0 Degrees Advance?? What gives?
Thread Starter
12 Second Club
Joined: Aug 2002
Posts: 115
Likes: 0
From: Tampa, Fl
0 Degrees Advance?? What gives? I've been logging my car for several months now, and I've noticed some really strange things. My biggest concern now is that I am seeing 0 degrees advance when running in Open Loop and no throttle (engine breaking, or just cruising after a WOT run). That just doesn't seem right. Here's an example:
<img src="http://andyj.ij.net/noadvance.jpg" alt=" - " />
It also drops down to about 6 degrees advance when shifting from 1->2, and 2->3 drops down considerably as well. To add to the confusion, my RPM's never drop below 4200 (I have 3000 stall) when shifting. Here's an example of that:
<img src="http://andyj.ij.net/shiftadvance.jpg" alt=" - " />
Anyone have any ideas?
<img src="http://andyj.ij.net/noadvance.jpg" alt=" - " />
It also drops down to about 6 degrees advance when shifting from 1->2, and 2->3 drops down considerably as well. To add to the confusion, my RPM's never drop below 4200 (I have 3000 stall) when shifting. Here's an example of that:
<img src="http://andyj.ij.net/shiftadvance.jpg" alt=" - " />
Anyone have any ideas?
TECH Addict
Joined: Nov 2001
Posts: 2,207
Likes: 0
From: College Station, Tx
Re: 0 Degrees Advance?? What gives? Try logging your injector pulse-widths when engine braking; many times they will pretty much shut off - after all, why do you need fuel when you are letting the inertia of your car turn your motor/accessories over?
It is also probably entirely normal for spark advance to go to 0 or so there - you aren't trying to make any power - infact you are using the engine to dissipate it. So why have any advance, and why burn any fuel?
The timing@ shift anomaly sounds like a torque management issue.
Chris
It is also probably entirely normal for spark advance to go to 0 or so there - you aren't trying to make any power - infact you are using the engine to dissipate it. So why have any advance, and why burn any fuel?
The timing@ shift anomaly sounds like a torque management issue.
Chris
On The Tree
Joined: Nov 2001
Posts: 168
Likes: 0
From: Michigan
Re: 0 Degrees Advance?? What gives? >>>I'm asuming you've got a stock GM programed PCM here!>>>
>>>0* timeing @ closed throttle deceleration: This is normal for a stock calibrated GM PCM. ...
I've seen my 99 TA A4 go to; ...
+0.5* @ 1700ish RPM
+10* @ 4000ish RPM
I've seen a buds 97 5.7 A4 truck go; ...
-5.0* @ below 1500ish RPM
... I feel its got something to do with engine brakeing. ... The truck engines seem to have great engine brakeing over the car engines (could also be the cam grind too). ... My 99 5.3 A4 truck seems to have a ton more engine brakeing over my 99 TA.
>>>drop to 6* between shifts: This is normal too ... GM's "tourque management".
I've seen my 99 TA A4 go;
-2.0*ish between 1/2 & 2/3 WOT shifts
... I feel this "TM" is GM's way of getting a trans to live behind the LS1 power.
FWIW: check out your WOT timeing map between 3.8K and 5.1K RPM. You might see go right down the toilet.
Ron
>>>0* timeing @ closed throttle deceleration: This is normal for a stock calibrated GM PCM. ...
I've seen my 99 TA A4 go to; ...
+0.5* @ 1700ish RPM
+10* @ 4000ish RPM
I've seen a buds 97 5.7 A4 truck go; ...
-5.0* @ below 1500ish RPM
... I feel its got something to do with engine brakeing. ... The truck engines seem to have great engine brakeing over the car engines (could also be the cam grind too). ... My 99 5.3 A4 truck seems to have a ton more engine brakeing over my 99 TA.
>>>drop to 6* between shifts: This is normal too ... GM's "tourque management".
I've seen my 99 TA A4 go;
-2.0*ish between 1/2 & 2/3 WOT shifts
... I feel this "TM" is GM's way of getting a trans to live behind the LS1 power.
FWIW: check out your WOT timeing map between 3.8K and 5.1K RPM. You might see go right down the toilet.
Ron
