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#30 by Mark(The Miser)UK on 17 Oct, 2011 08:51
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i do agree the advanced timing would make sense with the higher breaking pressure, but my car drives very smoothly and quietly at 1.15, if it were the regular pump that far advanced even with td injectors, i would think it would sound like a tin of marbles tumbling down the stairs. a different cam profile is something i had though as well, i could measure total life on my car i suppose.
It took a few seconds to work that one out... I'm glad you actually mean total lift
Next time you are changing the pump timing, then maybe do as I did and record every flywheel tooth from zero lift to max and over the other side. On the basic TD pump @ the operating region, it is about 5 thou/0.125mm per flywheel tooth, or 2.73 deg crank... -
#31 by RabbitJockey on 17 Oct, 2011 09:05
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ok i will follow that
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#32 by Mark(The Miser)UK on 17 Oct, 2011 09:17
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The reasoning goes, that in a swirl chamber, once the initial burn has started, the droplets are sheared by the swirl and vapourised by the heat. This will, naturally, work 'better' with finer particles...................................
Greater atomisation does not improve efficiency IMO in a swirl chamber engine.
Most DN0 nozzles are run at 130bar ish for n/a's and 150ish for TD's There are exceptions, and I'll dig them out that go down to 110bar and about 3 engines from other makers that use 175 to 190 bar. Not sure if they are swirl or not, but at 200bar we get into the DI world....
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Can you explain why you think that? My thinking is that greater atomization is always a good thing, so smaller droplet + swirl would combust more than bigger droplets + swirl.
However, the creator/developer of this particular style of swirl chamber, found that if fuel is too fine it does not penetrate the compressed air as effectively.
Research showed that tangential [cord]firing of the fuel in direction of the compressed air flow, is more efficient than aiming radially or even into the 'jetstream' Harry Ricardo, found that 8:1 swirl rotation compared with crank was also an optimum. [Key word search him, if you are not already aware of his work]
I'd personally include some of Trevor's thoughts too.
This IIRC is a Ricardo mkV head essentially, it's research dating back fom the 1920's to the 1950's
How thick is compressed air?
My research if I was doing it would be to use tungsten[ or other high melting point metal type chamber incased in firebrick.
Aluminium in water is not the correct direction IMO -
#33 by ORCoaster on 17 Oct, 2011 17:09
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2X on the larger droplet slower burn theory. Think small drops swirling and combustion speed. Bang all at once. Now large drops that have to burn up from the outside in. Takes energy and time. Granted we are talking microseconds here but that is why some bang and others not.
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#34 by Mark(The Miser)UK on 18 Oct, 2011 00:30
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You have to ask yourself:
Did the Early mk1 Rabbits suffer from poor mileage due to their initial settings of 130bar?
Legend tells me otherwise...
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#35 by carrizog60 on 18 Oct, 2011 05:09
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they were lighter too,that would also affect mileage
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#36 by Mark(The Miser)UK on 18 Oct, 2011 05:45
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they were lighter too,that would also affect mileage
Definitely, but by how much on a reasonable run? When people dropped 1.6 n/a 's into Rabbits what happened to the economy? The lower pressures certainly don't appear adverse.
My Quantum TD is driving at it's most economic at the moment with somewhere around 135 bar, but I did improve the compression ratio so that may have had a bigger influence; but timing, or more specifically tuning effects the whole lot. I'm still experimenting. -
#37 by carrizog60 on 19 Oct, 2011 05:08
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my passat(the one on the pic)has better economy now than in stock hp .
for every kind of driving style besides wot runs of course.
i have 155 bar,as stock but most people here raise opening pressure when tuning pumps for more power.
is it trend only?