Longtubes+Blower=? - Page 2

MiracleMax · 01-15-2001, 12:30 AM

Yeah NO SLO, was just looking at it from the perspective of the of Volumetric Efficieny. It surprised me when it called for an 1-7/8 at such a low RPM. But given the fact that most engines operate below 100% v.e it changes things. Let me try a typical motor here. Lets see?

.030 over 302 Windsor Jr heads, GT-40 Intake, E-303 cam, 9.50:1 comp, yadda, yadda, yadda.

the wiz-bang says such an engine would put out (ideally): 340 hp at 5500 rpm and 360 ft/lbs. of torque at 4000 rpm and a peak ve of 84% (or an engine of 257 cid @ 100% ve)

PPA: 1.72 (or 1-3/4)
PPL: 35.40

So its a header measuring 1-3/4 x 35 with a collector measuring 3-1/3 x 17.5 . I dunno where you could find a collect 1-1/3 inches in dia, so you would be stuck with a collector measuring 3 inches. That kind of header would support the engine at peak torque (which is where peak ve usually falls) and I would imagine if the intake side was bottle necked (say a stock intake) it would over scavenge. Hmmm...I've seen more than a few dyno engines run with 1-3/4 headers and the article reported an increase in power with the big headers? The only problem with using peak numbers is that they are only reached every so often. The motor would be soggy down low because the primary pipe is kinda big. I bet an average VE would make for a better header pipe? On average from 2000 to 7000 rpm the engine is 78.2% volumetricly efficient which makes it look like a 239 cid engine and would take a primary pipe measuring 1.61 inches o.d. 1-5/8 is equal to 1.625 so there you have it, a primary pipe measuring 1-5/8. As for the primary pipe length it can only be tuned to respond to a certain RPM. Given the smaller than optimal size at peak torque it would probably be a good idea to keep the 35 inches of pipe length. so that there is a stronger signal at peak torque. boosting scavenging at the peak torque rpm where the engine is at or arriving at peak VE. Incidentally by placing the cross-over twice the distance from the exhaust port will aid in scavenging. That would mean a cross-over at 70 inches or almost 6 feet.

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01-15-2001, 12:30 AM	#21
MiracleMax Registered Member Join Date: Apr 1999 Location: Hayes, Va, USA Posts: 798	Yeah NO SLO, was just looking at it from the perspective of the of Volumetric Efficieny. It surprised me when it called for an 1-7/8 at such a low RPM. But given the fact that most engines operate below 100% v.e it changes things. Let me try a typical motor here. Lets see? .030 over 302 Windsor Jr heads, GT-40 Intake, E-303 cam, 9.50:1 comp, yadda, yadda, yadda. the wiz-bang says such an engine would put out (ideally): 340 hp at 5500 rpm and 360 ft/lbs. of torque at 4000 rpm and a peak ve of 84% (or an engine of 257 cid @ 100% ve) PPA: 1.72 (or 1-3/4) PPL: 35.40 So its a header measuring 1-3/4 x 35 with a collector measuring 3-1/3 x 17.5 . I dunno where you could find a collect 1-1/3 inches in dia, so you would be stuck with a collector measuring 3 inches. That kind of header would support the engine at peak torque (which is where peak ve usually falls) and I would imagine if the intake side was bottle necked (say a stock intake) it would over scavenge. Hmmm...I've seen more than a few dyno engines run with 1-3/4 headers and the article reported an increase in power with the big headers? The only problem with using peak numbers is that they are only reached every so often. The motor would be soggy down low because the primary pipe is kinda big. I bet an average VE would make for a better header pipe? On average from 2000 to 7000 rpm the engine is 78.2% volumetricly efficient which makes it look like a 239 cid engine and would take a primary pipe measuring 1.61 inches o.d. 1-5/8 is equal to 1.625 so there you have it, a primary pipe measuring 1-5/8. As for the primary pipe length it can only be tuned to respond to a certain RPM. Given the smaller than optimal size at peak torque it would probably be a good idea to keep the 35 inches of pipe length. so that there is a stronger signal at peak torque. boosting scavenging at the peak torque rpm where the engine is at or arriving at peak VE. Incidentally by placing the cross-over twice the distance from the exhaust port will aid in scavenging. That would mean a cross-over at 70 inches or almost 6 feet.