Cons: Bit louder, totally illegal if we ever get emmision testing Pros: Bit louder, better flow etc
by_hdt,
May 24, 1:32am
wont make any difference one way or another unless they are ****ed. On some vehicles with downstream 02 sensors it can cause rough running. Had one idiot once with a hemi powered dodge ram, put a massive drain-pipe exhaust with no cats on it, then couldn't figure out why it was running like a turd. told him that it was his exhaust, "nah no way its gotta be something else" $10,000 later and its "still not the exhaust, my cousin did it and hes real on to it"
wrong2,
May 24, 1:37am
theres no way even a fully tuned exhaust is going to boost economy by that much
all a performance exhaust does is : release the HP that your engines tune naturally has
so you get more HP & (more importantly) torque which = not having to gas it as long & hard to get to legal speeds
your not making the engine burn less fuel - your making the engine perform better so your on the gas less
cats are absolutly horrible for flow - ditching them is ALWAYS a good thing for flow
resonators are badly understood & never needed - theirpromotion is down to a lack of knowledgeregarding proper muffler design
fordguy17,
May 24, 1:47am
If you only have an o2 sensor BEFORE the cat, ditch the cats. If you have one after and before, you need to keep the cats as it will trigger a fault code and also light up an engine check light on your dash. Cat's are very restrictive and hold back flow by increasing back pressure. They also muffle quite a bit of sound. Take the cats out and put in a straight through muffler instead of the stock style muffler and you will notice a bit of pedal feel.
cherrolet,
May 24, 5:08am
My ex wanted to supercharge my 91 ute.Told him to sod off, wasn't having my Newfoundland dogs flapping in the wind in the back with just their chains keeping them there.
Now sitting on just over 420,000Ks, it's still going strong.Dogs more spoilt as after we split took the Maloo air scoop off it and put a canopy on.
hamcouple4fun,
May 26, 10:28pm
just done it and its a lot cheaper on full and there is more power
dingo011,
May 26, 10:36pm
Have you considered taking out cat and with a long drill drilling out the contents of the cat and re fitting! looks stock but also free flow, times a couple of hours but only cost is the long drill bit.
im_andrew,
May 27, 1:22am
I wouldnt expect too much gain from it. It wont affect the oxy sensors as they are up in the y-peice. Why would you though! Get a 2.5" or 3" exhaust instead
wrong2,
May 27, 1:35am
more horsepower
more torque
a decrease in fuel consumption
standard exhaust systems are made to suitengine NVH criteria - notengine performance
im_andrew,
Apr 6, 9:01pm
Nah mate. Ive owned commodores. I have tried these things. minimal gain to be had from gutting a cat, all it does is put a big empty square box in the middle of your otherwise long, thin tube. Read up om helmholtz resonance and you will see what i mean.
There are decent gains to be had from fitting a set of extractors and a bigger exhaust system. You need a retune to see any real gains from that, though.
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