[Vwdiesel] Rabbit droppings # 57 --- ( Hagar goes scientific )
h_hagar at prcn.org
Sun Mar 28 11:44:32 EST 2004
Any Law saying that a Hillbilly can't go to school ? ---well I did.
I am writing this to try to explain some very important things about
diesels to Will Taygan , and some of the rest of you may need to be
We all started fiddling with Gasoline engines , and therein lies a problem.
The word " Timing" used in gasoline ally does not apply .
The piston goes up and down --and anywhere at all you can "TIME"
the spark to take place .Ergo you can drastically advance timing to a point where it destroys an engine in short order.NOT so in a diesel.
In a diesel you can not time ignition (with some exceptions) by turning the
pump. You can advance the pump say 30 degrees ----but that does not mean
that ignition is advanced by that amount.
The ignition point is set by the temperature in cylinder and Cetane number.
If fuel pools in cylinder before ignition point ----a problem arises . First it is not
a spray or mist.So it is not likely to completely burn before exhaustvalve opens.
It will create black smoke.
If fuel is injected after the ignition point (aircharge has cooled) we wind up
with a mosquito fogger class a one. If you turn your pump back a pencil line
you will see what I mean. Retard the pump and you get white smoke.Advance the pump
and we get fuelknock (big marbles)
Black smoke with proper timing of pump (injection of fuel not ignition) the fueling has to be reduced on pump.
The thousands of combinations come from the fact that these are not digital entities.
But the good news is, that regardless of how daunting it looks --- Performance
tuning of a VW diesel is very simple. But a very time-consuming process. NO
stealership will do it as a routine.
Now when it comes to the old very tired Rabbits ----NO amount of fiddling with
dial indicators no matter how precise , will do the job. So we may have to look at
HILLBILLY tuning as a last resort. I have 3 VW diesels here that I tuned that way.
And performance is hard to poo poo.
Sending the pump to be overhauled goes like this . 350 dollars ----great --why wait?.
Read the fine print ----- PLUS PARTS. An exchange pump done by Bosch is about
2000 dollars. -----Does Hillbilly tuning look better the more you hear ?
Part of Hillbilly tuning involves correcting things wrong with Pump and injectors.
Internal pump pressure being the most important. Under Injection pump I hope to
explain all the things I know can be done to the pump and the fuel.
I'm thinking somehow I could be 180 degrees off on the timing.
Will Taygan : If you line up timing marks on pump and sprocket that is no worry.
Will Taygan : please read archives all this has been explained by the Grand wizards
PS: it is possible to screw up firing order but pretty damned hard.When you look
at lines coming out of pump , remember that looking at distributor it rotates
CCW. Like some gasjobs.
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