Cat Delete??

[99GMarqLS]

Hi Thread, I was planning on removing the Cats off my 99 Grand Marquis and any help will be greatly appreciated. I already have a custom dual exhaust setup with Flowmasters. I'm somewhat a beginner to modding so please bare with me lol... I know by removing all four cats, an ECM tune will have to be done for the O2 sensors. But, what about just removing the secondary set? How much HP gain would I be looking at in either the secondary or full 4 cat delete? Will this make my exhaust sound more aggressive? Also, how much does it typically cost in both scenarios? Thanks!!

[BGoins12]

I'll be the first to say it's illegal... and if you get busted, the fines are hefty. Kid I know got busted with no converter on his Integra..... $1500 fine. No joke!

[99GMarqLS]

Well that pretty much kills that idea lol. What about high flow cats. Do the make them for MGM's and are they worth it as far as performance gains? oh yeah, and are they legal lol?

[91grandmarquis]

http://compare.ebay.com/like/3102369...=263602_263632

should be noted it wont pass emissions with these.

[1990LTD]

I don't know where you're located but check local laws

[mcninetyone]

I agree, check the laws. Around here unless you need them for smog check you can take anything you want off your car.

[1990LTD]

In my area, 1991 and up need original emissions equipment in working order.

[thunderbirdlver]

I removed my secondaries. Killed my fuel mileage but it's worth it to me for the noise. I pass inspection here in PA because there are still 2 cats there and all the smog crap.

[1987cp]

Is the vehicle still stock otherwise? If so, you have LOTS bigger performance corks than the catalytic converters.

If your fuel economy went down the toilet, that's a sure sign something is wrong. There's no reason economy and performance can't coexist. Here's a thread about making 360rwhp with 27-28mpg: http://sbftech.com/index.php/topic,5081.0.html (hafta join to read that, but it's worth it)

Extra noise? Please. If you're that stuck on extra noise, remove the mufflers, not the cats. Also, keep in mind that once you make your engine a little more serious and install large exhaust tubes, you'll likely be grateful for anything that'll make it quieter.

[99GMarqLS]

I don't know where you're located but check local laws

I agree, check the laws. Around here unless you need them for smog check you can take anything you want off your car.

As far as I know, there are no smog checks in my area. No one I know has ever had to pass an emissions test.

[99GMarqLS]

Is the vehicle still stock otherwise? If so, you have LOTS bigger performance corks than the catalytic converters.

If your fuel economy went down the toilet, that's a sure sign something is wrong. There's no reason economy and performance can't coexist. Here's a thread about making 360rwhp with 27-28mpg: http://sbftech.com/index.php/topic,5081.0.html (hafta join to read that, but it's worth it)

Extra noise? Please. If you're that stuck on extra noise, remove the mufflers, not the cats. Also, keep in mind that once you make your engine a little more serious and install large exhaust tubes, you'll likely be grateful for anything that'll make it quieter.

Yeah its still stock besides duals and mufflers. I already know about the other performance corks and in time I'll get to them.

I'm not stuck on extra noise, just wondering what kinda difference it would make.

[BGoins12]

Here in Ohio, they only check for the presence of converters. They could care less about the smog stuff, just as long as the emissions are within passing limits. My Dad was even told that when he had his '85 Chevy Van Echecked.

[99GMarqLS]

I'm in Ohio too, Columbus. They've never checked for emissions or Cats here so laws maybe different city to city. Or maybe they only check if there's excessive smoke in the exhaust.

[BGoins12]

Ah, Columbus.... that's why. Echeck is only in NE Ohio.

[zoomie]

I Also, keep in mind that once you make your engine a little more serious and install large exhaust tubes, you'll likely be grateful for anything that'll make it quieter.

yeah lol make sure you get full lenght exhuast otherwise youll end up with hella drone and noise i should know i have bbk headers with 2.5 pipes and they end at just past my rear dooor oh i have no cats either