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Timing
Hi All,
I got this off the Aussy Site, Have tried it and it has worked Brill for me on my LN130 2.4 L-TE Have ago and see what you think.
The fix for perfect timing
Disconnect positive battery leads, turn headlights on, wait 8 hours, reconnect battery leads.
Do this each time you mess with the pump or every couple of years anyway.
The result (for me)
[The timing definitely advanced by several degrees to what I believe is perfect timing. I have more power and more economy.
Starts easily without glowing - previously needed glow plus idle up.
Full boost (10) comes on at 2K. Previously 2.5+
Slightly more diesel knock in start up.
Max torque is now where it should be at around 2,200. My truck now rumbles around the city at no more than 1.5 to 2k revs.
I am looking a bit stupified at my trip meter. Its is showing 180k for 1/3 tank - well under 9 per 100 and this for worst
case city driving, lots of cold starts and short trips.
Much better acceleration.
No smoke whatsoever. None. Zilch.
So whats the explanation?
I cant get a workshop manual for the Denso pump - but I believe it is based on a Bosch design and I had the workshop manual
for the Bosch EFI. Based on that manual this is what I think happened. With this generation of EFI, the mechanic lines up
the distributor as a "basic setting". If you think about it, lining up the timing marks on the pump and the block is very
approximate. What is needed is exact timing so that the burn starts in the pre chamber while compression is still rising.
This gives a complete burn and highest cylinder pressure. With this generation of EFI the ECU once only takes the position
of the crank and uses this to adjust its internal mapping so that it then knows where TDC on the pump is. The ECU does the
fine pump timing adjustment ONCE ONLY and then it advances or retards according to the sensors. It does NOT go back to the
crank sensor.
I think there may be a bit of a flaw in the Denso EFI. On the Bosch, they stress that when the ignition is turned on ,
the first thing that happens is the crank reference is reset for that journey. Clearly the Denso is not doing this - as
giving the ECU amnesia by disconnecting the batteries and allowing enough time for the capacitors to discharge meant that
when the truck was restarted the ECU had to go to the crank sensor to get an updated reference and my timing changed from
poor to perfect.
When I look back my batteries have not been offline for more than an hour or so since I had the truck,
including when I changed the pump for a 5B300. The ECU had never fine tuned the new pump basic setting to the crank - the
ECU thought it was still driving my old pump!
Also, wear means that over the years the timing will retard. So it is good to reset so that the ECU compensates for
the wear.
Follow up
There may be a better way of quickly discharging the ECU perhaps by using the diagnostic connectors -
but I cant find any references. I dont know if 8 hours offline is required - but I do know that 1 hour is no good
I got this off the Aussy Site, Have tried it and it has worked Brill for me on my LN130 2.4 L-TE Have ago and see what you think.
The fix for perfect timing
Disconnect positive battery leads, turn headlights on, wait 8 hours, reconnect battery leads.
Do this each time you mess with the pump or every couple of years anyway.
The result (for me)
[The timing definitely advanced by several degrees to what I believe is perfect timing. I have more power and more economy.
Starts easily without glowing - previously needed glow plus idle up.
Full boost (10) comes on at 2K. Previously 2.5+
Slightly more diesel knock in start up.
Max torque is now where it should be at around 2,200. My truck now rumbles around the city at no more than 1.5 to 2k revs.
I am looking a bit stupified at my trip meter. Its is showing 180k for 1/3 tank - well under 9 per 100 and this for worst
case city driving, lots of cold starts and short trips.
Much better acceleration.
No smoke whatsoever. None. Zilch.
So whats the explanation?
I cant get a workshop manual for the Denso pump - but I believe it is based on a Bosch design and I had the workshop manual
for the Bosch EFI. Based on that manual this is what I think happened. With this generation of EFI, the mechanic lines up
the distributor as a "basic setting". If you think about it, lining up the timing marks on the pump and the block is very
approximate. What is needed is exact timing so that the burn starts in the pre chamber while compression is still rising.
This gives a complete burn and highest cylinder pressure. With this generation of EFI the ECU once only takes the position
of the crank and uses this to adjust its internal mapping so that it then knows where TDC on the pump is. The ECU does the
fine pump timing adjustment ONCE ONLY and then it advances or retards according to the sensors. It does NOT go back to the
crank sensor.
I think there may be a bit of a flaw in the Denso EFI. On the Bosch, they stress that when the ignition is turned on ,
the first thing that happens is the crank reference is reset for that journey. Clearly the Denso is not doing this - as
giving the ECU amnesia by disconnecting the batteries and allowing enough time for the capacitors to discharge meant that
when the truck was restarted the ECU had to go to the crank sensor to get an updated reference and my timing changed from
poor to perfect.
When I look back my batteries have not been offline for more than an hour or so since I had the truck,
including when I changed the pump for a 5B300. The ECU had never fine tuned the new pump basic setting to the crank - the
ECU thought it was still driving my old pump!
Also, wear means that over the years the timing will retard. So it is good to reset so that the ECU compensates for
the wear.
Follow up
There may be a better way of quickly discharging the ECU perhaps by using the diagnostic connectors -
but I cant find any references. I dont know if 8 hours offline is required - but I do know that 1 hour is no good
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