3" cat back

GhettoPop · 05-20-2003, 03:27 PM

I know a 2 1/2" cat back will bolt on to a stock 90 GT, will a 3" cat back bolt on as well? If not, what will I need to do?

Also, will a 3" cat back on a stock motor make the car lose some power? I know a 2 1/2" will build some power but I'm thinkin on a stock engine 3" might not provide enough backpressure.

Mountain Main · 05-20-2003, 05:34 PM

I've heard that if you have mufflers that is enough back pressure for a stock 302 efi engine. That is why a lot of people put MAC Off Road X Pipe. Of course if your car is OBD 2 you need some kind of Cats or the engine light will come on.

VeNuM · 05-20-2003, 06:08 PM

Yes, you probably will lose power going from 2 1/2" to 3". What you have is perfectly fine. Just another note: If you have an offroad pipe (no cats) your check engine light will not come on. ~Brian

red82gt · 05-20-2003, 11:19 PM

You won't lose any power. The whole backpressure thing is really kind of a myth. All you need is to have something extending beyond the headers to improve scavenging. Not to mention if you have a 2 1/2" H-pipe, there will be backpressure present anyways.

DemonGT · 05-22-2003, 07:36 AM

i was also wondering..will a 2 1/2 cat back bolt up to a 3 inch prochamber?

05-20-2003, 03:27 PM	#1
GhettoPop Gimme a Drink! Join Date: Dec 2002 Location: NYC Posts: 694	3" cat back I know a 2 1/2" cat back will bolt on to a stock 90 GT, will a 3" cat back bolt on as well? If not, what will I need to do? Also, will a 3" cat back on a stock motor make the car lose some power? I know a 2 1/2" will build some power but I'm thinkin on a stock engine 3" might not provide enough backpressure.

05-20-2003, 05:34 PM	#2
Mountain Main Registered Member Join Date: Feb 2003 Location: Minturn, CO 81645 Posts: 109	Mufflers I've heard that if you have mufflers that is enough back pressure for a stock 302 efi engine. That is why a lot of people put MAC Off Road X Pipe. Of course if your car is OBD 2 you need some kind of Cats or the engine light will come on.

05-20-2003, 06:08 PM	#3
VeNuM Registered Member Join Date: Apr 2002 Location: Downers Grove, IL Posts: 464	Yes, you probably will lose power going from 2 1/2" to 3". What you have is perfectly fine. Just another note: If you have an offroad pipe (no cats) your check engine light will not come on. ~Brian __________________ 1989 Black Mustang GT Hatchback, Underdrive Pulles, Electric Fan, Cold Air Intake, Headers, Offroad H-Pipe, Magnaflow catback, Steeda Tri-Ax, Fluidyne Aluminum Radiator, Timing at 14*, 3.73's Coming not so soon: 408w Ricer Hater's Club Member #59

05-20-2003, 11:19 PM	#4
red82gt Sober voice of Reason Join Date: Nov 1998 Location: Kelowna, B.C., Canada Posts: 1,514	You won't lose any power. The whole backpressure thing is really kind of a myth. All you need is to have something extending beyond the headers to improve scavenging. Not to mention if you have a 2 1/2" H-pipe, there will be backpressure present anyways. __________________ 393W: AFR 205's, hydraulic roller, TKO600.

05-22-2003, 07:36 AM	#5
DemonGT Registered Member Join Date: Aug 2000 Location: Wisconsin Posts: 879	i was also wondering..will a 2 1/2 cat back bolt up to a 3 inch prochamber? __________________ '91 GT,410W,10.5 to 1 comp,Victor Jr. heads,Victor 5.8 intake,FTI cam,Crane retro fit lifters,Scorpian 1.6 RR's,Melling HV oil pump,MSD distro.,Canton oil pan,FMS flywheel,Romac balancer,FMS timing chain,Accufab 90mm TB,C&L 76mm maf, 42lbers,HD clutch,K&N air filter,Mac long tubes,Pro dumps,powerchamber,FMS 9mm wires,180 thermostat,Ford Racing gauges,5inch Tach,centerline convo pro's,nitto DR's,Pro3i lower control arms,50/50 shocks,3.55 gears,TFS HD diff. cover Next year: Tremec TKO,Spec stage 3 clutch,alum driveshaft,complete fuel system www.angelfire.com/linux/demondan

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