Autospeed on many factors of ign timing
#1
09-25-2007, 10:30 AM
Autospeed on many factors of ign timing
The Austrailan teacher turned self-taught auto engineer
Julian Edgar consistently writes good stuff:
http://autospeed.com/cms/A_109132/article.html
as you read this,
consider these typical factory stock Magnum 5.9V8 readings
from an old post of 10/4/2000:
===
I have been playing around with the 'record' feature of the Actron ScanTool
with OBD-I Chrysler Cartridge on my 1995 5.9V8 auto with 3.21 differential
gears.
This records and stores 5 readings, 3 seconds apart, of what happened with the PCM computer sensors before you hit the button, and an additional 10 readings 3 seconds apart afterwards
Here is what the ScanTool recorded on some runs at full throttle in 2nd gear
up a pretty steep hill { I guess about 4% grade}. Outside temperature was in the 70's and the barometric pressure was 29.6 inches Hg.
MPH....RPM....SparkAdv..Vacuum....O2 voltsDC
40......2804.......19..........0.9..........0.86
48......3175.......19..........1.1..........0.90
54......3485.......18..........1.2..........0.90
60......3787.......21..........1.5..........0.90
65......4093.......24..........1.6..........0.90
71......4471.......24..........1.7..........0.92
76......4785.......28..........1.7..........0.90
80......5040.......28..........1.8..........0.90
Comments:
(a) I can't explain why the degrees of advance went down from 19 to 18 around 3400 rpm, but it read the same on two runs. Notice this occurs near the engine Torque peak, where cylinder pressures are highest.
(b) note that the O2 sensor stays fairly rich at 0.90 volts. 14.7 air/fuel
mixture is at 0.40 to 0.50 volts. Going by this graph:
0.90 volts would be something around 12 air/fuel mixture on an old O2 sensor that has 90,000 miles on it like mine does.
Kenne Bell says their more accurate 'wide range Horiba O2 sensor read 11.8 air tot fuel ratio on a model year 1998 5.9V8 Ram at full throttle.
(c) The maximum vacuum readings of 1.8 inches of mercury indicate that the
combination of air intake tube, air filter box and throttle body adds up to this amount, which is perhaps 0.8 higher than state of the art good design.
(d) I tried several ways to get data below 2500 rpm, but when you go to full
throttle the rpm's quickly go past 2000 rpm nearly instantly so the ScanTool
could not record low rpm readings. I would guess this means the 'stall speed' of the stock 46RH Torque Converter is something in the range of 1800 to 2000 rpm.
Intake Air Temperatures would start about 130 and drop to about 115F with the increased airflow at high rpms.
The coolant temperature started the runs at about 194 and went as high as 206 near the end of the thirty seconds runs at full throttle.
I made these runs after putting 7.5 gallons of 93 octane gasoline in a 26
gallon tank that showed 1/8th of a tank of 87 octane. This raised the fuel
gauge to 3/8ths of a tank. I would guess this blend worked out to be 89 to 90 octane. No pinging was heard at all during the runs - and I was listening
carefully for it. If I run straight 87 octane I hear slight pinging at 3800+
rpm.
This is the standard factory 1995 PCM computer with OBD-I software, not the
Mopar Performance Computer upgrade that specifies premium gasoline.
After 1996 the Ram's went to the OBD-II software inside the PCM computer, so I can't be sure these numbers would still apply. If your 1996+ Magnum engine has had the 'death flash' to reduce pinging I would guess your ignition timing at full throttle is considerably less.
Julian Edgar consistently writes good stuff:
http://autospeed.com/cms/A_109132/article.html
as you read this,
consider these typical factory stock Magnum 5.9V8 readings
from an old post of 10/4/2000:
===
I have been playing around with the 'record' feature of the Actron ScanTool
with OBD-I Chrysler Cartridge on my 1995 5.9V8 auto with 3.21 differential
gears.
This records and stores 5 readings, 3 seconds apart, of what happened with the PCM computer sensors before you hit the button, and an additional 10 readings 3 seconds apart afterwards
Here is what the ScanTool recorded on some runs at full throttle in 2nd gear
up a pretty steep hill { I guess about 4% grade}. Outside temperature was in the 70's and the barometric pressure was 29.6 inches Hg.
MPH....RPM....SparkAdv..Vacuum....O2 voltsDC
40......2804.......19..........0.9..........0.86
48......3175.......19..........1.1..........0.90
54......3485.......18..........1.2..........0.90
60......3787.......21..........1.5..........0.90
65......4093.......24..........1.6..........0.90
71......4471.......24..........1.7..........0.92
76......4785.......28..........1.7..........0.90
80......5040.......28..........1.8..........0.90
Comments:
(a) I can't explain why the degrees of advance went down from 19 to 18 around 3400 rpm, but it read the same on two runs. Notice this occurs near the engine Torque peak, where cylinder pressures are highest.
(b) note that the O2 sensor stays fairly rich at 0.90 volts. 14.7 air/fuel
mixture is at 0.40 to 0.50 volts. Going by this graph:
0.90 volts would be something around 12 air/fuel mixture on an old O2 sensor that has 90,000 miles on it like mine does.
Kenne Bell says their more accurate 'wide range Horiba O2 sensor read 11.8 air tot fuel ratio on a model year 1998 5.9V8 Ram at full throttle.
(c) The maximum vacuum readings of 1.8 inches of mercury indicate that the
combination of air intake tube, air filter box and throttle body adds up to this amount, which is perhaps 0.8 higher than state of the art good design.
(d) I tried several ways to get data below 2500 rpm, but when you go to full
throttle the rpm's quickly go past 2000 rpm nearly instantly so the ScanTool
could not record low rpm readings. I would guess this means the 'stall speed' of the stock 46RH Torque Converter is something in the range of 1800 to 2000 rpm.
Intake Air Temperatures would start about 130 and drop to about 115F with the increased airflow at high rpms.
The coolant temperature started the runs at about 194 and went as high as 206 near the end of the thirty seconds runs at full throttle.
I made these runs after putting 7.5 gallons of 93 octane gasoline in a 26
gallon tank that showed 1/8th of a tank of 87 octane. This raised the fuel
gauge to 3/8ths of a tank. I would guess this blend worked out to be 89 to 90 octane. No pinging was heard at all during the runs - and I was listening
carefully for it. If I run straight 87 octane I hear slight pinging at 3800+
rpm.
This is the standard factory 1995 PCM computer with OBD-I software, not the
Mopar Performance Computer upgrade that specifies premium gasoline.
After 1996 the Ram's went to the OBD-II software inside the PCM computer, so I can't be sure these numbers would still apply. If your 1996+ Magnum engine has had the 'death flash' to reduce pinging I would guess your ignition timing at full throttle is considerably less.