SD tuning for bracket racing
10-13-2009, 12:09 PM
#21
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If it's reading real outside air temp all the time, then there will be less fluctuation down the track. And zero out any IAT timing in the normal operating range.
My IATs (stock location) will drop around 10 degrees from start to finish of a 1/4 mile run. And you can just watch the wideband AFR going rich as the pass goes on. If you can get it to read outside air temp all the time fuel will be much closer during the run, so less chance of error based deviation from run to run.
http://speed-eng.com/store/exhaust-c...47b2e037b0bd34
There are 3 different length IAT extensions about 10 or so item down that page.
My IATs (stock location) will drop around 10 degrees from start to finish of a 1/4 mile run. And you can just watch the wideband AFR going rich as the pass goes on. If you can get it to read outside air temp all the time fuel will be much closer during the run, so less chance of error based deviation from run to run.
http://speed-eng.com/store/exhaust-c...47b2e037b0bd34
There are 3 different length IAT extensions about 10 or so item down that page.
10-13-2009, 12:34 PM
#22
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There's a plastic shield below the airbox and washer fluid tank. If you suspend the sensor in the air as suggested, there will be no effects coming from the radiator.
10-26-2009, 01:40 PM
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Well, I moved the IAT sensor to under the bumper as suggested and...It worked great. Car ran within 4 hund all night and I picked up around 2 tenths in et. Thanks all who chimed in on this subject. Set new Pb in et and 60'
10-29-2009, 02:37 PM
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now the real question....if I hook up a resistor(in line), and tell the computer that the air is 60 degrees all the time... What will happen to my times? Wouldn't this make my car even more consistent? What will happen when it is 90 outside but I'm telling the computer that it is only 60?
Oh, and thanks a bunch for your help!
Oh, and thanks a bunch for your help!
11-01-2009, 11:38 PM
#26
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now the real question....if I hook up a resistor(in line), and tell the computer that the air is 60 degrees all the time... What will happen to my times? Wouldn't this make my car even more consistent? What will happen when it is 90 outside but I'm telling the computer that it is only 60?
Oh, and thanks a bunch for your help!
Oh, and thanks a bunch for your help!
01-12-2010, 02:46 PM
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I moved my IAT using a thermistor of the right type, a
little bit of wire and heat-shrink, and shoved it up under
the black plastic cowl trim behind the little grille. It now
moves not at all w/ underhood temp (gets a little warm
from direct sun though). Spliced right into the harness
near the PCM.
SD tunes suffer from a kind of poor / inaccurate model
of air temp, aggravated by any IAT skew from the air
that is actually taken in. MAF, cares not at all. If your
game is consistency, either run a MAF or run in consistent
air.
little bit of wire and heat-shrink, and shoved it up under
the black plastic cowl trim behind the little grille. It now
moves not at all w/ underhood temp (gets a little warm
from direct sun though). Spliced right into the harness
near the PCM.
SD tunes suffer from a kind of poor / inaccurate model
of air temp, aggravated by any IAT skew from the air
that is actually taken in. MAF, cares not at all. If your
game is consistency, either run a MAF or run in consistent
air.
01-12-2010, 03:58 PM
#32
>If your game is consistency, either run a MAF or run in consistent
>air.
There ya go. Many guys also run on the lean side, so the car doesn't tend to pick up so much when it cools off at night. Not as fast, but if your just bracket racing, all it needs to do is run that shoe polish number on the window, right?
A lot of Stock and Super Stock guys do that until they have a no-break-out heads-up race, like when running class eliminations.
>air.
There ya go. Many guys also run on the lean side, so the car doesn't tend to pick up so much when it cools off at night. Not as fast, but if your just bracket racing, all it needs to do is run that shoe polish number on the window, right?
A lot of Stock and Super Stock guys do that until they have a no-break-out heads-up race, like when running class eliminations.
01-17-2010, 04:05 PM
#33
The best thing to do is keep the IAT sensor in the right (stock) location and prevent heat soak by not doing the free cut the bottom air box mod, or if you do have that mod install a shield that will prevent radiator heat from rising straight up into the air lid. My next free mod will be to put a piece of plastic or sheet metal in between the air lid base and the radiator to keep it open but prevent heat from getting to the air lid.
You need to get HPTuners or some sort of tuning software to really dial in a setup to the T like you want. It will datalog all your sensors and give you more data to use to help dial it in.
I've logged my car at the track multiple times and usually on a 70-80* day my IAT readings are in the 120 range at the start line and by the time I'm at the end of the track I'm reading near ambient air temps. My air lid base is still just open and is allowing radiator heat up into the air lid. That free mod works great in cooler weather and while moving but when you sit still it really kills your power because it just sucks in hot air all the time.
Also the reason I wouldn't move the sensor is because you don't want to give the PCM false readings. If the sensor is reading hot temps then that is the temp the air is entering your engine and either needs to be tuned to compensate or needs something to prevent heat from getting to your intake.
