Is bigger better...
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Is bigger better...
...for exhaust?
I am looking at installing an aftermarket cat back on my truck and I have noticed the Banks cat back or "Stinger" system is a 3 1/2 inch tail pipe to a 4 inch tip whereas all other cat backs are 3 inch to 3 1/2 inch (same as stock sizing). Is the larger sized pipe on the Banks going to make that much of a difference?
It also does not seem like anyone offers a true cat back since the stock pipe is always reused between the cat and the muffler. If the Banks cat uses a larger tailpipe wouldn't a larger pipe from the cat to the muffler also help?
Thanks for any help.
Dan
I am looking at installing an aftermarket cat back on my truck and I have noticed the Banks cat back or "Stinger" system is a 3 1/2 inch tail pipe to a 4 inch tip whereas all other cat backs are 3 inch to 3 1/2 inch (same as stock sizing). Is the larger sized pipe on the Banks going to make that much of a difference?
It also does not seem like anyone offers a true cat back since the stock pipe is always reused between the cat and the muffler. If the Banks cat uses a larger tailpipe wouldn't a larger pipe from the cat to the muffler also help?
Thanks for any help.
Dan
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From: Phenix City, AL
A larger pipe won't neccesarilly make you more power or torque. It can actually hurt your power, if it's too large.
Ideally you want the largest pipe area at the collector, from either headers or manifolds. This is because the exhaust is hottest here and moving the fastest. As the exhause cools, it becomes slower and more dense. If you increase the size of the pipes farther back, you are slowing the exhaust and decreasing exhausts ability to scavenge from the engine. So what you are doing is making the engine push the exhaust out, rather than the scavenging help to pull it out.
If you neck the pipes down farther back, you mantain the exhaust flow and the scavenging effect. So really, you want the 3 - 3 1/2 inch pipes in front of the cat, 3 after the cat, and 2 1/2 - 3 after the muffler. Not neccesarilly those exact numbers, but you get the idea. Size is the key to it, but maximizing the scavenging is what you're trying to achieve, not just volume.
The reason you see diesels running these huge 5" pipes is that they push such a high volume of air and the EGT is extremely high.
Ideally you want the largest pipe area at the collector, from either headers or manifolds. This is because the exhaust is hottest here and moving the fastest. As the exhause cools, it becomes slower and more dense. If you increase the size of the pipes farther back, you are slowing the exhaust and decreasing exhausts ability to scavenge from the engine. So what you are doing is making the engine push the exhaust out, rather than the scavenging help to pull it out.
If you neck the pipes down farther back, you mantain the exhaust flow and the scavenging effect. So really, you want the 3 - 3 1/2 inch pipes in front of the cat, 3 after the cat, and 2 1/2 - 3 after the muffler. Not neccesarilly those exact numbers, but you get the idea. Size is the key to it, but maximizing the scavenging is what you're trying to achieve, not just volume.
The reason you see diesels running these huge 5" pipes is that they push such a high volume of air and the EGT is extremely high.
Last edited by BFR250SD; Aug 22, 2005 at 04:14 AM.
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From: Vancouver Wash USA
Originally Posted by V10man
I never could figure out why Banks went with the 3.5" pipe. Maybe it was a sound thing? 
What is interesting, Ford now uses 3.5" tail pipes on the 05 V10. 3" to the muffler then 3.5 out.
What is interesting, Ford now uses 3.5" tail pipes on the 05 V10. 3" to the muffler then 3.5 out.
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I spoke to a Gibson rep today and Gibson's perspective is that the 3 inch pipe is sized right for several reasons.
1. They have experimented with a 3 1/2 inch pipe from the cat rearward but it altered the accoustics so much there was too much noise in the cab.
2. The 3 inch is sized right for the V10 as even though the V10 is a 10 cylinder motor, the cylinders are not large and anything larger than 3 inch would affect backpressure and torque would suffer.
3. The pipe size is not nearly as important as the design of the freer-flowing than stock muffler.
Hope this helps anyone interested.
Dan
1. They have experimented with a 3 1/2 inch pipe from the cat rearward but it altered the accoustics so much there was too much noise in the cab.
2. The 3 inch is sized right for the V10 as even though the V10 is a 10 cylinder motor, the cylinders are not large and anything larger than 3 inch would affect backpressure and torque would suffer.
3. The pipe size is not nearly as important as the design of the freer-flowing than stock muffler.
Hope this helps anyone interested.
Dan
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