skinny z

I've actually thought of using 3" from the single terminator box to the muffler. 3" pipe will flow about 800cfm (standard test pressure) and that's just enough for me at this point. I would have a 3rd gen application muffler that flowed as much. Then I could use the 4". In your case, because of your power requirements, you would have to fab something along the lines of 5" pipe for the box and 4" exhaust to the back. Is there enough room for 5"?
And then there's the issue of collector length. A terminator box at the closest merge between the collectors (just past the trans) will result in collectors being about 40" long. Most collector extentions I've seen in use are along the lines of 18-24".

Orr89RocZ

Thats going to be the problem. because of the how the pipes need to run, i fear i will not beable to do this exhaust tuning business. there is simple no room for the collector length i need to run. Now Allen is gonna run some numbers thru Pipemax for me to see what it may recommend.

I dont feel a ypipe is for me at this current point. I am 95% sure i'm doing true dual 3inch. i wanted to go over each axle if possible. I also want to run either powerstick chambered tubes like the one i have now or dynomax ultraflow round mufflers for abit quieter tone.

For me it will have to be 2 seperate termination boxes before the x pipe or H pipe if i run that. i wanted a x pipe tho.

true 3inch will be enough. At 2.2 cfm per hp, and if i have upwards of 500-550 hp, thats 1100-1200 cfm. each bank will need half that at 600 cfm or so. 3inch is more than enough and leaves room for nitrous

let me see if i can measure some things on my car to get a better idea of lengths
be right back

EDIT:

Got some numbers here. I'm estimating i got about 20 inches between where the header will exit and my spohn crossmember. If i ran a box, it have to be about 4inches beyond that point so a possible 24 inches plus the length of the header collector itself which seems to be around 8 inches? to the start of the termination box. Collector length of 32 inches may be achieveable with the right dimensions for the box. Shorter will be harder to do

to get shorter i would have to run the 4inch single pipe style if that will work as effective as a box. I have to read that article again and do some more research to see if that is as effective as a termination 'box' style box cuz i can dump the exhaust fromthe header into 4inch pipes for about 3 ft before i have to neck down to 3inch over the axle. That just may work

skinny z

David Vizard has mentioned how empty muffler cases can be used as termination boxes provided you pay attention to how the pipes enter and leave the box. (as 1989GTATransAm has reminded me)
I'm interested to see the results of the Pipe Max calculation. I wouldn't be surprised if 24-32" is far off.

Orr89RocZ

got the results from Allen's pipemax program. thanks again man!

For 6000rpm peak:
1. Best collector diameter is 2.80 inch OD 16 gauge.
2. Best tuned lengths.
A. 18.4" best power and recommended
B. 36.8" best torque
C. 73.7" longest with mufflers.
Note: you can go 9.2". Shortest recommended
Worst lengths are 27.6", 55.3" and 110.5"

For 6200 rpm peak
1. Best collector diameter is 2.85" inch OD 16 guage.
2. Best tuned lengths.
A. 17.8" best power and recommended
B. 35.6" best torque
C. 71.3" longest with mufflers.
Note: You can go 8.9". Shortest recommended
Worst lengths are 26.7". 53.5" and 106.9"


SO if my total exhaust system is 73.7 inches long before dumping to atmosphere, i should be tuned for 6000 rpms?

I want to stick to around 17-20 inches for peaks in the 5800-6200 rpms range. thats where i want my max power to reallly shine, since i SHOULD be shifting at 6400 and rpms will drop back into the upper powerband

If i go with 36inch for max torque, i wonder how much torque is gained and how much hp is lost

Orr89RocZ

About that, it appears the pipes need to enter about 1/2-1 inch inside the case to eliminate reversion effects. Am i understanding this correctly?

I can see the inlet being like that, but the outlet i would figure should taper back into the exiting pipe size or 3inch pipe in my case

1989GTATransAm

Correct on the inlet and as you stated to help prevent reversion. The outlet can be a taper as shown or a bellmouth also as shown in post 39.

I was wondering something that might help you guys. It has been stated the volume of the termination box at a minimum should be 8 times the volume of one cylinder. I was wondering if this is for a car with 8 cylinders. So if one was to have a termination box on each side of a dual exhaust would it only need to have the volume of 4 cylinders? If so that might help in fitting in a box.

I might go over to David Vizards web site and post the question.

Orr89RocZ

Found a great real world dyno test between stock collector length and pipemax determined length

Before with STOCK collector LENGTH


AFTER with PIPEMAX determined Correct collector LENGTH

Orr89RocZ

Thats what i was wondering abit ago..... if you run both banks into one big box, i can see it being 8 to 10 times as large, but if you run only half the motor into a box, it should be half as large or 4-5 times as large as one cylinder. that would be MUCH better for room under the car

1989GTATransAm

That is quite a difference regarding the power under the curve. In fact that is quite a difference. Hmmmm looks like the tuned exhaust is a worthwhile pursuit.

Edit: posted the question on David Vizards web site. Might take a week to get an answer. He seems to be one busy fellow.

Edit: To me it seems one of the sources for untapped power in our cars is in the exhaust system. Maybe the greatest source for new power. I think the guys with the long tube headers have a lot of potential in that area. Later in the year I will try and see if it works somewhat with shorty headers.

Orr89RocZ

yes its up a good bit down at the lower rpms, and around 10hp/tq at peak rpms. i think its worthwhile investment as well

skinny z

I've been pursuing this exhaust potential for over a year now. Most fellows with street/strip cars seem to be content with next larger cam or bigger carb as their next modification instead of exploring whats yet untapped from their combinations.
It's good to see a couple of other guys getting into the technology.
It'll really be interesting to see the results.

skinny z

Not to make it difficult for you Orr89 however the interpretation I get from Vizards books is that the terminator box has to be 8x the volume of one cylinder 'PER SIDE' with 11 to 15 times being better. This would explain why the resonator system he designed for his friends corvette runs the length of the trans tunnel with both collectors entering and dual exhaust leaving. That box must be at least 800 cubic inches.

