HP Tuners (Max Speed setting under spark advance)
11-09-2016, 11:26 PM
#1
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HP Tuners (Max Speed setting under spark advance) Can anyone tell me why you would ever set this variable so low? I ask because I had my car tuned and my assumption is that this controls when to use/not use the main spark table... Am I incorrect in assuming this? From the speed @ 10mph, that means anything over 10mph it will not use the main spark table?
Ok, after reading on HPTuners, I think what this is used for is basically if you are at WOT and lift off the gas pedal, it will look at the base timing instead of the main spark tables if either the TPS or the mph is exceeded.
IE: TPS showing WOT and your going 60mph. You lift, the TPS should now read 0 and since your going over 10mph it should disable the main spark tables to read from and use the base spark tables...
Hopefully I am understanding that correctly. I notice some tunes are set to 250mph in that setting and I couldn't see the benefit or reason to use it. My assumption is it has something to do with timing to help reduce knock after lifting off the gas pedal on a WOT type run.
Ok, after reading on HPTuners, I think what this is used for is basically if you are at WOT and lift off the gas pedal, it will look at the base timing instead of the main spark tables if either the TPS or the mph is exceeded.
IE: TPS showing WOT and your going 60mph. You lift, the TPS should now read 0 and since your going over 10mph it should disable the main spark tables to read from and use the base spark tables...
Hopefully I am understanding that correctly. I notice some tunes are set to 250mph in that setting and I couldn't see the benefit or reason to use it. My assumption is it has something to do with timing to help reduce knock after lifting off the gas pedal on a WOT type run.
Last edited by silvershark; 11-10-2016 at 12:00 AM.
11-10-2016, 04:33 PM
#3
I don't know. I don't change it. I'd rather not enter into my idle cells, even if they match the main timing cells. That's just something for the PCM to jump back and forth on.
And the reason is simple: you don't fall into a low enough airmass when you shut the TB after a WOT run for it to be a problem. You fall back down the RPM scale sort of linearly down the airmass. So if you're at 26 WOT and lifted your foot, you'd just fall from 1.04g to 1.00 to .96 and so forth down until you are back to idle. At those levels, I'm at 26 across the board down to .56g or so. Then it might creep up to the low 30s until idle. All of that results in a fairly controlled deceleration.
And the reason is simple: you don't fall into a low enough airmass when you shut the TB after a WOT run for it to be a problem. You fall back down the RPM scale sort of linearly down the airmass. So if you're at 26 WOT and lifted your foot, you'd just fall from 1.04g to 1.00 to .96 and so forth down until you are back to idle. At those levels, I'm at 26 across the board down to .56g or so. Then it might creep up to the low 30s until idle. All of that results in a fairly controlled deceleration.
11-10-2016, 06:11 PM
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I haven't changed mine, just curious why others are.... I am of the same thinking, if I don't know what it does, then why change it? Just trying to learn something was all.
11-11-2016, 09:04 AM
#5
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The stock value for a 2002 Camaro is 4 mph; which means that the main spark tables are used above 4 mph regardless of the throttle position.
Mine and others performance tunes have it set to 255 mph, which means the main spark tables are used with a TPS above 1.2% and the idle spark tables are used below 1.2%.
So basically a low value of e.g. 4 or 10 mph uses the main spark tables during coast down, while a high value of e.g. 250 uses the Idle-Drive spark table during coast down with a closed throttle.
Like Jake, my Idle-Drive and main High-Octane tables match each other very closely; therefore this MPH value would have almost no effect.
Looking at my C6 stock tune, the E38 ECM does not have this value; instead it has a Idle-Coastdown spark table.
Mine and others performance tunes have it set to 255 mph, which means the main spark tables are used with a TPS above 1.2% and the idle spark tables are used below 1.2%.
So basically a low value of e.g. 4 or 10 mph uses the main spark tables during coast down, while a high value of e.g. 250 uses the Idle-Drive spark table during coast down with a closed throttle.
Like Jake, my Idle-Drive and main High-Octane tables match each other very closely; therefore this MPH value would have almost no effect.
Looking at my C6 stock tune, the E38 ECM does not have this value; instead it has a Idle-Coastdown spark table.
11-11-2016, 09:58 AM
#6
My stock table shows 255.4 and 3% TPS. Haven't looked into it. But, I know my car uses the idle table, and if you have a huge delta of >2 degrees between main spark and idle, it does cause surging/hesitation on coast down.
Last edited by JakeFusion; 11-11-2016 at 10:13 AM.
11-11-2016, 10:13 AM
#7
James Short said this:
And Chris from HPT said this:
So yes, it goes into idle to allow for coast down. Setting it higher forces it to the idle spark table when you go to 0% TPS.
I usually set this to ~250mph on most tunes because if you are moving and you let off the throttle sometimes if it still uses the main spark table the higher ignition timing will cause the car to idle high, but by raising this speed you basically are telling the computer to go off the idle spark table if the throttle is closed while the car is still or moving.
If the TPS is above the thresholds the Main Table is active
If the TPS is below the threshold and if you are below this speed then the idle spark tables will be used (assuming the TPS is also less than the threshold).
If TPS is below but speed is above the threshold, then Main table is used.
If the TPS is below the threshold and if you are below this speed then the idle spark tables will be used (assuming the TPS is also less than the threshold).
If TPS is below but speed is above the threshold, then Main table is used.
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11-11-2016, 01:58 PM
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Ok, excellent. Thanks for the clarification. So it was doing as I thought, I just couldn't explain it well enough.
If your idle tables and main spark tables are different, that would be the main reason someone would change it would be my understanding... Otherwise, it really has no affect.
If your idle tables and main spark tables are different, that would be the main reason someone would change it would be my understanding... Otherwise, it really has no affect.