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#2295623 - 05/12/11 11:10 PM ??? about Cat Converter's and exhaust pipe sizes
lowmile97gm Offline
Member

Registered: 10/30/09
Posts: 108
Loc: Pensacola, Florida...US of Ame...
I'm looking for more info as to what I can do to improve my exhaust flow and hopefully my MPG at the same time. I'm not looking for major HP increases, just mostly allowing it to flow a little better so as to improve the MPG. I know we are restricted from talking about illegal mods on our forum and don't want anybody getting in trouble on here, but down here in Florida we don't even have inspections or anything right now, and anything I might do I will make it so that it will go back together the right way if needed. If anyone with proper knowledge is willing to discuss this with me and answer a few questions then please contact me at malibu_lvr@yahoo.com .Thanks in advance, Andrew
_________________________
'97 Gran Marquis

By malibulvr at 2011-05-06

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#2295651 - 05/12/11 11:51 PM Re: ??? about Cat Converter's and exhaust pipe sizes [Re: lowmile97gm]
BillyBishop Offline
Expert mechanic
Poobah

Registered: 02/06/11
Posts: 5164
Loc: KY
Just for the record, federal emissions laws do require vehicles to have catalytic converters, whether or not your state/county does have emissions checks.
_________________________
Originally Posted By: etcv97
forget this BS panther site your all just a bunch of [censored] holes..


1985 2 door vic-------2003 P71: Lots of mods-----1994 Buick Toastmaster
Past: 2002 P71, 1996 LTC, 2003 P71

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#2295656 - 05/12/11 11:58 PM Re: ??? about Cat Converter's and exhaust pipe sizes [Re: lowmile97gm]
Rizzo Offline
J-MOD Master
Metroplectic

Registered: 03/06/04
Posts: 28119
Loc: Romulus,MI
Does my exhaust flow freeier ?

Yes.

Is my Air Fuel mxture off due to the whacked out O2 input?

Yes again.

I would bet you lose all you would gain.

And yeah, I am missing some parts on my car wink
_________________________


The Jmod video is done! LINK!

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#2295686 - 05/13/11 02:26 AM Re: ??? about Cat Converter's and exhaust pipe sizes [Re: lowmile97gm]
Ogre Offline
Member

Registered: 07/24/09
Posts: 236
Loc: Bellefontaine, Oh
Well, I am assuming that you are turning your CV into a dedicated racecar and will NOT be driving this car on any public road.

if this is indeed your intention, you will do nothing but gain HP by running your "racing" exhaust and also you will see minimal gains in MPG on the return road back to the pits.

If this is not your intention DO NOT modify your emissions equipment in any way! Or the EPA could quite possibly hunt you down and kill you and all your family as you sleep.
_________________________
2004 CV LX Sport - 15.7@88
2000 expedition 4x4 for sale.
My non-pi car. 13.3@101
http://www.youtube.com/watch?v=DQSRHa2nVfE

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#2295687 - 05/13/11 02:28 AM Re: ??? about Cat Converter's and exhaust pipe sizes [Re: Ogre]
BillyBishop Offline
Expert mechanic
Poobah

Registered: 02/06/11
Posts: 5164
Loc: KY
Originally Posted By: Ogre
Well, I am assuming that you are turning your CV into a dedicated racecar and will NOT be driving this car on any public road.

if this is indeed your intention, you will do nothing but gain HP by running your "racing" exhaust and also you will see minimal gains in MPG on the return road back to the pits.

If this is not your intention DO NOT modify your emissions equipment in any way! Or the EPA could quite possibly hunt you down and kill you and all your family as you sleep.

^Everything he said is accurate wink
_________________________
Originally Posted By: etcv97
forget this BS panther site your all just a bunch of [censored] holes..


1985 2 door vic-------2003 P71: Lots of mods-----1994 Buick Toastmaster
Past: 2002 P71, 1996 LTC, 2003 P71

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#2295761 - 05/13/11 07:48 AM Re: ??? about Cat Converter's and exhaust pipe sizes [Re: lowmile97gm]
98VicP71 Offline
14.6@93MPH
Grand Poobah

Registered: 03/28/06
Posts: 12731
Loc: ATL
If you want to improve your exhuast flow for better economy but don't plan on modding the car for performance..

either get the direct fit magnaflow cats with down pipes for both side or get single high flow cats installed with new down pipes.

get 2.25" mandrel bent exhaust and you should be all set.

You could even get some quiet mufflers to keep it sounding as stock as possible.