On the SD vs. MAF part... it really depends on the MAF you are using. You will pick up CFM by removing the screen in the MAF sensor but it also gives jagged readings. I just did a datalog of dynamic airflow (SD calculated airflow) and Mass Airflow and the SD calculated airflow was a smooth reading all the way across but the MAF readings were very jagged, my stock MAF sensor was de-screened before I bought the car. I don't like spikes or jagged airflow readings because an engine will not fluctuate 30 g/sec within a tenth of a second at the same 100% TPS. So for consistancy to me I would have a collection of SD tunes for different DA/Temperatures! Or keep the screen in your MAF to keep the MAF reading correct airflow!
You need to get HPTuners or some sort of tuning software to really dial in a setup to the T like you want. It will datalog all your sensors and give you more data to use to help dial it in.
I've logged my car at the track multiple times and usually on a 70-80* day my IAT readings are in the 120 range at the start line and by the time I'm at the end of the track I'm reading near ambient air temps. My air lid base is still just open and is allowing radiator heat up into the air lid. That free mod works great in cooler weather and while moving but when you sit still it really kills your power because it just sucks in hot air all the time.
Also the reason I wouldn't move the sensor is because you don't want to give the PCM false readings. If the sensor is reading hot temps then that is the temp the air is entering your engine and either needs to be tuned to compensate or needs something to prevent heat from getting to your intake.
On the SD vs. MAF part... it really depends on the MAF you are using. You will pick up CFM by removing the screen in the MAF sensor but it also gives jagged readings. I just did a datalog of dynamic airflow (SD calculated airflow) and Mass Airflow and the SD calculated airflow was a smooth reading all the way across but the MAF readings were very jagged, my stock MAF sensor was de-screened before I bought the car. I don't like spikes or jagged airflow readings because an engine will not fluctuate 30 g/sec within a tenth of a second at the same 100% TPS. So for consistancy to me I would have a collection of SD tunes for different DA/Temperatures! Or keep the screen in your MAF to keep the MAF reading correct airflow!
Last edited by LSxPwrDZ; 01-17-2010 at 04:16 PM.
01-17-2010, 07:01 PM
#34
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My experience says that no stock location is "right".
Air box? Heat soaked. Real bad. Air box rear wall gets
cooked by engine bay air and the sensor is in a
backwater corner so lousy airflow to bring it 'round
(this is the Blackwing lid; is anyone still running a
stock lid?).
MAF? Some heat soak, better once air starts moving
but still skewed off the line.
An IAT sensor is not going to cool down as fast as
you need it to, if it's soaked. You've got seconds.
Thermal time constants are larger than that.
At WOT the real air is pretty damn near what an
outside-mounted IAT will read, if your cold air
setup is doing its job. Less of a hoax than the
in-engine-bay IAT for sure. If you're sucking up
hot air at low pedal, let the closed loop take care
of that. But give the thing a hot IAT reading and
cold actual air, and you'll pick up a significant
lean error in speed density. I'd rather fix a rich
error at part throttle (or let the computer do it)
than have a lean error at WOT (or its consequences).
Air box? Heat soaked. Real bad. Air box rear wall gets
cooked by engine bay air and the sensor is in a
backwater corner so lousy airflow to bring it 'round
(this is the Blackwing lid; is anyone still running a
stock lid?).
MAF? Some heat soak, better once air starts moving
but still skewed off the line.
An IAT sensor is not going to cool down as fast as
you need it to, if it's soaked. You've got seconds.
Thermal time constants are larger than that.
At WOT the real air is pretty damn near what an
outside-mounted IAT will read, if your cold air
setup is doing its job. Less of a hoax than the
in-engine-bay IAT for sure. If you're sucking up
hot air at low pedal, let the closed loop take care
of that. But give the thing a hot IAT reading and
cold actual air, and you'll pick up a significant
lean error in speed density. I'd rather fix a rich
error at part throttle (or let the computer do it)
than have a lean error at WOT (or its consequences).
01-17-2010, 08:33 PM
#35
It's not as extreme as you describe, plenty of people are running aftermarket lids with the IAT in the stock location (in the air lid). Not stating that it can't be done your way but there is a reason the sensor get's heated up in the first place... why not try to prevent that instead of band-aiding the problem?
01-17-2010, 08:46 PM
#36
It's not as extreme as you describe, plenty of people are running aftermarket lids with the IAT in the stock location (in the air lid). Not stating that it can't be done your way but there is a reason the sensor get's heated up in the first place... why not try to prevent that instead of band-aiding the problem?
And that is not the actual temperature of the air that is entering the engine, as you stated earlier..
