Hy Alll,


I'm rethinking my FD exhaust. Currently I have a 70mm HKS downpipe, stock cat and 70mm rear muffler (custom home made). The tone is really low, only wat WOT the tone goes up quite a bit, but never is there any pressure build up in the cockpit and at cruising speeds (60-80mph the is allmost no noise so you can talk without yelling.

Now 'm considering to redo the setup, keeping the 70mm downpipe and then replacing the main cat with a main muffler (70mm in to 2X60m out) continuing the dual tubing upto the rar muffler, also to be replaced with a dual 60mm in and out muffler.

My aim is to have better flowing exhaust, with a better/deeper tone than stock but no screaming thing like the JAp stuff.

How does a dual 60mm setup compare to single 70mm system when it comes to flow? can you say it's then 120mm in total or is there another equivalent for that?

I know there are easier solutions but I have access to good parts at low cost.


Thanx

 

The flow through the 70mm downpipe will be the restriction, assuming it is the smallest diameter in the exhaust. This means that even assuming 120mm total diameter through the rest of the exhaust, you'll never be able to "out-flow" the downpipe.

Also, using two 60mm pipes will not be an equivalent of 120mm, but I can't seem to find a good relationship.

 

The downpipe will stay on for the time being. i might reconsider when I go single.. someday.

Goal is to open up the exhaust without waking up the whole neighbourhood when I get home. Also to aintain my sleeper status.

I just don't like the loud Jap exhausts and want a low and deep tone throughout most of the rev range.

Can i assume the dual 60mm does not equate to 120mm but in any case more than the single 70mm?

 

anyone?Or are you all out for the 'load as hell exhausts'?

 

pie*r^2=area

2x60mm pipes = 5655mm^2
1x120mm pipe = 11310mm^2

It happens to be twice the area, kinda strange...

 

i have had a few different setups over the yrs. i have found what i think to be perfect compromise between performance and sound. i am running 3inch dp, pettit 3 inch resonated mp, and racing beat dual tip.

 

What is the best way to reduce noise in and FD, overall noise not just exhaust

 

Thanks, but the compariosn would then be

2x60mm pipes = 5655mm^2

vs

1X70mm pipes=?

 

rx7store midpipe

 

just use a chambered muffler

 

How did you figure this out...

(Two 60mm pipes = 30 * 30 * Pi * 2 = 5655mm^2)

And then fail at this one?

(One 70mm pipe = 35 * 35 * Pi = 3848mm^2)


I think calculating the area of a circle should be on the driver's test.

-Max

 

lol@maxcooper

I was pretty sure that 2x60 would be bigger than 1x70.

I always thought that if you use 2 pipes it's roughly (roughly!) the same size as 1 pipe that's 2/3 the size of their combined size.
so say 2x60mm = roughly 1x80mm.

2x60 = 5655mm^2
1x80 = 5030?mm^2 so close but not quite right

at any rate
it will outflow 70mm!

 

Hey MAx, I just copied it from the post above *blush*

I'm everything but a math wiz :-D.

I know it will be quite some work but. I might do this. I expect a dual runner system to be lower sounding than a single and have a higher flow rate.

 

I've got the Racing Beat and can't find any fault with it's sound or flow, it's got a nice tone not loud at idle ,quite comfortable at speed and wkes up under WOT, not to mention it has a stock appearence. The Apexi N-1 duals have gone the way your thinking but don't split till after the mid pipe and are very loud and annoying. Having a mid muffler may help but it's going to reduce flow and if you use a high flow muffler then you won't knock out much noise.

 

the N1 duals have a larger inner diameter. Probably that's why they fail to reduce the sound. I'm in Europe so ordering Jap or US parts implicates import taxes and waiting times. My current exhaust is also home made (neighbour is a very good welder and has all tools).

I'll post some pix when I get around with this. First need to set up my car lift