Performance header design-Am I doing it right???

[TheDullCarbide]

Paint it white with the cheapest spray paint you can find and it will burn the functional part of the pipe clean and you can cut off the rest. We used to paint header collector extensions on the drag car white and after a couple of passes you knew how long they needed to be.

This will only work with an open pipe. If it has a muffler you are peeing in a funnel.....

Doug

This is awesome information. But the muffler was going to be my next question. I was going to make a short cherry bomb muffler. Is there a way to work with the muffler or is it out of the question?

 

[FOMOGO]

This is awesome information. But the muffler was going to be my next question. I was going to make a short cherry bomb muffler. Is there a way to work with the muffler or is it out of the question?

Tune the header. Wax or paint. Get it right then add the muffler.

 

[TheDullCarbide]

Tune the header. Wax or paint. Get it right then add the muffler.

Should the muffler be added to the burnt or un-burnt section of the header?

 

[FOMOGO]

Should the muffler be added to the burnt or un-burnt section of the header?

Cut off the unburnt and add the muffler. It really wont make much difference on length when you add the muffler. Its a restriction that totally negates the tuning of the header....

Never tried tuning a pipe with a muffler but it might work if you left it long with the muffler and see how far it burns off the paint/wax. Probably will burn it right up too the muffler regardless of length.

Doug

 

[TheDullCarbide]

Cut off the unburnt and add the muffler. It really wont make much difference on length when you add the muffler. Its a restriction that totally negates the tuning of the header....

Never tried tuning a pipe with a muffler but it might work if you left it long with the muffler and see how far it burns off the paint/wax. Probably will burn it right up too the muffler regardless of length.

Doug

Thanks Doug, that answers all my questions (for this thread anyway). More stupid questions to come.

 

[minibikin']

^another great method. We used the wax because sometimes the pieces were purchased coated and we just cut them to length.


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[bob58o]

Calculation for Pipe Diameter....

Pipe Cross Sectional Area = (Displacement x RPM) / 88,200

1" Pipe with 0.065 wall thickness has ID of 0.87"
CSA of that pipe is 3.14 x r^2
r= 0.87"/2
r =0.435"
CSA= 3.14 x 0.435" x 0.435"
CSA = 0.59 sq inches

Displacement of 212cc = 12.94 cubic inches

CSA = (Displacement x RPM) / 88,200

For a 1" (0.065 wall) pipe...

0.59 = (12.94 x RPM) / 88,200
52,432 = (12. 94 x RPM)
RPM = 54,432 / 12.94
RPM = 4,052

So a 1" Pipe with 0.065" wall thickness is tuned for 4,052 RPM.
A predator with basic modifications might make peak torque at 2300 RPM and peak HP at 4700 RPM.

Using this formula to calculate the CSA of a pipe tuned for peak torque at 2300 RPM gives 0.34 sq inches.

0.34 = 3.14 x r^2
r^2 = 0.108
r= 0.33"
ID = 0.66"

So a pipe with Inner Diameter of 0.66" is tuned for RPMs around peak tourqe (2300 RPMs)
7/8" 0.109" wall thickness (found it online)


For 3900 RPM I'd use 1" 0.065" wall tubing.

All just theoretical of course. I don't have a dyno to test on, nor do I have multiple pipes to experiment with.

Without getting into wave tuning and Exhaust valve opening, shorter pipes fatten the HP curve post peak HP and longer pipes fatten the curve pre peak HP. But it is all just called exhaust "THEORY" right?

Also limited by what is tubing is available. 1" Pipe is good because it it will fall between peak torque and peak HP on most engines. For an engine governed to 3600 RPM I might use 1" 0.083" wall thick pipe.