: 96 deville N* cats question



hogstamogsta
03-15-06, 08:46 PM
i got a 96 deville wit the northstar and it has factory dual exhaust on it, i am going to put magnaflows or flowmasters or something on it within the next few weeks, i was wondering should i take the cats off or can i not because of the back pressure and what not? would it be louder if i took them off and better performance or what should i do..any suggestions please help:confused:

96-deville-man
03-15-06, 10:08 PM
I have flowmaster delta flow 40seris and i love them. i would leave the stock cat but remove the resantor. i still have my resantor but will be taking it off soon. its not duals just 2 mufflers.

fubar569
03-16-06, 12:35 AM
what you need is this

full custom bent 3" from as far up as your shop can go...no resonator, into flowmaster delta flow race mufflers (3"). this will make your car sound like none other on this planet. it will be loud. for more mellow go flowmaster 2 chamber...i plan on eliminationg my cat and getting MIL eliminator to fool the ECM.

so mine will be full 3", no cat and no resonator, 1 chamber flows. get ready to feel the thunder.

also, if i can get header flanges and a tubing kit, you may see one of the few devilles with custom long tube headers. imagine those on perhaps a true dual 2.5" system. simply badass.

hogstamogsta
03-16-06, 04:24 PM
yeah i plan on doing that, i just didnt know if it would run shitty without the cat cuz no matter what im takin the resenator off anyways...

auroradude
03-16-06, 11:33 PM
Whatever you do don't go that damn high -- 3" man. Get 2.5", anything over that and you will lose mad torque and these motors are gutless from the bottom anyway, why would you want to make it even worse.

fubar569
03-17-06, 03:39 AM
then corsa must be doing something wrong because their exhaust is a full 3" system. many people use it and report awesome gains, not to mention sound.

a single 2.5" is a restriction to these cars. my mustang was dual 2.5" and it was same displacement (4.6L) but only a 2v motor. i could've gone 3" very easily with what i planned on doing to it.

agreed some backpressure must be retained, but on a motor like this, a single 2.5" would be a worthless move, especially since the stock system is a 2.5" system on most northstar vehicles.

now with me wanting to do headers, a dual 2.5" would be more appropriate.

hogstamogsta
03-17-06, 08:01 AM
ok well im just gonna take the cats off then n go all out

chevelle
03-17-06, 03:01 PM
Putting 3 inch exhaust piping on is NOT going to cause any loss of torque. The "lack of backpressure causing torque loss" is a ricer fairy tale. BS.

hogstamogsta
03-17-06, 05:25 PM
should i do 2 mufflers or 1?

fubar569
03-17-06, 06:15 PM
it is possible to lose power by gong with too large of an exhaust, but with these motors this is just not the case. they like to breathe, we just don't have the room to run a proper exhaust...

I'd do 2 just to keep the looks of stock. some nice polished tips will look good. not to mention single outlet exhaust on a V8 = teh gheyness

davesdeville
03-19-06, 07:55 AM
should i do 2 mufflers or 1?

2... the car came with 2 so 1 would look stupid IMO.

And chambered mufflers (flowmasters fall into this category) suck. Well they sound good but are more of a restriction.

auroradude
03-19-06, 12:02 PM
How about dynomax?? what the hell would you recommend for power and sound? I hope not corsa. i Dont like the exotic sound they have, it just doesnt sound right on this V8.

96-deville-man
03-19-06, 01:45 PM
i love my flowmasters! i gain so seat power you know but not sure how much.

danbuc
03-19-06, 02:18 PM
How about dynomax?? what the hell would you recommend for power and sound? I hope not corsa. i Dont like the exotic sound they have, it just doesnt sound right on this V8.

Exotic? What the hell are you talking about?

Removing the cats is great if you never plan on getting your car inspected again, seeing as how it will almost certainly fail. Headers are pretty much useless on these cars since the factory manifolds are not very restrictive. Ask Mark, he said that he asked about getting the stock manifolds extrude honed and was told that they didn't really need it, seeing as how they already flow pretty damn good.

96-deville-man
03-19-06, 03:16 PM
Exotic? What the hell are you talking about?

