Thanks in advance for your input everyone.

I've been reading forums and watching countless videos trying to pick the best exhaust for my LaCrosse Super. So can you shed some light on this exhaust setup? Any improvements/comments please.

Doug Thorley Headers
Magnaflow 51659 cat
ZZP 3" downpipe tail
ZZP 3" SS Catback
Magnaflow 12641 for Resonator
2x Borla ProXS or other mufflers

 

You don't need a downpipe with the headers, everything else is personal preference. I would just verify the ZZP exhaust system fits the Buick.

 

so couple things

DT doesnt sell those headers anymore, so your stuck with OBX at this point
magnaflow cats are far too expensive for their quality, i recommend you stick to a thunderbolt from performance-curve for half the price.
the ZZP 3" tail works fine but remember you will need to build the rest of the DP off the Y section of the headers, it does not include a downpipe.

Your cat back is all preference of sound, you can either buy one premade with the mufflers, or get a pipe kit from trubendz and put your own mufflers on it.

 

The headers have their own DP, just need to run some straight pipe up to it from your existing exhaust.

 

i went with a flowmaster cat, it was cheap and seems to flow fine. i actually bought it to quiet down my exhaust, didnt help in that department lol

 

I heard the obx were terrible with clearance issues

 

my OBX fit perfectly with no modification the first time, only thing you have to watch for is the aluminum coolant lines that run around the motor, but they hit everything, not just the crossover. They are easy to adjust as well.

 

Ah okay I'll keep that In mind, I think I'll do headers next year

Edit; do the obx run well compared to the dt? I know they were priced cheaper but any difference?

 

they are virtually identical, and they dont rust like the DT's do lol

 

Never had a rust issue with dt headers in the 2+years I've had it. Plus there ceramic coated...big plus in keeping Temps down

 

Only place my DT headers are rusting is where it's welded to the rest of my exhaust. I live in an area with lots of snow and salty roads in the winter though.

 

Everyone likes to talk about personal taste/noise, but I focus on the performance aspect a little more. You can get a quiet/stock tone using an OEM style muffler from another high performance car (any vehicle with OEM 500bhp I suppose) if quiet is your thing.

But besides that, the length and diameter really are what count. If you have a naturally aspirated engine, using a 3" exhaust, even just a single 3", is too big for most OEM rev-limited engines (not very high power: 350rwhp~). These engines only require 2.25" or so, perhaps 2.5" diameter system. The idea is to keep the exhaust gas velocity highest where you drive the engine mostly, i.e. if you spend alot of time driving from stoplight to stoplight, in a daily driver, you will be in the mid-range alot (2k-3k) so you want a very high exhaust velocity in that RPM range for optimal cylinder fill, a small exhaust would work better than one that gave more peak horsepower ( you arn't holding the engine near redline to get from stoplight to stoplight like you would in a real drag race to 120+MPH with 350bhp).

Yes, the larger diameter will usually make more peak power (bigger dyno peak) and this will usually give you a better trap speed MPH, but overall the vehicle may be slower around town simply because you don't hit that peak RPM the same way around town, the way you do at a strip (it spends more time in the lower range around town). Once you open everything up with a converter/gears/HCI mods then sure, the engine spends more time up top from that... but it will cost some economy at that point. So focus what I am saying: for mildy/unmodded engines (1hp/cube), a smaller diameter exh would work better than a larger exh, for the style of driving (daily/stoplights). If you pass into the "heavily modded" category such as with a turbocharger, then yes use the 3" downpipe which supports 600bhp or more probably.

 

Curious - why do the gm trucks with a similar power and displacement use 3" (2 3/4" in some applications as well) in an application that needs low-end torque.

 

what 5.3 GM trucks come with a factory 3" exhaust?

 

NBSS..
May be 2 3/4" or 3", story seems to vary

 

I'm sticking with bolt one pretty much...and maybe a cam

 

This guy has no idea what he is talking about.

 

one thing to remember about this vid, is that this engine is huge compared to the LS4, the LS4 requires a comparison of like 2" to 2.25 to 2.5" lol

 

I watched that the other day, pretty good stuff.
Food for thought; it's also 3" vs 2.5" off of each bank and not the entire motor.

 

Breaking it down this video highlight Dual exhaust in the 2.5 to 3.0 inch upgrade arena. Which makes it completely irrelevant towards a ls4 single application. For optimal performance you want 3.0 inch