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post #1 of 26 (permalink) Old 12-07-2009, 11:43 AM Thread Starter
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Deleting Cats Do i need a tune?

Ok i already have that 3rd cat (as i call it [Y-pipe]) deleted but my question is will deleting my remaining cats cause the car to run way too lean and barely run? Will i have to get a tune just to run the car? Or will it just simply throw a code? Its already throwing a code because i have a 75mm TB on there so im not really worried about that.
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post #2 of 26 (permalink) Old 12-07-2009, 12:45 PM
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Why? Get some high flow cats, and don't even worry about them. I replaced mine and my car runs a lot better (170,000 on original cats, they weren't the best anymore) and I don't have to deal with O2 sims or codes.

Needs more stall.
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post #3 of 26 (permalink) Old 12-07-2009, 01:20 PM
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Quote:
Originally Posted by damascusmotorsports View Post
Ok i already have that 3rd cat (as i call it [Y-pipe]) deleted but my question is will deleting my remaining cats cause the car to run way too lean and barely run? Will i have to get a tune just to run the car? Or will it just simply throw a code? Its already throwing a code because i have a 75mm TB on there so im not really worried about that.
A 75mm TB should not throw a code. I would repair the code before I did anything else.

And as Nitemare said, there is no reason to remove the cats unless you're having problems with them.

But just my .02.

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post #4 of 26 (permalink) Old 12-07-2009, 03:27 PM Thread Starter
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Well it says that bank 2 is running lean plus EGR is faulted which is on my list just waiting on weather to clear up. Well my thing with deleting the cats is that i want it to sound "throatier" which maybe high flo cats will do, i wasnt really sure. I already have a true dual exhaust with cherry bomb mufflers. However my question is yet to be answered, do i need a tune to drive it without cats? My friend seems to think that it wont run without them, that the car will bog out and die. However he also thinks u can just throw gears in a rear diff and call it a day without adjusting them.
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post #5 of 26 (permalink) Old 12-07-2009, 03:40 PM
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You don't need a tune you can just build or buy a set of MIL eliminators. The rear 02 sensors need to be faked out with the eliminators or a tune. Will it sound throatier and louder yes it will.

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post #6 of 26 (permalink) Old 12-07-2009, 03:57 PM
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Quote:
Originally Posted by damascusmotorsports View Post
Well my thing with deleting the cats is that i want it to sound "throatier" which maybe high flo cats will do, i wasnt really sure. I already have a true dual exhaust with cherry bomb mufflers.
I have high flow cats, true dual 2 1/4", and no mufflers. That will get you "throaty."
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However my question is yet to be answered, do i need a tune to drive it without cats? My friend seems to think that it wont run without them, that the car will bog out and die. However he also thinks u can just throw gears in a rear diff and call it a day without adjusting them.
On the gears, I used the original pinion shim and original side shims, and checked everything and it was perfect. Backlash was a tad bit on the low side but still within specs.

Needs more stall.

Last edited by Nitemare; 12-07-2009 at 11:28 PM. Reason: I'm an idiot sometimes.
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post #7 of 26 (permalink) Old 12-07-2009, 06:10 PM
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Dont ya love it when you get good and lucky on the rear end shims?? ive only ever once had that happen what is even better is the guys that think you can just hammer fit the .006" preload for the bearings on the carrier into an alunimum case. all that does is fill your rear end with shavings. you need to use a case spreader to do it right. and thats what i have too for the exhaust. high flow cats, x pipe, true duals and no mufflers and 3" stainless angle cut tips. sounds awsome!!! IMO the way to go for loud throaty exhaust

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post #8 of 26 (permalink) Old 12-07-2009, 07:55 PM
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You will either need a tune or O2 sims, otherwise no it will not run right.
Wrong. The rear oxygen sensors do not affect the way the car runs at all. The CEL will constantly be on, but that's it.

