I believe i found another way to eliminate detonation, assuming all other fuel and sensor components are set and working correctly.
Has anyone tried inserting a resistor across the octane plug wires?
i found that there is a wire (red stripe on grey) that connects to the temperature sensor and the octane plug- found it to be the same wire using a electronics tester. in fact this grey and red wire seems to be connected to all of the common sensors that control engine behavior ie; TPS, IAT, CTS... pretty much all of these sensors are based on controlling computer response by resistance varied by heat or mechanical position. the coolant temp sensor controls fuel and timing based on a range of resistance varied by the heated element on the sensor. it also has the biggest influence on engine behavior in terms of fuel and timing curves (aside from using an EEC tuner). resistance goes down as the engine get hotter, thus retarding the timing and changing the fuel curve as appropriate. i measured the resistance between the wires on the octane plug and found it to be 1600 ohms. normally by default the octane plug is closed (connected), and if you pull the plug out it retards the timing by 3 degrees (in effect inserting 1600 ohms of resistance), turning the SC into a performance slug. interaction between the temp sensor and octane plug setting by that common wire indicates that the computer controls the timing under various engine conditions by altering the resistance in ohms. you can control resistance by inserting a certain resistor value across the octane plug thus setting the timing anywhere from default to - 3 degrees. i found you can also alter the timing curve (and richen the fuel curve) slightly by inserting a certain resistor value on the green lead in series coming off the temp sensor.
here are the resistor values i chose that completely eliminated the detonation without perceiving a loss of performance;
inserted (spliced in alligator clips temporarily) a 1300 ohm 1/2 watt resistor across the octane plug leads. this is a very precise adjustment- you can experiment resistor values here and see what works best- higher resistance=less timing, lower=more timing.
inserted with alligator clips a 3300 ohm 1/2 watt resistor in series on the green lead off the temp sensor. you can vary this up to 4500 ohms without running into detonation again. this seems to sharpen throttle response on my SC (similar to when you first start up with a cold engine). I did not notice this resistor to degrade cold start up performance.
if you still get detonation with these values, increase the resistance across the octane plug in increments of 100 ohms until it's gone.
Results??
no detonation whatsoever (could not hear any pinging or clicking sounds) under any hard acceleration loads in any gear or WOT.
At least by my seat of pants feel, the car is much more responsive than ever, and it does not bog down like it used to at certain rpm's/loads. top end power got better also. the car didn't feel as heavy. it's worth it to me-
some of you reading this will probably criticize the hell out of this and think that i'm crazy because i'm not doing it the "right way" with an EEC tuner, but the way i look at it... somebody's got to experiment and try to unlock the secrets of managing control of this car and achieving similar results without too much complication or money spent. I think my way is better because the resistor mods are subtle and it stays closer to stock computer settings assuming you have a mildly modded SC. the computer should not "learn" these changes out because these mods will not set a code or go outside of internal lookup table parameters. Modifying the electronics a little bit does not necessarily make this the "wrong way". You have to understand overall how ford sensors interact and change fuel and timing parameters. I mean if ford did it right the first time we wouldn't be going thru all of this. And if i wanted the ultimate performance machine it would not have bought the SC.
like i said, it works for my SC very well, maybe because the engine is old and carbonized. it's been running it this way for a couple of weeks now with absolutely no drivability or starting problems (cold or hot) other than the leaky injector thing when the engine is hot. i felt i had to share this info. to other SC'ers that are going thru challenging times with their cars.
sorry about the long thread.
Has anyone tried inserting a resistor across the octane plug wires?
i found that there is a wire (red stripe on grey) that connects to the temperature sensor and the octane plug- found it to be the same wire using a electronics tester. in fact this grey and red wire seems to be connected to all of the common sensors that control engine behavior ie; TPS, IAT, CTS... pretty much all of these sensors are based on controlling computer response by resistance varied by heat or mechanical position. the coolant temp sensor controls fuel and timing based on a range of resistance varied by the heated element on the sensor. it also has the biggest influence on engine behavior in terms of fuel and timing curves (aside from using an EEC tuner). resistance goes down as the engine get hotter, thus retarding the timing and changing the fuel curve as appropriate. i measured the resistance between the wires on the octane plug and found it to be 1600 ohms. normally by default the octane plug is closed (connected), and if you pull the plug out it retards the timing by 3 degrees (in effect inserting 1600 ohms of resistance), turning the SC into a performance slug. interaction between the temp sensor and octane plug setting by that common wire indicates that the computer controls the timing under various engine conditions by altering the resistance in ohms. you can control resistance by inserting a certain resistor value across the octane plug thus setting the timing anywhere from default to - 3 degrees. i found you can also alter the timing curve (and richen the fuel curve) slightly by inserting a certain resistor value on the green lead in series coming off the temp sensor.
here are the resistor values i chose that completely eliminated the detonation without perceiving a loss of performance;
inserted (spliced in alligator clips temporarily) a 1300 ohm 1/2 watt resistor across the octane plug leads. this is a very precise adjustment- you can experiment resistor values here and see what works best- higher resistance=less timing, lower=more timing.
inserted with alligator clips a 3300 ohm 1/2 watt resistor in series on the green lead off the temp sensor. you can vary this up to 4500 ohms without running into detonation again. this seems to sharpen throttle response on my SC (similar to when you first start up with a cold engine). I did not notice this resistor to degrade cold start up performance.
if you still get detonation with these values, increase the resistance across the octane plug in increments of 100 ohms until it's gone.
Results??
no detonation whatsoever (could not hear any pinging or clicking sounds) under any hard acceleration loads in any gear or WOT.
At least by my seat of pants feel, the car is much more responsive than ever, and it does not bog down like it used to at certain rpm's/loads. top end power got better also. the car didn't feel as heavy. it's worth it to me-
some of you reading this will probably criticize the hell out of this and think that i'm crazy because i'm not doing it the "right way" with an EEC tuner, but the way i look at it... somebody's got to experiment and try to unlock the secrets of managing control of this car and achieving similar results without too much complication or money spent. I think my way is better because the resistor mods are subtle and it stays closer to stock computer settings assuming you have a mildly modded SC. the computer should not "learn" these changes out because these mods will not set a code or go outside of internal lookup table parameters. Modifying the electronics a little bit does not necessarily make this the "wrong way". You have to understand overall how ford sensors interact and change fuel and timing parameters. I mean if ford did it right the first time we wouldn't be going thru all of this. And if i wanted the ultimate performance machine it would not have bought the SC.
like i said, it works for my SC very well, maybe because the engine is old and carbonized. it's been running it this way for a couple of weeks now with absolutely no drivability or starting problems (cold or hot) other than the leaky injector thing when the engine is hot. i felt i had to share this info. to other SC'ers that are going thru challenging times with their cars.
sorry about the long thread.
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