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What resistor do I need to pull 6 degrees of timming?

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Old 01-18-2012, 07:18 PM
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Default What resistor do I need to pull 6 degrees of timming?

I looked through the stickys but could not find what value resistor to install in the intake air temp circuit to pull 6 degrees of timing? I want to spray a 150 shot and want to just wire up a resistor so I can flip a switch and kill 6 degrees of timing. I have already found a post showing the wiring through a relay I just need to know witch resistor to buy.
Old 01-18-2012, 08:38 PM
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IDK that you can. I haven't found anything about pulling that much out without using a twister or lingenfelter stuff. I will be watching this to see if anyone says.
Old 01-18-2012, 08:41 PM
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Originally Posted by hoopty
I looked through the stickys but could not find what value resistor to install in the intake air temp circuit to pull 6 degrees of timing? I want to spray a 150 shot and want to just wire up a resistor so I can flip a switch and kill 6 degrees of timing. I have already found a post showing the wiring through a relay I just need to know witch resistor to buy.
I can tell you that it is whatever is equal to 149* for your 2000 Corvette in your signature...not necessarily the same in other years, or in other makes...
but I do not know what ohm value it needs to be for that...
Old 01-19-2012, 10:04 AM
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I hope that someone can start me off with a base line of what they are using and how much it affected the timing.
Old 01-19-2012, 10:21 AM
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Originally Posted by hoopty
I hope that someone can start me off with a base line of what they are using and how much it affected the timing.

heres the table that your pcm will use...

figure out the resistance based on your IAT temperature, and you can know exactly how much timing it will pull..
easiest way is to grab a cheapy cooking digital thermostat...
find a way to heat some water with the digital thermostat in the water...
find a way to hold the tip of the IAT sensor in the water... and measure resistance when you get it to where you want it based off of this table...
use the 100kpa line as your reference for how much timing it pulls at various values
Attached Thumbnails What resistor do I need to pull 6 degrees of timming?-untitled.png  
Old 01-19-2012, 10:24 AM
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and actually... with the corvette...you can see iat on the dash...
so just buy a potentiometer, wire it in place of the IAT and twist it until you see the IAT value on the dash to do the timing.,.. then measure and buy the resistor(or multiple resistors to equal the correct value)
Old 01-19-2012, 10:25 AM
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Thanks!!!!......This should help get me in the right direction!!!
Old 01-19-2012, 10:28 AM
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This set up will be used on my Mustang.....The LS1 and PCM are from a 1999 Trans Am but I think they are very close to being the same.
Old 01-19-2012, 10:32 AM
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Originally Posted by soundengineer
and actually... with the corvette...you can see iat on the dash...
so just buy a potentiometer, wire it in place of the IAT and twist it until you see the IAT value on the dash to do the timing.,.. then measure and buy the resistor(or multiple resistors to equal the correct value)
I have pulled and cleared codes and programed key fobs through the dash display but I don't know how to pull up the IAT .
Old 01-19-2012, 10:33 AM
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they are not the same...
you cant pull out more than 3* on a stock tune on a 99-02 fbody pcm
Attached Thumbnails What resistor do I need to pull 6 degrees of timming?-99-fbody.png  
Old 01-19-2012, 10:37 AM
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Originally Posted by soundengineer
they are not the same...
you cant pull out more than 3* on a stock tune on a 99-02 fbody pcm
So are you saying this won't work?
Old 01-19-2012, 10:38 AM
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Originally Posted by hoopty
I have pulled and cleared codes and programed key fobs through the dash display but I don't know how to pull up the IAT .
maybe I'm thinking ECT... but I could swear you could see IAT on the DIC...maybe just on some of the newer ones...cant remember..its been a while since I've played with one
Old 01-19-2012, 10:41 AM
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Originally Posted by hoopty
So are you saying this won't work?

not without somebody changing the tune so that it can pull more timing...
in which case... have somebody set the 194* to the amount of timing you need to be pulled, then you dont have to know an exact amount for the resistor... just need anything that is above 194*
Old 01-19-2012, 10:47 AM
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Originally Posted by soundengineer
maybe I'm thinking ECT... but I could swear you could see IAT on the DIC...maybe just on some of the newer ones...cant remember..its been a while since I've played with one
The Tech2 scan tool that I used at the dealership I worked at can show everything. I have a friend with a preditor sport that shows timing and I have another friend that uses HP tuner Pro to retune. He wants to retune the mustang with an open loop speed density tune but as I understand it it won't referance the IAT or O2 sensors at all so I am not sure I want to go that way.
Old 01-19-2012, 10:53 AM
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Originally Posted by hoopty
The Tech2 scan tool that I used at the dealership I worked at can show everything. I have a friend with a preditor sport that shows timing and I have another friend that uses HP tuner Pro to retune. He wants to retune the mustang with an open loop speed density tune but as I understand it it won't referance the IAT or O2 sensors at all so I am not sure I want to go that way.

