Fuel Injection Quanity-Injection Timing

LanduytG

Vendor
Joined
Sep 5, 2001
Location
Greenfield, IN
TDI
99 NB 82 Westfalia Diesel
Well I went and looked at what I had again, this is what I had.

Inj Quantity 1.8
Inj Timing .4
Inj Timing 2.4

I did have the shudder around 1800 rpm, and it did smoke a lot. This is what I changed it to.

Inj Quantity 3.0
Inj Timing 2.2
Inj Timing 2.4

Runs much better, shudder is gone and no smoke.

Greg
 

LanduytG

Vendor
Joined
Sep 5, 2001
Location
Greenfield, IN
TDI
99 NB 82 Westfalia Diesel
Been playing with the Vag Com and what should the injection quanity and injection timing be at idle in group 001 block 1 and block 4? I did a search because I know its been discussed many times but can't find it.
Thanks
Greg
 

GoFaster

Moderator at Large
Joined
Jun 16, 1999
Location
Brampton, Ontario, Canada
TDI
2006 Jetta TDI
with engine warm (coolant temp > 80 C) and all accessories switched off:

Specification range for fuel injection quantity at idle is 2.2 to 9.0 mg/stroke but they seem to run best between 3.0 and 4.0 mg/stroke. Smaller than that range, shudder issue. Bigger than that range, not really a big deal but a bit less power.

Injection timing - depends on ECU - I've seen from 0.4 to 2.0 degrees BTDC but the important thing is that the "duty cycle" is small and that the "requested" and "actual" are not different by more than a degree or so. Better to use the group 0 "basic settings" / Bentley graph method.

If someone has done something that they shouldn't be doing with the adaptation settings, the requested (and actual) timing may be outside this range. Don't ever change the timing adaptation for any reason whatsoever - too risky.
 

LanduytG

Vendor
Joined
Sep 5, 2001
Location
Greenfield, IN
TDI
99 NB 82 Westfalia Diesel
Seems to me if its calling for 2.4 and its not getting it that move the adaptation to 2.4 should hurt? The duty cycle remained the same at 2.8%.
My timing is at 69-110 also and thats in basic settings.
Greg
 

GoFaster

Moderator at Large
Joined
Jun 16, 1999
Location
Brampton, Ontario, Canada
TDI
2006 Jetta TDI
Your mechanical pump timing is slightly too far advanced, that's why the duty cycle remained low.

Adjusting the adaptation to match the too-far-advanced mechanical setting is the WRONG thing to do. You need to adjust the mechanical setting so that it is correct for the default (non-adapted) timing in the ECU. If your pump is slightly too far advanced at idle, it will not be too far advanced under load, the ECU will get what it wants. But if you change the adaptation, you have now requested a couple degrees more timing advance under ALL speed and load conditions including full load!!

Every 2 degrees of actual timing advance at full load raises peak cylinder pressure by 15 bar and raises piston temperature by an unknown amount.

I'd suggest that you put your adaptation back. I wouldn't touch the mechanical setting - it's close enough. If you watch what it does under load and at different speeds, you'll find that the ECU is getting what it wants under all conditions except it's a little advanced at idle and close to zero engine load.
 
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