ok, so my 1985 camaro berlinetta is equipped with an LG4 305. any mechanic can tell you the best way to unlock performance is getting the air in, and out, as fast as possible.

after testing 3 systems these were my results ( i work at an exhaust shop, so very very cheap for me to test)

system 1: 2 1/2 single system. the first thing i noticed is that it gave a huge rumble to the car. driving it in town the drone got a little annoying, it was just the right tone that i couldnt take my focus off of it. when it came time to hit the highway, i noticed a HUGE performance difference on accel.

system 2: 3" single system. right away, we noticed it seemed quieter that the first system. driving it in town the engine sputtered a few times, nothing major. the drone was moslty gone, hit the highway and was not too impressed. performance felt very close to stock, maybe a little better.

system 3: 2 1/4 true dual system. i went basic, not worrying about tailpipes, just turndowns before the axle, which significantly lowered ground clearance. performance-wise, no different from the first. a few sputters when it was warming up. driving in town it did drone a little, but it wasnt too bad. hit the highway and noticed once again, no different from the first.

overall after all this, i ended up going back to the first. not only was it the cheapest, it didnt fill the car with exhaust like the dual did. obviously tat could be fixed with tailpipes, but they cost a fair bit and were alot of work.

*all tests done with V-Force mufflers, the midas national brand in canada, and i do not guarantee your results would be the same, so please leave your negativity on another post, this is just me and my results.

by the way, the first had the fullest sound too

 

My set up is pretty just like the first...I have stock manifolds, no cat, straight pipe back to the muffler which is a v-force (one in/dual out) and pipes out the back. Its loud when i'm in town going easy and hard accel, But once you get on the freeway it sounds good and is not loud... louder then stock but doesn't drown out the radio.

 

2.5" system would be fine on a stock LG4 thats why you didnt notice any difference...now build a 350 or 383 and do those same test all over again and there will be a huge difference. Onother reason you probable did not notice a difference is because of crap flowing factory manifolds. Replace manifolds with headers and 3" y pipe then run a 3" system all the way back and it will flow.

 

i have headers, and it was 3" front to back

 

LG4 though! Heads dont breath enough to take advantage of 3"...like I said put a motor in it and then do the same test 2.5 vs 3 vs dual and post dyno results.

 

stock LG4 or even a LB9 done flow enough for a single 3" a single 2.5" mandrel bent system is an upgrade for both systems but a 3" would be needed for a larger displacement like a 350 or 383.

i like how u tested 3 diff setups, good deal.

now im running no cats, headman LT's, 3" headman header extensions, 3" summit Xpipe, and a pair of 3" FORCE mufflers with turndowns and SPORTLINES... i still got ground clearance. thats lowered to 25 3/4" front tire and 26.5" rear. i love the exhaust and the exhaust fumes make me feel happy and industructable