removing cats...

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tclndcrz

tclndcrz

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Mar 30, 2003
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966
Location
Beaufort SC
Two basic questions

If i remove my cats and replace with bolt in straight pipe will i get better gas milleage?

If i remove my cats and replace with bolt in straight pipe will i gain performance?

I have a 40 series flowmaster with 2.5" pipe but its obvious to me that my cats are holding my motor back. In SC and MT we dont have emissions so it is not a worry plus if i have bolt in straight pipes then i can always put the cats back on.

thanks
-Thomas
 
I replaced my stock cat last summer with a newer high-flow cat. 1/3 the size, supposed to be less restriction. (Replaced it for emissions reasons.) Noticable "improvement" in sound. I have a 40 series flowmaster, now with the high-flow cat I have a much less restricted sound. No mileage difference. No performance difference.
 
import silvia said:
You will gain nada and polute more for no reason.
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Actually, I noticed a nice improvement in highway performance after I straight piped my cats. I didn't gut them, as many like to do (it'll cause turbulence in the system and might even reduce flow), but I had bolt-up replacement pipes made which work great. I'm gonna need new downpipes soon so I'll have straight tubing all the way to the muffler without even bolt-up spots for the cats. Less chance for leaks and with the cats off and a Flowmaster 50 series, it sounds real nice.
 
I saw a seat of the pants increase when I removed mine. If the engine stays well tuned up the cats shouldn't be doing much.

I think the flowmaster is too loud. I like my Dynamax Super Turbo. Matter of preference.
 
I run dual 40 series Flowmasters on my V8 FJ55, and my V8 FJ40. They seemed to resonate the sound through the cab, but they sounded bad-ass on the outside. Now that the stock FJ60 is my DD, and my exhaust is needing replaced, I think Im gonna look at the Dynomax setup. Id like it to be a little quieter, and I think the Flowmaster would sound goofy on a inline 6.

Hodag
 
im not too concerned with the sound because right now i can not hear the exhaust even with the windows down. obviously the cats are doing a lot to silence the exhaust and that makes me think they are also greatly restricting the flow.

if i put my head near the exhaust i can hear the flowmaster sound and it sounds awesome its just real quiet. so no i dont think it will sound goofy with an inline 6
 
The sound with my 40 series muffler on my 60 is pretty cool. It resonates through the cab just a little bit, but the biggest difference is the sound that people hear behind me. All my friends dig it!
 
My truck has a noticeable seat of the pants effect when I wash it ;)
 
Our old cruisers polute enough with them in. It does not make a whole lot of sense to take em out for marginal performance gains. Makes even less sense on a vehicle shaped like a brick. Do the planet a favor and put them back in or get better ones installed.

Karl
 
euclid said:
If the engine stays well tuned up the cats shouldn't be doing much.

QUOTE]


My understanding of the 2F is that it has a relatively poor intake manifold which supplies a richer mixture at cyls 3 & 4 and a leaner mixture at cyls 1 & 6. To keep the mixture rich enough at 1 & 6, 3 & are getting too much fuel. This leads to incomplete combustion and a lot of crud headed out the exhaust. The cat is most definitely needed to clean up the exhaust. A V style engine with shorter intake runners and better flow characteristics should run cleaner even with a carb. IMO.
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60wag said:
euclid said:
If the engine stays well tuned up the cats shouldn't be doing much.

QUOTE]


My understanding of the 2F is that it has a relatively poor intake manifold which supplies a richer mixture at cyls 3 & 4 and a leaner mixture at cyls 1 & 6. To keep the mixture rich enough at 1 & 6, 3 & are getting too much fuel. This leads to incomplete combustion and a lot of crud headed out the exhaust. The cat is most definitely needed to clean up the exhaust. A V style engine with shorter intake runners and better flow characteristics should run cleaner even with a carb. IMO.
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You have a point, but I think euclid was referring to the 3FE, which has much better mixture control thanks to the fuel injection. Granted it could be even better, but it's still far beyond a carb's abilities with the way our intakes are designed.
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my engine is a 3fe and unlike the 2f that has one cat mine has two. the 3fe also has fuel injection which helps keep the pollution levels down. i am not concerned about my truck polluting. the people you should really be concerned about are people who have smoke coming from their exhaust or are dumping oil on the ground by not keeping their truck maintained well enough.

i only asked two questions about better performance and better gas mileage. i do not want to be preached to about polluting

so with that said do you think i will get better gas mileage?
 
tclndcrz said:
my engine is a 3fe and unlike the 2f that has one cat mine has two. the 3fe also has fuel injection which helps keep the pollution levels down. i am not concerned about my truck polluting. the people you should really be concerned about are people who have smoke coming from their exhaust or are dumping oil on the ground by not keeping their truck maintained well enough.

i only asked two questions about better performance and better gas mileage. i do not want to be preached to about polluting

so with that said do you think i will get better gas mileage?
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Barely. I gained maybe .5 MPG after doing mine. Where you'll notice a difference is with your performance on the highway.
 
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