Header Collector Extensions: Drag Strip Tuning

-
1

12many

Well-Known Member
Joined
Dec 14, 2016
Messages
3,571
Reaction score
4,689
Location
SC
This is a topic that has been discussed here in the past as well as covered in the Mopar Performance engine books regarding ideal collector extension length. Taking another look at this myself and came across a nice in depth article regarding collector extensions. Many may have been there done that and moved on to other things, have used the paint or crayon method to find the ideal length but I think this is a good read nonetheless for anyone on the path of tuning & testing.

Header Design Comments - Cheap Performance Gains.

With my setup and the 1-5/8” Dougs, runs at the track have developed a blued pattern (after jetting for Max Mph) that ends at about 7-1/2” on these 12” stainless Pypes extensions. I’ll likely source some cheap ones to hack down vs. chopping on these for the time being.....see what it yields at the track.
1E6474AD-4875-4696-BF4C-DD73AD69A67E.jpeg


What have some of you found during your track based exhaust tuning? :)
 
Subbed. I bought the same mufflers you did, and plan on leaving my 3.5 x 18 inch "s" extensions in place on the collectors, even when racing. Hell, if it doesn't hurt it through the mufflers, I won't even bother taking them off. I have the extensions mounted, and already see the wideband is WAY more stable, obviously with less reversion, but I probably had 13 inches total with those little bullet looking "anti reversion chambers" after the O2. The extra 5 inches has made it very nice for tuning
 
Johnny Mac said:
Subbed. I bought the same mufflers you did, and plan on leaving my 3.5 x 18 inch "s" extensions in place on the collectors, even when racing. Hell, if it doesn't hurt it through the mufflers, I won't even bother taking them off. I have the extensions mounted, and already see the wideband is WAY more stable, obviously with less reversion, but I probably had 13 inches total with those little bullet looking "anti reversion chambers" after the O2. The extra 5 inches has made it very nice for tuning
Click to expand...
From everything I’ve read these mufflers won’t cost much if any power over an open exhaust. You’re mounting them to the extensions and dumping, minimal pipe right? My system is shorter than most that dump at the axle
26C6CD6F-D04E-49A4-AEBA-7A5A534D3797.jpeg
but I remove both assemblies and just run the extensions (saves about 40 lbs total) at the track. Interested in the gains if any from optimizing the extensions on anyone’s setup. Have you mounted the mufflers yet and had a chance to hear them??
 
I have some collector extensions, but I can't play with them here.
Mufflers are required at both my local tracks. (Supposedly)
Enforcement is sketchy at best. Had an10,000 rpm uncorked n/a Mazda rotary at the track Thursday night. Loud enough to wake up Democrat voters (the dead).
 
"...saves about 40 lbs"
I hear that. If I change from street steelies to the lightweight wheels and slicks, and pull off the 3 1/2" to the back bumper exhaust, I lose about 150 lbs.
 
33IMP said:
"...saves about 40 lbs"
I hear that. If I change from street steelies to the lightweight wheels and slicks, and pull off the 3 1/2" to the back bumper exhaust, I lose about 150 lbs.
Click to expand...
150 lbs is huge! Anytime I hit the track I try to keep everything the same as much as possible, that I can control at least. I just ran the 1/4 with about 15 gallons of fuel vs my usual 5, and left my west coast mirrors sticking out. Lazy and rusty I guess. That is a good bit of Mph lost right there, and a smidge on et. I thought about leaving my exhaust in place before running, but wisely ended up dropping it.
 
12many said:
150 lbs is huge! Anytime I hit the track I try to keep everything the same as much as possible, that I can control at least. I just ran the 1/4 with about 15 gallons of fuel vs my usual 5, and left my west coast mirrors sticking out. Lazy and rusty I guess. That is a good bit of Mph lost right there, and a smidge on et. I thought about leaving my exhaust in place before running, but wisely ended up dropping it.
Click to expand...
The pipes and the giant flowmasters are eighty pounds at least, and the centerline skinnies and slicks are eighty pound lighter that the 15x7 and 15x8 steelies and t/a radials.
The mufflers alone are almost 25 lbs each.
 
