I've been piecing together a a stroker lq4 for a LS-based FFI swap for a while now, and the "itch" to drive my car ('96 Firebird) has been unbearable. I have now decided to just "toss" a 5.3 FFI engine in the car for now...so I can enjoy the car while I build the nasty LQ4. I'm trying to make as many pieces/upgrades right now that CAN be used with the 5.3, but will ultimately end up bolted to the LQ4. Fuel system upgrades are being done, as are chassis and trans mods...but I'm feeling kinda lost as far as which way to go with exhaust.

I suppose that I should step back for a moment, and re-state that the LQ4 will not be an "all-out power" build, but will hopefully net me 750-800 DEPENDABLE HP to the pavement once it is complete....at least that is the goal.

With that being said, I'm really wanting suggestions/recommendations from others here with regard to a relatively quiet exhaust system for every-day street driving. I'm just not sure what exhaust configuration will be needed to support my power goals. I've considered running a y-pipe off the turbo dump into dual 3 inch pipes/mufflers, but as yet I'm not sure what all I can fit. To make matters a little more interesting, I need to have catalytic(s) in the system as well....so suggestions here would be welcomed as well.

Thanks in advance!

 

That's a lot of air to be pushing through converters. I bought a set of steel Magnaflow metal substrate cats for $100 each. They are pretty compact, and are probably the best ones on the market short of something from Random Technologies - Random is supposed to be the best. They are also considerably more expensive, but might be worth it for your requirements. I am thinking that you would want to run two cats - one on each outlet of your Y pipe, so that each cat will only have to process half of your exhaust volume. The cat is supposed to be as close to the engine as possible, so you'd probably want put them very close to your Y pipe. The cats should also quiet down your exhaust. On the other hand, Random Technologies might have some sort of product that would allow you to run just one big cat, which will let you run a single pipe from the turbo to the muffler. This would probably make your exhaust simpler and cheaper, as you could use the factory routing areas and bolt-on mufflers designed for your car.

Muffler selection may require some compromise to get the sound or performance you want. Your best bet would be some sort of straight-through design, like Borla, Magnaflow, Dynomax Bullet, Hooker Max-Flow, etc. These mufflers generally run the exhaust through a preforated tube surrounded by some sort of accoustic packing. Each of them are probably going to get the job done with very little back pressure, and it is largely going to come down to your preference in sound. Check out ls1sounds.com for some clips of each muffler.

Larger tubing is going to make your exhaust louder. Don't go larger than you have to.

Make sure you will be able to drive your vehicle when you are done! I know CA has some rules that make it very tough to get highly modified cars to pass emissions testing. I don't know about Oregon, but if I were you I would find out immediately what you can get away with and what you can't. It would suck to build an awesome car and then not be able to get it registered.

-Dave

 

Thanks Dave.

I guess that the biggest confusion right now, is exactly what size piping (single or dual) would be required to reach my goal. I have a friend that is going to supply whatever needed 304stainless I might need, and then is going to be nice enough to purge-weld the whole system once it's fabbed. I'm just not sure where to look to find exhaust-sizing info. As far as the cats, they would primarily be in the system to try and meet emissions regulations, but I realize that I will more than likely have to have 2 different "tunes" for the car....one for "real world" driving, and one for emissions testing purposes. I'm not exactly sure what the actual testing process is here in Oregon, but I'm currently looking in to it. I'm pretty sure it's a sniffer that checks idle emissions, and then a 3000rpm emissions check, but again I'm not sure.

Thanks for you help

 

No problem.

Be carefule on the emissions testing - a lot of places have a "visual" check that you must pass in addition to the sniffer. They can get very specific and picky, so get all your testing info 100% straight! I was not satisfied until I spoke with a state emissions enforcement officer on the phone... if that's what it takes to be crystal clear, do it.

As for piping size, there are some standards to follow. Buy the book "Maximum Boost" by Corky Bell. Hands down the best $25 you will spend on your project. He has a chart in the book that helps you calculate the size piping you need, whether it's duals or a single. I would give you the number, but I lent my copy out.

-Dave

 

Whaddya think of this?? I was thinking of using 2.75 pipe running off from a "y" at the turbo dump into dual hi-flow cats..and then out the back like this.