Best exhaust under $1.5k

VCM OTR
Ace. Except when you want to do the right thing and keep the air filter clean, have to basically disassemble and uninstall to remove element to clean. Orssom OTR is same performance different execution but piss easy to maintain.
Pacemaker headers
Those are basic 4-1 straight pipes into merge cone that by its nature has one rpm peak and that's out of reach 99% of the engine's operating range. Same with all 4-1, ok if you want to make noise and spruik about the hp screaming tits off at peak rpm, like most people do BTW. Other than that a stupid waste of money, but nowhere as ridiculous as buying Difilipo oversized POS which deliver worse performance 95% of time (like strapping fire hose to garden tap).
Also if you are going to the extent of proper aftermarket headers you need a custom tuned secondary / collector. Otherwise all these designs are next to useless. The ones you need are PH5387 with diffuser extension before the HFC.
High flow cat????
Yes, they are all made in China from spin steel with coated steel substrate, can pay too much for shiny ones with nice logo just get 200 CPI 4" barrel 2.5" in/out. Price ~$150-$350 each.
HSV VF Centre section
Excellent and simple, extreme value. The only negative is that the x-pipe is more a balancer hence acts like H-pipe, is in the correct location in that regard. However you will get better usable torque with a proper x-pipe device in the correct location (likely tuned further back just behind tunnel brace).
Standard VF muffler
Of course the rear muffler makes a massive impact to sound character and the latest stocko ones are good I think FWIW.

 

So the pacemaker PH5387 are the go??I see you can get ones with the cats on there as well.
I'd rather useable power than just the ability to show people a dyno sheet with high rwkw

Also a collector?

Also I see the centre section doesn't have O2 sensor bung holes. Will I need to somehow get an o2 sensor on there?

 

Yes definitely. I haven't seen the Pacemaker cats fitted as a solution, can you show the link please?

 

http://m.ebay.com.au/itm/Pacemaker-...%3A0ad9384415d0abd99a0e4813fff3622e%7Ciid%3A2

Are you able to link a collector please?

 

Thinking of the exact same setup Red Lion, just waiting on Monstar's final review of it and my tax return!

 

O2 sensor fitting bungs are there of course, at a good location, this is a precisely engineered piece of kit. Harness is included with the one linked on eBay, has the HFCs too, the main thing is that's all the bits except still no collector section (secondary pipe).

How to make a megaphone diffuser (collector)
Dimension of the megaphone collector is 2"diffuser expanding to 3.5" for a length of 18.7" from merge point to nozzle at exit wall (past end of HFC substate).

Mandrel Megaphone Device

Fortunately PH5387 has a mini diffuser already built-in from merge to flange:

2.25" at Merge 2" long

So 2.25" at merge to 3" at flange exit:

3" at Flange

Over 12" there is a small expansion to join HFC entry at 3.5":

470 kW Megaphone (3"in / 3.5"out)

Then 4" HFC barrel and 2.5" exit nozzle:

Secondary pipes with megaphone diffuser as "collector"

Header flange exit to nozzle at rear of HFC is 16.5":

4" Spun Steel Barrel Cat (HFC)

Total PWTB (tuned resonator) volume is 187ci (3.07 litres) per bank:

Pulse driven HFC theory

Expansion chamber theory

Cakewalk for an exhaust bloke worth his salt! If there are three or four members interested I can get a good price to fab up and supply all the headers, collectors with HFCs, ready to install

 

Literally been lurking in these forums since I bought my VFSS and been looking at this thread with interest. I wanted to get a bit more shove out of the car given the choke chain the standard SS exhaust is. Saw all the bits and pieces and just got confused. If there is a group buy on this exhaust all jimmied up I would be very interested! I travel to and from Kingaroy fortnightly so this is perfect if I needed to pick it up!

Cheers

Gav

 

Yeah might be the go, have contacted Pacemaker to kick off a deal will post back.

 

Nothing new there, it's a pressure wave termination chamber. Whatever you have after the expansion chamber is pretty much irrelevant. The measurement from the end of the secondaries to the start of the expansion chamber is the critical one. Also, the chamber has to be twice as big as the displacement of the cylinders running into it. EG for a 6.0L V8 with twin pipes and two chambers, each chamber has to have a volume of 6.0L. And by the way, you don't want reversion from the chamber, you are only creating back pressure. To prevent reversion you will need a short stub of exhaust protruding in from both ends of the chamber. Expansion chambers work on 2 strokes because they need back pressure to stop the intake charge from escaping the crank case. It has a negative effect on a 4 stroke.

 

Oh, the only other thing is that the price listed is with 100 cel cats, with 200 and 300 cel optional.

But regarding the other posts, all that stuff about collectors and megaphones confuses me! But I'd be keen to buy the extractor/megaphone/cat setup as well, would just need it posted!

 

Yeah forget that eBay link I will price up with 100, 200 and 300 (never seen those) on a group buy of half dozen then.

 

Sounds good @monstar

 

Slightly off topic,

But cheapest place to buy a vcm OTR?

https://www.ebay.com.au/itm/201079289253

 

Yes about right. As I mentioned the Orssom is much easier to install and maintain, I've had both.

 

Legend! I'm very interested, depending on $.

 

This whole expansion chamber theory for 4 strokes is new to me. I understand re 2 strokes. The back pressure helps keep fuel air mix in the cylinder on the up stroke, as there are no valves. But, I dont understand how this reverse pulse back pressure helps scavange the exhaust gasses from a 4 stroke? Can you shed some light in the theory Monstar?

 

Yes mate simply it is an extractor at the end of the primary tubes, not a device at the start near the exhaust port. See diagrams above, and this thread.
Under high thermal load the catalytic substrate creates an air-breathing valveless pulsejet engine, driven by an alternation between high and low pressure. This alternation is not maintained by any mechanical means, rather by the natural acoustic resonance of the rigid tubular engine structure.
It works by alternately accelerating a contained mass of air rearward and then breathing in a fresh mass of air to replace it. The energy to accelerate the air mass is typically provided by the incoming exhaust pulse.

 

Any sort of wave reversion is back pressure, you don't want it on a 4 stroke.

Exhaust pulse tuning can and always has, only been to attain the peak torque at a given rpm range, primary size and length is the ONLY thing that affects this. Having another device further down the exhaust stream does nothing apart from creating an expansion point that terminates the pressure wave. You don't want it reverting and heading back up the exhaust as this is back pressure.

 

No, there is no reversion caused by this collector. Actually creates propulsion, ie can be measured as thrust...

 

The discussions above are only for NA applications though correct?

So if I were to go supercharger in future, the gain is a relatively free flowing exhaust?