1989GTATransAm

Ok here you go from PipeMax and this is just ballpark. With real dyno information we can dial it in pretty close.

A. 4th harmonic is 18.4". Highly recommended and best torque curve.
B. 3rd harmonic is 36.8". More bottom torque.
C. 2nd harmonic is 73.7". Longest recommended with mufflers.

Orr89RocZ

hmm highly recommended we go with the 4th harmonic.. i wonder just how much i'd be givin up if i went with the 2nd instead?

skinny z

It just has to be determined if the mufflers of choice behave in the appropriate way.
I lifter this from a Super Chevy article written by Vizard.

SOME HEAVY-DUTY QUOTES FROM ENGINE MASTERS WINNERS

John Kaase: "I used a straight-through glass pack muffler design specifically because of the high-flow they can deliver. My dyno testing left no doubt as to how important collector length was and that a straight-through glass pack contributes to that length. By getting the collector/muffler length right, which in our case was about 40 inches, the torque at 3,500 was increased substantially. That gain is probably what won the Engine Masters deal for me the first time. I have seen an incorrect length along with less than the critical minimum flow cost 40 hp. Short change efforts on the collector/secondary and it will short change you."
Joe Sherman: "If you are building a serious performance system, then assuming you have a near-optimal header set-up, the place that is most critical when it comes to avoiding power loss is from the collector back. Also, don't be fooled into thinking that big tailpipes contribute to power. In all my years of dyno testing, I never have seen that work. For me, the straight-through Magnaflows when used as part of the collector length, show only very small losses in power over an open pipe. It's all about the right length and sufficient flow. I have seen mistakes in this area cost 85 horsepower."

Do Ultra Flos perform like a glass pack? By glass pack I assume they're talking about the classic Cherry Bomb.
I'm not familiar with the chambered tubes you refer to. GMMG.

Orr89RocZ

dynomax ultraflo is basically a straight thru core muffler and is packed with fiberglass to sound deaden the exhaust

its like the race bullet but the bullets have no insulation...and is just straight thru. Powersticks/chambered tubes are straight thru but instead of just holes inside the cases, they look like a cheese grater, with flipped up pieces of metal that get in the way of the flow path to create that sound

They still flow good but not quite as good as a ultraflo or bullet


sounds like he tuned for the mid length 3rd harmonic and picked up massive torque amounts. I wonder if that hurts hp as much? Cuz i could do this easier than the 18inch length and probly gain massive torque, but i dont want too much torque lol. An 11 to 1 383 should make massive torque as is

skinny z

Remember too that the Engines Master builds are for area under the curve and not just peak horsepower. In fact many will sacrifice those big top end numbers for larger amounts of torque and more average power.

Orr89RocZ

thats what i figured... question remains does that car run faster with more average power? I'm trying to get good hp numbers but track times are abit more important to me than a dyno queen

1989GTATransAm

My vote is for more average power under the curve.

Orr89RocZ

well i hope to drop the motor in by tommorrow night so we'll see if i can get that done

if i do, i can get a much better look at how the exhaust runs down and if need be, i'll make a best torque overall exhaust just to be brutal on the street and track

skinny z

Drag racing engines tend to run in a narrow power band and the area under the curve dosen't matter quite so much because you don't use much of the curve. You tune for peak power and try to keep the engine at maximum power as much as you can with your gearing. Do you use 3000 rpm at the track? My 3000 stall and 6000 red line keep me to that. With a close ratio trans, the band can be even less. However for a more dual purpose vehicle (or anytime you run on the street) it's a different story. Seems that the smart money is on the broad range of power approach.

skinny z

Here are a couple of interesting pics. You can see how the 4" pipe could easily be modified to act as a resonator box.

Attached Images

	more exhaust.jpg (385.6 KB, 47 views)
	4%20inch%20exhaust.JPG (462.6 KB, 51 views)

Orr89RocZ

If i was to do that exhaust i'd just keep it a single 4 inch and throw out the box idea. nice looking system tho

skinny z

You would lose the tuned collector length in that case.
It seems like more trouble than it's worth however I would like to know what the possible gains could be over a more conventional design.
Still working on mine. Looks like my fabricator is putting me off for another couple weeks.

Orr89RocZ

for a single 4 inch system like that, it be harder to make a box than a dual setup or a smaller exhaust like a single 3.

but shows you can have 2 pipes from the headers go into a single LONG box. If you could make it long and wide enough you could make a single termination box joining 2 banks

skinny z

I would think that would be the plan all along. One terminator box like Vizards corvette piece.
A 4" pipe would need to be about 60" to get 800 cubic inches. Thats 8 times the cylinder volume per bank times two banks.
Not a lot of room.

Orr89RocZ

it wouldnt be a single, you'd have to make it like 7 inches wide by 3.5 inches tall to join two 2.5 or 3 inch collector pipes from the headers. Then it would have to be 32-33 inches long to achieve 800 cubic inches. If you could fab that box it would fit i'm sure if you angle it right

still cant get 18 inch total collector length if you do that tho.. you'd have to shoot for 36 inch for average power or most torque.

skinny z

The short collector lengths (18"+/-) were always going to be problematic. That's part of the reason I'll go the open header route for track days. At least for now.
If I can experiment, maybe I'll find that a 36" collector will perform just fine. A terminator box can be built to suit at that point. I'd really like to be able to drive to the track and not have to do much more than put on the slicks instead of uncorking the pipes and tuning the fuel curve. Having the open header power available all the time ( with the terminator ) would also be sweet.

