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Another one. Exhausted

426Cuda

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Yep, you guessed it. It's an exhaust question.
The engine oil cooler on my MSE has forced my hand. I won' be using the HSV 340 tri-y shorties I have. :(
So the Q's are:
1. Long 4-2-1 or 4-1???
2. Primary pipe diameter 1" 3/4 or 1" 7/8? (It may only be about 3mm difference, but it's girth lads! Oh, and I already said I was going long.:D).
I've read up on the pros and cons and best applications of all three designs from the experts. Also diameter. I thought I knew a bit about headers? I was right. But only a bit. I learned some really interesting stuff. Fun maths too haha. It even helped put some of @monstar 's nutty professor ramblings into perspective. ;)

So, this is the cross road I'm at.
I've read up on the theory, as I'm no expert, so I got it from the experts. I'm deciding between 1" 3/4 4-1's and 1" 3/4 long 4-2-1's.
I'm not trying to start a war here. I know the two brands I'm leaning towards. I'm interested to hear from anyone whom has tried both on a VE or VF or VF2?
Seat of the pants dyno stuff. Dyno results if available. Sound. Clearance Clarence. Bottom end tourqe. Mid range. Top end. So on.
If my learnings from the theory are correct I'm thinking there'll be a bees dick between them on paper. The long 4-2-1's will have marginally better bottom end and mid. 4-1's will start a little later, then possibly dip a bit, and be marginally better up high. The 4-1's will sound better.
The major thing I want to know is how the 4-1's perform down low compared to the long
4-2-1',s in our cars.
Any practical knowledge would be appreciated.
Cheers!
 
Last edited:

monstar

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Yep, you guessed it. It's an exhaust question! Will
Love to help mate but you’re gonna have to use your words to talk to city folk.
 

blackve76

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Yep, you guessed it. It's an exhaust question.
The engine oil cooler on my MSE has forced my hand. I won' be using the HSV 340 tri-y shorties I have. :(
So the Q's are:
1. Long 4-2-1 or 4-1???
2. Primary pipe diameter 1" 3/4 or 1" 7/8? (It may only be about 3mm difference, but it's girth lads! Oh, and I already said I was going long.:D).
I've read up on the pros and cons and best apllications of all three designs from the experts. Also diameter. I thought I knew a bit about headers? I was right. But only a bit. I learned some really interesting stuff. Fun maths too haha. It even helped put some of @monstar 's nutty professor ramblings into perspective. ;)

So, this is the cross road I'm at.
I've read up on the theory, as I'm no expert, so I got it from the experts. I'm deciding between 1" 3/4 4-1's and 1" 3/4 long 4-2-1's.
I'm not trying to start a war here. I know the two brands I'm leaning towards. I'm interested to hear from anyone whom has tried both on a VE or VF or VF2?
Seat of the pants dyno stuff. Dyno results if available. Sound. Clearance Clarence. Bottom end tourqe. Mid range. Top end. So on.
If my learnings from the theory are correct I'm thinking there'll be a bees dick between them on paper. The long 4-2-1's will have marginally better bottom end and mid. 4-1's will start a little later, then possibly dip a bit, and be marginally better up high. The 4-1's will sound better.
The major thing I want to know is how the 4-1's perform down low compared to the long
4-2-1',s in our cars.
Any practical knowledge would be appreciated.
Cheers!
Keeping your stock cat back/has location? ?
 

426Cuda

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Keeping your stock cat back/has location? ?
Sorry. I'll use the 340 cat back initially and the stock rear cans. If its raspy I'll change the cat back. Hi-flow cats, OTR and tune too of course.
 

blackve76

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Sorry. I'll use the 340 cat back initially and the stock rear cans. If its raspy I'll change the cat back. Hi-flow cats, OTR and tune too of course.

I had tri Ys on VE SS and changed to 4>1 pacies and lost nothing down low and picked up from 3000rpm upwards(think total 7rwkw photobucket has my dyno sheet nowdays grrr) with slight retune so difference insn't much but 4>1's sound heaps better.

