[Vwdiesel] injectors

[James Hansen]

Well, I find that it starts better with higher break pressures.
Perception of power, economy, all seem not to be effected, but I will
guarantee you, my cars will be the last ones to not start in the cold. Real
cold, like -40 and below, not plugged in etc.

The progression of the flame front proceeds at the rate of oxidation
reaction, atomization has not too much to do with it.  Better atomization is
only better to a point, since the fuel is essentially injected from a point
source, and displaces the available oxygen as it is injected.  You can get
it a tad faster with compression (early timing equals more compression
sooner, hence hotter).  The fire only burns so quickly, as the oxygen needed
is surrounding the cloud of unburned fuel droplets.  The fuel burns at the
oxygen/fuel interface. Like any chemical reaction, it will speed up when
hotter, and turbulence will also speed this up, so a good swirl from
induction path coupled with a direct injection should hasten this, and
enhance power.

Multistage injection sort of creates it's own turbulence from more
convection within the air charge spreading the fuel cloud around, and it's
hotter, hence a faster reaction when the subsequent pulses are injected.
Instead of one big fire, that is a huge cloud of fuel burning steadily
inward to the center (and very hotly), you get two or more injection events
that get a compression rise initially, so the subsequent injection events
use more of the available oxygen in the cylinder, with a lower egt, less
nitrogen emissions.  Same amount of fuel injected in one pulse gets much
higher emissions and egt.

Parasitic losses are a factor, yes.  I have done this on everything from a
nearly worn out Jetta1.6td  to a 97 1.9td. the car ran better in both cases.

Racer boy?  heh.
Next race this sunday.
Much fun will be had.

-James

-----Original Message-----
From: vwdiesel-bounces+jhsg=sasktel.net at vwfans.com
[mailto:vwdiesel-bounces+jhsg=sasktel.net at vwfans.com]On Behalf Of Mark
Shepherd
Sent: Wednesday, September 14, 2005 9:11 AM
To: vwdiesel at vwfans.com
Subject: [Vwdiesel] injectors


Interesting...
If we use N/A injectors then due to the lower break pressures  injection
will start earlier.
Poorer atomisation? Maybe.
    Do we want ultra atomisation? Doesn't this lead to explosion rather
than burning? Hence a noisier engine which is why TDi's squirt in two
stages (don't they?)
 Only boy racers need to inject quickly for their gasser like rpms... James
etc LOL
Penalty of higher pressures is more work done by pump and belt and engine
leading to higher wear of first two and all for the search for better
atomisation. Lord Jake didn't feel there was much if any benefit to higher
pressures economy wise IIRC
Secret to good fuel economy apart from driving style is correctly operating
injectors [at any pressure] and experimental tweaking of pump/aneroid.
Miser

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