2FoetySx wrote:Matina210 wrote:
<groan>
I am an engineer...
Then engineer an exhaust lol ^^
lol The last time I did that, I had a little bit of difficulty getting the muffler shop to build what I wanted. This time was worse, even though the local muffler shop had an example of an N1-style exhaust. My S13 had an HKS Hi-Power cat-back on it (installed 2 or 3 owners ago). It turned out to have about a 60mm pipe. As bad as the torque felt, I could have sworn it was the 85mm version for a turbo motor.
Hitman, the following info may help your customers decide what they want, as I’m using MagnaFlow mufflers like you.
For my new exhaust, I have two MagnaFlow mufflers in series. There’s a 2.5” (63mm) pipe for coming out of the catalyst housing, a 22” long “resonator” (cylindrical muffler) with a 2.5” core. The resonator is followed by a 2.25” pipe and a 2.25” muffler at the exit. The muffler shop tried to follow the routing of the N1 exhaust.
(parts + labor cost about $431. Kudos to Top Gun Muffler of Fort Walton Beach)
The exhaust sound now has more bass. The sound at idle is less like a buzz and more of a throbbing noise. This might be due to the 22” resonator.
The shop with the dyno can’t fit me in until at least tomorrow, but the “butt dyno” says the torque is better. On the drive home, I was shifting at lower RPM than before. Maybe 300-500rpm lower. I can now cruise around smoothly at 2000rpm (but not anywhere below that). Previously, the engine was really unhappy below about 2500. Since the pipe size is nearly the same as before, the torque might also be due to the length of the resonator. Whatever the reason, I’ll take it.
I think the sound could stand to lose about 5-10 dB. If I was going to do it over, I’d go down at least one pipe size: 2.25” upstream, followed by 2” through the 2nd muffler and the outlet. Or maybe I’d just stick with a 2.0” pipe and mufflers.
Actually, I may do it over. I like the sound better than before, but it’s still loud. It’s almost as loud as the HKS pipe without the silencer. I’ll give myself a couple of weeks to get used to it, but this amount of noise might fail the “girlfriend test”. ...And my experiment may need more test samples before I'm satisfied.
I read somewhere that my DC Sports header has a diameter of 2.1” at the collector.
I’ve also looked for specs for my stock catalytic converter, and it appears to have a 2” diameter at the inlet and outlet.
Knowing this, a KA24DE should run really well if you use a 2” exhaust, and just take the bends out of it. Straight-through mufflers (like MagnaFlow or DynoMax Ultra Flo SS), and routing like an N1 exhaust.
I can rationalize using a pipe a little bigger than 2”, because a larger diameter gives you a better ratio of cross section to surface area. The surface of the pipe slows the flow through friction, but too big a cross section (especially if the cross section changes abruptly) slows the engine in other ways.