- Dec 9, 2020
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- VF II SSV Redline Ute
I think most aftermarket rear mufflers are too small and generally speaking in most sports exhaust systems, you need the "biggest" rear mufflers that'll fit in the car and the stock muffler can is a good size. Alternatively if starting from scratch, I'd probably roll up a round muffler can at least 8" in diameter and 14" long.Hey @RevNev, do you have any more photos of what you did to the internals? Currently in the middle of changing my exhaust around and looking for some out of the box ideas. Currently testing out HM headers, Manta centre section with DPE bi-modal mufflers. Previously had DPE centre section in place.
The design I call the "Lukey open chamber", is a design that Lukey Mufflers (VIC) pioneered in the 1960's using an open centre chamber in a straight through perforated tube fibreglass packed muffler to introduce a Helmholtz resonator to further quieten the exhaust system. If you imagine welding two 12" hot dogs together with 3" inches of straight 3.5" pipe in the middle, you'd end up with a hot dog 27" long with an open centre section and no perforated tube and fibreglass packing. Lukey also did their single inlet/dual outlet mufflers the same way and that's how I modified the stock bimodals.
The inlet end of the muffler is a 2.25" perforated tube fibreglass packed section and 3" of open chamber in the centre. The outer side of the muffler can, has a twin 2" perforated tube fibreglass packed section and the inner tailpipe has the bimodal valve attached. When closed, the exhaust enters at 2.25" and reaches the open chamber in the centre (Helmholtz resonator) then steps down to exit in one 2" outlet. Open of course, it exits via both 2" outlets and flows more than the 2.25" inlet. Twin 2" flows the equivalent of a 2 5/8" single pipe.
Ultimately, we're reducing the muffler flow and noise level by at least 50% with the valves closed.
In relation to a VF LS3, I'm testing the HSV 340 headers, 1 cell cats (use your imagination), and the 2.5" HSV R8 midpipe. I've changed the two 12" hot dogs to 12" long 4" diameter 2.5" perorated tube fibreglass packed resonators as the factory hot dogs step down to 2.25" I think is too early to step down from 2.5" to 2.25". With only an X-pipe and the 2 resonators in the midpipe with the modified bimodals, it's about as loud as your typical 2.5" bolt on with the valves open, loudish but not over the top loud to attract police attention. In fact, it's quieter than I expected to be honest.
Why I'm not jam packed with midpipe mufflers/resonators, is the size of the rear mufflers the aftermarket never use. They go too small in the rear mufflers then try and quieten the exhaust with midpipe muffling like DPE with their 3 foot long hot dogs (crazy!)
Here's the midpipe that isn't overly muffled compared with the aftermarket when using "big enough" rear mufflers they tend to avoid.