Paul Workman
12-23-2008, 07:09 AM
Yesterday Bob G and I together took a close look at my new "3 inch" Magnaflow system and together we noted some...er..."discrepancies"??
In short, I don't think either of us would call it a pure 3" system, towit:
The 3-bolt flange on the passenger side - the flange ID is smaller than 3", and thus an approx 2-1/2" dia. X approx. 2-1/2" long "choke" point exists. (That's one)
The X pipe appears to be a 2-1/2 or 2-3/4 ID, as does the inlet to the resonator - another choke point. (That's two)
Inside the resonator, on closer look, the (narrower than 3") X pipe outlets funnel out to morph with what appears to be a short single section of 3" tubing - maybe 8" long - essentially another "X" pipe...sorta...another choke point...before splitting to form what appears to be a 2-3/4" (not a 3") outlet junction onto the 3" tail pipes. (I wouldn't count this as a choke point as the ID is simply morphing from the narrow(er) resonator output to slightly wider 3" tubing.)
Then at the muffler input, the 3" tubing is again sharply choked down to what might be no more than 2-1/2" dia. inlet - definitely a choke point (more on that).
The muffler inlet is internally split into a pair of perforated tubes, approx 2" in dia that appeared (to me) to funnel out to about 2-1/4 to 2-1/2" each before morphing into more or less a pair of 3" outlets. (Note: Two 2" tubes has less cross-sectional area than a single 3" tube, FWIW)
Physics, being a discipline of mine in a previous life, lends me enough knowledge about fluid dynamics to be really dangerous. :rolleyes: So, when Bob and I were examining the system up close, the choke points I mentioned raised some questions about overall impedance of the system as compared to a true (nothing less than) a 3" system. In particular, there were some abrupt changes in ID that are much more concern than gradual transitions; especially the X pipe and the second "Y" inside the resonator, and the muffler inputs.
I don't know to what extent these choke points are significant, but they certainly are not going to enhance flow dynamics. And, if a 3" system is baseline for a big displacement LT5, I would prolly keep looking or perhaps get cozy with a good exhaust man and do some modifications.
All that said, the Magnaflow system is beautifully made and sounds great (on Dom's car). I'm going to install it for now, but I'll be revisiting it later, after I get the rest of my "stuff" done. In the mean time, the "best exhausts" topic never gets old (to me - it's that physics thing, yaknow:sleepy1:)).
P.
In short, I don't think either of us would call it a pure 3" system, towit:
The 3-bolt flange on the passenger side - the flange ID is smaller than 3", and thus an approx 2-1/2" dia. X approx. 2-1/2" long "choke" point exists. (That's one)
The X pipe appears to be a 2-1/2 or 2-3/4 ID, as does the inlet to the resonator - another choke point. (That's two)
Inside the resonator, on closer look, the (narrower than 3") X pipe outlets funnel out to morph with what appears to be a short single section of 3" tubing - maybe 8" long - essentially another "X" pipe...sorta...another choke point...before splitting to form what appears to be a 2-3/4" (not a 3") outlet junction onto the 3" tail pipes. (I wouldn't count this as a choke point as the ID is simply morphing from the narrow(er) resonator output to slightly wider 3" tubing.)
Then at the muffler input, the 3" tubing is again sharply choked down to what might be no more than 2-1/2" dia. inlet - definitely a choke point (more on that).
The muffler inlet is internally split into a pair of perforated tubes, approx 2" in dia that appeared (to me) to funnel out to about 2-1/4 to 2-1/2" each before morphing into more or less a pair of 3" outlets. (Note: Two 2" tubes has less cross-sectional area than a single 3" tube, FWIW)
Physics, being a discipline of mine in a previous life, lends me enough knowledge about fluid dynamics to be really dangerous. :rolleyes: So, when Bob and I were examining the system up close, the choke points I mentioned raised some questions about overall impedance of the system as compared to a true (nothing less than) a 3" system. In particular, there were some abrupt changes in ID that are much more concern than gradual transitions; especially the X pipe and the second "Y" inside the resonator, and the muffler inputs.
I don't know to what extent these choke points are significant, but they certainly are not going to enhance flow dynamics. And, if a 3" system is baseline for a big displacement LT5, I would prolly keep looking or perhaps get cozy with a good exhaust man and do some modifications.
All that said, the Magnaflow system is beautifully made and sounds great (on Dom's car). I'm going to install it for now, but I'll be revisiting it later, after I get the rest of my "stuff" done. In the mean time, the "best exhausts" topic never gets old (to me - it's that physics thing, yaknow:sleepy1:)).
P.