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 Post subject: cats and mileage
PostPosted: Tue May 19, 2009 11:03 am 
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Joined: Sun Mar 15, 2009 7:46 pm
Posts: 27
Location: Wisconsin
Anybody know what the effect of a Catalytic Converter has on mileage on these cars?

My '90 verts center pipe busted, so I bought a whole catback exhaust (Bosal #287-631) http://info.rockauto.com/Bosal/Detail2.html?03705050.gif THEN after I received the new exhaust I checked it out, found out my current setup has no cat and that the downpipe had just become disconnected. I used a little JB Weld on it and now it's good as new.

So now I am wondering if I should buy the new catalytic and put it on with the new catback, or continue to go without. If it's going to make my mileage any worse I won't do it.

Anybody have any experience with this?

Thanks


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 Post subject: Re: cats and mileage
PostPosted: Tue May 19, 2009 8:33 pm 
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Joined: Tue Apr 08, 2008 9:08 pm
Posts: 1254
Location: Ashtabula, Ohio
I replaced my plugged cat with a straight pipe and did notice an increase in mileage, but of course, it was plugged. A new cat should not really effect fuel mileage in my opinion since these cars also run a resonator and muffler along with the cat. Maybe someone else could give you a definitive answer?

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 Post subject: Re: cats and mileage
PostPosted: Wed May 20, 2009 11:19 am 
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Joined: Wed Jul 12, 2006 11:29 am
Posts: 83
Location: Kentucky, USA
I've run several different exhausts including one with and without a cat and I was not able to measure a difference. I think that cruising down the road making 20 hp does not require much from a exhaust system and so long as it not plugged the back pressure should stay low under these conditions. City driving when the pedal is floored quite often might show different results.

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 Post subject: cats and mileage
PostPosted: Thu Jan 07, 2010 4:27 am 
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Joined: Tue Jan 05, 2010 6:58 am
Posts: 3
Location: NY
I was torn on the idea of doing this and decided not to because I did not want to have a cel light on and actually trcick the computer into actually getting worse mileage. There is just no possible way that you don't have one on in your car due to the down stream o2 readings being off. Unless of course you have an o2 simulator but since you made no mention about it.

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 Post subject: Re: cats and mileage
PostPosted: Thu Jan 07, 2010 11:29 am 
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Joined: Tue Aug 04, 2009 9:27 pm
Posts: 824
Location: walsh,alberta,canada
i removed both cats on all 3 of my fireflys,did not make the computer "code"or check engine light come on,engines run cooler with less backpressure,more power,better mileage,only downfall,alittle noisey-r,but just turn radio up :-P will not pass emisions,if you are worried about that.get a muffler shop(or build it yourself)a straight pipe to replace converter,change it out when you go for a sniff test,when you pass test,go home,remove cat,replace with straight pipe.P.S. keeping exhaustfree flowing,cooler,will lessen the chances of #2 cylinder exhaust valve from getting "burnt", typical problem with 3cyl~plugged cat/exhaust. 2 1/4 pipes help to,mandrel bent,free flowing muffler,resonator if you dont want it to raspy :D

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89 1.0 turbo firefly
2"exhaust,no cats/resonator
3 tech 6*gear
3 tech turbo grind cam
3 tech cylinder head/w/port,polish,blend,oversized s/s valves
gti brake swap
89 white gti twincam....need I say more?
92 metro aka ''blue lump of coal''
92 white metro lsi vert
91 blue chevy sprint (gas sipper)


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 Post subject: Re: cats and mileage
PostPosted: Fri Jan 08, 2010 9:25 am 
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Joined: Fri Aug 22, 2008 3:58 pm
Posts: 157
Location: Kokomo, IN
My cats been off for several months on my 3 banger 96 Geo. The old cat had just rusted off and was working properly before that. I have had no difference in mpg or performance. In order for a CEL not to come on about every 300 miles I had a resistor spliced into the downstream O2 sensor wire.

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05 SRT4 / 12.79 @ 111 mph / 40.1 mpg!
01 Voyager V6 / no mods yet / 24 mpg
84 Horizon / 1760 lbs / was 17.9, now 23.0 mpg
96 Geo Metro / 1590 lbs / was 46.2, now 60 mpg!
95 Neon / unk mpg so far


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