02GF74
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| posted on 19/9/06 at 01:40 PM |
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volumetric efficiency?
can it be over 100% for normally aspirated engine? (I've read that by careful design of valve timing it can but onoy over a limited range).
anyone confirm or otherwise, perhaps with linky to web site that discusses this?
ta.
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clockwork
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| posted on 19/9/06 at 01:47 PM |
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Look up "pulse tuning"
or read
http://www.pumaracing.co.uk/power2.htm
EDIT: er yes it can be over 100%
[Edited on 19/9/06 by clockwork]
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02GF74
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| posted on 19/9/06 at 01:56 PM |
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perfect!! thanks.
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NS Dev
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| posted on 19/9/06 at 02:09 PM |
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yes, it can, as no doubt explained by Dave Baker in the article above.
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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smart51
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| posted on 19/9/06 at 02:48 PM |
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Volumetric efficiency is the amount of air that gets into the cylinders compared with the volume of the cylinder. Because there is a slight vacuum in
the inlet manifold, volumetric efficiency is usually less than 100%
Engines are designed with valve overlap. The speed of the exhaust gases would create a partial vacuum in the exhaust manifold if there was no
overlap. instead, this "suction" helps draw in a fresh charge. The same applies to the inlet valve timing. the valves can be timed to
close just after BDC. this allows the inlet air velocity to force a little bit more in before the valves close. Add a bit of ram air and you might
just squeek over 100% volumetric efficiency. Or you could fit a turbo.
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matt_claydon
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| posted on 19/9/06 at 04:39 PM |
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And if you're talking about filling in the table for an FI system then unless your req_fuel (as it's called in Megasquirt) is spot on then
your VEs in the table may be well above or below the genuine value being acheived.
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Findlay234
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| posted on 19/9/06 at 04:50 PM |
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yes its all in the pulse tuning to do with intake and exhaust length. look for previous threads on this subject
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martyn_16v
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| posted on 20/9/06 at 09:01 AM |
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quote:
Originally posted by matt_claydon
And if you're talking about filling in the table for an FI system then unless your req_fuel (as it's called in Megasquirt) is spot on then
your VEs in the table may be well above or below the genuine value being acheived.
The VE table in MS is a bit misleading, it's not actual VE the table is based on. The values are actually VE / lambda, so where the table is set
to produce an AFR of 14.7:1 (lambda=1 for petrol) then the value is the actual VE. In areas where you want a richer outcome (i.e. lower lambda) then
the value is higher than the actual VE, hence why you'll see a lot of tables with values way above 100 at WOT.
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