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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