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RE: Another stump-the-chump question

To: "drmayf" <drmayf@mayfco.com>, "John Staiger" <lsrvette@yahoo.com>
Subject: RE: Another stump-the-chump question
From: "Dave Dahlgren" <ddahlgren@snet.net>
Date: Wed, 4 Oct 2006 20:51:05 -0400
all quite possible over a limited rpm band.. happens every day acutally when
you get physics to work for you instead of against you.. the trade is a
narrower but acceptable rpm band of interest the tuning does work within..
Dave

> -----Original Message-----
> From: owner-land-speed@autox.team.net
> [mailto:owner-land-speed@autox.team.net]On Behalf Of drmayf
> Sent: Wednesday, October 04, 2006 7:09 PM
> To: John Staiger
> Cc: land-speed@autox.team.net
> Subject: Re: Another stump-the-chump question
>
>
> John, I am sure Dave Dahlgren can explain it really good. But, yes it is
> possible to get more charge in to the engine than normal pumping by the
> atmosphere. Ram tuning on the intakes will help do that. Although that
> sounds like a lot.  Do their intakes face into the wind so to speak?
> Could they be counting on some forward motion to increase the flow?
>
> mayf, off base in Pahrump, as usual
> John Staiger wrote:
>
> >Yes - I'm the chump.  Since I had a spare minute today, I was
> playing with
> >some numbers and this generated my puzzlement:  I have an ex-IRL
> 4.0L engine
> >with certain "published" data - i.e. the GM Race Shop build
> manual.  When I
> >model some of the numbers the results are quite bizarre. hence
> I'm wondering
> >what I'm doing wrong.
> >
> >
> >
> >The build manual lists the following facts; 1) bore=3.661", stroke=2.85",
> >maximum RPM=10,500 (limited by rule).  Therefore if I apply and
> old formula
> >(theoretical cfm = (displacement * (rpm/2) * VE) / 1728) or 243.54in3 [or
> >3.99L] x 10,500 / 2 * 1.00 / 1728 where VE = 1.00 or a perfect engine, I
> >should get the theoretical maximum air flow of the engine [pump] or
> >739.9cfm.
> >
> >
> >
> >This is were I mention the last piece of published data  -- the
> GM race shop
> >build manual puts the engine air capacity at 925cfm.  Further,
> the hp specs
> >and dyno references by several sources fall in line with the
> 925cfm number
> >(more math).  So if I go back to the formula above - VE would
> have to equal
> >1.25????  This does not compute...  Is this possible. My head hearts.
> >
> >
> >
> >John
>
>
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