Removing the cats is great if you never plan on getting your car inspected again, seeing as how it will almost certainly fail. Headers are pretty much useless on these cars since the factory manifolds are not very restrictive. Ask Mark, he said that he asked about getting the stock manifolds extrude honed and was told that they didn't really need it, seeing as how they already flow pretty damn good.

the tech section says that the stock manifolds are pretty restrictive. or is it just the cross pipe?

fubar569
03-19-06, 04:12 PM
it's the crosspipe, but to really eliminate that restriction, you have to redo everything else. that means tubular headers. mine would have all fittings & such.

as for no cat, we have no sniffer, only visual. i could take the shielding off, weld it on new pipe, and no mechanic here would ever know the difference

danbuc
03-19-06, 04:21 PM
Only visual you say.......Damn, wish I had that. In that case....go for it. You might as well do it then. Tubular headers still aren't gonna make much of an improvement wihtout bypassing that crossover piece though.

96-deville-man
03-19-06, 04:25 PM
i think im just gonna have the cross over redone. ill take it to a muffler shop and have them cut out the part where it gets small to go under the tranny and replace it with pipe. then take the plate that goes under it and have my friend modife it to fit. that should make a diffrence.

fubar569
03-19-06, 04:29 PM
mine are gonna be long tube headers, not tubular manifolds...i will have true dual collectors and a very efficient Y pipe made to fit. there will be no crossover...well maybe if i go true dual exhaust i will add an X section where they come together.

96-deville-man
03-19-06, 04:36 PM
im not gonna run true duals just to much work. but i will have a better flow then stock.

danbuc
03-19-06, 05:00 PM
What are you going to do abotu the lack of cround clearence once you run the pipe directly under the car? These cars are already really close to the ground to begin with.

fubar569
03-19-06, 05:07 PM
What are you going to do abotu the lack of cround clearence once you run the pipe directly under the car? These cars are already really close to the ground to begin with.

instead of a round pipe, i was thinking a rectangular pipe with the flow equivalent of a 3 or 4" pipe (pipe itself no more than 1 to 1.5" tall) to make up for it. i've also thought about routing 4 seperate primaries for the front header under the pan and situating the collector behind the motor. i think the rectangular pipe would bet he best option as it would allow me to keep the primaries close to the same size.

96-deville-man
03-19-06, 05:10 PM
What are you going to do abotu the lack of cround clearence once you run the pipe directly under the car? These cars are already really close to the ground to begin with.

my cross pipe will only be 1/2 inch at the most lower.

danbuc
03-19-06, 05:16 PM
Hmm...sounds just liek the design behind the crossover pipe. Taking a nice round pipe and then suddenly squishing it flat, even if it still has the same overall diameter, is going to creat some sort of restriction. The Crossover pipe has to squish flat in or to fit between the engine and trans. This pipe is going to have to be at least 2-3 inches wide under the car. Not to mention that heat shielding would be a good idea, seeing as how you'll be running the pipe directly under the transmission pan.

fubar569
03-19-06, 05:22 PM
it's gonna be a very gradual reduction in overal height, but the width of the pipe will be at least 3-4" to make up for it. i'll have to run the numbers if i can remember formulas for area of a circle & stuff. it should realistically be no flow difference between a 3" round pipe and what i plan on doing. it won't be a restriction at all.

fubar569
03-19-06, 05:34 PM
area of a circle = pi*r*r

so 3.14 * 1.5 * 1.5 = 7.0685.....

reducing the height to 2", increasing width to 3.5 (rectangle)

area of rectangle = length * width

so 2 height times 3.5 width = 7.0000 even....a vry minor difference.

as long as the transitions are gradual and the area stays the same, it should pose no restriction.

reducing height further to 1.5" and increasing width to 4" only yeilds 6.0000 even.

to get close to a 3" pipe,the outside dimensions would have to be something like 1.5 high and 4.7 wide. this of course would only be for the pipe directly underneath the powertrain.the rest would be either dual 2.5" or single 3+" pipe

danbuc
03-19-06, 05:34 PM
Hmm...sounds like you've got it all planned out. I would still leave room for heat shielding though. That pipe is gonna get pretty hot under there.

fubar569
03-19-06, 05:41 PM
oh thatsection wil be coated and shielded...taking no chances

96-deville-man
03-19-06, 10:28 PM
yea it gets really hot under there. my cat temp was 800+.