Optimizing timing
The way I did it was to drive around collecting KR data and
using the max retard histogram, adding 2 degrees to any cell
that saw no KR and subtracting 1 from any cell (MAP*CylAir)
that did. It took a while since at the time there wasn't the
whole-histogram-subtract function in HPTuners that there
is in later releases. That gets you to a condition where every
cell is borderline for ping. Knowing that MBT timing is a few
degrees before ping onset, subtract your margin-of-comfort
(I took out 3 degrees if I recall) and you're there. Of course
you might prefer to back off more than a couple of degrees
in places where max torque is not really necessary (like
low/mid throttle, where more torque is to be had for the
asking by pedal). And realize the closer you tweak it up
on one day, the more you depend on the quality of the
ECT, IAT spark adders and consistency of fueling to keep
you on the right side of it when the weather changes and
the blacktop gets to cookin'.
I haven't repeated the exercise since the cam swap but it
sounds like it wants it, in spots.
using the max retard histogram, adding 2 degrees to any cell
that saw no KR and subtracting 1 from any cell (MAP*CylAir)
that did. It took a while since at the time there wasn't the
whole-histogram-subtract function in HPTuners that there
is in later releases. That gets you to a condition where every
cell is borderline for ping. Knowing that MBT timing is a few
degrees before ping onset, subtract your margin-of-comfort
(I took out 3 degrees if I recall) and you're there. Of course
you might prefer to back off more than a couple of degrees
in places where max torque is not really necessary (like
low/mid throttle, where more torque is to be had for the
asking by pedal). And realize the closer you tweak it up
on one day, the more you depend on the quality of the
ECT, IAT spark adders and consistency of fueling to keep
you on the right side of it when the weather changes and
the blacktop gets to cookin'.
I haven't repeated the exercise since the cam swap but it
sounds like it wants it, in spots.
Thread Starter
TECH Enthusiast
Joined: Dec 2003
Posts: 535
Likes: 0
From: Warner Robins, GA
That sounds like a pretty good plan Jimmyblue. Have you ever monitored a PID that reflected the engine's efficiency such as calculated HP/torque or perhaps fuel injector pulse wiidth? I know this would be very time consuming but might provide accurate results.
I've been able to make some timing determinations by watching instantaneous fuel milage and tweaking the timing +/- a few degrees. This is also quite distracting while driving and not recommended to do by yourself.
I've been able to make some timing determinations by watching instantaneous fuel milage and tweaking the timing +/- a few degrees. This is also quite distracting while driving and not recommended to do by yourself.
Originally Posted by jimmyblue
Knowing that MBT timing is a few
degrees before ping onset, subtract your margin-of-comfort
(I took out 3 degrees if I recall) and you're there.
degrees before ping onset, subtract your margin-of-comfort
(I took out 3 degrees if I recall) and you're there.
Teching In
Joined: Nov 2006
Posts: 8
Likes: 0
From: Colorado Springs, CO
WOW! I am sorry, but using a $25 sensor as your break point for max timing is not the way to do it whether you do offset calculations for MBT or not!
RedHardSupra is absolutely correct. I tune for a living. I have seen plenty of tunes come in from other shops in the Colorado area that seems like they are tuning using knock sensed as the break point. As RHS stated...max power and torque may show at 20-25* and knock does not get sensed until 30-36* of timing. The bad part is weekend tuners or "pro" tuning shops may be underrating the clients car by as much as 10-15HP and 8-10ft/lbs by using maximum timing that is offset by a knock sensor.
Anyway...I do not wish to step on anyone's toes here, but to tune with a knock sensor absolutely is the wrong way to tune properly.
-Kenny
RedHardSupra is absolutely correct. I tune for a living. I have seen plenty of tunes come in from other shops in the Colorado area that seems like they are tuning using knock sensed as the break point. As RHS stated...max power and torque may show at 20-25* and knock does not get sensed until 30-36* of timing. The bad part is weekend tuners or "pro" tuning shops may be underrating the clients car by as much as 10-15HP and 8-10ft/lbs by using maximum timing that is offset by a knock sensor.
Anyway...I do not wish to step on anyone's toes here, but to tune with a knock sensor absolutely is the wrong way to tune properly.
-Kenny
Thread Starter
TECH Enthusiast
Joined: Dec 2003
Posts: 535
Likes: 0
From: Warner Robins, GA
I tend to agree that tuning for max power and torque is best done on a dyno. That pretty much is a given but, what I was asking and what jimmyblue was inferring is that for other than WOT settings, ie. high vacuum, low load such as seen in highway cruising, tuning for KR and then backing off several degrees might not be a bad way to go.
Before I would take this route though, I would like to see some empirical evidence such as could be accumulated from some serious dyno time, the type of dyno that simulates road conditions.
Before I would take this route though, I would like to see some empirical evidence such as could be accumulated from some serious dyno time, the type of dyno that simulates road conditions.
