Do different 4-1 header designs sound different?

[07GTS]

The greater exhaust issue on the VE/VF platform, is the compulsion to use 3" exhausts with engine's that can't use and don't need such a big exhaust to make maximum horsepower.

that 3'' on everything is like a virus, i only went 3'' on mine after the blower when i was chasing more power, n/a LS a good 2.5 is plenty

 

[RevNev]

that 3'' on everything is like a virus, i only went 3'' on mine after the blower when i was chasing more power, n/a LS a good 2.5 is plenty

Absolutely! A good 2.5" system will flow 550hp flywheel and that's a pretty serious NA road car engine. The only 3" I've fitted to our cars within the company is the VE ute with the Magnuson blower on E85. The rest of ours are all 2.5" with tri-y headers. I had the impression the 1 7/8" header and 3" exhaust option was aimed at supercharged engines, not NA engines unless radically modified.

 

[PeteSS]

that 3'' on everything is like a virus, i only went 3'' on mine after the blower when i was chasing more power, n/a LS a good 2.5 is plenty

I went backwards. Bough the car (blown and cammed) with 3 inch exhaust (1 7/8th headers ands 100cel cats) .sounded sensational, but waaaay too loud.

Went to 2.5 inch catback with 200cel cats. when the car went back to the original tuner for something else, they threw it on the dyno and found it lost little to no power with the smaller exhaust when they did some power runs.
If anything it felt a bit punchier down low

 

[07GTS]

I went backwards. Bough the car (blown and cammed) with 3 inch exhaust (1 7/8th headers ands 100cel cats) .sounded sensational, but waaaay too loud.

Went to 2.5 inch catback with 200cel cats. when the car went back to the original tuner for something else, they threw it on the dyno and found it lost little to no power with the smaller exhaust when they did some power runs.
If anything it felt a bit punchier down low

yea sounds about right bout opposite to what mine done, i had 1-7/8 headers into 3'' cats into 2.5'' then i changed cats and the rest back to DPE 3'' i had to add in bout 10% fuel up top but i could also feel a slight loss of torque down low and could take a smidge fuel out down there

 

[RevNev]

yea sounds about right bout opposite to what mine done, i had 1-7/8 headers into 3'' cats into 2.5'' then i changed cats and the rest back to DPE 3'' i had to add in bout 10% fuel up top but i could also feel a slight loss of torque down low and could take a smidge fuel out down there

When an exhaust post header makes torque, it actually tells us the headers aren't right, either too big in the primaries, too short or the collector is too big. It's where a tri-y header is more forgiving to imperfection than a 4 into 1 on an NA road car engine, as header design is largely focused on fitting into the chassis and accommodating cats etc. often with insufficient room to optimise the header design for a particular engine.

Back in the day I thought "big is better", an old bloke good at header design on an engine dyno showed me why "big" isn't always better. He told me to always use the smallest primary pipe size that doesn't rob the engine of top end horsepower to maximise cylinder scavenging! When you're "in tune" with cars, you can feel a difference down low on the seat of your pants with an exhaust change absolutely!

 

[daves8]

When an exhaust post header makes torque, it actually tells us the headers aren't right, either too big in the primaries, too short or the collector is too big. It's where a tri-y header is more forgiving to imperfection than a 4 into 1 on an NA road car engine, as header design is largely focused on fitting into the chassis and accommodating cats etc. often with insufficient room to optimise the header design for a particular engine.

Back in the day I thought "big is better", an old bloke good at header design on an engine dyno showed me why "big" isn't always better. He told me to always use the smallest primary pipe size that doesn't rob the engine of top end horsepower to maximise cylinder scavenging! When you're "in tune" with cars, you can feel a difference down low on the seat of your pants with an exhaust change absolutely!

What are your thoughts on the shorter 4-1 headers like the REX I have? They are essentially same length primaries but all merge kinda straight into the cats with no secondary pipe like the traditional DPE or pacemaker 4-1s.

I have always wondered what impact the design had.

The fella that owns Liverpool exhaust and designs hurricane told he thought it was a flawed design, but I imagine as it wasn’t his product I was using he may have been more critical

 

[The91kwbeast]

What are your thoughts on the shorter 4-1 headers like the REX I have? They are essentially same length primaries but all merge kinda straight into the cats with no secondary pipe like the traditional DPE or pacemaker 4-1s.

I have always wondered what impact the design had.

The fella that owns Liverpool exhaust and designs hurricane told he thought it was a flawed design, but I imagine as it wasn’t his product I was using he may have been more critical

This and the Sureflo 4-1 headers that finish at the standard position are both reasonably unique products, can't find many others that finish in the standard spot.

Someone needs to have the stepped REX headers run back to back with 1 7/8 long tube 4-1s I both with 100 cell cats and try and find a catback that is somewhat comparable to see.

 

[RevNev]

What are your thoughts on the shorter 4-1 headers like the REX I have? They are essentially same length primaries but all merge kinda straight into the cats with no secondary pipe like the traditional DPE or pacemaker 4-1s.

I have always wondered what impact the design had.

The fella that owns Liverpool exhaust and designs hurricane told he thought it was a flawed design, but I imagine as it wasn’t his product I was using he may have been more critical

4 into 1 headers work best at higher RPM in a narrow RPM band and good for sprint car engines, drag racing or circuit race engines with close ratio gear boxes where an engine doesn't drop below 5000rpm on corner exit etc. For road car engines using a wide RPM band, I don't use 4 into 1 headers on naturally aspirated engines and prefer tri-y's that have much better scavenging at low to mid-range RPM used the most in street driving.

4 into 1's collecting into a cat is a design priority to incorporate a cat and isn't possible with such a large collector to create any scavenging effect. To work effectively, 4 into 1's need to join into a proper merge collector to create a venturi effect and no VE/VF headers I've seen are designed like that.

 

[daves8]

4 into 1 headers work best at higher RPM in a narrow RPM band and good for sprint car engines, drag racing or circuit race engines with close ratio gear boxes where an engine doesn't drop below 5000rpm on corner exit etc. For road car engines using a wide RPM band, I don't use 4 into 1 headers on naturally aspirated engines and prefer tri-y's that have much better scavenging at low to mid-range RPM used the most in street driving.

4 into 1's collecting into a cat is a design priority to incorporate a cat and isn't possible with such a large collector to create any scavenging effect. To work effectively, 4 into 1's need to join into a proper merge collector to create a venturi effect and no VE/VF headers I've seen are designed like that.

So to paraphrase my Rex headers wouldn’t perform as well as a DPE 4-1 header set up?

I understand the concept of high vs low rpm, but have always felt 4-1 give a better “beatier” note that try y.

 

[RevNev]

So to paraphrase my Rex headers wouldn’t perform as well as a DPE 4-1 header set up?

I understand the concept of high vs low rpm, but have always felt 4-1 give a better “beatier” note that try y.

Which header would work the best between Rex and DPE needs dyno testing at various RPM points to determine, but if a 4 into 1 doesn't terminate into a merge collector (pictured below), it'll never work optimally. Note wise, it depends on what your ears prefer, but sometimes mid-range, a V8 can sound the best on stock cast iron manifolds. The exhaust has the greater note impact than the headers in most cases until reaching high RPM.