using more gas

[cru]

Lhi guys, just a random question....... i took off my rear muffler on the weekend coz it sounded like it had stones in it, but it turned out to be the oval tip that was making the rattle noise, before i put the muffler back on i took it for a drive with out it to see what it would sound like. sounded pretty good, i realised it had used more gas than normal for the 5-10 min drive. why would it use alot more gas? just because i took the back muffler off. i was thinking of getting a straight pipe made to replace the back muffler but if its going to chew the gas i wont bother doing it.
just want ur thoughts in why its doing it and will it do it if i get a pipe made up

thanks

exhaust system is a medium sound coby
engine 5.7L V8 2005 Calais

 

[MYVESSV8]

higher flow rate of exhaust (caused by increase in sound and heavier foot to hear more of said sound)

 

[cru]

will it wreck the engine if i have a straight pipe and not have the rear muffler?
i have the middle mufflers in still

 

[MYVESSV8]

shouldn't be a problem, don't have them on mine and haven't for 100,000klm

 

[Nut Kracker]

will it wreck the engine if i have a straight pipe and not have the rear muffler?
i have the middle mufflers in still

Might wreck your account balance if you get caught with out it.
Pretty sure it's a Road Worthy requirement to have a rear muffler.

Could be wrong though......

 

[EYY]

Must retain the same number of mufflers in the original location according to vsi8 iirc. That's for aus though. New Zealand is probably different

 

[cru]

Must retain the same number of mufflers in the original location according to vsi8 iirc. That's for aus though. New Zealand is probably different

been to a couple of exhaust places today, they said i can do what ever i want to it as long as it doesnt go over the Deciable reading when going for a warrent (here in NZ)
i unbolted the rear muffler and started the car (cold start) and it was reading 85db but went down to about 75-80 after about 2-3 mins. thats with the exhaust noise bouncing under the car but
should be ok once the straight pipe is out the back properly, will make a pipe myself and laser cut another bolt flange so if its too loud i can bolt the original muffler back on with out rewelding it back on.
not too sure what the db reading here in NZ.

i think its around 90db will need to check that out