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  #21  
Old 11-01-2011, 01:05 PM
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Quote:
Originally Posted by JaysinSpaceman View Post
Looking at other information about terminator boxes the blue car above doesn't fit the bill, it just uses a fancy H pipe fabricated out of sheet metal.

E- that is some really interesting reading that you have there and it prompted me to do some further research where I found an enormous amount of information. Seems like there would be some fun experiments there for a person with a dyno.

Cool stuff, thanx
Jaysin
I was lucky to spend a decade in and around an extremely well set up engine development facility. We pushed the limits and I had a blast. We tested all kinds of products and theorems and learned a bunch along the way.
Now if I could just figure out how to build such a facility I could easily spend the rest of my life continuing to learn.
Oh well, I doubt I ever do, so I'll just continue to be an old desert rat muttering on the internet
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  #22  
Old 11-02-2011, 07:06 PM
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as to the flowz....

my old 9.25:1 355 ci bracket car dropped 2/10s in the 1/8 mile when changing from 2.25" dual "turbo" mufflers to 2.5" 40 series flowz, hooker 1.625 primarie long tube headers, no crossover pipe,just my observation.
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  #23  
Old 11-02-2011, 07:41 PM
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Originally Posted by CarterKraft View Post
as to the flowz....

my old 9.25:1 355 ci bracket car dropped 2/10s in the 1/8 mile when changing from 2.25" dual "turbo" mufflers to 2.5" 40 series flowz, hooker 1.625 primarie long tube headers, no crossover pipe,just my observation.
That's good!
Did you try any other configurations?
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  #24  
Old 11-03-2011, 12:28 PM
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E- what muffler Do you like? I am fond of magnaflow and borla and hear them to be some of the best sounding..

thanks for learnin us on termination boxes, I think I'm going to try my and at it on my VW rabbit track car. very cool stuff!
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  #25  
Old 11-03-2011, 01:22 PM
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Originally Posted by Sarcastro View Post
E- what muffler Do you like? I am fond of magnaflow and borla and hear them to be some of the best sounding..

thanks for learnin us on termination boxes, I think I'm going to try my and at it on my VW rabbit track car. very cool stuff!
My first choice is what fits in the place I have to work with and flows the most CFM and sounds right... Termination Boxes are just not going to fit in some (many) chassis.
I have been using Dynomax for years because they hold up, don't break the bank and are rated CFM by Dynomax. I will use a Flow on occasion and I do like the Borla line. Magnaflow is a good brand but I have no idea how they flow. If there is one I flat out will NOT use it is Supertrap, unless I need a spark arrester. Basically I most often use what the Customer dictates and try to factor it into building the best compromise possible.

We once ran a straight through Borla and a Flow on the Dyno. The Borla was something like 30DB louder and swapping in the Flow made a few more HP. Just for drill I swapped back and shortened the Borla system and gained 20HP over the Flow, I tried everything to get the Flow to equal the peak power but somethings just don't happen. Most of the BBFord racers I know do not use Flowz because they drop power compared to say the Borlas.

On my 429 I'm running a set of less then optimal Block-Huggers (Sanderson) into 3" duals (mandrel) no balance tube, and I ran them into Dynomax Race Bullets, that was cool it gave off a concussive sound wave, it literally rattled windows and wasn't that loud(legal), but I got tired of setting off car alarms as I drove around. So I went to the Dynomax 3" Super turbos, the big round ones.
I had to lengthen the pipes a bit and I had to readjust the idle due to the increased restriction, the Bullets are straight through. When I started out about the best you could get easily were the so called "Turbo Mufflers" They sucked but sounded good, until they fell apart. I always used 3" ones no matter what the size of the system.

In the off road world I have come to realize that building quiet is the number one design criteria, unless you are racing closed course. It is just not good for our image to be loud!!!!! If I could figure out how to be nearly silent and still make power I would, but realistically 500BHP comes with noise, so I aim to be as silent as possible, plus it is easier to sneak away when necessary
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  #26  
Old 05-09-2013, 06:26 PM
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I'm starting to rethink my exhaust system and was happy to find this old thread. I really appreciate all the great points made by entropy - thanks as always for the great contributions.

I found another great article from David Vizard on this subject with some rules of thumb that could help with exhaust design:
http://www.popularhotrodding.com/eng...re/0505em_exh/

I am at a point in my build where I want to think about this more seriously, so here's where I'm at.

Texas Speed did a chassis dyno on a very similar engine combination to mine (same cam, same heads, same intake, slightly higher compression 10.4 vs 10.25, slightly larger bore 4.065 vs 4.030, different headers of the same primary size, catted exhaust vs my yet unplanned). Their results were 450rwhp with a torque peak somewhere around 5,000rpm (though it's very broad with this VVT cam). If I assume 20% loss through the auto drivetrain, that puts their engine at about 562.5hp at the crank. I am about 3% smaller on displacement due to the slightly different bore, so I'll take a guess that my combo is worth about 540hp with a torque peak around 5,000rpm for planning purposes.

