Removed Rear Cats

96ninjaman · May 1, 2006

I got the rear cats removed Friday. The guys opened up the pipe to 2.5 inches as far up as they could to mate up with the catback and further increase flow. I know it's not my imagination, and it may be because I was specifically looking for it, but I can feel the small loss of torque down low and can also tell a decent difference in horsepower. Additionally, it sounds great. I know it's probably not loud enough for some of you, but it was exactly what I was hoping for. Most important, it didn't trip my check engine light. I know there was a question a while back from someone in NC about that. I'm actually registered in NC and during my last inspection the guys told me as long as the check engine isn't on I should be good to go. One of my buddies said it sounds like a totally different car, and a lady friend said for me to log on and tell you that it does increase hp. Granted that was just after going a fair amount sideways on a 1-2 shift

propellerhead · May 1, 2006

I will guess the CEL will come on in about a week.

sgarlic · May 1, 2006

I'm still waiting on a midpipe before and after dyno with no other mods done. I seriously believe I lost power across the entire power band when I put my mac pipe on there.. just took it back off last week for the stocker, and it feels like a completely different car now (more torquier, etc.) Doesn't feel any slower up top to me with stock pipe back on, but like I said, I'd like to see a dyno.

imblown-ru · May 1, 2006

if someone will give me 50 bucks and a factory midpipe, i will do the dyno test, but my car isnt stockk...

scupking · May 1, 2006

sgarlic said:
I'm still waiting on a midpipe before and after dyno with no other mods done. I seriously believe I lost power across the entire power band when I put my mac pipe on there.. just took it back off last week for the stocker, and it feels like a completely different car now (more torquier, etc.) Doesn't feel any slower up top to me with stock pipe back on, but like I said, I'd like to see a dyno.

Do you have an O/R mac? You guys are makeing me think, now I don't know if I want to buy an MRT-H.

HoustonGT · May 2, 2006

If anyone says that didn't gain anything from a midpipe, the'yre smoking crack. Take off your stock midpipe and compare the crimp bends crappily made by Ford which reduce flow to the nice mandel bends in most any aftermarket midpipe. I've owned 2 GT's and on both noticed a pretty good difference after installing the midpipe. Of course it'll fit a bit slower down low due to the loss in back pressure, but it pulls alot harder up top and is noticeable.
My GT ran a 13.8@100.99 with nothing but a midpipe and catback and on the chrome 18" rims pictured below wrapped in BALD ****ty Kumhos (2.1 60' ). I think thats proof enough right there

BLUE03GT · May 2, 2006

propellerhead said:
I will guess the CEL will come on in about a week.

Well, ur guessing wrong.

I've had my rear cats off for a year now and no check engine light. It sounds 10x better and i felt a minor power gain up top

96ninjaman · May 2, 2006

I can't imagine not getting a really decent gain out of a midpipe, but you will in turn loose some torque down low. Torque loss or gain is probably more evident by SOTP. With the combination of 2.5" mandrel bent pipe and high flow or no cats at all, you have to gain hp. Of course the more engine/intake mods you have the more significant the increased exhaust flow will be.

merc123 · May 2, 2006

When I put my o/r H I lost some torque and gained some HP. Regardless, it made it louder and wouldn't trade it for my stocker

propellerhead · May 2, 2006

BLUE03GT said:
Well, ur guessing wrong.

I've had my rear cats off for a year now and no check engine light. It sounds 10x better and i felt a minor power gain up top

No MIL Eliminators or tune? That's wild. The CEL will come on when the rear O2 sensors tell the EEC that the rear cats aren't doing what they should be doing.

SigmaPride · May 2, 2006

I don't think you are losing torque. You are probably increasing it, but it is now higher up in the power band. This subject has been beat to death in some other posts.

BLUE03GT · May 2, 2006

propellerhead said:
No MIL Eliminators or tune? That's wild. The CEL will come on when the rear O2 sensors tell the EEC that the rear cats aren't doing what they should be doing.

The guy who removed them told me that my check engine light would come on or so he thought, but my friend and I both did it (he has 03 Cobra)... and no light ever came on. Im pretty sure the o2 sensors are attached to the cats up front and not the rear cats. If you are looking for a bit more sound and a bit more power and dont want to pay for a mid-pipe i recommend it. I think the sound is awesome. shop did it for me under the table for $50

sgarlic · May 2, 2006

HoustonGT said:
If anyone says that didn't gain anything from a midpipe, the'yre smoking crack. Take off your stock midpipe and compare the crimp bends crappily made by Ford which reduce flow to the nice mandel bends in most any aftermarket midpipe. I've owned 2 GT's and on both noticed a pretty good difference after installing the midpipe. Of course it'll fit a bit slower down low due to the loss in back pressure, but it pulls alot harder up top and is noticeable.
My GT ran a 13.8@100.99 with nothing but a midpipe and catback and on the chrome 18" rims pictured below wrapped in BALD ****ty Kumhos (2.1 60' ). I think thats proof enough right there

Well, I don't smoke crack. However, I did dyno a pathetic 233rwhp with no mods besides an o/r h, flows, and a K&N. I haven't seen a dyno showing either of the other 2 mods to cause a loss of hp. As I'm sure you know, most completely stock cars are dyno'ing above that. Guess I'm the only one.

Black Stang 97 · May 3, 2006

im not running any cats and no CEL is on....its been like that for the past 4 months.....and yes my check engine light turns onfor a few seconds when i turn the key to the acc position...

propellerhead · May 3, 2006

BLUE03GT said:
The guy who removed them told me that my check engine light would come on or so he thought, but my friend and I both did it (he has 03 Cobra)... and no light ever came on. Im pretty sure the o2 sensors are attached to the cats up front and not the rear cats. If you are looking for a bit more sound and a bit more power and dont want to pay for a mid-pipe i recommend it. I think the sound is awesome. shop did it for me under the table for $50

Your front cats must be cleaning the exhaust then.

HoustonGT · May 3, 2006

sgarlic said:
Well, I don't smoke crack. However, I did dyno a pathetic 233rwhp with no mods besides an o/r h, flows, and a K&N. I haven't seen a dyno showing either of the other 2 mods to cause a loss of hp. As I'm sure you know, most completely stock cars are dyno'ing above that. Guess I'm the only one.

NOT saying you smoke crack Just that a midpipe will not lead to a loss in power. What kind of dyno was it?

96ninjaman · May 3, 2006

The CEL still hasn't come on, but it's still less than a week. I had seen questions asked about removing cats in the past and just wanted to share my experience since I've gained a lot of knowledge from this forum. If it does come on later I will post again at that time (hope I don't have to).

I agree with Blue03GT about it being a good low cost mod if you don't want to spring for a mid-pipe. I too, got the work done for $50. I would have to say it was probably the best $50 I've ever spent on a car. The sound by itself is worth more than that.

BLUE03GT · May 3, 2006

If all you have is a catback, and dont want to spend a lot more money for sound purposes primarily, removing the 2 rear cats is awesome. I dont know how to explain the sound increase and slightly different tone, but its the sound ive always been looking for(Louder than just a cat-back, but not extremely loud).
- As far as power increase is concerned, it seems to pull better up top and doesnt feel as restricted. Down low i havent really noticed much of a change, maybe just rolling out of a stop slowly, but if you're drag racing, i think it even helps your hole shot(however, if you rev up you are still gonna spin the tires regardless, i just found it easier to launch)

Removed Rear Cats

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