Semi-Dyanmic diesel timing procedure

[Tim]

Okay, first of all, I have used this method for years and have had
absolutely no ill effects. My 81 Rabbit with 240K on the clock will
attest to this. I discovered this method by tinkering and constantly
looking for ways to improve performance and economy. If you don't mind
a little more "dieseling" noise, then this is the best way to
dynamically time your diesel without all the special equipment.

Start the engine and let it run until the fan operates at least once.

Stop the engine and loosen all of the injection pump mounting bolts. Not
to the point where the pump can be pulled away from the mounting plate,
but just enough to turn the pump. You might want to mark the position
of the pump as a reference point, in case you want to set it back to
it's original position. Now snug one of the bolts down to hold the pump
in position. Pull the cold start knob and start the engine. Loosen the
bolt that you previously snugged down and start rotating the top of the
pump toward the engine. Pay particular attention to the engine speed,
by the sound. When the engine 'just' starts to slow down, STOP! Now,
rotate the top of the pump back until the idle increases back to the
previous speed. Snug that bolt down again and stop the engine. Using a
scribe or awl, scribe a line across the pump mount flange and the pump
mounting bracket to mark it's current position. Loosen that bolt again
and rotate the top of the pump away from the engine until the scribed
line is broken and the two lines have a 1.5mm to 2.0mm gap between them.
Tighten all the pump bolts and push the cold start knob in. That's it.
If the extra noise bothers you, then you can use a cetane boost
additive or buy a fuel heater. The "dieseling" noise is the sound
created by delay between the fuel injection and the fuel igniting.
Increased cetane or warmer fuel will shorten this delay and reduce the
noise.

[Tim]

Tim wrote:

By the way, using the above procedure does improve performance a great
deal. My 81 Rabbit has a NA 1.6L diesel and a GP coded 4 speed. When
statically timed, I can barely get it up to 70mph. With the above
timing, the top speed is 81 mph. MPG started at 46 highway and is now 51.

[racer...@hotmail.com]

Just one question. Is this whole procedure done with the
cold start knob pulled out? I'm assuming yes, because you
said to pull it at the beginning, but you never sad to push
it back. Is this correct?

[Tim]

racer...@hotmail.com wrote:

Yes, push the cold start back in AFTER everything is done.

[Roger Brown]

Tim wrote:
> By the way, using the above procedure does improve performance a great
> deal. My 81 Rabbit has a NA 1.6L diesel and a GP coded 4 speed. When
> statically timed, I can barely get it up to 70mph. With the above
> timing, the top speed is 81 mph. MPG started at 46 highway and is now 51.

Have you followed up and measured the actual pump timing that results?
Would be curious to see how close it comes to the published values.

I just timed my 1.9D pump (an old 1.6 pump) to the top end of the
performance range (1.03mm) and noticed a decent performance increase
(was at 0.86mm or so).

[Tim]

Roger Brown wrote:

As a matter of fact, the actual measurement of the plunger was 1.09mm.
The pump is a non-yellow dot pump. I took the car to my friend's diesel
shop and checked the timing with an optical timing device that screws
into the glow plug hole. The actual ignition occurs, on average, at 10
degrees BTDC. On my friend's Jetta, the pump setting was 1.05mm and the
actual ignition occurs at about 9 BTDC. If I static time my engine to
.98mm , ignition occurs at between 5 and 6 degrees BTDC when checked
dynamically. As you can see, setting the timing with a dial indicator
can give varied results. The pump settings have little to do with the
actual ignition point. Factors such as pump wear, fuel cetane, injector
opening pressure, and fuel viscosity all play a role in actual ignition
timing. The best thing, I have found, is to add a fuel warmer to the
system. This will, at least, keep the viscosity low and lower the
amount of heat in the cylinders needed to reach the fuel's flash point.
Spontaneous combustion occurs sooner, noise is lowered, extreme
pressures are lowered (as the fuel burns more evenly instead of one big
flash), mileage increases due to "more" dynamic timing advance, and
better power is achieved through efficiency. Just remember to use a
good additive that adds lubricity to the fuel. The lowered viscosity
means less shear strength and more pump wear.