First off header primary diameter. The heads I'm using are stock L92s. Testing I've found indicates about 190cfm at my peak lift. Per Vizard's charts in the article above, the primaryr ID should be between 1-5/8 for a steet header and 1-3/4 for a race application. I selected headers based on fitment and price and they are 1-3/4" OD. At 16gauge, the ID should be about 1-5/8" which puts these in the range for street. I can see why 1-7/8 headers are sought by people modifying their LSx, but this is what was available off the shelf for my application so this is what I am using.

Now primary length and equalness - I get no say in that other than having long tube headers, I pretty much got what I got with the headers I chose. Vizard gives no guidance in the article on what length is right, but he does suggest equalness isn't all that important, which I am happy to hear as the headers I've got make almost no attempt at equal length. Here's what they look like: http://www.jegs.com/images/photos/700/776/776-d3337.jpg

Collector diameter: again the headers are what they are (3" collector), but Vizard gives a rule of thumb of 1.75 times the primary diameter. For my diameter of 1-3/4" that comes out to 3.0625in. Looks like my headers fit the rule of thumb, so that's a good indicator.

Collector/secondary length: finally something I have control over. Here is what Vizard says about length:

Quote:
If you want to bump up torque at the point a stock converter starts to hook up the engine, you may want a secondary as long as 50 inches but something between about 10 and 24 is more normal. The shorter of these two lengths would be appropriate for an engine peaking at about 8,500 rpm whereas the longer length would be best for an engine that peaked at about 4,800-5,000 rpm.
My torque peak should be in the neighborhood of 5,000rpm, so that would indicate a 24"ish secondary length makes sense.. This tells me I need to "terminate" the system somewhere around 24" from the collector, which i think is measured at the mid-length of the cone-down area where the primaries end and the true 3" diameter starts. I'll have to get under the car and see what's in that area, but I doubt I'll have much room. I'd like to try designing some kind of terminator box to fit the space. This will ensure pressure waves are reflected from the 24" point which should optimize the power output.

Finally secondary pipe sizing. Vizard is nice to include some rules of thumb about pipe sizing and muffler flow. Above a certain point, all you're trying to do is prevent significant power loss. In the article he explains this occurs around 2.2cfm/hp. For a 540hp application, that means I need pipe and mufflers capable of flowing about 1188cfm. He also provides the rule of thumb that a pipe will flow about the 115cfm/in^2. Assuming dual exhaust, 1188cfm would need about 2.564in diameter pipe to meet this goal. I am just shy of that now at 2.5in, so I will need to consider if I want to up sizing to the next available size - probably not. Furthermore I need to find data on the mufflers I have to see if they flow around 600cfm each - somehow I doubt it, so changes may be forthcoming.

At any rate, I just wanted to get my thought process down and see if anyone had thoughts or ideas for the terminator box and the general thinking behind my exhaust. I'd also love some ideas on how to build a terminator box to fit in the space under my Nova.
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  #27  
Old 05-09-2013, 06:38 PM
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Funny I was looking for CFM data on my Flowmaster mufflers and this is what they have in their FAQs on the website:

Quote:
How do Flowmaster mufflers rate on a flowbench (CFM)?
Many muffler manufacturers advertise, test and rate the performance of their mufflers with me use of a flowbench. The problem with this methodology is that a flowbench produces a steady, low temperature stream of air and lacks the acoustical and thermal dynamics that are produced by an internal combustion engine. Flowmaster designs, tests and proves its products under real world conditions in the dyno cell, at the track and on the road. After all, when was the last time you raced a flowbench?
I guess I need to take my car to Flowmaster so they can design, test and prove their products on my car.
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  #28  
Old 05-10-2013, 10:38 AM
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Here is an interesting example on a '69 Camaro: http://www.yellowbullet.com/forum/sh...d.php?t=323835







Unfortunately he doesn't go into results in that thread.
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  #29  
Old 05-13-2013, 01:18 PM
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Interesting stuff. I'm glad to see this thread dragged back to the top again.

FWIW, Vizard's chart is the ID of the pipes, not the OD. So if your 1-3/4" primaries are 16 gauge tubing, they're closer to 1-5/8" ID.

It is interesting to read his take on whether or not to make the primaries equal length. Other sources (like Headers by Ed) claim this is absolutely critical.

