what I'm saying is this:



+

this:


welded to this:


and bolted together = a badass set of headers for pennies

 

According to this they are all ready 2.5, what is that reducer pipe going to go from 2.5 to 2.25?

and the primaries are 1 3/4, IMO given the short length of the merge and 2.5 collector that is why I posted the 3in collector I did.

 

I just got to thinking and what is the point to have a 3" collector if all you are going to do is reduce it to a 2.5" to run the exhaust? If they make a smooth transition with the 2.5" that is on them and just continue on to a 2.5" pipe wouldnt that be better then reducing them?

 

no, not reducing them, little end goes toward the header(2.5"), big end goes toward the back(3"), capiche?

 

The point is to give the exhaust pulses from each tube to interact with each other (scavenging). The 4 pipes come together in an open area and as each pulse goes threw the header it actually sucks on the other 3 tubes, then the next pulse comes threw and suck on 3 more tubes. You have a compression pulse that inturn creates 3 suction pulses on the other 3 tube. It is the key behind tuned headers......

 

That would decrease exhaust velocity....

 

"The concept of a merge collector is similar to the theory behind a carburetor venturi, and in both cases, they work on the principle of building velocity through the venturi effect. Air passing through an hourglass-shaped venturi accelerates as it passes through the narrowest part of the venturi then slows down and expands as it emerges on the other side. This expansion creates a pressure drop, in effect siphoning air into the low-pressure side of the venturi and drawing more volume through the venturi. In a carburetor, velocity has the effect of increasing airflow and fuel atomization; in a header collector, the venturi effect improves exhaust velocity and scavenging. By the nature of the design of a multiple-tube header, there is a large change in area as the gasses from the primary tubes merge into the collector. This rapid reduction in area causes an equally rapid decrease in the velocity of the exhaust gas, which reduces the scavenging ability of the exhaust system. Merge collectors are designed to minimize this change in area at the transition from the primaries to the collector, which allows the gasses to maintain the greatest possible velocity."

 

I am not saying your wrong or right. I am simply stating what I have read and what I have seen. I agree that when you reduce tube diameter pressure will increase on the smaller side. I don't understand how reducing and then increasing again will increase exhaust velocity and scavenging. It seems to me it would slow it down again and cause a backup/restriction..... IMO if you are going to reduce the pipe size to increase velocity and scavenging then keep it at the same size until you add more airmas like a into a y-pipe.

I am not trying to get into a pissing contest, just a fun debate on what would be better and why. I am not expert by any means...

 

Grippy, I'm with you on that. I was just looking at a way to copy the orig. design of the AEM setup and without cutting or welding (as some guys on here just don't have the means)

 

I was not bashing your idea or anything, sorry if I came across that way, I would just go with your orginal idea and get the bolt on connectors with the O2 sensor bungs. You might be able to get away with bolting the headers in and being about to reuse your stock Y-Pipe and just use some pipe clamps to attach it or get that Pacessetter y-pipe or jegs has a stock Y-pipe with no cats u could probably cut some off and use.