spawne32

iTrader: (2)

We don't have a single exhaust system, we have a partial dual system. Which means you have to do your calculations by 1.5. 2.2CFM per horsepower x 350hp = 770cfm, Dual 2 1/4 inche pipes at the smallest section of the tail pipe, 408cfm x 1.5= 612cfm total possible flow through the tail section. The mufflers are only capable of flowing UP TOO 700cfm each. Not to mention it even says in the article "The table above is probably over-estimating pipe size, but you can see that a 400 hp vehicle with a dual exhaust system only needs 2 1/4 – 2 1/2 inch pipes. Anything larger is overkill."

91parkave

iTrader: (4)

The part to the puzzle your missing is that dual exhaust refers to header back. We doffer not have a header back dual exhaust. We have a **** single pipe running to the back with a split at the end. So your calculations become out the window.

spawne32

iTrader: (2)

I am already running 3" for a large section of the single pipe that runs to the dual section, then it briefly reduces to 2.5" before the split. Your getting into a whole different realm of possible theories there, we could talk about exhaust velocity and scavenging at the point. I am not saying that a 3" probably wouldnt net a little more power, it probably would, but not enough to warrant the extra noise, weight, and cost for me. Very confident that without the cat in place, this system flow just plenty for the volume the engine produces.

blkchevyz

if you already have 3 inch back why not just replace the y-pipe with a 3 inch in and dual 3 inch out muffler? then just have a shop make the rest.

i did that with my factory exhaust but with 2.5 in and dual 2.5 out. sounded pretty good and got rid of that tiny y-pipe.

rottonj

iTrader: (4)

That factory main pipe isn't 3, damn thing is more like 2.75 but yours has been modified already. My exhaust is stock, and appears to be in good shape still for a nine year old car. I love the sound, and I have had plenty of obnoxious cars before that I liked too. Your daily drive might not be favorable to ultra loud, so in the end as always the decision is yours to make based on what your needs are. I feel the reason we are all pushing is we cant understand your reasoning on this. Theoretically it will work sure for exhaust scavenging.BUT! You have a 4 inch cone air filter, 4 inch maf, 90mm tb ported intake manifold with cam, headers and a modified down pipe with high flowing cat, and now you want to go small on the exhaust? If Leonard Nimoy was alive he would say, this is not logical lol.

spawne32

iTrader: (2)

All things being equal, i would agree with you, but things are not equal. LOL

spawne32

iTrader: (2)

Spock quotes aside, i understand the suggestions, you just have to have faith that I know what I am doing because I have experience with this. I have had too many cars, from wbody cars to honda's that have lost low end torque by double digits from oversizing the exhaust. I always default to the minimum required size based on my calculations now and it usually nets me good results. Common logic is to always go to something really big because the thought behind it is that a big engine requires a big exhaust, so everyone always defaults to 3" without actually knowing why. And sure you can make big power on a dyno running a 3" exhaust, I am sure, but there are other factors to consider like i said. Regardless of the size of my intake or the mods I have done, this car probably puts down somewhere between 300-315hp to the wheels, modestly. There is no reason at all for a 3" exhaust on this car, and barely enough justification for a 2.5".

http://www.gomog.com/allmorgan/exhaustbackpressure.html

91parkave

iTrader: (4)

So if you understand the principle behind the engine being a air pump why do you not understand more air needs to be pushed out? You keep going to these sites saying airflow for a dual system or airflow per pipe. But that does not out line efficiency. Not to mention your websites get the majority of my information from eras where tbi was still the new thing. Your never gonna lose tourqe on a 3inch system either it's simply a shift in the power band

Hell gm decided to use 2.5 inch piping already on 4.8 trucks and such. I don't see how you come to this conclusion that a cammed 5.3 do sent need more.

spawne32

iTrader: (2)

I've already told you, its based off my own interpretation of my needs and my previous experiences. I am not saying that nobody should be running a 3" exhaust system, I am saying I feel for my car its a complete waste. You guys are welcome to design your exhaust however you see fit, but without definitive back to back dyno results, you cannot say one way or another that there are going to be significant gains between this and a 3" system. Dynomax rates this setup at flowing up to 700cfm, thats enough for me.

rottonj

iTrader: (4)

Any chance of you getting to the dyno before install? I'm not saying this to be a dick or try to prove you wrong somehow, you should know me better than that by now. Just would be good to actual have some before and after type results. These manufactures all claim nice results, but those are never the real story. I know when the K+N system first came out for these I believe it said like 28hp, now I think it says 13.48 lol. Those mufflers will sound good for sure, and are not overly loud as I have used them on a few cars in the past.

spawne32

iTrader: (2)

If i can find someone who has decent prices for 2-3 runs then yeh ill do a dyno before and after. I still have quite a bit to do before this exhaust is completed, i have the procomp wideband gauge I have to setup and get this zzp trans mount installed. Also gotta figure out why my steering still feels funny. It feels like im running something over in turns, but the suspension is all tight and everything seems to be fine. Tires are also screeching at low speed in some turns.

spawne32

iTrader: (2)

heres the dynomax tail section vs the OEM section

91parkave

iTrader: (4)

Did you do struts?

spawne32

iTrader: (2)

Just did strut mounts, struts were in good shape, no leaks, and rebounded quickly.

rottonj

iTrader: (4)

What is the ZZP trans mount. Poly? thought you would have replaced the mount already. Grab a pic of the install too.

rottonj

iTrader: (4)

Well the Dynomax is better, but both look like crap compared to the Trubenz section. I could not put either of those on.

spawne32

iTrader: (2)

i like the trubendz, trust me, like i said i considered alot of factors, cost being one of them. I got these pieces at a fraction of the cost, plus they are slip fit which makes it easy as pie for me to do in the driveway. Pictures dont do it justice its quite a bit larger, the smallest section on that pipe is 2 1/4, the ends are 2 1/2 or just under on the ID. The mufflers are huge compared to the stock ones. There is a couple hundred CFM bump here regardless of how it looks.

Koren

Looks like that 3" inch exhaust would drag under a lowered car...that's massive...however I've been following your guys exhaust thread and I'm still not sure what set up I wanna do. If I'm following correctly, a 3 inch set up is good no matter what, with or without mods, or if I'm mistaken that's a 2.5 set up cause stock is like 2.25? and also spawn I wanted to ask do you use your gxp as a DD?

91parkave

iTrader: (4)

I've been in 3inch since day 2 of owning the car, I'm also the most lowered as a daily driver. These cars can easily tuck a 4inch exhaust if one ever wanted to. But you will be more than fine with a 3inch system

Koren

Wow really? So was it 3 inch all around or....? And how did you deal with a lot of the drone? I remember you telling me I could push the pipes back a bit outwards of the rear.

Edit; I just noticed you said even as a DD, I'm assuming that also is even with your cam and intake etc...