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post #9 of 26 (permalink) Old 12-07-2009, 07:57 PM
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Originally Posted by damascusmotorsports View Post
Well it says that bank 2 is running lean plus EGR is faulted which is on my list just waiting on weather to clear up. Well my thing with deleting the cats is that i want it to sound "throatier" which maybe high flo cats will do, i wasnt really sure. I already have a true dual exhaust with cherry bomb mufflers. However my question is yet to be answered, do i need a tune to drive it without cats? My friend seems to think that it wont run without them, that the car will bog out and die. However he also thinks u can just throw gears in a rear diff and call it a day without adjusting them.
Where in the reasoning about this problem did you deduce that a lean code is the cat's fault? Catalytic converters do not affect the A/F ratio of the car, nor do they affect the way the car runs unless they are broken apart and clogging the exhaust.

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post #10 of 26 (permalink) Old 12-07-2009, 11:27 PM
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Wrong. The rear oxygen sensors do not affect the way the car runs at all. The CEL will constantly be on, but that's it.
Duh, I'm an idiot. I was thinking the fronts when I said that. I should have thought of that, my back O2's have set a code ever since I got the car and I've just ignored them because of that.

Needs more stall.
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post #11 of 26 (permalink) Old 12-08-2009, 11:24 AM Thread Starter
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Where in the reasoning about this problem did you deduce that a lean code is the cat's fault? Catalytic converters do not affect the A/F ratio of the car, nor do they affect the way the car runs unless they are broken apart and clogging the exhaust.
Never said it was. It has to do with my EGR being faulted i believe and I'm sure the 75mm TB does not help either. I want to delete the cats for the sound increase.
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post #12 of 26 (permalink) Old 12-08-2009, 11:30 AM Thread Starter
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Wrong. The rear oxygen sensors do not affect the way the car runs at all. The CEL will constantly be on, but that's it.
So basically wat your saying is that i can just delete the cats and dont need to buy the MIL eliminators at all or did i get that wrong? Cuz i was looking at like $60 for the pair.
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post #13 of 26 (permalink) Old 12-08-2009, 11:39 AM
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I just noticed: You're in southern California and you're asking about cutting off the cats?!??!

Is this for a non-street legal car?

Have you tried running straight pipes right off the cats without mufflers or anything?

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post #14 of 26 (permalink) Old 12-09-2009, 11:17 AM Thread Starter
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Originally Posted by 94 Daily Driven 4.6L View Post
I just noticed: You're in southern California and you're asking about cutting off the cats?!??!

Is this for a non-street legal car?

Have you tried running straight pipes right off the cats without mufflers or anything?
No this is a daily driver. The shop i work at does smogging so im not really worried about passing. haha. I had a friend with just straight pipes with the stock 2 cats no mufflers and it was really raspy. I want it to have a lil bit of a lope to it at idle. And sound healthy at WOT.
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post #15 of 26 (permalink) Old 12-09-2009, 12:41 PM
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Originally Posted by damascusmotorsports View Post
I want it to have a lil bit of a lope to it at idle.
You can get the lope from doing one of two things or both of them. Neither has anything directly to do with whether cats are on or off the car.

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post #16 of 26 (permalink) Old 12-09-2009, 08:15 PM
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Like many other guys here I have a 2 1/4" exhaust with high flow Magnaflow cats. I also run the center Magnaflow dual in dual out muffler with no mufflers in the back. This is a really good sounding setup. It sounds better than my 2004 Mustang GT. I wouldn't tempt fate in California. Just get a set of High Flow cats.

If you really want more sound, install a set of PI cams, or better yet PI heads and cams.

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post #17 of 26 (permalink) Old 12-09-2009, 10:36 PM
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If his car is a 95 he needs 96+ heads or PI heads to use PI cams.

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post #18 of 26 (permalink) Old 12-13-2009, 11:21 PM
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Originally Posted by 94 Daily Driven 4.6L View Post
I just noticed: You're in southern California and you're asking about cutting off the cats?!??!

