Question about Collector lengths
Thread Starter
Racer
Joined: May 2005
Posts: 436
Likes: 0
From: Stavanger
Question about Collector lengths
I have done a lot of searching and reading on the net about headers.
I am looking foe headers for a 73BB vette. Want lots of torque in the bottom / max power between 2000 and 5500rpm
What i have found regarding info are:
-Thinner and long primaries will help low end torque.
-collector should be 1,75 times larger than primaries on a V8.
-Most engines benefit best from a collector between 10" and 20". Longer collector help with low end torque.
But what i cant find any info on, are how the exhaust effect the collector length? Does someone have any info?
My current plan are to run hookers with 1 7/8" primaries, 30" long. 3"collector at 8". This i plan to connect into a Magnaflow exhaust system with mandrel bent 2,5" pipe and "x tube".
Would i benefit if i was able to extend the collector to 20" before going down to the 2,5" exhaust right before the cross member and the x tube?
Hope somebody have some info here, i have been reading and searching for days.
I am looking foe headers for a 73BB vette. Want lots of torque in the bottom / max power between 2000 and 5500rpm
What i have found regarding info are:
-Thinner and long primaries will help low end torque.
-collector should be 1,75 times larger than primaries on a V8.
-Most engines benefit best from a collector between 10" and 20". Longer collector help with low end torque.
But what i cant find any info on, are how the exhaust effect the collector length? Does someone have any info?
My current plan are to run hookers with 1 7/8" primaries, 30" long. 3"collector at 8". This i plan to connect into a Magnaflow exhaust system with mandrel bent 2,5" pipe and "x tube".
Would i benefit if i was able to extend the collector to 20" before going down to the 2,5" exhaust right before the cross member and the x tube?
Hope somebody have some info here, i have been reading and searching for days.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
merge collectors are actually the best, but as to your question: The collector length is only applicable when it empties into the open air. open tuned headers.
I use all 3 inch pipe clear to the mufflers with the exhaust passing under my custom cross member.
I use all 3 inch pipe clear to the mufflers with the exhaust passing under my custom cross member.
Melting Slicks
Joined: Mar 2008
Posts: 2,666
Likes: 289
From: Spring Park MN
Our C3's don't lend themselves well to exhaust that you can separate the primary tuning from the secondary tuning and make it possible to use the secondary tuning which is the collector length you speak of. George is partially correct when he states that the collector length is only applicable to when it dumps to open air, but you can fool the system into believing it is dumping into open air. What you need is a large abrupt change in area at the end of the desired collector length. This can be into a box or a chambered muffler. It is best to have the collector tube extend slightly into the chamber so the pressure wave will see this as the pipe ending at atmosphere and the pressure wave will bounce at that point. There really isn't the room to do this under a C3 so the next best thing you can do is join the pipes in an X pipe (a box would be better) as close to the headers as the transmission mount will allow. I use a BTO trans mount and it lets me get pretty close to the back of the tranny. It's not ideal, but it works well.
Here is the best article I have seen on the subject.
http://www.superchevy.com/technical/...exh/index.html
Here is the best article I have seen on the subject.
http://www.superchevy.com/technical/...exh/index.html
Thread Starter
Racer
Joined: May 2005
Posts: 436
Likes: 0
From: Stavanger
Our C3's don't lend themselves well to exhaust that you can separate the primary tuning from the secondary tuning and make it possible to use the secondary tuning which is the collector length you speak of. George is partially correct when he states that the collector length is only applicable to when it dumps to open air, but you can fool the system into believing it is dumping into open air. What you need is a large abrupt change in area at the end of the desired collector length. This can be into a box or a chambered muffler. It is best to have the collector tube extend slightly into the chamber so the pressure wave will see this as the pipe ending at atmosphere and the pressure wave will bounce at that point. There really isn't the room to do this under a C3 so the next best thing you can do is join the pipes in an X pipe (a box would be better) as close to the headers as the transmission mount will allow. I use a BTO trans mount and it lets me get pretty close to the back of the tranny. It's not ideal, but it works well.
Here is the best article I have seen on the subject.
http://www.superchevy.com/technical/...exh/index.html
Here is the best article I have seen on the subject.
http://www.superchevy.com/technical/...exh/index.html
Would i be ok if i had 3" pipe to the crossmember (20" +) and then over to 2,5" true the crossmember and into the x-tube.?? That means that i would go down to 2,5" before the x-tube.
is 3" eletrical cut outs someting to evaluate?
Last edited by kayosnes; Mar 25, 2010 at 04:08 PM.
Thread Starter
Racer
Joined: May 2005
Posts: 436
Likes: 0
From: Stavanger
A 3" exhaust pipe on a 3" collector. Wont that result in a several meters of collector? Looks good. But i am looking for the beat way to do this with 2,5" exhaust (and x-pipe). And i was wondering how large the collector should be then.
Drifting
Joined: Aug 2005
Posts: 1,682
Likes: 3
From: League City TX
Collectors that are too short can cost you enough power to feel SOTP.
Also, transitioning to a smaller pipe diameter really doesn't terminate the collector length. You have to increase cross section to do that.