However plan on forking out some coin to have it done.
_________________________
1993 Lincoln Town Car 150k+ - RIP 5/10/2011
1998 Ford Crown Victoria P71 - RIP 12/25/2006
2001 Ford Crown Victoria P71(Count blackula) 180k+ - Ummmmmm evil

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#2295843 - 05/13/11 10:31 AM Re: ??? about Cat Converter's and exhaust pipe sizes [Re: lowmile97gm]
lowmile97gm Offline
Member

Registered: 10/30/09
Posts: 108
Loc: Pensacola, Florida...US of Ame...
Well I am not wanting a race car and as stated not really looking for performance gains. I just have heard of removing the rear set of cat converters and leaving the front set on there. But I don't want to have any warning lights coming on or have to do a tune. I have a complete factory HPP dual exhaust system that I can install, but was thinking of having an H pipe made from 2.25" or 2.5" and then ordering some larger tailpipes also. I am just in the quest of improving my MPG while also improving my performance a little too.
_________________________
'97 Gran Marquis

By malibulvr at 2011-05-06

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#2295880 - 05/13/11 11:56 AM Re: ??? about Cat Converter's and exhaust pipe sizes [Re: lowmile97gm]
Chevyguy Offline
Poobah

Registered: 01/04/04
Posts: 8050
Loc: Winchester Mass
Rear cat delete is a lazy mod with only two benefits

You get a louder exhaust note

Some older cars have the H or Y pipe flange fused to the cats, so the lazy installer just cuts the rear cats off.

Only the 95 models have the the second O2 sensor after the second cat (and only one of them at that) So this does not cause any Check engine light issues but does alter the flow velocity and usually kills some of the torque.

Stainless works long tube headers and cats will wake up the car and even fit the stock exhaust.

Aftermarket stock type replacement cats will make a very minimal gain, and improve the sound somewhat. Not really worth doing unless you already need cats.
_________________________
2004 MarauderM79 104K miles Jmod!! Lidio 93 tune for the track BOC 91 octane street tune 14.85 @95.63
2004 Crown Vic LX 145K Silver Birch Light flint leather FMX1 04 P-71 PCM swap 70 mm TB Custom shorting wire harness. 28/ 21mm MM swaybars Monroe severe duty shocks. Marauder subwoofer and painted cap heated mirrors. GT-500 Wheels NEED DUAL EXHAUST


Project car 74 Chevy Laguna type S-3, # match 400 SBC

Previous rides
93 P-71 2001 P-73, 94 TC Exec, 96 TC Signature

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#2295926 - 05/13/11 02:09 PM Re: ??? about Cat Converter's and exhaust pipe sizes [Re: Chevyguy]
ImpulseRocket89 Offline
Over the Hill

Registered: 08/23/09
Posts: 1799
Loc: Omaha, NE USA
Unless you want your car to be obnoxious in both sound and smell I would agree with the suggestion for high flow cats. The couple of WHP lost from having them on your exhaust are generally made up for by the typical gain in torque and broader power band. Not to mention being able to drive your car and not be annoyed by the noise (personal experience lol). Maybe I have just gotten older, but I like quieter now. If you have the money, there are high CPI(Cells Per Inch^2 - very important aspect of a cat) cats that flow almost as well as a straight through muffler and work almost better than most factory cats. Problem is, at $400 a piece, not the most budget friendly.


Edited by ImpulseRocket89 (05/13/11 02:10 PM)
_________________________
2005 Crown Vic LX: Eaton 1.5" P71 drop springs & KYB Gas-A-Just P71 shocks. Heinous Control arms. Addco sway bars. 18x8.5 Fanblades. Mini D2S Projector retrofit - 50W w/ 5000k. Mach 1 Chin Spoiler, Kenwood head unit, upgraded speakers, Infinity Bass-link. Cryostop Rotors, and Porterfield R4S Pads. Trickflow Upper plenum, AFe Stage 2 intake, Steeda UD Pulleys, Catco high flow cats, Factory Duals w/magnaflow 11224's, MMC Driveshaft w/ Fabtech spacer, BOC Tune.
1988 Isuzu Impulse Turbo: Torn to bits, being built and collecting dust. (2.6L engine, 7670 EFR, MUA-5 trans etc. etc.)

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#2295957 - 05/13/11 03:24 PM Re: ??? about Cat Converter's and exhaust pipe sizes [Re: lowmile97gm]
Danno1985 Offline
Over the Hill

Registered: 03/14/10
Posts: 2215
Loc: Milwaukee, WI via NY
I would add that by changing your exhaust diameter, I don't think you are going to gain anything. According to this http://www.therangerstation.com/Magazine/Summer2010/Ford_4-6.htm, the '97 with dual exhaust made 270 lb/ft or torque when new. Let's face it we aren't talking about big-block 60s muscle car numbers here. By upping the pipe diameter to 2.5" you are going to decrease the delta pressure of the exhaust and probably lose some torque, which is going to force your engine to work even harder and rev higher to lug the car up hills and around town. Especially with 2.73 gears. I would not go that route. Bolt up the HPP duals you already have, keep driving conservatively and see how that works for you before you spend a huge chunk of money on hi-flow cats and custom exhaust.
_________________________

2000 Crown Victoria LX. 160K. Duals, 3.73 trac-lok, currently rocking rally wheels with 215/65r16 Dunlop snows. Mobil 1 0W40 in the crankcase, Royal Purple 75W90 in the back. Still kicking'.