Is this for a non-street legal car?

Have you tried running straight pipes right off the cats without mufflers or anything?
hhaha so true, It took me so long to find a place in california to cut off my 3rd cat. I actually went through my friend and his friends shop xD.

Anyways I myself wouldn't cut off my last 2 cats. MY CAR IS SO LOUD AS IT IS xD

My set-up consist of a mid mounted muffler with all new Y-piple underneath that leads to chrome tips. At times it sounds very good but in the morning when its cold it sounds like ass, i have to admit.
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post #19 of 26 (permalink) Old 12-14-2009, 07:54 AM
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PI Cams in a 1995?

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If his car is a 95 he needs 96+ heads or PI heads to use PI cams.
Sorry this is off the topic of the original post, but is this true? Is there that much of a difference between the F2AE/F4AE (pre-1996) and F5AE castings that you can't put the PI cams in? They're all NPI, and I thought sure I've read where some of you guys have done the PI Intake/Cam swap on the 1995. This is important to me because this is a mod I'm planning on doing to my '95!
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post #20 of 26 (permalink) Old 12-14-2009, 08:14 AM
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The extra lift of the PI cams will cause interference problems on the early heads. I can't remember off the top of my head if you end up with coil bind or if you hit the valve stem seals.

But which ever the case, the PI cams won't work on the early heads.

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post #21 of 26 (permalink) Old 12-14-2009, 08:46 AM
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Found a useful post

Quote:
Originally Posted by 94 Daily Driven 4.6L View Post
The extra lift of the PI cams will cause interference problems on the early heads. I can't remember off the top of my head if you end up with coil bind or if you hit the valve stem seals.

But which ever the case, the PI cams won't work on the early heads.
Bummer, found this thread too: http://forums.tccoa.com/showthread.php?t=34124

Oh well, thanks for the info and Happy Holidays!!!
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post #22 of 26 (permalink) Old 12-14-2009, 10:09 PM Thread Starter
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Like many other guys here I have a 2 1/4" exhaust with high flow Magnaflow cats. I also run the center Magnaflow dual in dual out muffler with no mufflers in the back. This is a really good sounding setup. It sounds better than my 2004 Mustang GT. I wouldn't tempt fate in California. Just get a set of High Flow cats.

If you really want more sound, install a set of PI cams, or better yet PI heads and cams.
Im not really looking into doing anything to this motor as i already have a DOHC MkVIII motor setting aside. I heard using 98 or prior intake cams and 03/04 exhaust cams is almost equivialent to that of after market cams. I've yet to do my research on that yet. I'd really like to get it to sound as close as a Non-Termmy Cobra as possible.
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post #23 of 26 (permalink) Old 12-16-2009, 06:38 PM
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removing third cat

I see you removed the third (center)cat at some point. What happened? any warning lights.? any change in operation?AZ is an emission state too.

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post #24 of 26 (permalink) Old 12-16-2009, 06:44 PM
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The third cat isn't monitored by the computer, so removing it has no effect on anything.

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post #25 of 26 (permalink) Old 12-17-2009, 12:03 AM Thread Starter
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I see you removed the third (center)cat at some point. What happened? any warning lights.? any change in operation?AZ is an emission state too.
As master486 stated it has no connection to the computer so naturally no signals got thrown. Personally i think i lost some performace because of lose of back pressure. Maybe im just imagining things but i felt as if my off the line performance dropped, basically like i lost some torque. I can't prove it thought, just a feeling. As far as passing smog havent had to smog it since i deleted it however my buddy did not have any issue, but he does have new hi-flow cats.
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post #26 of 26 (permalink) Old 12-17-2009, 01:33 AM
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If you gutted it and put the empty case back on, then you probably have lost a small amount of power. If you replaced it with a properly sized y-pipe, then there won't be any adverse effects.

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