Attached Images

Vette exhaust.jpg (46.1 KB, 22 views)

Orr89RocZ

Thats understandable, i was just making sure. Its still doable if fabricated right

skinny z

Fabrication aside, I may just go the open header route with collector extentions (I'm looking for a copy of Pipe Max) and tune for track days.
I'll talk with my fabrication guy when the car is on the hoist. I will say that if anyone can build the system from scratch it's Tom from Altered Images. He's a drag chassis builder. His custom headers are a work of art but of course it comes with a price. (glad he owes me money!)
In the meantime, I'll be watching to see what you guys are doing.
Good luck.

Orr89RocZ

good deal i hope to order headers this week....i gotta check the funds Once thats done, i can start assembly of the motor and put it in the car to see where the headers dump and how to mod the crossmember. Eh..its not gonna be easy


I'd rather not have cutous with extensions cuz i dont like the looks of all that, but it may be the last best bet option

1989GTATransAm

OK here is the answer from David.

"1989GTA,

Each termination box needs to be 8-10 times the volume of one cylinder - for each bank. also a 2 inch tube joining the two boxes is prefered..
DV"


This really puts crimp in my plans. I will have to give it another work over.

skinny z

Fabrication aside I think it's cool that you got a response from David Vizard.
Now considering the fab work, it's not getting any easier is it? In my case that's a 700+ cubic inch enclosure. That's a 4" pipe 60" long!
I showed my builder the terminator box that Vizard built for his friends vette and building it is not a problem. Stainless or mild steel he asked? There's just no place to put it. Once my car is in the air I may think differently but it's not looking good.

1989GTATransAm

"There's just no place to put it"

Yep that looks to be the problem. I was thinking two pipes could feed into one 355 cubed resonator box for my application. That looked like it might be doable. Having two separate 355 cubed resonator boxes per David's reply is most likely going to be too much.

I agree that fabricating something is not the problem. It is the room.

Yes it was nice of David to respond and so quickly. I must have ask him just at the right time.

Orr89RocZ

yeah well that is dissappointing. I can still do it tho since i plan to run true duals anyway.

And what do you think the deal is with the crossover 2inch tube? If i already plan to run a x pipe or h pipe, why would the boxes need a cross over tube as well?

For my collector length of 18 inch, there is NO way to run a tube connecting the boxes without serious clearance issues.

I'm starting to think collectors and cutouts are the way out of this mess Atleast if i try that first, and see how much power i'm giving up running a muffled exhaust over the straight tuned headers, then i can go back and make boxes to work since i will know how much power i can expect to gain.

if its only 10hp then i may not do it since i dont feel 10hp is justifiable for my build. But if its alot of low end power and torque all over the curve, then yes i will do it.

skinny z

In case all of you haven't read this article, here's what all the fuss is about.

http://www.superchevy.com/technical/...exh/index.html

Kind of makes me think back to my college days and the 68 Chevelle I was trying to make fast. Lots of room under that car!

skinny z

With respect to running tuned length collectors with cut outs, personally I think thats the simplest way to go providing you don't mind getting to the track and spending an hour getting the car prepped. Then there's the tuning to take advantage of the open headers. I would say that there's no substitute for the open headers, you just don't have that extra hp on tap for your Sunday drive..(unless you ARE David Vizard and have tuning capabilities coming out your ***). The real benefit of the resonator box is having that power available all the time. I'm pretty sure it would be worth more than 10 hp too.

Rayzor32

yeah one 3" would definetly being choking it, a 383 needs DUAL exhaust. Dual 3" pipes would be killer, and dump before the axel and youll have even more flow.

Orr89RocZ

this would be the easiest/quickest thing for me to do at this point to see how much power over the full length muffled exhaust i will gain when switching to open headers.

if i do gain alot, then hells yeah, i'll look into refabbing the exhaust to allow a resonator box. I think it can be done, but the BEST way will MORE than likely be a 4 inch pipe but i dont understand how that piece of pipe will act the same as a box of the same volume.

I understood it to be large crossectional AREA, not volume and a 3inch to 4inch doesnt seem to me a large section of area.

However a 36 inch length of 4inch pipe, radius being 2inch, i would have a volume of exactly 452 cubic inches, which is great for my 383 for each bank. thats about 9.5 times the volume of my cylinder.

i know for a fact i can fit 4inch pipe under there and 3 ft long sections. If it will act like a resonator, then by all means i will use it.

However the only down side is the cross over balance section. i wanted a xpipe and i dont think 3ft of pipe will alow that x pipe. H pipe would be the only option but it have to be custom.

Could i install a single 2.25 or 2.5 inch pipe between the two 4inch resonators to act like the balance tube? I think it would still act like the resonator and as David Vizard has said, he prefers a 2inch pipe connecting them.

that may be a way to do this

1989GTATransAm

Hehehe. I see we are still at it. Looking at what Vizard did as shown in the picture for the Corvette in post 62 it looks like the termination boxes are long and skinney. So Jason I think your idea will still work.

As for me the only it would work is with the attached sketch I did. I would have to use 3" square tubing as shown in the sketch. I could bore a 2" hole in there somewhere. Maybe a little larger on the square tubing but not much.


Edit: One bank of cylinders would be tuned for best all around and the other bank would be tuned for best torque. Only way it will fit.

Here is the sketch.

Attached Images

GTA Termination Boxes 2.JPG (1,012.9 KB, 28 views)