Technical question about custom s50 exhaust...

[mazur]

I'm putting the motor into an E30 so I will be doing a customs exhaust setup. I'm planning on doing a single 2.5'' single pipe exhaust. This will include one cat, one 22'' Magnaflow resonator, and a Magnaflow muffler. (This is actually a setup I saw on here).

The problem is that the muffler has a 2.25'' inlet, and I'm not sure if this will hurt the performance. But I was thinking because of the smaller diameter, it might help speed up the gases entering the muffler and help it exit the system more quickly at the end of the exhaust stream, but I'm not sure if that's how it works.

Maybe someone knows of a muffler that looks similar for a reasonable cost?

I'm open to all suggestions about my planned setup. I'm hoping not to be too loud or have an annoying drone with this setup, and even more so, not raspy.


This is the muffler BTW. 3'' tips, like most e36 cat-backs.

[mazur]

I just found this chart and it seems that a single 2.5'' pipe might be too small and 3'' might be the way to go. I think most aftermarket e36 m3 exhaust systems are dual 2.25'' which has significantly more area than a single 2.5''.

Exhaust Layout Cross-Sectional Area Increase vs. Stock
2 x 45 mm 4.29 in² 0%
1 x 2.50 in 4.45 in² 4%
2 x 2.00 in 5.55 in² 29%
1 x 3.00 in 6.51 in² 52%
2 x 2.25 in 7.13 in² 66%
2 x 2.50 in 8.90 in² 107%
1 x 3.50 in 8.97 in² 109%

[matt]

I just found this chart and it seems that a single 2.5'' pipe might be too small and 3'' might be the way to go. I think most aftermarket e36 m3 exhaust systems are dual 2.25'' which has significantly more area than a single 2.5''.

Exhaust Layout Cross-Sectional Area Increase vs. Stock
2 x 45 mm 4.29 in² 0%
1 x 2.50 in 4.45 in² 4%
2 x 2.00 in 5.55 in² 29%
1 x 3.00 in 6.51 in² 52%
2 x 2.25 in 7.13 in² 66%
2 x 2.50 in 8.90 in² 107%
1 x 3.50 in 8.97 in² 109%

Single 2.5 is plenty. Your results will be better with 2.5 than with 3" pipe. Don't let it choke at the muffler, use a 2.5" muffler with seperate tips.

[Schniddy]

I have one listed in the FS section if anyone wants to save some money on one!

[e30polak]

i hope u already got on ur exhaust, but i run 3" from the header back, i have a 6-1 turbo manifold as a header for clearance, and i run a 3" high flow vibrant cat, a borla straight thru 3" race muffler(as a resonator) and a vibrant street power 3" turbo muffler, it sounds amazing on my s52, 3" is pretty loud though, anything over 5 grand and u can hear me over a lock away

[BigD]

How do you guys figure that 2.5" is plenty and 3" is too much when stock is 2x2.25"?

[matt]

Its not 2x2.25... the pipes have heat shields. It's 2x under 2 inch.

[MR 325]

Stock is roughly dual 1.75"

[Mike B.]

What's the advantage to a single pipe vs. dual? Or vice versa...

[matt]

Dual will have better sound control, better ground clearance, single is lighter.