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Ve 3.0L new exhaust, different size?

duca1991

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Hi guys, i asked this question on streetcommodores but i want a few more opinions just to feel satisfied with what has happened.

Hi there,
I have a ve omega series 2. I got a xforce catback put on at an exhaust shop. I asked for a 2.25". But out of curiosity i looked under the car for model numbers on the piping to see if i got what i asked for. They put the xforce 2.5" up the front of the car to the rear axle. Then where it connects at the rear the muffler part number is 2.25". I rang them up and they said xforce had ran out of stock in Australia at the point in time and i had to wait 6 weeks. so they could not supply a complete 2.25" all the way, which i think is bullshit. They they could only supply the 2.5" center muffler/piping. Does this affect the car in a negative way as opposed to having 2.25" all the way? Do i lose power? My fuel consumption seems good at 12.31 L/100 at an average speed of 34.
I just dont want to get worse fuel economy.
Thanks

Someone said it makes no difference having a bigger center piece as the rear piping is smaller and determines flow?
 

VTSS304

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Well theoretically the gas is leaving the engine in a small pipe and then having free flow in the bigger 2.5, then being slowed at the 2.25 so it shouldnt have a negative effect as such its just the restriction is further back in the system rather than at the cats. so the only real difference would be a slight difference in the sound through the resonator in the centre section of the exhaust.

Please correct me if im wrong guys. but I couldnt imagine it having any effect at all, certainly not noticeable.
 

PIR4TE

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^^ I agree, it won't affect your car in a negative way at all, rather the opposite. By the time exhaust gas reaches axleback it suits a reduction in diameter to maintain velocity.
Some of the fastest VE/G8s run stock (2.25") axleback on their hi performance systems for that reason.
 

duca1991

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Cool guys, thanks for that, bit more relieved now. Makes sense to me when i read both posts. Thanks again!!
 
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