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Exocet
Dodge Dakota
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10/25/2002
13:57:04
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 Subject: 4.7L Maximum Air Flow
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Does anyone know what the maximum air flow (in CFM or SCFM) of a stock 4.7L is? I remember seeing this listed on the Speed Tweaks site some time ago, but I can't seem to find it now. Thanks.
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Demon Dakota
DakotaEnthusiast
10/25/2002
14:57:37
|  RE: 4.7L Maximum Air Flow
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Message:
I "thought" it was right around 600 CFM. I may be mistaken, but that number sticks in my head.
K&N Drop in AF
True Dual exhaust and removed third cat
HO Cams & HO Intake
Modified TB
Autolite 3923 Plugs
TPS @ .76 VDC
IAT Adjuster Mod
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Art
Dodge Dakota
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10/25/2002
15:38:33
| RE: 4.7L Maximum Air Flow
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To find cfm requirments of a N/A engine use this
CFM=(RPMXCID}/3456 so the 4.7=287 CID
so say (4000rpmx287)/3456=332cfm minimum
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Demon Dakota
DakotaEnthusiast
10/25/2002
16:39:37
| RE: 4.7L Maximum Air Flow
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Check out this web site and see if it tells you what you need to know.
http://dodgeram.org/tech/gas/Cammer/4_7_v8.html
K&N Drop in AF
True Dual exhaust and removed third cat
HO Cams & HO Intake
Modified TB
Autolite 3923 Plugs
TPS @ .76 VDC
IAT Adjuster Mod
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Exocet
Dodge Dakota
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10/26/2002
08:33:49
| RE: 4.7L Maximum Air Flow
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Message:
Two numbers I remember seeing are around 400 CFM and around 600 CFM. Using Art's equation you get 415 CFM at 5000 RPM. Also, the stock air filter is rated to flow 380 CFM. Although this is probably a fairly restrictive filter, you would think the engineers would have it's flow rating matched pretty well to the engines flow needs. That's not saying that the engine couldn't flow more air with simple intake and exhaust mods.
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Art
Dodge Dakota
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10/26/2002
17:21:01
| RE: 4.7L Maximum Air Flow
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You gota remember that equation wil represent a minimum required for any engine,a change in cams,supercharging etc will change what is needed,now I dont remember the exact #`s on the flow of the 68mm 0r 65mm 4.7 throttle bodys,seen it on I think F&B website?? but I think you are right it was over 600cfm so that is more than enough flow in stock trim and will keep the power band where you want it and the stock air filter I pulled out had flow rating stamped on it and it was like 720cfm,around there,the stock airfilter really is not a bottle neck on this engine
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Exocet
Dodge Dakota
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10/28/2002
19:07:04
| RE: 4.7L Maximum Air Flow
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Art - My stock air filter is stamped at 10.6 cubic meters per min. With 35.9 cu ft per cu meter, that comes out to about 380 CFM. It is interesting that your filter is rated at 700+ CFM.
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Cotharyus
GenIII
10/29/2002
07:15:32
| RE: 4.7L Maximum Air Flow
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Message:
And besides that, the more air you can potentially flow through the filter, the less load your intake is putting on the engine. Thats why places like K&N use filters that have massive flow rates for engines that don't really "need" it (usually the filter will flow 3-4x what the engine will) - the greater the flow of the filter in proportion to the engine, the closer you are to having an open (non-filtered) feeling intake.
2001 QC 4x4, 4.7,5 spd, LSD, 255/70-15's, K&N Gen II Intake, Robert Shaw 180 Stat, Hanson Enterprise custom front bumper, Highflow cat
Check out my Dak
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Canucker
Dodge Dakota
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10/29/2002
12:29:50
| RE: 4.7L Maximum Air Flow
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If I could throw this out too:
287 cu. in. = .1661 cu. ft.
So if you take 6000 RPM as max RPM (stock rev limiter) .. the most you could possibly flow is 6000 X .1661 = 997 CFM (cu. ft. per min.) in N/A form.
That's assuming 100% volumetric efficiency (VE), and the same air temp being drawn into the cylinder as into the air filter ... a BAD assumption.
More realistic for VE is 70-80% ?? correct me if I'm wrong. So that would put you at 700-800CFM ... again, still assuming the same air temps ... if you want to pin point it more, start throwing some more equations at it, but that's a good rough idea of MAX. CFM required.
a realistic guess ... maybe more like 600CFM at 6000RPM
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Art
Dodge Dakota
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10/29/2002
20:04:24
| RE: 4.7L Maximum Air Flow
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I looked around for the old filter and I cant find it,you have yours and your numbers come out right so lets say yours is right "not sure why I had that cfm # in my head" so at the flow rate of 380cfm you would reason that the engine would be gasping for air at high rpms buts its really not so whats going on here then?Our engines are a 4 stroke air pump and so they are not all taking a air charge at the same time,man I tried numbers a few different ways and I`m just confusing myself further.
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Dominic
Dodge Dakota
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10/30/2002
13:42:54
| RE: 4.7L Maximum Air Flow
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Canucker,
Me being a math dork, I like to check other people's math. Since these engines are four stroke, air is brought into each cyclinder once every two revolutions, therefore you need to divide your answer by two. So 997/2 = ~498.5 cfm.
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Canucker
Dodge Dakota
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10/30/2002
15:11:01
| RE: 4.7L Maximum Air Flow
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Message:
yeah, you guys are right. My bad.
So the 380CFM on the stock filter makes sense. We could probably guess that the max airflow is around 400-450CFM then ...
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