Some HPT questions...
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12 Second Club
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From: Clarksville, TN
Some HPT questions... I keep getting these spikes when I'm logging. anyone have any ideas?
Also, I can't figure out why my timing table at WOT is getting dips. I'm not reading any KR or anything else... (in the red box. Drops from 28* to 20* and jumps around in there for a bit.
Also, I can't figure out why my timing table at WOT is getting dips. I'm not reading any KR or anything else... (in the red box. Drops from 28* to 20* and jumps around in there for a bit.
The "spikes" could be spurious data output or could be
reactions to some noisy sensor data coming in; the second
chart looks like injector duty is responding to a MAF blip
(other charts do not display MAF airflow). If this is a
consistent relation then you may have problems with the
MAF signal being corrupted (like by underhood EMI). That
would also corrupt the Dynamic Cylinder Air value that is
the index for spark timing tables. Try more extensive logging
of the MAF frequency and airflow values, look for spikes or
peculiar action in the MAF, see if it tends to be at a particular
RPM or MAF output frequency (a "beat note" that might
indicate EMI from some local source, coupling in). Review the
MAF table and be sure you do not have some gross spike or
divot that messes up the translation from raw frequency to
airflow value, that would make a discontinuous airflow value
as the continuous airflow, frequency output slides across it.
Look for timing or fueling spikes in the absence of MAF spikes,
which would disprove this EMI theory. Log the Dynamic
Cylinder AIR PID and see where you are sitting, WOT and
upper RPM where you don't like the spark activity; look in that
region of the table and see if the surface is smooth or messy.
Finally, check the sensor outputs that can modify fuel and
spark - IAT, ECT - for correlation to the oddities; I have seen
an intermittent ECT sensor connector really whack spark
around, real-time, but the ECT is very obviously busy in such
a case.
reactions to some noisy sensor data coming in; the second
chart looks like injector duty is responding to a MAF blip
(other charts do not display MAF airflow). If this is a
consistent relation then you may have problems with the
MAF signal being corrupted (like by underhood EMI). That
would also corrupt the Dynamic Cylinder Air value that is
the index for spark timing tables. Try more extensive logging
of the MAF frequency and airflow values, look for spikes or
peculiar action in the MAF, see if it tends to be at a particular
RPM or MAF output frequency (a "beat note" that might
indicate EMI from some local source, coupling in). Review the
MAF table and be sure you do not have some gross spike or
divot that messes up the translation from raw frequency to
airflow value, that would make a discontinuous airflow value
as the continuous airflow, frequency output slides across it.
Look for timing or fueling spikes in the absence of MAF spikes,
which would disprove this EMI theory. Log the Dynamic
Cylinder AIR PID and see where you are sitting, WOT and
upper RPM where you don't like the spark activity; look in that
region of the table and see if the surface is smooth or messy.
Finally, check the sensor outputs that can modify fuel and
spark - IAT, ECT - for correlation to the oddities; I have seen
an intermittent ECT sensor connector really whack spark
around, real-time, but the ECT is very obviously busy in such
a case.
Thread Starter
12 Second Club
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From: Clarksville, TN
Foff667: 42#'ers. I was running 130% duty cycle with my stockers so I thought I'd step-up a bit 
Jimmyblue: all great suggestions! I checked the other inputs and I've got fairly static readings on everything until something will spike like that. It's fairly random what will go, too. My MAF's been unplugged for about 2-3 months, so it SHOULD be out of the picture, other than it spiking all along, too. My timing tables are FLAT at 28* all around the affected cells. IAT and ECT are both look proper. Anything else I'm overlooking?
Jimmyblue: all great suggestions! I checked the other inputs and I've got fairly static readings on everything until something will spike like that. It's fairly random what will go, too. My MAF's been unplugged for about 2-3 months, so it SHOULD be out of the picture, other than it spiking all along, too. My timing tables are FLAT at 28* all around the affected cells. IAT and ECT are both look proper. Anything else I'm overlooking?
TECH Senior Member
Joined: Nov 2001
Posts: 7,036
Likes: 1
From: Lake Zurich, IL
i may have missed it... but is this with a usb to serial adapter or w/the MPVI unit? (raw usb)
If it's an adapter, verify your serial settings as far as buffers and such match the help file... another option is to create new filters so that values outside valid ranges won't be included and skew the data
Sounds like it's a data burb so to speak between the interface and hte laptop.. .if you're running a usb to serial then that's likely the culprit... changing the buffers may help
If it's an adapter, verify your serial settings as far as buffers and such match the help file... another option is to create new filters so that values outside valid ranges won't be included and skew the data
Sounds like it's a data burb so to speak between the interface and hte laptop.. .if you're running a usb to serial then that's likely the culprit... changing the buffers may help
Thread Starter
12 Second Club
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From: Clarksville, TN
straight serial port cable to serial port...
I checked out a log I did of my buddy's car from this weekend... It's spike free. I think I may have figured this out...
I went through and relooked all my old log files. It seems that after a certain point in time all the logging I did by myself (aka laptop on passenger seat) has spikes and the ones with the laptop on my GF's lap are spike-free what I can't figure out is why all the logging I did by myself BEFORE that (not sure exactly when this certain time was) doesn't have the spikes.
I've been leaving the cable plugged in the car lately, even when not connected to the laptop. Think that might be part of the issue?
I checked out a log I did of my buddy's car from this weekend... It's spike free. I think I may have figured this out...
I went through and relooked all my old log files. It seems that after a certain point in time all the logging I did by myself (aka laptop on passenger seat) has spikes and the ones with the laptop on my GF's lap are spike-free what I can't figure out is why all the logging I did by myself BEFORE that (not sure exactly when this certain time was) doesn't have the spikes.
I've been leaving the cable plugged in the car lately, even when not connected to the laptop. Think that might be part of the issue?