01-17-2010, 09:02 PM
#37
Obviously the engine temperature heats up the air to an extint which is where the IAT/ECT Bias table comes to play within the tune. You must bias that table in the right way one way or the other to get optimal results. I've got 2 different LS1 cars with both having the IAT sensor in the air lid with no issues. AFR's look great throughout the runs! The fix to the issue is to block incoming heat from getting into the air lid, not moving it out of the intake duct cause then it really wouldn't read the correct air temperature. I see the argument you have of the actual sensor heat soaking and taking nearly 10 seconds for it to cool down to the correct air temperature but by preventing the sensor from getting heat soaked from the get go will give more accurate readings, but I personally don't think taking the sensor out of the intake air duct is the proper way of solving the issue.
Last edited by LSxPwrDZ; 01-17-2010 at 09:07 PM.
01-17-2010, 09:17 PM
#38
Obviously the engine temperature heats up the air to an extint which is where the IAT/ECT Bias table comes to play within the tune. You must bias that table in the right way one way or the other to get optimal results. I've got 2 different LS1 cars with both having the IAT sensor in the air lid with no issues. AFR's look great throughout the runs! The fix to the issue is to block incoming heat from getting into the air lid, not moving it out of the intake duct cause then it really wouldn't read the correct air temperature. I see the argument you have of the actual sensor heat soaking and taking nearly 10 seconds for it to cool down to the correct air temperature but by preventing the sensor from getting heat soaked from the get go will give more accurate readings, but I personally don't think taking the sensor out of the intake air duct is the proper way of solving the issue.
The 2 cars you got running SD?
You're not going to block heat from getting to the sensor in the stock location. You just claimed a 40 degree swing from IATs to actual temp. You think you can block all of that out?
I run a ram air kit from under the bumper to a sealed airbox and an SD setup with my IAT in stock location. Sometimes I get a 10 degree swing from start to finish on a 1/4 mile run. You can see that the AFR gets richer toward the end as the temps come down. If I just go for a drive with no time for the IAT to heat my AFR stays consistent the whole time.
01-18-2010, 12:18 AM
#39
Yes both of mine are running SD. I switch back and forth from time to time between MAF and SD just cause I can, I run SD on my 98 TA just for the simple fact I'm maxing out the frequency on the MAF table. I've not blocked off my airbox to the radiator which is most of my problem but I tuned around the issue. I'm going to a completely different setup intake wise to help the high air temps on the start line. It wont completely keep heat out cause it's nearly imposible to do so but can still help by sealing the radiator heat from getting to it and heating it up to an extent. I will locate the sensor in the air intake tubing further toward the front of the car to keep from heat soaking but I wont remove it from the intake duct itself cause then it's not an Intake Air Temp sensor but rather an ambient air temp sensor lol.
With the SD tuning the IAT is very very important though because it calculates the air density entering the motor and with false air density readings the VE table cannot correctly calculate the right amount of air the cylinders are getting therefore it cannot provide the right amount of fuel for those cylinders.
Like I said before if you want one tune the MAF is going to be the most consistant between the 2 without going extremely in depth with tuning one SD or having multiple SD tunes for different DA's. I'm personally running the same tune now in 20-30 degree weather that I ran on 90 degree day's and my afr's arent off. But I also have tremendous amounts of time tuning on my car as well.
For the regular tune's I try to convince customers that the MAF is not a bad thing! They do meter the air entering the engine and do so very well! And when both the VE and MAF is tuned properly it will run flawlessly. Our car's reference both VE and MAF from the factory up to 4000rpm. I'm probably going to go with a big MAF on my Camaro this spring to see any difference in the SD alone. I want to fully use the strength of the computer and by only using SD your only using half the computer. I see it that you can use SD (VE) and MAF to help more accurately calculate airflow, I'll change the factory settings to allow the use of Dynamic Airflow calculations (VE/SD) all the way up to redline instead of 4000rpm's though that way it doesnt only rely on MAF above 4000rpm like stock.
Hope none of this is unclear... I kinda got into a rambling on and on in this post lol
With the SD tuning the IAT is very very important though because it calculates the air density entering the motor and with false air density readings the VE table cannot correctly calculate the right amount of air the cylinders are getting therefore it cannot provide the right amount of fuel for those cylinders.
Like I said before if you want one tune the MAF is going to be the most consistant between the 2 without going extremely in depth with tuning one SD or having multiple SD tunes for different DA's. I'm personally running the same tune now in 20-30 degree weather that I ran on 90 degree day's and my afr's arent off. But I also have tremendous amounts of time tuning on my car as well.
For the regular tune's I try to convince customers that the MAF is not a bad thing! They do meter the air entering the engine and do so very well! And when both the VE and MAF is tuned properly it will run flawlessly. Our car's reference both VE and MAF from the factory up to 4000rpm. I'm probably going to go with a big MAF on my Camaro this spring to see any difference in the SD alone. I want to fully use the strength of the computer and by only using SD your only using half the computer. I see it that you can use SD (VE) and MAF to help more accurately calculate airflow, I'll change the factory settings to allow the use of Dynamic Airflow calculations (VE/SD) all the way up to redline instead of 4000rpm's though that way it doesnt only rely on MAF above 4000rpm like stock.
Hope none of this is unclear... I kinda got into a rambling on and on in this post lol
