Vz ss stock exhaust question

[BLAQSSHEV]

Searched my heart out no luck whats the standard size of vz ss exhaust and any idea on technically how restrictive standard extractors and cats are on this model are? Thanks in advance for any responses.

[Wonky]

I always thought they were 2 1/2" but I've seen a few references to them being 2 1/4". No VZ (even HSV) runs extractors and the stock cats are typically fairly restrictive.

[SammyK]

I've been told when i was looking into getting my zorst that VZ's have the worst cats of any of the commodores - very restrictive

[BLAQSSHEV]

Ah ok interesting so far so I would have dramas maybe with putting in pacemaker or the like centre mufflers or even cats because the pipes on either of them are 2.5" and would be loose fit over my stock exhaust pipes if it is in fact 2 1/4?? Hmmm any further thoughts .

[SV8TUFF]

The standard cats are crap but its the pipes on either side that are worse there squashed flat at the top for more clearance to get them higher up i seen few people re use the cats and put extractors and custom piping on standard cats to join on the rest of the exhaust. by the way a 2 1/2 inch cat back system will bolt on standard exhaust no trouble or well i didnt have any trouble with mine vy sv8 but same floor pan etc...

[wadevzss]

Yes, apparently the standard exhaust is twin 2 1/4. I have changed my catback to a redback dual 2 1/2. Still tossing up on whether to retain the cats in the standard position, and going with genie or sureflow shorties and high flow cats and pipework all changed to 2 1/2 to suit.

Or moving the cats to pre VZ, getting long Pacemaker or similar, high flow cats and getting tune adjusted to cancel the warning light that will happen when the cats are moved. Still undecided on the best/easiest way to go?

[SV8TUFF]

Di Filippo stainless headers and twin 2 1/2 high flow cats are the go thats what i got awsome i also got custom 2 1/2 cat back. well worth the money

[BLAQSSHEV]

YEah ok, so far I have gone the budget approach got rid of rear muffler and now wanted to change the 2 centre mufflers for Lukey or Pacemaker, whatever has the best note but retain the so called (sports exhaust) that came standard..

I mean at the end of the day the actual standard pipes 2/ 1/4 will be able to get rid of the exhausts on an unopened MAF tuned 5.7l..

[BLAQSSHEV]

Ok so ordered pex 2.5"cat back system without rear muffler. Question? what aftermarket cats will bolt onto stock extractors as I might get some cats? Appreciate any help. Thanks

[Wonky]

...........onto stock extractors ...........

No stock VZ runs extractors. Sureflo Ballistic cats are very free flowing (100cpsi), excellent quality (haven't heard of any failures yet and know plenty of people with them) and excellent prices! :goodjob: They're not flanged though, but that's easy to rectify if required.

[BLAQSSHEV]

Ah thanks wonky shows how much I know. So will the sureflow cats or similar bolt up to the vz exhaust manifold?

[AllWheelSlide]

Mate, If I lived in Newcastle I would save my coin up get a day off work some time and go down to Sydney and see Greg at Sureflo.

[OMR346]

As said, stock VZ SS exhaust is 2 1/4". And squashed in a few places. I originally swapped my ctback for a twin 3" X-force, which bolted straight up behind the standard cats and headers. Then i swapped the cats and headers for Pacemaker 4-1's and hi-flo cats. Then later on i swapped those cats for 100cpi stainless cats. Bigger 4-1's will come eventually.

[BLAQSSHEV]

As said, stock VZ SS exhaust is 2 1/4". And squashed in a few places. I originally swapped my ctback for a twin 3" X-force, which bolted straight up behind the standard cats and headers. Then i swapped the cats and headers for Pacemaker 4-1's and hi-flo cats. Then later on i swapped those cats for 100cpi stainless cats. Bigger 4-1's will come eventually.

Nice one thanks for idea. Yeah saw the flattened out bits near centre mufflers my new pex catback will delete this issue, now just have to bolt up what I have to existing cats and manifold. What would you think would be the greater restriction out of my stock cats and stock zorst manifold?

[Tangles]

I was about to say 2.5 would be large for a stocky!..especially when an upgraded exhaust is 2.5...which is what my old man plans to get on his VE. Still, 3 inch would be my choice + a CAI...

[OMR346]

Im presumming VZ would be the same here, but i do know on a VZ that the headers were the biggest restriction. Ive seen tests done on a VE SS ute. They done back to back dyno testing, aswell as testing for flow figures, ect. First they swapped the cat back for an aftermarket one. The gains were not that big. Then they tested cats, and the cains were bigger. Then they tested the headers, which were the biggest gain. Then with the whole system swapped around, it was obviosuly a decent gain all up. That was done with a bog stock VE SS ute.

Ive got the dyno sheet around here for it somewhere. If i can find it, ill post up a pic of it.

[BLAQSSHEV]

OK thanks for that info, may have to do Headers and Cats in one operation down the track when I get some more flow together.

Certainly should see some gains because of this crimped flat spot I just checked out behind centre mufflers which would easily reduce overall diameter to 2" even on both pipes :)

Thaks to all that posted. :goodjob: