i have been searching around for about four months now for an exhaust, and was pretty convinced on a true dual system (hooker LT's, magnaflow X and cats, and Magnaflow 4x9 ovals) but with all of the trouble of 02 sims, 02 extensions, crappier gas mileage, all of the custom fabbing to get it to fit right just didnt seem worth it. so then i decided i was going to go with a magnaflow catback and later on add a catted Y and LT's but i didnt like comments of the raspieness of the magnaflow catback, i am stuck and dont know what to do!!! any suggestions???

 

I fail to see how true duals will cause crappier gas milage on a stock car. If there is any change its probably no worse milage going from stock 16" wheels to 18's...

If you run any headers you'll need 02 sims/extensions or get the rear O2's tuned out. Just run a cut out until you get headers.

Either way, welcome to modding. You have to pay to play.

 

were you being sarcastic on the gas mileage change with different wheels??

but really, the true duals are not that bad to fab up, although i think the magnaflow X is a questionable item. depending on how you want to run the duals, it may not be the best choice.

if you're planning to run duals side by side out the back than the mf unit is ideal, since it has parallel inlet and outlet tubes.

but if you plan on dumping the setup before the axle, a regular X will work better.

i guess i don't see how o2 sims and extensions are a "hassle"....that's kindda like saying an air filter is a hassle when installing a lid.

 

If i go with a Y pipe setup, do i still need to run o2 sims? With the true duals im running them out the back so, which is the best way to route em?

 

I think yes you would, if you're going with LT Headers.

I believe anything with LT Headers are going to require O2 extensions or Sim's.

Hey let me know what you come up with though because thats also going to be my next mod...

 

will the stock panhard rod be in the way when i run TD's? Will anything else be in the way like the steering shaft for the Lt's? Also, can TD's be made to pass emissions??

 

Totally unnecessary with dual 2.5". I have a single 4" over my axel.

 

Quite.

 

hmm...some of this is confusing...

the panhard probably won't be in the way if you stick with 2.5" pipes, side by side, over the axle. seen it done several times. i think doing the panhard thing from BMR allows you to run 3" over the axle side by side. it MAY make it easier to route the 2.5" as well...worth looking into.

nothing else should be in the way, especially not with the headers themselves. LTs on an LS1 don't require routing the one primary around the steering shaft.

TDs can be made to be emissions legal, depending on the policy of the area you live. technically ANY change in location of the cats is illegal. therefore the very act of installing LTs will make it fail some emissions tests (visual). now if you only have a sniff test, you should be able to install some cats behind the LTs and pass. now...i can't say i've ever heard of anyone trying to pass emissions with TDs...since it would be obvious that it's not stock. although if you run the exhaust out the back, it may not be so obvious.

now on the o2 sims. if you are gonna run cats you can probably keep the rear o2 sensors. you'll have to have the shop weld in the threaded bung for them behind the cats, but i would think it would work. it would be easier if you just ran sims. if you go with a Ypipe setup, unless it's got cats in it, and the bungs for the rear sensors...you'll still need the sims (or a tune to remove the code).

ok...i think i got all of them...any other questions?

if you want to see one badass true dual setup, that runs over the axle, do a search for mrr23 on here and go to his website...his bassani is awesome and should give you an idea of how to route the setup.

 

thanks so much teke, you have realy helped me out. SO now exactly what parts do i need to run true duals successfully. (02 extensions, welded bungs for the 02s on the cats or for 02 sims, etc..) i know youve already answered this but hopw much clearance willl i lose with 2.5'' pipe, and will it sound different than 3''?? for the A/F ratios is there anything that i can buy thats cheap so my car doesnt run rich after the TS install??

 

headers and exhaust should have minimal affect on the a/f ratio. i would just leave it be untill you get more mods and then get a tune.

for the LTs you'll need the o2 extensions, which go on the front sensors. and then if you plan to run the rear sensors, you'll need the bungs welded in after the cats (and probably extensions for those too...doubt stock is long enough). other option on that is to install cats, and just use sims to fool the computer (or get it tuned out). the rear sensors are only there to indicate if the cats are bad, they have no affect on the runing condition of the engine.

if routed properly...you should not lose much clearance at all. there are other parts of the car that are as low as the exhaust will be. MAYBE1/2 or 3/4" at most.

sound should not be any different from 2.5" to 3"....why would it??

oh...another thing...

while you are installing the LTs...buy some poly motor mounts and put them in. it will nearly eliminate all movement of the engine under load and prevent 99.9% of clearance problems associated with headers and exhaust. with my stock mounts, as the engine twisted under load the exhaust would move 1/2-3/4" under the car...causeing it to hit the frame. now it doesn't even move. not saying you WILL have problems, but it's cheap insurance against it. especially since the mounts are easy to get to when the manifolds are off, and probably impossible once the headers are on.

 

K, my only other problem is i dont want the system to be loud? i dont want to be pulled over every time i take the car out. it will be 2.5'' with magnaaflow cats and ran all the way out the back? any drone to this setup? And will any low end tourque be lost?? WIll all full exhaust setups, either TD's or Y pipe be loud?

 

This will depend on what mufflers you use. A turbo style muffler will drone much less than a blowmaster.

I used to run dual Dynomax race magnum mufflers (straight through style) w/2.5" pipes on my 70 w/LTs and of course no cats. Cruising around, it was quieter than 5.0 Mustangs with their 4 cats and blowmasters. I met a guy running a very strong 455 in a mid 70's TA that had LT's (no cats again) 3" duals and turbo style mufflers and he was quieter than my car.

 

i will be using magnaflow 4x9 ovals

 

Magnaflows would be like the Dynomax's I had. I got some drone cruising around 2500-2600 RPM IIRC. The car had 4.11 gears and a 10" converter so that was in the normal cruising range for it. Everywhere else it wasn't bad. Just resonated at that RPM.

My bro-n-law's stock 5.0 w/a blowmaster catback was still louder.