Last edited:
12many said:
This is a topic that has been discussed here in the past as well as covered in the Mopar Performance engine books regarding ideal collector extension length. Taking another look at this myself and came across a nice in depth article regarding collector extensions. Many may have been there done that and moved on to other things, have used the paint or crayon method to find the ideal length but I think this is a good read nonetheless for anyone on the path of tuning & testing.

Header Design Comments - Cheap Performance Gains.

With my setup and the 1-5/8” Dougs, runs at the track have developed a blued pattern (after jetting for Max Mph) that ends at about 7-1/2” on these 12” stainless Pypes extensions. I’ll likely source some cheap ones to hack down vs. chopping on these for the time being.....see what it yields at the track.View attachment 1715813290

What have some of you found during your track based exhaust tuning? :)
Click to expand...

tried it on the old hemi belvedere , didnt do squat for that car !
 
12many said:
From everything I’ve read these mufflers won’t cost much if any power over an open exhaust. You’re mounting them to the extensions and dumping, minimal pipe right? My system is shorter than most that dump at the axle View attachment 1715813333 but I remove both assemblies and just run the extensions (saves about 40 lbs total) at the track. Interested in the gains if any from optimizing the extensions on anyone’s setup. Have you mounted the mufflers yet and had a chance to hear them??
Click to expand...
My s bends look very similar to yours. I do have those mounted. Then I have 54 inch of straight pipe, with the mufflers before the axle and turn downs. I have not got them fully mounted. Was waiting on hangars. I did slip them on with it running. It for sure took some cackle out of it. I'm sure it'll sound better with it sealed and clamped.
 
Very cool. Exhaust tuning on a VAN. Who'da thunk it. LOL I love it!
 
Motor Trends Engine Masters apparently did an episode on this topic (#69) Wonder what their findings were? Anyone?
 
12many said:
Motor Trends Engine Masters apparently did an episode on this topic (#69) Wonder what their findings were? Anyone?
Click to expand...
I have that episode on my dvr, but it's 200 miles away.
If memory serves.... any extension is better than none. They started with something like three feet, and chopped off four inches per pull. As mopowers said, 12-18" was about right. The most dramatic difference was in midrange torque versus no extension at all.
 
33IMP said:
The most dramatic difference was in midrange torque versus no extension at all.
Click to expand...
I’ve read quite a few articles/posts elsewhere during searches about the gains (if any) being in the midrange. Being I launch at about 3500 flash stall and after shifts drops the rpm back into the mids I’m thinking maybe I could gain a little something vs. if I had a looser converter where I’m thinking extension length would likely have no effect, as some have mentioned. Something to play around with....
 
12many said:
This is a topic that has been discussed here in the past as well as covered in the Mopar Performance engine books regarding ideal collector extension length. Taking another look at this myself and came across a nice in depth article regarding collector extensions. Many may have been there done that and moved on to other things, have used the paint or crayon method to find the ideal length but I think this is a good read nonetheless for anyone on the path of tuning & testing.

Header Design Comments - Cheap Performance Gains.

With my setup and the 1-5/8” Dougs, runs at the track have developed a blued pattern (after jetting for Max Mph) that ends at about 7-1/2” on these 12” stainless Pypes extensions. I’ll likely source some cheap ones to hack down vs. chopping on these for the time being.....see what it yields at the track.View attachment 1715813290

What have some of you found during your track based exhaust tuning? :)
Click to expand...
Engine Masters did a show on this very topic and they have shown that header extensions Benefit the low rpm band. A rpm area you may not be using at the track. Helpful on the street though!
 
And they (engine masters) concluded that the results will likely change with different camshaft profiles and engine combos. The answer is always test test test.
 
You must log in or register to reply here.
-

Back
Top