2" to 3" exhaust... Worth it?

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rumblefish360 said:
The best way to get the most torque is with the same size exhaust pipe as the collector for a certain amount of inches, which varies. Engine masters did a thing in that. I don’t want to blanket statement “Use an 18” length of pipe…” At the pipes end, you need a pressure cancellation box or at least as many square inches as the engine is. Then continue with the exhaust pipe into the muffler.
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From David Vizard's "How to Build Horsepower", cross-plane V8s (like we deal with) are much more sensitive to secondary tuning length than primary. According to the book even adding just 12" to the collector length gave a boost of 40 ft-lbs and 12 hp on a ~370 hp engine. David says, "On occasion I have built V-8 exhaust systems for street use with a secondary as long as 60 inches. This proved to be capable of boosting low-speed (2,000 to 3,000 rpm) torque as much as 20 ft-lbs over a more usual 20- to 30-inch collector."

Makes sense you see that "equal-length headers" are much more commonly available for 4- and 6-cylinder engines since primary tuning has more of an effect on those configurations than secondary tuning. Equal-length primaries on a V-8 don't really do anything, it's everything downstream of where the primaries merge that matters.
 
I have the book as you can tell plus the engine masters episode backing it up. The overall length will have an effect. How long is the correct length? IDK! To many variables. But what the engine masters show did was the Diminishing returns. A continuation of pipe may have hurt and then Adding some more could have brought it back up. Since the pressure wave can be mathematically figured out, bust out the pencil and paper!!!
 
rumblefish360 said:
I have the book as you can tell plus the engine masters episode backing it up. The overall length will have an effect. How long is the correct length? IDK! To many variables. But what the engine masters show did was the Diminishing returns. A continuation of pipe may have hurt and then Adding some more could have brought it back up. Since the pressure wave can be mathematically figured out, bust out the pencil and paper!!!
Click to expand...

The kinds of things where, yeah it'll run good if you don't bother with the details, but getting the details right will give "free" benefits if you do your homework.
 
rumblefish360 said:
The best way to get the most torque is with the same size exhaust pipe as the collector for a certain amount of inches, which varies. Engine masters did a thing in that. I don’t want to blanket statement “Use an 18” length of pipe…” At the pipes end, you need a pressure cancellation box or at least as many square inches as the engine is. Then continue with the exhaust pipe into the muffler.
Click to expand...
Pressure cancellation box ?? Pls educate me
 
rumblefish360 said:
I have the book as you can tell plus the engine masters episode backing it up. The overall length will have an effect. How long is the correct length? IDK! To many variables. But what the engine masters show did was the Diminishing returns. A continuation of pipe may have hurt and then Adding some more could have brought it back up. Since the pressure wave can be mathematically figured out, bust out the pencil and paper!!!
Click to expand...
Old racers trick, add a 2 foot Section of pipe to the collector, make a heavy grease pencil mark the entire length of the pipe, cut it where the mark changes color
 
Brooks James said:
Pressure cancellation box ?? Pls educate me
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Sure, continue with it after the below post, adding in…

Brooks James said:
Old racers trick, add a 2 foot Section of pipe to the collector, make a heavy grease pencil mark the entire length of the pipe, cut it where the mark changes color
Click to expand...
This old racers trick is often misused and done wrong or at the very least, not resulting in the findings vs a dyno result. When adding on a straight pipe the same size as the collector, your effectively making a longer collector. This move adds low end torque. If you use this added power, at the starting line launch, it’s an edge off the line.

Tye best way to know for sure is through dyno testing. The amount of added collector pipe will be a certain length. This length is variable where only a dyno test will show exactly or via testing and measuring the guessed lengths show over trial and error over time the best results at the track. This is where the exhaust ends for max power. It may be OK at the track to run no mufflers, it may not be. If it is not OK to run open headers as is the case with most street cars, how do you keep that added power and quite down the exhaust?

Where the added collector pipe ends, form a box shaped like a Hersey chocolate Kiss to attach at the end of the collector pipe. This is where the exhaust pulse effectively ends and send the negitive pressure wave back up the exhaust pipe and header tubes for the next induction cycle.

