Confusing scan
02-12-2017, 07:26 PM
#1
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Confusing scan
A friend showed me a scan he did on his cammed '07 A6 base. His other mods are Vararam, headers, Yank 4000 converter, FAST intake manifold, an upgraded trans, a 3.42 gear, and a tune by one of the better tuners in the area.
He normally runs 11.0x - 11.1x, but the speed is never over 121. I knew something was wrong and finally got him to do a scan on a couple WOT runs. Without it in front of me now, here's some brief info.
He spun in first and most of second before it hooked, so I disregard that. Around 70 mph and 4600 rpm in 3rd gear it's hooked up solid. From there to about 100 mph and 6500 rpm the advance is dead steady at 21*, while the injector duty moves from the low 80's to low 90's.
Then the shift to 4th drops the rpm to around 5800, which is higher than the 5000 I expected. The mph continues up at a steady rate, but the rpm gain is much slower to about 6300 at 115 mph. Then a totally unexpected instant advance drop to 12* for about 1 second that jumps back to 21* again, while the rpm falls off to 5800. The rpm slowly increases to almost 6000 by the time the mph is 120. The injector duty matched the 3rd gear rate.
I'm guessing the injector size needs increased, but I think the bigger problem is that his tune is either trying to lock the converter at the 3-4 shift and it never locks or the trans is slipping in 4th. I'm leaning more toward a trans problem, so anyone with opinions?
He normally runs 11.0x - 11.1x, but the speed is never over 121. I knew something was wrong and finally got him to do a scan on a couple WOT runs. Without it in front of me now, here's some brief info.
He spun in first and most of second before it hooked, so I disregard that. Around 70 mph and 4600 rpm in 3rd gear it's hooked up solid. From there to about 100 mph and 6500 rpm the advance is dead steady at 21*, while the injector duty moves from the low 80's to low 90's.
Then the shift to 4th drops the rpm to around 5800, which is higher than the 5000 I expected. The mph continues up at a steady rate, but the rpm gain is much slower to about 6300 at 115 mph. Then a totally unexpected instant advance drop to 12* for about 1 second that jumps back to 21* again, while the rpm falls off to 5800. The rpm slowly increases to almost 6000 by the time the mph is 120. The injector duty matched the 3rd gear rate.
I'm guessing the injector size needs increased, but I think the bigger problem is that his tune is either trying to lock the converter at the 3-4 shift and it never locks or the trans is slipping in 4th. I'm leaning more toward a trans problem, so anyone with opinions?
02-13-2017, 12:40 PM
#2
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HOXY, the 1 second timing "blip" may be fuel/injector related, if it may be on the lean side...........the trans. issue does seem to be like it could be a factor.........especially if/when the converter locks, as the older GM transmissions would have potential issues with overheating the clutch plates if it didn't lock.......something to do with internal hydraulic routing through the auto trans. valve body on prior versions............I did inquire from a GM C6 trans. auto person on this, awaiting info. but could PM you what he states...........
02-13-2017, 10:14 PM
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HOXY, the 1 second timing "blip" may be fuel/injector related, if it may be on the lean side...........the trans. issue does seem to be like it could be a factor.........especially if/when the converter locks, as the older GM transmissions would have potential issues with overheating the clutch plates if it didn't lock.......something to do with internal hydraulic routing through the auto trans. valve body on prior versions............I did inquire from a GM C6 trans. auto person on this, awaiting info. but could PM you what he states...........
The A6 trans weakness seems to be centered around the 3-4 shift. It's why I'm suspecting slipping clutch plates more than a converter issue.
BTW, You'll get to meet RR Bob, the car owner, when you visit on the 28th.
02-14-2017, 07:11 AM
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The timing blip on the scan only occurs in 4th gear and it has the appearance of a square wave. It has no sequence that remotely resembles knock retard. My more recent thought is that the tuner was hand entering 21* incrementally and had fat fingered a 12 rather than a 21. Makes sense now knowing that it doesn't resemble knock retard
The A6 trans weakness seems to be centered around the 3-4 shift. It's why I'm suspecting slipping clutch plates more than a converter issue.
if that is the case, similar to the older 4 speed autos. which I am more familiar with.......would think GM kept the internal hydraulic routing the same as to them it worked in the past....