he obviously should not be tuning if he thinks he should put your mustang ls1 in open loop speed density...
it wont reference the o2's at all...

the only reason to put it in open loop speed density, is if its is an all our racecar, with open headers, and never see's any street time

and then you better have a laptop and your hptuners with you every time you go out to correct the tune for the day's weather, and you better have a clue about what you are doing.

the IAT is always referenced, all the time...even if its unplugged..its still referenced,it just shows as the lowest value possible... -40* If I remember correctly
Old 01-19-2012, 10:59 AM
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Originally Posted by soundengineer
he obviously should not be tuning if he thinks he should put your mustang ls1 in open loop speed density...
it wont reference the o2's at all...

the only reason to put it in open loop speed density, is if its is an all our racecar, with open headers, and never see's any street time

and then you better have a laptop and your hptuners with you every time you go out to correct the tune for the day's weather, and you better have a clue about what you are doing.

the IAT is always referenced, all the time...even if its unplugged..its still referenced,it just shows as the lowest value possible... -40* If I remember correctly
Yes it will only be used on the track but I agree with you. I want the pcm to work with the IAT and O2 sensors to compensate for DA changes...And yes I have already ran the engine without an IAT and it showed -38 degrees. In your opinion do you believe a closed loop speed denisity tune would be much better?
Old 01-19-2012, 11:05 AM
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Originally Posted by hoopty
Yes it will only be used on the track but I agree with you. I want the pcm to work with the IAT and O2 sensors to compensate for DA changes...And yes I have already ran the engine without an IAT and it showed -38 degrees. In your opinion do you believe a closed loop speed denisity tune would be much better?
knowing that it is a track only car... I would be ok with an open loop speed density tune, assuming you are correcting at the track every time you go.


but I still prefer a closed loop tune when possible

the pcm will only compensate for part throttle..but if its been tuned for both part throttle and WOT, then the issue becomes daily weather...
if your car adds fuel for part throttle, it will add some at WOT, but not enough typically...and I wouldnt want to spray a 150 shot too often if the pcm wasnt adding that little bit of extra fuel for when it did need it for that day's weather...

the other direction, if its rich...it will pull fuel at part throttle, and do nothing to the fueling at WOT..so it might be a little bit rich....and you might see a little bit of a performance drop, but that is about it.
Old 01-19-2012, 11:12 AM
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Originally Posted by soundengineer
knowing that it is a track only car... I would be ok with an open loop speed density tune, assuming you are correcting at the track every time you go.


but I still prefer a closed loop tune when possible

the pcm will only compensate for part throttle..but if its been tuned for both part throttle and WOT, then the issue becomes daily weather...
if your car adds fuel for part throttle, it will add some at WOT, but not enough typically...and I wouldnt want to spray a 150 shot too often if the pcm wasnt adding that little bit of extra fuel for when it did need it for that day's weather...

the other direction, if its rich...it will pull fuel at part throttle, and do nothing to the fueling at WOT..so it might be a little bit rich....and you might see a little bit of a performance drop, but that is about it.
The problem is I won't be correcting for the DA every time I will be at the track and if the open loop tune doesn't look at the IAT I won't be able to pull timing by using a resistor. I would rather run a little rich and give up some performance to keep the engine happy.
Old 01-19-2012, 11:13 AM
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Originally Posted by hoopty
The problem is I won't be correcting for the DA every time I will be at the track and if the open loop tune doesn't look at the IAT I won't be able to pull timing by using a resistor. I would rather run a little rich and give up some performance to keep the engine happy.

I just said in an earlier post.......
IT ALWAYS REFERENCES THE IAT...does not matter if its open or closed loop
Old 01-19-2012, 11:20 AM
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Originally Posted by soundengineer
I just said in an earlier post.......
IT ALWAYS REFERENCES THE IAT...does not matter if its open or closed loop
That's good.....So it sounds like the resistor will pull the correct amount of timing when the car is retuned and set up for that in the tune. And if it is set up a little on the rich side the most I would give up would be a little performance with a open loop speed denisity tune correct?


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