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post #1 of 12 Old 01-11-2015, 02:46 PM Thread Starter
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ACT trickery

I'm used to the ls world and not familiar with the mustang tuning, despite my searching i can't seem to find an answer to my following question, so im hoping some of the gurus here can help out

With an ls1 you can use a resistor in place of the intake air temp sensor (called air current temp on 5.0's) and it will lie to the computer telling it that the air is around 53 degrees, which makes the computer pull about 2-3 degrees of timing.

has anyone done this on a 5.0 stang?

More importantly, can someone tell me what the computer uses to determine the temp, does it reference the volts from the sensor or something else?

Also, what is the reference signal the computer gives to the sensor, i think it gives it a 5v reference but i don't know at what amperage.

I'd try to track it down using a multimeter but i'm at school for the semester and am away from the car, so, to stay interested, im doing some research for when i can get back to the car

Thanks for anybody that can help or point me in the right direction!

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post #2 of 12 Old 01-11-2015, 06:25 PM
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Quote:
Originally Posted by _Grady02 View Post
I'm used to the ls world and not familiar with the mustang tuning, despite my searching i can't seem to find an answer to my following question, so im hoping some of the gurus here can help out

With an ls1 you can use a resistor in place of the intake air temp sensor (called air current temp on 5.0's) and it will lie to the computer telling it that the air is around 53 degrees, which makes the computer pull about 2-3 degrees of timing.

has anyone done this on a 5.0 stang?

More importantly, can someone tell me what the computer uses to determine the temp, does it reference the volts from the sensor or something else?

Also, what is the reference signal the computer gives to the sensor, i think it gives it a 5v reference but i don't know at what amperage.

I'd try to track it down using a multimeter but i'm at school for the semester and am away from the car, so, to stay interested, im doing some research for when i can get back to the car

Thanks for anybody that can help or point me in the right direction!
You wont get any help with this here , Ford people generally believe it tuning stuff the correct way , not by adding dumb resisitors to input wrong data to the PCM

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post #3 of 12 Old 01-11-2015, 07:29 PM
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Quote:
Originally Posted by _Grady02 View Post
I'm used to the ls world and not familiar with the mustang tuning, despite my searching i can't seem to find an answer to my following question, so im hoping some of the gurus here can help out

With an ls1 you can use a resistor in place of the intake air temp sensor (called air current temp on 5.0's) and it will lie to the computer telling it that the air is around 53 degrees, which makes the computer pull about 2-3 degrees of timing.

has anyone done this on a 5.0 stang?
Why? If you want to retard timing, just set the base timing back 2-3 degrees. Or do you want to pull timing at higher loads and not at idle?

Why would an EEC from the late 80's Mustangs be like the PCM in an LS1? The Mustang doesn't pull timing when air is cold. It pulls it when air is too hot.

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More importantly, can someone tell me what the computer uses to determine the temp, does it reference the volts from the sensor or something else?
It measures an ACT sensor's resistance via a fixed voltage reference though a pseudo constant voltage source with fixed ESR. As sensor resistance changes with temperature, the voltage at the EEC ACT terminal changes. 5v is the nominal open circuit voltage with infinite sensor resistance. It is a NTC element, temp up=resistance down.

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Also, what is the reference signal the computer gives to the sensor, i think it gives it a 5v reference but i don't know at what amperage.
It is a simple voltage division circuit that follows Ohm's law. The current is not constant, it varies with sensor resistance and is in the micro-amperes and milliamperes, depending on temperature. For example, at 50k resistance it would be roughly about 100 uA.

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I'd try to track it down using a multimeter but i'm at school for the semester and am away from the car, so, to stay interested, im doing some research for when i can get back to the car
Why would you want to screw up the ACT reading? It doesn't do much (within reason), but could cause some problems with cold starting performance economy.

Why would someone want to disable the sensor?


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post #4 of 12 Old 01-12-2015, 05:31 PM Thread Starter
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by pull timing i meant advance not retard as in pull it from 28 to 30 degrees advance, sorry i wasn't clear

I don't want to disable the sensor, i wanted an easy way to get 2-3 more degrees of timing when i go to the track and then be able to remove the resistor and drive home like normal

So, if i were to add more resistance, it would falsely tell the computer the intake air is cooler correct? It is my understanding from more research that the mustang pcm won't advance timing for cool air, it will only retard timing for warm air, so at least i could lie to the computer to keep it from retarding the timing when underhood temps climb and intake temps warm up
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post #5 of 12 Old 01-12-2015, 06:57 PM
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I think with the old ford ecu's altering the coolant temp may be the better way to go. Something to search anyways.
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post #6 of 12 Old 01-14-2015, 05:18 PM Thread Starter
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Ok, from more searching, that included pages of extremely boring and irrelevant reading i've found that the ecu will retard timing by 4 degrees when very hot coolant temps are seen and an additional 2-3 degrees when hot intake temps are found.

By using a 47k resistor in the ACT sensor circuit the computer will think it has about 55 degree air and leave timing alone

similarly by using a 4.7k resistor in the ECT sensor circuit the computer will think the engine has around 165 degree coolant and leave timing alone.

While this isn't exactly gaining me any more timing advance, it is keeping the computer from retarding timing so effectively I ended up gaining 3-7 degrees when the engine is at temp, depending of course on which circuits, or both, i add the resistors too
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post #7 of 12 Old 01-14-2015, 06:44 PM
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Originally Posted by _Grady02 View Post
Ok, from more searching, that included pages of extremely boring and irrelevant reading i've found that the ecu will retard timing by 4 degrees when very hot coolant temps are seen and an additional 2-3 degrees when hot intake temps are found.

By using a 47k resistor in the ACT sensor circuit the computer will think it has about 55 degree air and leave timing alone

similarly by using a 4.7k resistor in the ECT sensor circuit the computer will think the engine has around 165 degree coolant and leave timing alone.

While this isn't exactly gaining me any more timing advance, it is keeping the computer from retarding timing so effectively I ended up gaining 3-7 degrees when the engine is at temp, depending of course on which circuits, or both, i add the resistors too
So what you are saying is you want to remove the detonation protection when the engine overheats, and screw up the engine warm up and other properties.

You want to make it not be any faster, not learn fuel correction correctly, not pull back timing if coolant gets to 236F or intake air from 160 to 240F, and have less advance and drive worse at lower temps?

Is that what you are after??


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post #8 of 12 Old 01-15-2015, 09:30 PM Thread Starter
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Nope, not at all what im after

What im after is a way to keep the computer from pulling timing only when i'm at the track. If i see any signs of detonation, I can always run a higher octane fuel to combat the pinging.

I only really want to do this on rare occasion to get those couple degrees at the track.

During street driving and even during warm up, i plan to leave everything alone.
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post #9 of 12 Old 01-16-2015, 01:10 AM
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you don't want to mess with the ACT circuit, its critical to the MAF and VE calculations

you don't want to go screwing with ECT either, its a crucial input as well

if all you want is a switch you can adjust timing by a set amount the ecu already has this function, its called the 'octane bar' if you un-ground the ecu octane bar input the ecu will remove timing usually 3 degrees or so, you can adjust this in the tune or even enable it in the tune if your ecu doesn't have this option from the factory (most eec-4s require a chip to enable this feature)

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post #10 of 12 Old 01-16-2015, 01:11 AM
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Why not just run locked out timing?

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post #11 of 12 Old 01-16-2015, 01:30 AM
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horrible efficiency and he wants to be able to change it rather conveniently

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post #12 of 12 Old 01-18-2015, 11:10 AM
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Decipha...check your PMs
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