Hi Bob, all
The general knowledge in this area seems to be changing rapidly.
Hadyn Gooch of Uniflow Aust recently did a test with a 1960's alpha GTA
spec, that has a lot of engine characteristics similar to a race datsun
2000.
The owner spent heaps on dynoing and after trying several models including
trapdoor and enclosed airbox, the model they came up with was basically an
airbox made of filter material. A cold air flow was pointed to this but
not connected to it. (And screened from engine heat).
My main problem with a trap at the back is that it must be filtered
otherwise whenever the car is stationery you are sucking in dirt and dust
with dramatic reduction on ring and bore life (even for a short life race
engine) amongst other adverse things.
Anecdotal evidence from the supplier to BMW Motorsport works team for 2
lite super production cars is that they use, or at least used up to last
year or so, a trap at the back of their airbox that was computer
controlled. But then their budget goes to more than ten million.
I think a leafblower would help to simulate at least some air affect when
dynoing, even if it did not give the flow effect of 100 mph . (not tested,
so I may be bullxxxx on that)
Static pressure: sure it is equal throughout, but doesnt the issue of air
flow dynamics come in here. It would be great to have some inexpensive way
of measuring these flows and their impact.
But here I am talking race stuff, not road. Personally I like tractability
for the road.
Regards
Howard
Aussie
-----Original Message-----
From: Calvin Grandy [SMTP:cmgfam@sover.net]
Sent: Friday, 10 December 1999 2:08
To: Bob Mann; Dan Neuman; datsun-roadsters@autox.team.net
Subject: Re: Air boxes
In the field of motorcycle engine performance the airbox size (volume)
is
an important part of the power curve. It is then another element of engine
tuning not unlike porting, cams, and headers. The airbox becomes a
resonant chamber that is generally optimized to offset deficiencies of the
other components. We could expect considerable low end performance
improvements with the 2 liter engines and Solex carbs The fact that the
market would rather hear of "Ram Air" etc. does not change the role of this
element. Inlet design needs to slow the fast moving airstream in order to
build pressure. Real air flow improvements come from properly designed
inlet opening, taper and length. The correct sizing often looks a bit
"throttled", but is correct. This is a rather lengthy topic that is best
covered in some of the specialty books on the subject. This may be the
next hot item for aftermarket!
"Ram Tuned Cold Air induction!" Bolt on horsepower and economy for your
Roadster. Only $999.99! ;-)
On another automotive list, someone was considering adding a leafblower as
the forced air system. Hmmmm?
Regards
Calvin Grandy
Vermont
----------
> From: Bob Mann <RWM@RWMann.com>
> To: Dan Neuman <dneuman@stars.sfsu.edu>; datsun-roadsters@autox.team.net
> Subject: Re: Air boxes
> Date: Thursday, December 09, 1999 9:28 AM
>
> A relief vent at the rear of the airbox is unnecessary, and if it were
> to flow substantially, it could siphon from the carb stacks.
>
> The only time you see airbox venting is in very carefully designed (i.e.
> flow visualized/modelled and wind tunnel tested) situations when
> extremely high speeds might cause excess drag, a la F-1 or Sports Racers
> (LeMans, etc.). You will also note that those cases clearly throttle
> the amount of air entering the airbox, via creative nacelle design.
>
> As for the front-to-back argument, static pressure is static pressure,
> thoughout the plenum.
>
> - Bob Mann, '69 2000 Solex
>
> Dan Neuman wrote:
> >
> > Hello All,
> > I wanted to bring up the subject of making an airbox for the
> > roadster. I had posted to the list about how all the 510 guys had them
with
> > a big tube leading to a little K&N air filter out in front of the rad.
I guess its
> > sorta a cold air induction system?? Remember??
> > Everybody said that if you do that you have to cut the back of
the
> > box up to make sure the rear carb was not seeeing more pressure.
> > My question is why does the rear carb see more pressure??
> > If you have ever looked at a modern inline four motorcycle they have
seperate
> > carbs for each cylinder and they look darn like the solex's..four
little air horns
> > right in a row.. But they are fed by one airbox. ONe sealed airbox.
This airbox
> > must make the carbs see equal pressure. WOuld it not be possible to do
the
> > same thing to a roadster???
> > Do you see where I am going with this?? Make the airbox thing
work
> > and then upstream of the airbox add one of those new style belt driven
> > superchargers.....and away I go.....
> >
> > Boy this years AnchorSteam Xmass Ale is really really good...
> >
> > Daniel 69 2000-
> > SF CA
>
> --
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