You'll have to cut you cat back to suit after market headers/cats though, I got the GM ramjet 4>1 on my VF 2 due to stock cat back location but unsure if would clear your oil cooler
 

SnowDoggyDogg

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Had 4 into 1 DiFillipos on my old VF wagon. Great sound but scraped like crazy because I dropped an inch on the ride. So I had to do the crab walk over every speed bump and it got old as a daily.
I'v had try ys on my VE SSV (Pirates off cuts) and it had a great sound but not as deep. No underbody issues as they tuck up nice and high like a Thai ladyboy.
 

monstar

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I recently experimented with an LS3 fitted originally with Pacie tuned 4-1, then tuned 4-2-1 then my custom set of 4-2-1 with 180º cross-over. Bottom line is all can reach same Volumetric Efficiency at WOT, peak RPM. No contest as there is no practical argument, only theory and dyno discrepancy.
The overall challenge is maintaining velocity, hence torque, at part throttle below the engine's Maximum Peak Torque speed (4600 rpm). Lack of pumping velocity (scavenging) at low speed affects efficiency, drivability (due to poor low speed tuning) and unwanted NVH. Huge difference here, by design. There's more to the story than WOT pull on rollers for six seconds, looking at graphs or listening to a member chime in reckons brand x is king:
Part throttle low load low rpm (like 1100-1750 flat highway) hardly noticeable but is easier to tune 4-2-1 for better performance and economy. Part throttle high load low rpm (like foot down in gear highway) needs velocity to clear. That's where 4-2-1 excels.
Part throttle low load low-med rpm (1750-3000 undulating Highway) there's noticeably more useful torque 4-2-1. Part throttle high load low-med rpm (chasing ricers through mountain pass) also noticeably more useful horsepower 4-2-1.
WOT low load low rpm (like blipping throttle at lights or in a car park) 4-1 sound old school basic but great. WOT high load low rpm (like taking off from idle at lights) 4-1 sounds old school comical to me, like a boat. More complexity to sound and measurable performance 4-2-1 without setting hair on fire, low down power without screaming damaging revs.
WOT low load low-med rpm (1750-3000 undulating Highway) is frustrating, but the biggest disappointment 4-1 is WOT high load low-med rpm (when the heat is on).
WOT high load med-high rpm (3000-4600 LS3 peak torque) 4-2-1 feels strong but 4-1 comes from nowhere and kicks in. This is where 4-1 starts to shine, non-linear progression as efficiency catches up through proper scavenging is a blast. Same level of torque and HP as 4-2-1 but feels good by comparison to the doughy doldrums prior. WOT high load high RPM... well the bottom line is that 4-2-1 are used in NASCAR, World Record Holders in Super Stock and Bracket Racing because the recovery torque is available from middle of the engine's operating range. Whereas 4-1 are designed for a single hp peak way above torque peak, which is fine design for a close ratio small displacement two stroke motorbike but not a cross plane 6.2 litre V8 pulling two tonnes.
Bottom line sound is objective, I can attest that the 4-2-1 setup on my wagon, makes 640 BHP and 825 Nm, are noise compliant and don't drone.
Here is the LS3 (cammed stroker) on which we recently tried tuned different header setups, this is the final design which met the legal stationary target 88dB:
 

Immortality

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So to sum up ^^^^

4-2-1 = more beneficial in the rpm ranges the engine will spend 90%+ of it's time in a daily driver, might not sound quiet as good as the 4-1.

4-1 = better if you have a 4000rpm converter, big gears and drive around with your boot planted 90% of the time with potentially more ground clearance issues.

I don't think you can compare pacemaker style 4-2-1 headers Vs NASCAR headers. Yes they are both 4-2-1 but totally different when it comes to primary/secondary lengths.

PH5387.jpg

62d107cf.jpg

NASCAR headers are a piece of art all by themselves.
 

White Swan

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If what a lot of my friends say is true and you can't really feel any seat of the pants difference then why not choose the ones that you prefer the sound of and who goes WOT on the streets these days to pick the difference anyhow.
If you don't live in an area full of speed humps and steep driveways why worry about clearance given that some manufacturers offer better clearance than others.
 
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