[Vwdiesel] Diesel octane or why can you run a diesel engine lean?
H . Hagar.
h_hagar at prcn.org
Thu Mar 17 18:16:03 EST 2005
I think I will join this "Furball" ---- now that Val ,James,Loren,Kelly and more.
joined ---- we may all have to rethink a few things.
" Banjo Duel " ? ---
Answer : You can run a diesel lean -- because it will not detonate like
a gasser. The gasser detonates because the fuel ignites under pressure and heat.
Normally a gasser charge ignites from the spark ---then moves slowly across the
combustion chamber ---flamefront moves at about 80 MPH. A diesel is different
the fuel is added during the combustion cycle Not ahead of it. Thus no detonation possible.
A gasser during detonation ignites all over the place. With the resultant rapid
very rapid increase in cylinder pressure ----known as KNOCKING.
If you lean a gasser the octane rating of the fuel decreases ---and you may get
knocking. -----it knocks ? turn the fuel back up.
If you LEAN a diesel ? the cetane number stays.
To understand the lean issue ask Gavrik Peterson to write the explanation of
how the fueling screw works. I know but my english is not up to it.
It has to do with the function of the metering sleeve in the VE pump (Rabbits).
The fueling screw , for you Gasoline sniffers ---is NOT a valve ---it is only a
mechanical stop ----to restrict the movement of the metering sleeve.
Right hand thread ---in more fuel out less fuel. ---------
So HOW ? does Hagar run superlean ?-----simple if you know HOW.
First you need to know that VW used a swirlchamber not a pre chamber like GM.
Why do we need a swirl ? --- look up combustion process. ---all oilburners and
boilers like a lot of SWIRLING.
Then we need lots of pressure in intake manifold when intake valve opens --- getting
it ? ---inrushing air creates a super swirl at say 50 psi.
Better combustion ? you bet --same amount of fuel --BUT better burn. Low soot
loading in lube oil , less smoke out behind. ----- I did it so you cant argue that it will not work.
Start of leaning out the cocpit ? -----05 Mar 2003. ----- "Bunny Bondo" just humms like
PURRS ? like a kitten . And yes part of it is NEW nozzles as recommended by Loren
and breaking pressure high end of range according to James Hansen. And Hillbilly
tuning (a consentrate of everybodys knowledge in this forum).
Forget about the dial --it will NOT do on an OLD Rabbit. Start at timing marks and then
fine TUNE. 20 year old Rabbit doing 78 miles on a gallon imp does not convince you ?
Like James Hansen said ---there are gassers designed to run LEAN and mean- and
I mean very lean. - So lean that a spark will not fire charge.
And by the way, the way I remember flamefront speed ? it is slower at RICH.
and Octane is 145 at RICH and 115 at lean.
And yes Water injection is used to cool aircraft engines at high powersettings.
And yes excess gasoline does make the engine run COOLER.
WHY ? a moot question --- evaporating gasoline ? yes , less---- detonation ? yes.
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