BTW, You'll get to meet RR Bob, the car owner, when you visit on the 28th.
looking forward to the trip........for more than the weather..........stilll waiting to hear from my contact related to the A6 at this time...............
The A6 trans weakness seems to be centered around the 3-4 shift. It's why I'm suspecting slipping clutch plates more than a converter issue.
if that is the case, similar to the older 4 speed autos. which I am more familiar with.......would think GM kept the internal hydraulic routing the same as to them it worked in the past....
BTW, You'll get to meet RR Bob, the car owner, when you visit on the 28th.
looking forward to the trip........for more than the weather..........stilll waiting to hear from my contact related to the A6 at this time...............
02-14-2017, 12:47 PM
#5
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A friend showed me a scan he did on his cammed '07 A6 base. His other mods are Vararam, headers, Yank 4000 converter, FAST intake manifold, an upgraded trans, a 3.42 gear, and a tune by one of the better tuners in the area.
He normally runs 11.0x - 11.1x, but the speed is never over 121. I knew something was wrong and finally got him to do a scan on a couple WOT runs. Without it in front of me now, here's some brief info.
He spun in first and most of second before it hooked, so I disregard that. Around 70 mph and 4600 rpm in 3rd gear it's hooked up solid. From there to about 100 mph and 6500 rpm the advance is dead steady at 21*, while the injector duty moves from the low 80's to low 90's.
Then the shift to 4th drops the rpm to around 5800, which is higher than the 5000 I expected. The mph continues up at a steady rate, but the rpm gain is much slower to about 6300 at 115 mph. Then a totally unexpected instant advance drop to 12* for about 1 second that jumps back to 21* again, while the rpm falls off to 5800. The rpm slowly increases to almost 6000 by the time the mph is 120. The injector duty matched the 3rd gear rate.
I'm guessing the injector size needs increased, but I think the bigger problem is that his tune is either trying to lock the converter at the 3-4 shift and it never locks or the trans is slipping in 4th. I'm leaning more toward a trans problem, so anyone with opinions?
He normally runs 11.0x - 11.1x, but the speed is never over 121. I knew something was wrong and finally got him to do a scan on a couple WOT runs. Without it in front of me now, here's some brief info.
He spun in first and most of second before it hooked, so I disregard that. Around 70 mph and 4600 rpm in 3rd gear it's hooked up solid. From there to about 100 mph and 6500 rpm the advance is dead steady at 21*, while the injector duty moves from the low 80's to low 90's.
Then the shift to 4th drops the rpm to around 5800, which is higher than the 5000 I expected. The mph continues up at a steady rate, but the rpm gain is much slower to about 6300 at 115 mph. Then a totally unexpected instant advance drop to 12* for about 1 second that jumps back to 21* again, while the rpm falls off to 5800. The rpm slowly increases to almost 6000 by the time the mph is 120. The injector duty matched the 3rd gear rate.
I'm guessing the injector size needs increased, but I think the bigger problem is that his tune is either trying to lock the converter at the 3-4 shift and it never locks or the trans is slipping in 4th. I'm leaning more toward a trans problem, so anyone with opinions?
02-20-2017, 09:20 PM
#6
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When the trans shifts their are several ways the ECM will remove TQ during the shift in order to have less stress on the engine and trans----
There are 3 ways the ECM removes TQ
1 throttle control
2 fuel cutoff
3 timing reduction
Many tuners will leave most of this shifting TQ MGMT in place--However I always delete all the timing reductions at shifting----Mostly for the reason you mention is that you will get a low timing value briefly and this hurts the RPM ramp up and throttle response
Are you sure it is not "burst knock " ?? I always delete all the burst knock above 3600 RPM's by zero ing out the table only at WOT and above 3600RPM
There are 3 ways the ECM removes TQ
1 throttle control
2 fuel cutoff
3 timing reduction
Many tuners will leave most of this shifting TQ MGMT in place--However I always delete all the timing reductions at shifting----Mostly for the reason you mention is that you will get a low timing value briefly and this hurts the RPM ramp up and throttle response
Are you sure it is not "burst knock " ?? I always delete all the burst knock above 3600 RPM's by zero ing out the table only at WOT and above 3600RPM