Engine Info
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From: Fort Worth,Tx
Engine Info
according to ford the 4.6L is a 281 correct?
well the non PI 97-98 had a bore and stroke off 3.6"x3.6" and the PI had 3.55"x3.54"
PI Non PI
Stroke CI: 35.02 36.36
Total CI: 280.16 290.8
Total CF: 23.34 24.2
so since its a 4.6L engine then every 16RPM is each cylnder firing once and 4.6L of air is displaced through the system. so at 500 RPM ur engine is moving 4.6L of air 31.25 times. which comes to 143.75L of air is being used at 500RPM. so at 5000RPM ur using 1437.5L of air... which converts to 5.07CFM. that is how much air moves through your IAC while at idle.
so ur PI 280CI motor is a 4.5896 and my non PI is a 4.7662L motor
well the non PI 97-98 had a bore and stroke off 3.6"x3.6" and the PI had 3.55"x3.54"
PI Non PI
Stroke CI: 35.02 36.36
Total CI: 280.16 290.8
Total CF: 23.34 24.2
so since its a 4.6L engine then every 16RPM is each cylnder firing once and 4.6L of air is displaced through the system. so at 500 RPM ur engine is moving 4.6L of air 31.25 times. which comes to 143.75L of air is being used at 500RPM. so at 5000RPM ur using 1437.5L of air... which converts to 5.07CFM. that is how much air moves through your IAC while at idle.
so ur PI 280CI motor is a 4.5896 and my non PI is a 4.7662L motor
Last edited by Faster150; Apr 11, 2005 at 09:12 PM.
Interesting info sir. 
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From: Fort Worth,Tx
im confused myself but the math is right.. ive ben going over it for hours and still always come up with 5.07cubic feet of air moved because there is 28.3L in 1 cubic foot.... which would mean 5,000 RPM ur engine is using 50 CFM??? does anyone have any input on where i went wrong...i cant think to well today so its been keeping me occupied
Last edited by Faster150; Apr 11, 2005 at 09:13 PM.
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From: Fort Worth,Tx
okay i think i figured this out...had some bad information... follow me here since it takes 2 RPM for all 8 cylnders to fire then.so ever 2 RPM is 4.6L of air. so its 500/2=250 and 250x4.6=1150 and 1150liters of air is used at 500RPM which converts to 40.63CFM of air is used at idle... and 406.3CFM of air is used at 5,000RPM
Last edited by Faster150; Apr 11, 2005 at 10:02 PM.
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From: Easton, Pa.
The internal combustion engine is a variable efficiency air pump.
It is subject to pumping losses in the intake tract at wide open throttle and is also affected by the camshaft timing.
The power/efficiency produced is in the 75 to 85% range, of it's total air pumping capacity.
This is why "meaningful" improved breathing (not air filter and such) will raise power levels toward the 100% of pumping volume level for natural asperation.
A 302 engine will move less than 500 cfm of air at 6000 rpm considering the loss of efficiency involved.
The only ways to increase total airflow pumping capacity is;
1. increase displacement.
2. increase rpm.
3. force feed (supercharge).
4. oxygen adding ( nitro, nitrous etc.).
5. special intake and exhaust tuning for race application.
Increases in efficiency comes from higher compression, optimized cam and ignition timing, improved combustion chamber design, reduction/tuning in flow losses.
There is a lot to it.
The 4.6L is 281 cu/in. ; less than the size of the first 289 v8 engine way back in the late 60s and smaller than the first 283 chev back in 1957.
Opinion:
the design concept is fine but the way Ford has exacuted it since inception has been a travisty.
So far, I have a good running 4.6 but it does not make up for the overall design faults where there are three different sizes, made in at two or more locations with dozens of design changes, and still the problems go on for the last 12 years.
A bunch of Elves could do as well.
It is subject to pumping losses in the intake tract at wide open throttle and is also affected by the camshaft timing.
The power/efficiency produced is in the 75 to 85% range, of it's total air pumping capacity.
This is why "meaningful" improved breathing (not air filter and such) will raise power levels toward the 100% of pumping volume level for natural asperation.
A 302 engine will move less than 500 cfm of air at 6000 rpm considering the loss of efficiency involved.
The only ways to increase total airflow pumping capacity is;
1. increase displacement.
2. increase rpm.
3. force feed (supercharge).
4. oxygen adding ( nitro, nitrous etc.).
5. special intake and exhaust tuning for race application.
Increases in efficiency comes from higher compression, optimized cam and ignition timing, improved combustion chamber design, reduction/tuning in flow losses.
There is a lot to it.
The 4.6L is 281 cu/in. ; less than the size of the first 289 v8 engine way back in the late 60s and smaller than the first 283 chev back in 1957.
Opinion:
the design concept is fine but the way Ford has exacuted it since inception has been a travisty.
So far, I have a good running 4.6 but it does not make up for the overall design faults where there are three different sizes, made in at two or more locations with dozens of design changes, and still the problems go on for the last 12 years.
A bunch of Elves could do as well.
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From: Fort Worth,Tx
yeh... it seems like the PI engines have more problems then the non PI..like spitting plugs out even though the PI heads have twice the threads as the non PI's lol... sometimes i wonder about these for engineers... chevy has some great breathing heads... why cant ford make some???