Does Fuel Injected Need Cats?
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Junior User
Joined: May 2004
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Does Fuel Injected Need Cats?
I have heard that fuel injected vehicles need to have a catalytic convertor or you will burn up your valves because there isnt enough back pressure without one. I have no idea if this is true, but I was not planning on using cats when I have my exhaust made. If anybody knows if it is bad for my engine to not use them please let me know.
Senior User
Joined: Jun 2004
Posts: 353
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From: Mid-Missouri
No, they don't need cats. Cats only reduce emissions. A side effect is the back pressure they create. Some back pressure is actually good.
When you do your new exhaust, don't make the pipe too big. About 2 1/8 per side is sufficient. Too big and you start to reduce your low end torque.
I would shoot for 2" for each side. You can still go bigger at the tips / resonators to change the exhaust tone.
When you do your new exhaust, don't make the pipe too big. About 2 1/8 per side is sufficient. Too big and you start to reduce your low end torque.
I would shoot for 2" for each side. You can still go bigger at the tips / resonators to change the exhaust tone.
Senior User
Joined: Mar 2004
Posts: 284
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From: Slippery Rock University
in some states ie PA they are required for VISUAL inspection. they may be there, but who's to say they work... then again this all goes for the average Joe that dont have a buddy or 2 with their inspection license...
Senior User
Joined: Jun 2005
Posts: 173
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From: maryland
no you do not have to have cats on your vehicle. Some stated require them for inspection but all they do is flash mirrors underneath. so if you can find a pair of junk cats, then just drive a pipe thru them. if you plan on running straight pipe, i used to have a 95 f150 and had 2 1/2 inch straight pipe. it ran fine but when i seen a cop i just let off the gas
Senior User
Joined: Mar 2004
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From: Slippery Rock University
the only reason im not running straights is cause i cant hold a convo in my truck w/o screaming. i had it like that for 6 months. nor did i have a cat... that includes a spacetaker upper
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Fleet Mechanic
Joined: May 2005
Posts: 1,575
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From: Puyallup, WA
A well designed cat just like a well designed muffler / exhaust system has very little back pressure, certainly nothing that cannot be worked around with a bit of exhaust system design.
Now as far as OFF ROAD ONLY, I would never run a cat, not because of "restriction" but more because of the extra heat of the fuel reaction. No need to start a fire and burn your truck up.
Leave the cats on for the street, they do not hurt performace nearly as much as many think and we can all breath a bit easier.. (look at the lightning truck, what 360 hp with cats! Check out how that exhaust system is designed, it works very well)
Oh, and while some states don't have emmision inspections, you technically have to have them on most 8500 and less GVW vehicals built since 1975, it is a Federal thing.. darn federalies anyways!
my two cents !!
Now as far as OFF ROAD ONLY, I would never run a cat, not because of "restriction" but more because of the extra heat of the fuel reaction. No need to start a fire and burn your truck up.
Leave the cats on for the street, they do not hurt performace nearly as much as many think and we can all breath a bit easier.. (look at the lightning truck, what 360 hp with cats! Check out how that exhaust system is designed, it works very well)
Oh, and while some states don't have emmision inspections, you technically have to have them on most 8500 and less GVW vehicals built since 1975, it is a Federal thing.. darn federalies anyways!
my two cents !!
Last edited by dmanlyr; Jun 10, 2005 at 11:28 PM.
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Elder User
Joined: May 2004
Posts: 506
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From: Edwards Air Force Base
For what it's worth (FWIW). Magnaflow makes some high flow cats that dont' restrict if you decide to stay legal. I put on a newer model they just released a year ago or so. One cat took the place of both my stock ones. I love it. Passed California emissions no problem and I have no back pressure. I got the dual 2 1/2 in to 3" out and built my own custom exhaust.
FWIW - I made my truck breath too well. I lost a bit of low end but get my best gas mialge at high speed due to my headers, high flow cat, muffler and big pipes. I should have probably used 2" out of the headers instead of 2 1/2.
Good Luck,
Lee
FWIW - I made my truck breath too well. I lost a bit of low end but get my best gas mialge at high speed due to my headers, high flow cat, muffler and big pipes. I should have probably used 2" out of the headers instead of 2 1/2.
Good Luck,
Lee
Posting Guru
Joined: Jun 2005
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From: charlotte, nc
speaking of exhaust, how do yall think dual glass-packs would sound on a 350? i found a kit that includes everything that i would need from the caty back, it has one of those "fake" dual exhaust systems with glasspacks at the tips. i ound the kit for 185, with all new pipes, which is way about the same price as one good flowmaster.
Yea, my caty has been "modified" with a piece of 1 inch cast iron drain pipe.
Yea, my caty has been "modified" with a piece of 1 inch cast iron drain pipe.