I'm about to buy a copy of PipeMax for when I build the headers for my next project. It requires a bunch of info about your application and computes the various harmonics in the system, giving best and worst lengths for primaries and secondaries. For $40, I think it's probably hard to go wrong.
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  #30  
Old 05-13-2013, 01:30 PM
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Quote:
Originally Posted by entropy View Post
Back when Mr. F started Flowmaster they were being attached to the end of a racing exhaust system that presumably was close in its configuration to being optimal; so bolting a suitcase to the end of it really had little effect because the volume in the muffler mimicked the open collector! Under 100Db, little loss: Now that is a win!
Hey E,

You figure that's true for their collector mufflers? I have a set of these:

http://www.flowmastermufflers.com/?p...rtno=7350300-6

That I was considering running on my sprint car when it finally gets finished. The track we're going to run has a 100 dB limit. The only real downside to running them in the damned things are HEAVY. But it's as low as you can get on the car.
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  #31  
Old 05-13-2013, 01:50 PM
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Thanks for pointing out my error on the pipe ID vs OD. I am still not clear whether the estimate of 115cfm/in^2 is based on pipe ID or OD. ID would make the most sense, but in the article he calculates for a 2.5in pipe and it would appear he used OD & 115cfm to get 560cfm for that size.

I thought about getting PipeMax, though I'm not sure what theory it's based on - I just haven't read up on it. I'm not sure where you see it for $40 - the site I found lists it at $75.
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  #32  
Old 05-13-2013, 03:07 PM
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Hmmm....the price went up or I had it wrong to start with. The website says $75, though.

From what I've seen on the SpeedTalk forum, it's pretty good.
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  #33  
Old 05-13-2013, 03:53 PM
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This is timely, as I've been deciding on my exhaust system. From several of the links, it seems you want a volume for the termination box of 8 times the vol of one of the engine cylinders. The shape doesn't seem to be important, so for my 2.3 liter engine, I calculated a volume of 645 cu in, which works out to a tube with 5" diameter and 33" long. If so, I could fit that in my driveshaft tunnel without too much trouble. For those of us with little pip-squeak 4-bangers, we need all the power we can get!

Has anyone actually tried this?
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  #34  
Old 05-13-2013, 04:09 PM
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Quote:
Originally Posted by Graham08 View Post
Hey E,

You figure that's true for their collector mufflers? I have a set of these:

http://www.flowmastermufflers.com/?p...rtno=7350300-6

That I was considering running on my sprint car when it finally gets finished. The track we're going to run has a 100 dB limit. The only real downside to running them in the damned things are HEAVY. But it's as low as you can get on the car.
Could be depending on the volume of the muffler and the location With few exceptions putting the change in volume within say 36" and the collector flange is a power loser; there are always exceptions.

E
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Old 05-13-2013, 04:28 PM
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Remember; be it FEA, CFD or any other software there is no substitution for reality! The only way to get exhaust "right" is to test it, preferably on the Dyno, but lap times will work.

The problem with exhaust system design is there are so many foolish theory's based on . . . vapor; it can be hard to get real data. I have yet to see a program that actually gets it correct in the real world. Close, I have seen but not correct. When considering software the quality and quantity of the data required to be input is a good indicator of the level of output.
Small quantity and simple data yields garbage generally, might get you in the ballpark but won't get you onto the field.

Not saying that Pipe Max is or is not junk!
Just saying
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  #36  
Old 05-13-2013, 04:30 PM
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Could be depending on the volume of the muffler and the location With few exceptions putting the change in volume within say 36" and the collector flange is a power loser; there are always exceptions.

E
I would be right on the edge of that...28-30" primaries + collector. I may give them a shot, especially if the car comes out light.
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Old 05-13-2013, 04:49 PM
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I would be right on the edge of that...28-30" primaries + collector. I may give them a shot, especially if the car comes out light.
OOP's. I'm speaking about the distance after the primary tube merge point or the beginning of the collector, not from the back side of the valve.
E
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  #38  
Old 05-19-2013, 12:35 AM
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Here is another version similar to the one above. This person mentioned some bad oil canning vibration that he resolved by welding in some rods to connect the top and bottom.

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Old 05-21-2013, 10:49 AM
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Looking at the various boxes in this thread; any box is going to disrupt flow and in reviewing some of these boxes they are going to flat 'confuse' flow; most of them appear to be incorrectly sized to be TermBoxes: Disrupted flow and wrong volume, I question the efficacy... BUT I may also be missing the real point out of ignorance on my part.

E
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Old 05-21-2013, 11:00 AM
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Are you talking about the last two that I posted? The thing I don't like about either of them is they really look like an H-pipe that's been added onto to create a volume. The transition is not abrupt from collector to terminator box. If the goal is to reflect the pressure pulse at the transition and attenuate harmonics within the box, it seems the transition should ideally replicate an open ended pipe. On these some portion of the pipe entering the box continues on out of the box, so I don't see a strong reflection point from the collector and I suspect the flow would remain attached to the wall. I'm not sure if that's a bad thing or not. Perhaps it would weaken the reflection, but spread it out over a very slightly wider RPM band.

I really have no idea what I'm talking about (as usual)
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