On the small end or exit end of the cancellation box, continue with your exhaust pipe into your muffler system. As long as the muffler has a flow rate capacity of 2.2 cfm per HP as taught by David Vizard, you’ll have an effective no loss (or really close to a zero loss) exhaust system. So choose your muffler(s) wisely.

This is the book you should read (IMO)
Proceed to chapter 13, then 14.

331C40F3-B550-4E05-ADF5-61919F77FEF4.jpeg
 
Last edited:
rumblefish360 said:
Sure, continue with it after the below post, adding in…


This old racers trick is often misused and done wrong or at the very least, not resulting in the findings vs a dyno result. When adding on a straight pipe the same size as the collector, your effectively making a longer collector. This move adds low end torque. If you use this added power, at the starting line launch, it’s an edge off the line.

Tye best way to know for sure is through dyno testing. The amount of added collector pipe will be a certain length. This length is variable where only a dyno test will show exactly or via testing and measuring the guessed lengths show over trial and error over time the best results at the track. This is where the exhaust ends for max power. It may be OK at the track to run no mufflers, it may not be. If it is not OK to run open headers as is the case with most street cars, how do you keep that added power and quite down the exhaust?

Where the added collector pipe ends, form a box shaped like a Hersey chocolate Kiss to attach at the end of the collector pipe. This is where the exhaust pulse effectively ends and send the negitive pressure wave back up the exhaust pipe and header tubes for the next induction cycle.

On the small end or exit end of the cancellation box, continue with your exhaust pipe into your muffler system. As long as the muffler has a flow rate capacity of 2.2 cfm per HP as taught by David Vizard, you’ll have an effective no loss (or really close to a zero loss) exhaust system. So choose your muffler(s) wisely.

This is the book you should read (IMO)
Proceed to chapter 13, then 14.

View attachment 1715845529
Click to expand...
It Sound like you are describing Car Chemistry collector inserts
 
No thanks! I don’t know enough about them to comment. I just didn’t like what I saw. I could be proved wrong about them. They would have to be a plus in every situation. Or at least in the one there designed and intended for. I have not seen this as the case in multiple ways. Have they been used correctly by the car/engine owner, builder, tester? Things I don’t know and that would be a lot!
 
70aarcuda said:
Engine Master Season 6 Ep 83 they do a test between crunch bent tubing and mandrel bent tubing ,,,,,,with and with out mufflers....

how the tubing was bent made no difference on a 500 hp engine......and Dynomax Turbo Muffler made as much power as the straight thru muffler

you can get Motortrend for 3 dollars a month.....join now before the price goes up....LOL
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We get MT and the wife and I DVR the Engine Masters. Roadkill, Road Kill Garage.
The fact that the crush dis as good at that power level. And the single 3 inch was as good as duels in a smaller size was a surprise.
His screaming slant six with the blower was also great.
 
Brookes, David spoke about the use of large empty box or a center in, center out flowmaster type of box right at the end of the headers to enable the exhaust gas/pulses to rapidly expand into it and drop the pressure, sort of like it does at the end of the tailpipes.

I think this is sort of simplistic way to describe what he meant by a " large pressure cancellation box".
 
Ott, thank you so much for sharing this video. David found so many things early on and I remember his MINI book very well. We were fortunate that much of our testing matched his. Cyclone Sonic Turbos were great mufflers and some of the other stuff he says on this matches what we found regarding muffler flow and sound control.
I feel honored that I got to talk with him and confer back then. It was cool to verify that what we were seeing was accurate in regards to what he was learning in similar tests but with different engines.
 
Those were my first mufflers ever. Loved them. Awesome sound on my ‘Cuda. It was very disappointing years later when I tried to find another set and could not.
 
I had a set from testing too and they were very good mufflers and so much like the Dynomax Super Turbos with a slight bit less flow and a slight bit more sound. I'l have to look up my data to verify this but it is what I recall.
 
Funny you mention my second muffler ever.. LOL!
For a turbo muffler, the Dynomax is top shelf. I favor this muffler for my go any and everywhere drivers.
 
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