Not enough back pressure?

Lethal5Oh · 03-11-2007, 07:01 PM

Well i got my stang out of storage the other day and put the cats back on for my emissions test. It feels to me like that car has better power with the converters on then off. Am i nuts? the car has 100k miles on it. Any one have a idea on this? Thanks

goodyear1984 · 03-11-2007, 08:33 PM

whats up man...what kind of exhaust do u have

Coupe50h · 03-12-2007, 11:47 AM

Hmm, good post, cuz ever since i cut my tailpipes off, i havent been able to run as fast in the 1/4, but pretty close.
I wonder if it hurts the torque that much?
Im pretty sure an n/a 5.0 will feel more torque with Some backpressure, anyone have any dyno test to confirm this?

Lethal5Oh · 03-12-2007, 12:53 PM

Well i did some research and found that you can infact have too little backpressure. Without the back pressure you get too much scaveging and actuallly suck fuel and air out the exhaust causing a lean condition, killing torque. To conteract you have to have a fuel injection system that can correct for this problem. Im getting a adjustable fuel pressure regulator and see if i can richen it up. If that doesnt work i guess ill get the upr cat xpipe.

Coupe50h · 03-12-2007, 01:28 PM

i seem to have a rich condition, but of course it may seem that way because i smell more exhaust, and with no cat's, i almost want cat's so it wont stink as much, do you have the smog pump?

USMC302 · 03-12-2007, 01:38 PM

I picked up a tenth and .5mph with dumps.....

03-11-2007, 07:01 PM	#1
Lethal5Oh Registered Member Join Date: Jun 2002 Location: Portage Posts: 239	Not enough back pressure? Well i got my stang out of storage the other day and put the cats back on for my emissions test. It feels to me like that car has better power with the converters on then off. Am i nuts? the car has 100k miles on it. Any one have a idea on this? Thanks __________________ '95 GT convert. K&N, C&L mass air meter, Performance distributors sreamin demon coil, dyna mod, live wires, king cobra clutch, flowmaster american thunder exhaust, UPR billet adjustable shift handle, Crane Cams Fireball HI-6 box,underdrive pullies, 255lph fuel pump, UPr short throw shifter, caster camber plates, 03 cobra lower A arms, bullit suspension, cobra front brakes

03-11-2007, 08:33 PM	#2
goodyear1984 Registered Member Join Date: Dec 2006 Location: new york Posts: 482	Re: Not enough back pressure? whats up man...what kind of exhaust do u have __________________ 347 stroker all forged,arp everything,stud mains w/girdle,7qt pan,full roller, custom cam, aluminum heads swirl valves 5 angle valve job.quick fuel 750,areomotive pump,cobras w/nitto drags,and m/t et drags for the track, ford racing 373 gears,centerforce clutch,tko500,underdrive pulleys,bassani x-pipe,flowmasters ^best et so far 11.6 1.61 60ft coming soon 9sec et's 1992 mustang gt 2001 gmc 1500 4x4 78 century boat 92 skidoo

03-12-2007, 11:47 AM	#3
Coupe50h Registered Member Join Date: Aug 2002 Location: SanAntonio, Tx Posts: 957	Re: Not enough back pressure? Hmm, good post, cuz ever since i cut my tailpipes off, i havent been able to run as fast in the 1/4, but pretty close. I wonder if it hurts the torque that much? Im pretty sure an n/a 5.0 will feel more torque with Some backpressure, anyone have any dyno test to confirm this? __________________ X-Texas highway patrol ssp 1990 coupe - exploder Gt-40 iron heads, Explorer intake, 19 lber's. E-cam. crane 1.7 rollers. 190fp. 75mm maf. 65mm tb, tubular subframe connectors, mac cai, Asp crank pulley, T-5, king cobra clutch, flowtech 1-5/8 unequals, mac X-pipe Frpp driveshaft, lakewood Lca's. race weight 3,160 12.69 @ 107.35, 1.71 60' 26x8.5 drag's 3.90 gear 13.20 @ 106.91 - 235/60/15 firestones 2.3 60' 3.27 gear

03-12-2007, 12:53 PM	#4
Lethal5Oh Registered Member Join Date: Jun 2002 Location: Portage Posts: 239	Re: Not enough back pressure? Well i did some research and found that you can infact have too little backpressure. Without the back pressure you get too much scaveging and actuallly suck fuel and air out the exhaust causing a lean condition, killing torque. To conteract you have to have a fuel injection system that can correct for this problem. Im getting a adjustable fuel pressure regulator and see if i can richen it up. If that doesnt work i guess ill get the upr cat xpipe. __________________ '95 GT convert. K&N, C&L mass air meter, Performance distributors sreamin demon coil, dyna mod, live wires, king cobra clutch, flowmaster american thunder exhaust, UPR billet adjustable shift handle, Crane Cams Fireball HI-6 box,underdrive pullies, 255lph fuel pump, UPr short throw shifter, caster camber plates, 03 cobra lower A arms, bullit suspension, cobra front brakes

03-12-2007, 01:28 PM	#5
Coupe50h Registered Member Join Date: Aug 2002 Location: SanAntonio, Tx Posts: 957	Re: Not enough back pressure? i seem to have a rich condition, but of course it may seem that way because i smell more exhaust, and with no cat's, i almost want cat's so it wont stink as much, do you have the smog pump? __________________ X-Texas highway patrol ssp 1990 coupe - exploder Gt-40 iron heads, Explorer intake, 19 lber's. E-cam. crane 1.7 rollers. 190fp. 75mm maf. 65mm tb, tubular subframe connectors, mac cai, Asp crank pulley, T-5, king cobra clutch, flowtech 1-5/8 unequals, mac X-pipe Frpp driveshaft, lakewood Lca's. race weight 3,160 12.69 @ 107.35, 1.71 60' 26x8.5 drag's 3.90 gear 13.20 @ 106.91 - 235/60/15 firestones 2.3 60' 3.27 gear

03-12-2007, 01:38 PM	#6
USMC302 Registered Member Join Date: Apr 2001 Location: Gallatin, Tn Posts: 1,326	Re: Not enough back pressure? I picked up a tenth and .5mph with dumps..... __________________

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