360 la headers & straight pipe
To get loud, you need;
high cylinder pressure together with
an early-opening exhaust valve;
or a really really short, small-diameter exhaust pipe.
Guys, to clarify;
I did not say to put a small-diameter full length pipe on a HotRod! that's just totally wrong.
What I said was, and I quote;
"or a really really short, small-diameter exhaust pipe" I mean, I even emphasized the "really" part.
You know, like a Zoomie or an open-header without anything behind it; or you know, like a roto-tiller, lol.
The earlier you open the exhaust valve, the more energy will be in the exhaust, and the louder it will be; and,
the bigger the TAILPIPE is, specifically the last couple of feet, the more it will act like a trumpet. I mean,
I thought we all knew that.
I'm sorry if my post got too complicated, lol, but it looks like at least three guys, maybe 3.5, were able to figure it out.
To further clarify, Notice, I said
"to get loud you need;
high cylinder pressure together with
an early opening exhaust valve."
I wrote that in a way that I thought would force the reader to figure out the "together with", part.
In other words; Neither the high cylinder pressure, NOR the early opening exhaust valve, by themselves, will create the Loud part. You need BOTH.
The more cylinder pressure your engine is able to make while cranking, the higher that pressure will be multiplied to,
by the heat of combustion, under load.
The theoretical maximum expansion ratio, of gasoline, inside the cylinder, without detonation, might be around 9 or 10 to one. Lets use 9/1; but it will depend heavily on the efficiency of the engine.
Lets say your 7.8Scr 360 is at 60%, and it makes 120psi cranking. That would math out to;
120 x 9 x 60%=648psi
let's say your Eoa (Exhaust opening angle) of 116*, sucks so much energy out of that, that it leaves the chamber at I'm guessing, 188psi, and by the time it hits atmosphere out the back, the exhaust system has cooled that right down, and so there is very little heat left in it.
Now lets wind that cranking cylinder pressure up to 190 psi, and lets set the Eoa to 102*, and thus figure the engine efficiency at 80%
Now the numbers look like;
190 x 9 x .80= 1368psi, . So then, imagine the cylinder pressure is down to 400 psi just before it exits the cylinder, and then, it exits the 3" pipes pretty darn hot!
Heat is energy, so, it's gonna be a lot louder.
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All psi number are made up on the spot, and are for effect. I may have exaggerated but you get the idea. The thing to remember is that exhaust heat, is energy, and the driving force behind the level of loudness.
And that is why I have 3" duals all the way. Which is to provide more radiating area, to suck more heat out of the gasses as they are on the way to the back bumper, which was a move for to have less remaining energy in the exhaust around town, and therefore less obnoxious noise. Plus, you know, I ordered those pipes with turn-downs, which slams thos hi-frequency soundwaves into the gravel
From 2.25 to 3 is plus 33% radiating area. On 16ft of exhaust, that adds up.
Happy HotRodding.