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#2295963 - 05/13/11 03:43 PM Re: ??? about Cat Converter's and exhaust pipe sizes [Re: lowmile97gm]
Bondfreak13 Offline
Over the Hill

Registered: 12/15/05
Posts: 3472
Loc: Palm Bay, FL.
The motor dumps raw fuel into the cat to cool them off. So yes, removing them will give a small bump in MPG.
_________________________
2000 Crown Vic.
K&N and Duals w/ H-pipe, Addco group buy 1 1/2 front Sway bar and 1 1/4 rear sway bar w/ polly bushing. Bilstein stocks. Metco Upper and lower contorl amrs with Metco Watts link.
5.4 SOHC swap coming Soon. (There is no Replacement for Displacement, no substitute for cubic inches)

Intelligence is knowing that a tomato is a fruit, Wisdom is knowing not use a tomato in a fruit salad.


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#2295972 - 05/13/11 03:57 PM Re: ??? about Cat Converter's and exhaust pipe sizes [Re: lowmile97gm]
KayTar Offline
Poobah

Registered: 05/13/09
Posts: 7153
Loc: Alberta, Canada
I hate how bad things can get when cats fail. I owned a 1993 Probe GT 2.5 V6. I remember noticing the car really struggling/straining to rev higher than 4000rpm. Along with that, one night after having driving the Probe hard I was walking beside the car I could feel excessive heat from under it. Long story short, went to an exhaust shop chopped out the cat and the result? Freer reving, better gas mileage didn't feel anymore intense heat from under the car. When the mechanic cut the cat out first thing he said was "Well that's your problem" It was damn near plugged solid even caused my O2's to over heat and cook.



Edited by KayTar (05/13/11 03:59 PM)
_________________________
2003 P71 - MZT, 3.73s, Victor Jr intake, OBX kit, 78MM TB SOLD
2005 P71 - K&N Intake, various tint rest stock SOLD
2010 Challenger RT Classic - JBA longtubes, Pypes exhaust SOLD
2008 P71 - Vortech V2-SQ, 3.4" pulley, 2nd cats removed, yeah it goes.

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#2297183 - 05/15/11 07:47 PM Re: ??? about Cat Converter's and exhaust pipe sizes [Re: lowmile97gm]
DreadfullyDespized Offline
Over the Hill

Registered: 07/25/04
Posts: 3778
Loc: Hutchinson, MN 55350
Jumping on the bandwagon. From what I am gathering.. Removing the secondary cats is more so a con then a pro?... One of mine got hit by a bad road bump on the driver side and has a huge rattling sound when I am in park and idling. It is quite an annoyance. Though I was debating on chopping off the secondary cats and putting 2.25inch pipe through instead. But if the removal of the cat causes lack in torque and more engine work that alone makes me less likely to do it. Which then makes it more realistic to stick with just doing a high flow aftermarket cat-back exhaust setup. Would someone be able to correct me if I am wrong? Just trying to understand with better detail.
_________________________
DD Security Inc.
Console modding/electronics repair/Airsoft

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#2297199 - 05/15/11 08:09 PM Re: ??? about Cat Converter's and exhaust pipe sizes [Re: DreadfullyDespized]
cragantler1 Offline
Over the Hill

Registered: 11/19/07
Posts: 1785
Loc: Fla. Cracker in Southern Maine
The bad thing about your noisy cat is the same issue I had. When the pulled the rear cats off, the passenger side was empty and the driver's side, you could see the brick bounicing around.
Worse case scenario is the brick could come apart and clog up your muffler. My passenger side cat most likely failed when I still had the stock muffler.
_________________________
2004 Arizona Beige P-73


Click to reveal..
2004 P-73,113k+
Performance & Handling:
P-71 H-pipe with Flowmaster 50s/Rear Meow delete/ADTR P&P plenum/70mm TB/Marauder swaybars/MZT/BOC tune/J-Mod/ 2006 P-71 rear coils/Gatorback belt/2005 17" Mustang GT Premium rims with Pirellis/ FRPP 3.55's / FRPP Trak-Lok
best time, pre-gear change: 15.4 @ 91.6mph

Appearance:
Honeycomb color matched grille/lower grille mesh mod/S-55 tail/reverse lights mod/bumper tuck/window chrome and wood dash delete/black reflective rear fascia/side marker mod/15% rear, 35% front tint/Marauder gauge cluster/1999 Lincoln Continental console and floor shift/Marauder gauge pod with "real" Autometer gauges/ Ford Focus driving lights with 5000K HID's wired to Marauder light switch for factory operation/repaired LCM/Marauder corner lights


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#2297271 - 05/15/11 09:42 PM Re: ??? about Cat Converter's and exhaust pipe sizes [Re: lowmile97gm]
DreadfullyDespized Offline
Over the Hill

Registered: 07/25/04
Posts: 3778
Loc: Hutchinson, MN 55350
Well there was a heatboil in the road from winter to summer quick changes and it first hit the skidplate then I turned before it hit the tranny and instead dented my driverside cat.
_________________________
DD Security Inc.
Console modding/electronics repair/Airsoft

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