbo inlet/airfilter? Are you using IAT sensor temps to pull timing?
With your timing being so conservative and driven off your custom MAP, I'd try installing the sensor some where it won't get heat soaked and has open airflow to it. That way it will only make slight adjustments based on outside air temps.
Wouldn't your tables be alot closer if you mounted the IAT right at the turbo inlet/airfilter? Are you using IAT sensor temps to pull timing?
With your timing being so conservative and driven off your custom MAP, I'd try installing the sensor some where it won't get heat soaked and has open airflow to it. That way it will only make slight adjustments based on outside air temps.
02-06-2014, 05:31 PM
#32
Aren't the GM based tables basically going off ambient temps? There shouldn't be rapid changes in ambient temps. I can see why changing locations to charge piping would drive the tune all over the place.
Wouldn't your tables be alot closer if you mounted the IAT right at the turbo inlet/airfilter? Are you using IAT sensor temps to pull timing?
With your timing being so conservative and driven off your custom MAP, I'd try installing the sensor some where it won't get heat soaked and has open airflow to it. That way it will only make slight adjustments based on outside air temps.
Wouldn't your tables be alot closer if you mounted the IAT right at the turbo inlet/airfilter? Are you using IAT sensor temps to pull timing?
With your timing being so conservative and driven off your custom MAP, I'd try installing the sensor some where it won't get heat soaked and has open airflow to it. That way it will only make slight adjustments based on outside air temps.
ambient temp sensor is only on newer vehicles that report outside temeratures from a seperate sensor that is for creature comfort and doesnt really control anything except for a thermometer display on the dash
the problem is that the IAT sensor in the intake tubing is often times skewed by engine heat warming up the housing and skewing actual values...
the thermistor in the end is sensitive enough that you get quite a big swing between sitting still and rolling down the road.
and unfortunately because of its compact design and physical limits to keep it cost effective, this also means it has design flaws which allow it to transfer some of the body heat to the thermistor itself...causeing skewed readings.
some of the OP's problem may be related to the tune, and adjusting some of the parameters to add fuel or remove fuel based on IAT... Most people dont even know how to data log that and usually dont even try to correct for IAT based fueling issue...
but its just as important as the rest of the tune...
unfortunately, its not a fast process to adjust those tables....it takes some time to get the right data to be able to mess with them...
and you have to get the IAT bias problem solved as well or your data is going to be crap anyways.
02-06-2014, 05:36 PM
#33
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GM IAT tables are based off of the IAT sensor...in the intake tubing...
ambient temp sensor is only on newer vehicles that report outside temeratures from a seperate sensor that is for creature comfort and doesnt really control anything except for a thermometer display on the dash
the problem is that the IAT sensor in the intake tubing is often times skewed by engine heat warming up the housing and skewing actual values...
the thermistor in the end is sensitive enough that you get quite a big swing between sitting still and rolling down the road.
and unfortunately because of its compact design and physical limits to keep it cost effective, this also means it has design flaws which allow it to transfer some of the body heat to the thermistor itself...causeing skewed readings.
some of the OP's problem may be related to the tune, and adjusting some of the parameters to add fuel or remove fuel based on IAT... Most people dont even know how to data log that and usually dont even try to correct for IAT based fueling issue...
but its just as important as the rest of the tune...
unfortunately, its not a fast process to adjust those tables....it takes some time to get the right data to be able to mess with them...
and you have to get the IAT bias problem solved as well or your data is going to be crap anyways.
ambient temp sensor is only on newer vehicles that report outside temeratures from a seperate sensor that is for creature comfort and doesnt really control anything except for a thermometer display on the dash
the problem is that the IAT sensor in the intake tubing is often times skewed by engine heat warming up the housing and skewing actual values...
the thermistor in the end is sensitive enough that you get quite a big swing between sitting still and rolling down the road.
and unfortunately because of its compact design and physical limits to keep it cost effective, this also means it has design flaws which allow it to transfer some of the body heat to the thermistor itself...causeing skewed readings.
some of the OP's problem may be related to the tune, and adjusting some of the parameters to add fuel or remove fuel based on IAT... Most people dont even know how to data log that and usually dont even try to correct for IAT based fueling issue...
but its just as important as the rest of the tune...
unfortunately, its not a fast process to adjust those tables....it takes some time to get the right data to be able to mess with them...
and you have to get the IAT bias problem solved as well or your data is going to be crap anyways.
02-07-2014, 02:17 AM
#35
My screw in style IAT is behind my foglight in the charge pipe right after the IC.
Just extended the wiring a little. When cruising down the road I see within a 2-3* above ambient. In stop and go the temps will rise slightly and just idling the temp rises into the 120s when its 90*+ outside.
Whenever I sit say when I'm live tuning the VE table I think the compressor housing starts to actually transfer heat into the air since the air flow is minimal at idle thus heat soaking the fmic and the iat begins to see that.
if you mounted your iat like mine far from the motor I don't think you'll get the false heat soak of the sensor it's self anymore. Instead you will still see when the air actually starts to get hot like on mine.
also once you start driving again and are is flowing through the turbo and the fmic the temps trickle back down 1-2* maybe say every 5 sec. or so. I'd say it responds quickly
Just extended the wiring a little. When cruising down the road I see within a 2-3* above ambient. In stop and go the temps will rise slightly and just idling the temp rises into the 120s when its 90*+ outside.
Whenever I sit say when I'm live tuning the VE table I think the compressor housing starts to actually transfer heat into the air since the air flow is minimal at idle thus heat soaking the fmic and the iat begins to see that.
if you mounted your iat like mine far from the motor I don't think you'll get the false heat soak of the sensor it's self anymore. Instead you will still see when the air actually starts to get hot like on mine.
also once you start driving again and are is flowing through the turbo and the fmic the temps trickle back down 1-2* maybe say every 5 sec. or so. I'd say it responds quickly
Last edited by 95bowtie; 02-07-2014 at 02:35 AM.
02-07-2014, 10:27 AM
#36
its almost never pipe/compressor heatsoak that you see...the air is moving too quickly for that
its a combo of the IAT sensor being heatsoaked, and your intake sucking in hot air from the engine bay
this is why the IAT bias is so important....because its not heatoak... the air is not getting warm because you are going slow...its actually warm air that everything is seeing, plus a skewed IAT because the IAT sensor itself does heatsoak
even with an air filter seemingly outside the engine bay...when you are sitting still, the heated engine bay air bellows out all directions...and will get to your intake opening.
its a combo of the IAT sensor being heatsoaked, and your intake sucking in hot air from the engine bay
this is why the IAT bias is so important....because its not heatoak... the air is not getting warm because you are going slow...its actually warm air that everything is seeing, plus a skewed IAT because the IAT sensor itself does heatsoak
even with an air filter seemingly outside the engine bay...when you are sitting still, the heated engine bay air bellows out all directions...and will get to your intake opening.
02-07-2014, 01:54 PM
#39
I messed around with the bistable quite a bit yesterday and could not come to a setting that I like what I ended up doing was installing a 4.7 K om resistor in the wiring which showed 57 degrees Fahrenheit and I drove the car around for an hour but like 60 miles on the car and the tuna spot on everything was great I had no variance is even letting it idle for 20 minutes at one point in a parking lot everything was happy and I know that isn't ideal for a lot of people and some others might even think it's stupid but I know these combinations really well and how far I can push them safety wise I can always check the attempts on a bowl on the dyno or at the racetrack and obviously I'm not going to beat the **** out of the car when its 20 degrees outside also if I'm concerned I can just install a methanol kit and I 80 is are almost the relevant at that point