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Re: Why just fix the leak when you can eliminate the choke points?

Posted: Wed Nov 11, 2020 11:47 pm
by CapriceX2
I finished up the passenger side hanger bracket above the muffler this afternoon. I'll load a couple photos of some welds that came out looking decent. I'm getting more of these (decent looking welds) as I go, but it is tricky to get the heat just right. I've also got photos of the complete bracket loose and installed. Passenger side is done except for finishing two welds and deciding on the tip. I haven't decided what I want for tips yet.
Hoping for some more progress on the driver side tonight.
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Driver side progress

Posted: Fri Nov 13, 2020 4:01 pm
by CapriceX2
Driver side is coming along. One more 90 will get it connected to the muffler. Then I’ll need to make another hanger similar to the passenger side.

If I can get that stuff done tonight, then tomorrow I should be able to pull the whole system out to finish a couple welds and try to stiffen up the expansion chamber.
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Re: Why just fix the leak when you can eliminate the choke points?

Posted: Sat Nov 14, 2020 3:43 pm
by CapriceX2
Finished up routing the pipes to the driver side muffler and made the last hanger. Amazing how much better things go the second time around after learning some things.
Fired it up with the mufflers in place and it is quieter than I expected. That's a very good thing for me since it will also keep the noise down from the passenger seat. If I can just get rid of the noise from the expansion chamber, I think I'm gold.
Heading to the shop now to tack 4 slip joints in place before pulling the complete system out to complete those welds. Then I'll turn my attention to the expansion chamber. If things go well or even just OK, I'll have it back on the ground today.
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Re: Why just fix the leak when you can eliminate the choke points?

Posted: Sat Nov 14, 2020 7:05 pm
by CapriceX2
Pic of the old next to the new. Pipes are all welded. Starting to stiffen up the expansion chamber. Unfortunately, I’m going to run out of stainless rod. 2 more boxes should be here Tuesday.
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Re: Why just fix the leak when you can eliminate the choke points?

Posted: Tue Nov 17, 2020 5:06 pm
by CapriceX2
While anxiously waiting for the arrival of the welding rod I went out yesterday and bolted the system back up and just supported it with blocks in a couple places. Then I put pressure on the expansion chamber in different areas to try to determine where the noise is coming from. I had expected it to be the top or bottom plates since those are the biggest, but I found it is actually the side plates that are vibrating.

I put a ratchet strap around the whole thing with a couple wood blocks against the sides so that I could give it some revs to make sure there was no vibration showing up at other frequencies. It seemed to work great! Hopefully adding a rib to each side does the job as effectively as the ratchet strap. As long as no drone shows up after final installation and a test drive, I think this will work out very well for me.

Re: Why just fix the leak when you can eliminate the choke points?

Posted: Thu Nov 19, 2020 12:52 am
by storm9c1
Cool! Looking great. Love this thread.

I think I asked this before, but if the expansion chamber turns out to be a bust with noise, what about replacing it with a X-pipe and see what happens? By your description, the rest of the exhaust appears to sound reasonable, and swapping the chamber for an X may be all you need to smooth it out. Then you have a fairly traditional exhaust system design.

I'm still really curious about this adventure... because expansion chambers are usually "tuned" in some way to make use of the pressure wave reflections, but you've dispensed with that step. I think it's cool that you are trying it out. But unsure if it's really doing anything positive for the system without the chamber tuning. In a "just guessing" scenario, it could have negative, positive or no impact on performance, there's no way to know without testing (ie: dyno). Noise is a secondary consideration as well, and you won't know until you drive various speeds and RPMs. Either way, it's still great to see it all come together, boom or bust, and we all learn something from the journey.

Re: Why just fix the leak when you can eliminate the choke points?

Posted: Thu Nov 19, 2020 3:22 pm
by CapriceX2
I’m glad you’re enjoying it. I like reading this stuff too. I don’t really enjoy documenting it all, but I think it makes the forum a better place.

I’m pretty sure I’ll be able to quiet down the chamber, but if I can’t I’m not sure which direction I’ll take. An X pipe is definitely an option. I could also try building 2 separate chambers out of 4” stainless I have left over from my truck exhaust – however 4” is not much bigger than 3” and probably not a big enough area change to reflect the negative pressure wave. Or just cut it out and put pipe in to get the project done for now and worry about it later. I’m really hoping not to have to jump off that bridge.

This is what I took down for notes after reading Vizard’s articles on exhaust design:
Secondary length is much more critical than primary length. Longer, smaller diameter tends to help low end. Shorter, larger diameter help top end. 10 to 24” lengths are normal with a 10” length being better for 8500RPM power peak and a 24” better for a 4800 to 5000RPM peak. Secondary lengths up to 40” can work well in some applications especially with lower stall converters.

I don’t remember if the articles say it, but I gathered that the expansion chamber has the effect of making the engine “see” only the part of the system up to the chamber. The chamber makes the system act like it is dumping at that point. So in my case, the engine thinks it is running with slightly ported manifolds dumping into a 3” open exhaust that is around 48” long (I should measure that…). 48” is really too long and is a compromise based on space. I expect the extra length to drop the torque curve a bit (and peak power at the same time of course) from what it could be – and I’m ok with that. I’m also not too concerned about this extra length because it will change drastically if/when I put on headers. The primaries will take up a bunch of the length and I expect to be left with secondaries that are much closer to the correct length.

Do I think this will give up any power over a more traditional straight, H, or X-pipe? No. Definitely not. Even with no reflected wave or a wave reflected to coincide with low RPM, I don’t see that this will be any kind of restriction over another setup.

Do I expect it to add 80 HP throughout the power curve? Wouldn’t that be nice? No, I really don’t think that is realistic. Honestly, I’m hoping I can get similar results to what Mooseman reports here: ... 9&start=40. He has Maximizer headers and an intake resonator delete that I don’t have, but I have a cam that I expect to more than make up for that.

I didn’t get a lot of time to work last night. I had a shower valve leaking inside the wall and water running out under the wall that had to be fixed first. But I did get ribs welded to the sides of the chamber. I expect to put one more rib on the bottom and bolt the system up tomorrow night.

Re: Why just fix the leak when you can eliminate the choke points?

Posted: Thu Nov 19, 2020 7:05 pm
by Fandango
Making good progress, cool. Interesting that the smaller panels are flexing, glad to see that you got that figured out.

Re: Why just fix the leak when you can eliminate the choke points?

Posted: Fri Nov 20, 2020 9:22 pm
by CapriceX2
I had a few minutes to work before driving my wife to an appointment. The exhaust is bolted back in and the ribs took care of the buzzing.

When I get home I’ll tighten the manifold bolts again, put on some slash-cut 2.5” tips, and get it back on the ground for a test drive.


Posted: Sat Nov 21, 2020 6:23 pm
by CapriceX2
I got a test drive in last night. I’m happy with the idle and WOT, but there is a slight howl at some cruise speeds. Not very loud, but I don’t like it.

I’ll work on getting a video put together.

I wanted to do twin 3” tips per side, but got lazy and just polished up some heavy wall 2.5” that I had scavenged.