> -----Original Message-----
> From: Kyle Kozubal
>
> The RC-5040 filter flows 660.91 CFM, which is more
> than enough air flow for my 4.7L V8
>
> I have had great results when using a 900-1000 cfm
> filter on both the 3.9L V6 and the 5.9L V8 motors.
I'm curious how you define "great results". While I agree that larger
filters don't hurt anything, they also don't help anything when they are
"capable" of flowing more than your engine can pump.
For those who may have overlooked this, an engine is just an air pump.
Within it's design parameters (combination) it can only pump so much air at
a given rpm. Any filter large enough to prevent a restriction will allow
the engine to breathe all it can. Larger won't give it any more power
because the engine can't pump any more.
Another thing to consider is that air flow is proportional to rpm. For
example, let's say our 4.7's could pump 600 cfm at 5200 rpm. During a
typical drag strip pass with a 4.7 you will only reach max rpm twice (1-2 &
2-3 shifts) and you are only at that rpm for a fraction of a second. The
rest of the time you are below that rpm and the engine's air flow
requirements are considerably less.
> I have a 68.50 MM TB on order and was looking to
> increease ait flow into the TB, to around 850-1000
> CFM.
The same principle applies to throttle bodies. Larger than the engine
requires will do no good whatsoever. 2001 and newer 4.7's come with a 68
mm TB. I've found this to be more than sufficient for an internally stock
engine. My 2000 came with a 65 mm TB and swapping in a stock 68 mm did
improve performance at the track. However, replacing that stock 68 with a
ported 68 showed no gain. (note to those with a stock 65 mm....I can
highly recommend the Fastman 68 mm. It's a beautiful piece and reasonably
priced. If you already have a stock 68 though, save your money until you
do some internal mods.)
> <snip>
>
> I am going to install a larger filter and remove the
> heatshield, and see what happens.
Heat is the biggest enemy to producing power. Anything you can do to cool
the intake air will improve performance. Cool air is denser and contains
more oxygen than hot air.
Ray
2000 Jeep GC, 4x4, 4.7 - 400+ drag strip runs.
1992 Dakota 5.2 - 2400+ drag strip runs.
http://www.dragtruk.com/ENTRIES/20KM1FD2KWBP.html
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