Exhaust sizing/design opinions for 3.4l V8

[HumberSS]

So I am starting to work my way down the list on my V8 Dyna build, having now finished the headers I'm wanting to know thoughts on designing a good exhaust system for it. I've built the headers using 34mm or 1-3/8" tubing, which essentially matched the port sizes, and these go into a 2.5" collector. I chose the collector size as A) I had some bits of 2.5" pipe, and it felt about right in terms of cross-sectional area. 

The thing to keep in mind is, although physically the largest engine on the planet, is cubic capacity is way small at 3.4L. it will likely not exceed about 150kw/200hp ish either. Im neither want a droning/raspy POS nor do I want to oversize and lose power. I actually want it fairly quite, but want to maximize the ponies available..

My thinking at this stage is in order to maintain exhaust velocity I need to drop the diameter down to 1.75-2" right out of the collector. My next thought, is owing to space, I'd like to go straight into a (reasonably large) offset in/out chambered muffler on each bank right away. I'm not really sure if that's a good idea though? Often mufflers are further back but I wonder if that's to improve muffling rather than exhaust velocity?? I'm also wondering if pipe diameter is still a bit large? Anyway, I'd then like to come out the back of the mufflers and merge into a single 2.25-2.5" pipe and continue out the back to another muffler at the back with a droopy tip to reduce projected sound. I don't want it whisper quite, but very 'mild mannered'. Think something like a factory poverty spec v8 ss commy. I had actually considered getting a factory system off something and chopping it up to suit, but think that would be a headache..

Love to understand people's thoughts here. 

Churr.

[chris r]

Go 2.5" from headers back imo. 

I've got a set of cheap rock auto resonator and super turbo muffler on one of my vehicles and it's a really nice volume for a daily. 

If your feeling flash you can go for the adrenalinr mid mufflers. Sold heaps of them at my last job and had no complaints about them 

 

[kpr]

run the biggest glass pack straight through muffler /resos  you can fit for the  first mufflers.  put the chambered ones at the back

sizes yeh you can drop down smaller, but need to do it at the merge.   then go back out kinda like a megaphone setup.  if you do it right and place  said above mufflers in right place.  will gain  power off the bottom. 

 

[HumberSS]

13 hours ago, kpr said:

run the biggest glass pack straight through muffler /resos  you can fit for the  first mufflers.  put the chambered ones at the back

sizes yeh you can drop down smaller, but need to do it at the merge.   then go back out kinda like a megaphone setup.  if you do it right and place  said above mufflers in right place.  will gain  power off the bottom. 

 

Thanks mate, what do you mean by drop down smaller at the merge? My thinking is that this is essentially 2 x 1.7l n/a 100hp engines side by side, so thinking that 2.5" is a lot of pipe for that...

[kpr]

looking at your thread you have something like below.  and are thinking of dropping smaller after the 2.5" collector?

 

This is what i was meaning. angle straight down to 2" or so  where all 4 pipes collect.    The big straight through is key to making it work.  think of the exhaust ending after them.   what you do after isn't so important.  long as the pipe size is big enough not  restrict airflow.   merging into a single 2.5" probably fine in your case.   but you cant make it too big. just makes it harder to cut the noise down.   all the power is in the headers and the section before the first reso's

 

 

 

 

[HumberSS]

26 minutes ago, kpr said:

looking at your thread you have something like below.  and are thinking of dropping smaller after the 2.5" collector?

 

This is what i was meaning. angle straight down to 2" or so  where all 4 pipes collect.    The big straight through is key to making it work.  think of the exhaust ending after them.   what you do after isn't so important.  long as the pipe size is big enough not  restrict airflow.   merging into a single 2.5" probably fine in your case.   but you cant make it too big. just makes it harder to cut the noise down.   all the power is in the headers and the section before the first reso's

 

 

 

 

Cool so from your above description you are saying drop it down to 2" out of the collector then straight into some nice big resonators, then from there onwards I can proceed to merge into a 2.5" single and big chambered muffler at the back? That sounds like a pretty good plan. Should I run flexi joints after the headers/before the resonators?

[Bearded Baldy]

I will just add. Flanges. Everywhere you can fit them. 

[HumberSS]

21 hours ago, Bearded Baldy said:

I will just add. Flanges. Everywhere you can fit them. 

Good idea. It will be a cunt if I don't anyway.

[Tiger Tamer]

On 18/04/2023 at 22:03, chris r said:

Go 2.5" from headers back imo. 

I've got a set of cheap rock auto resonator and super turbo muffler on one of my vehicles and it's a really nice volume for a daily. 

If your feeling flash you can go for the adrenalinr mid mufflers. Sold heaps of them at my last job and had no complaints about them 

 

I used Adrenalin mufflers on the Tiger and have no complaints as well. They were being made locally in Hastings so I went and checked them out. Not to load but sound cool.