[Vwdiesel] "leaning out" diesel????????

[slatersfb at aol.com]

-----Original Message-----
From: hwy9fergs at comcast.net
To: vwdiesel at vwfans.com
Sent: Thu, 08 Dec 2005 18:06:07 +0000
Subject: [Vwdiesel] "leaning out" diesel????????


From: "Svend M  Kjong" <svend at prcn.org>
Subject: [Vwdiesel] Rabbit talk for beginners ---(  Back to basicks )
To: <vwdiesel at vwfans.com>
Message-ID: <000201c5fc12$902398b0$66ed7240 at bunneyblue>
Content-Type: text/plain;   charset="iso-8859-2"

If you lean a turbo diesel significantly you will merely increase pumping losses 

and
decrease fuel economy.  You'll also destroy any performance.

Andrew

Good morning, You guys have me confused, and I haven't had my coffee yet, so 
that's not fair. I wanted to clarify something that has bugged me for a long 
time.  In my way of thinking, the "richer" and "leaner" concept really doesn't 
apply to these little buggers we run.  For instance with the NA engines, we 
don't have direct throttle control of how much air goes into the engine.  For a 
given rpm, we will always have the same amount of air going in, regardless of 
the throttle setting. (This might be slightly influenced by increased cylinder 
scavenging at higher loads, but that topic is for another time)  The only thing 
we really control is the amount of fuel that is injected and when it is 
injected.  Turning down the fueling screw ("leaning"????) merely limits how much 
fuel the pump will deliver.  Much the same as deciding you are only going to 
push the throttle pedal down just so far, and only that far.  The rich and lean 
concept applies much more so to gas cars.  (IMHO). But if you must, these 
diesels are "leanest" at idle, "richest" at full throttle and somewhere in 
between the rest of the time.  Bottom line is, the more fuel you put in, the 
faster and hotter it will go.  I think I'd best go have some coffee now.  
Thanks, Doug
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This topic has come up before with it's attendant confusion. I have spent some time 
poking around in an old pump recently, and Doug, I think you are correct as far as you
have taken it. There is more to it though, as I see it. Complicated stuff.
You are cruising down the road in top gear at 60 mph. It takes a certain amount of 
fuel to do this. A hill comes along and you press the pedal to the floor to increase fueling.
Speed will not increase because of the hill.
If you had your way thick black smoke would
now be pouring out the tailpipe. But,
thankfully there is a governor opposing your exuberance. The governor compares your 
demand for power to what is reasonable without blowing wasted fuel out the pipe with no real power gain. 
How much fuel the governor allows in response to our demand could be called "rich" or "lean", since speed has not
increased. Actually, if we ignore the automatic advance, injection of fuel always begins at the same point, relative
to piston position. Our demand, opposed by the governor, determines injection duration.
This stuff gives me a headache. 
Bob in the Entire State