Orr89RocZ

Ok now that the motor has been in the car for a few week, i need to get this exhaust done so i can start using the car

I have no idea what i'm gonna run. I'd love to keep this exhaust science stuff going but i'm having a hard time figuring out what I will beable to do with this car

I got s-extensions for my headers and they will not work to get around the frame or crossmember so i will have to cut and custom fab up a piece to get around the Spohn member. Shouldnt be too bad i would think but we'll see

After that i'm looking to make a quick setup where its dumped before the axle. Cant decide on mufflers, but i'm leaning towards dynatech split flows. I was thinking dynomax ultraflo rounds but at 6inch diameter thats losing clearance. I dont want the car to be super loud but i dont wanna lose power The Split Flows will be loud but flow awesome and give me some good power numbers. Pretty expensive tho

The other option is magnaflo 4x9 x 14inch long case mufflers. They flow good and are alot quieter but still pretty loud

I also dont know whether i want x pipe or H pipe

i got to check to see how much room i have under the car. I will have a good idea what i can do with this system now that the headers and motor are in place. Motor is 95% done, awaiting exhaust and oil/coolant/priming tool

Orr89RocZ

well its not looking good at all

there is simply NO room under this car to do anything worth driving on except maybe a single 4inch system. I dont know how others have done true duals. My car sits too damn low. my car underneath seems to be different than most. I just dont see how other systems on other cars will work with mine

I will not beable to do a terminator box at any length. So this sucks. I may be able to do a cutout but even thats pushing it room wise under this car....AT 18-19 inches it would sit just in front of the trans pan, and i need a custom bend just to get around the crossmember/trans pan so i'm not sure i can fit a cutout there.

I could still do true dual 3inch running down the stock location but its gotta be perfect and staggered to work. Mufflers will HAVE to be located behind the axle which i did NOT want to do. Driveshaft loop on the spohn crossmember will 90% more than likely need cut off. Possible relocation but i doubt it. Maybe a rear mount one? idk, i got to do something to be legal. i'll have to custom mount one. But nonetheless, the drivers side i believe has to move back over to the passenger side. Else it will sit pretty low and run right against the fuel lines and i dont want the exhaust heating those lines.

magnaflow x pipe will be necessary and both tubes will have to run down stock location. In order to go over the axle, i think the one pipe will have to run over to the drivers side again underneath the torque arm. Should be enough room i think but its hard to say

Now the problem arises with the mufflers i wanted to run, the car will now have LONG collectors and suck on the top end.... its well over 90 inches of pipe and probly closer to 110-120. this is horrible.

I'll have to think about this longer and really get the car in the air and plan this out. I only jacked up the front end and played around for alittle while with some spare 3inch pipe. Just isnt looking good at all

Single 4inch would be the best way out at this point i think

1989GTATransAm

I think a single 4" pipe will do you quite well with your combination. I'm running a single Mufflex 3.5" on my car. After my results I have decided the exhaust is good enough. With your long tubes it should be even better.

So run 3" after the headers into a 3"x4" wye and then run the 4" in the stock locations. I don't think this will hurt you at all if done correctly.

Orr89RocZ

i'm kinda torn right now..i really wanted duals for the sound but i was hoping i could get away from running in the stock location. But its cheaper to do the single 4 inch so I believe i'm gonna go that route

Plus seeing your results gives me hope i'm not losing much and will make the power i planned. But then again if you ran cutouts at proper length, how much will you gain?

now heres the thing. i'll run a single 4 inch I pipe over the axle and split it like i did before. so thats 3inch tubes into a long single 4 and back out to 3". So in effect will that long 4inch somewhat act like a resonator? i'm estimating the length would be closer to 70 inches, making volume of about 880 cubic inches. Single box about 8 times 1 cylinder then times 2 for both banks would be 766 inches SO would it act like a box?

skinny z

Do you have the flow capacity of any of the mufflers you're considering?

Orr89RocZ

i dont know yet on that... but i'll tell you the 3 i'm considering at the moment

Borla XR1 in a 4 inch
Dynatech split flow in a 4inch if they make it i havent checked

Dynomax Ultraflo welded round, 4inch inlet 6 inch body


thats what i'm thinking. i need 1100 cfm of flow at least. More on the spray. Each of these should flow around 1100 i would think. they are all straight thru and being 4 inch they should flow near 1400 like 4inch straight pipe does

skinny z

What were you results?
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Orr89RocZ

else i can do this

split it over the axle again as i do plan to do inorder to have dual exits again then run a muffler on each of the 3 inch legs like a GMMG or something

should easily cover the flow i need then. i would consider magnaflow 4x9's then


dynatech split flow is just like the borla but cheaper. ultra flow i've seen advertised at 1000 cfm for a 3inch version i think

skinny z

If you pay attention to the entry and exit details I don't see why it shouldn't. It's just difficult to bring two 3" pipes into one 4" and accomplish that. One 3" into a 4" looks more feasible although that means dual pipes from front to back including over the axle.
You could then run a pair of mufflers at the back either in the stock location or where the tail pipes usually are.
Think there's room for parallel 4" pipes?