Turbopowered68 wrote: ↑Tue Jan 26, 2021 6:15 am
pleas put it on a scale before installation.
what do you figure? north of 30#s
I checked it last week and it weighs in at a hefty 31 lbs. I still haven't weighed the factory parts to see how much things are changing. They are buried deeper in the snow now.
xcidmigs wrote: ↑Fri Jan 29, 2021 4:06 pm
What is the end goal here? silencing the now basically open exhaust? Is there a perforated tube inset inside this box? Or is it an X or H pipe inside? This seems like a again like what magnaflow and others have created already with the x pipe mufflers that have 2 in/2 out setups.
The photos I posted on January 21st show the inside of the chamber. There is nothing in it except a couple of braces.
- There is no perforated tube.
- It is not a muffler and is not intended to quiet anything.
It IS an expansion chamber - It is a significant change in the cross sectional area of the 3" pipes that will reflect a negative pressure wave back to the cylinder head. For more information on expansion chambers check out this superchevy article.
http://www.superchevy.com/how-to/exhaust/0505phr-exh/
There is a lot of information in that article so I'll give you a couple bullets points that I found most interesting:
- Header primary length is not very important. Anything between 24 and 36" will work just fine. Note that this also means putting effort into equal length primaries is not a good use of your time.
- Size the primary pipe diameter to the exhaust port flow of the head.
- Secondary length is much more important than primary. The secondary length must be terminated with a significant change in cross sectional area like dumping the headers to atmosphere or (in my case) an expansion chamber. Simply reducing it down to meet up with the rest of your exhaust is likely going to leave significant power on the table.
- Secondary diameter should be about 1.75 times primary diameter.
- After the expansion chamber, what you do with the exhaust is largely irrelevant as long as it can flow enough to meet your HP. A 500 HP engine needs exhaust that can flow 1100CFM total, or 550CFM per side. It doesn't matter if you have pipes, bends, resonators, mufflers, or a dump... as long as everything can flow 550 CFM it will not be a restriction. You can have the power of open headers yet maintain a relatively quiet setup
My setup has a lot of compromises. FIrst, I don't even have headers (yet). My primary length with manifolds is nearly non-existent. Second, my secondary length is really long. I had measured it at one point and I don't remember exactly what I found. I think it was around 4'. I'm ok with that since eventually I will probably put headers on and the secondaries will get cut to a more appropriate length.
NOW... A progress update:
I spent almost the entire day Saturday in the shop and got the system welded up and installed. Sunday we drove it about 3 hours round trip. The system fits up well. I do hear a "ting" once in a while on some of the bigger bumps on back roads, but nothing that annoys me too much. I will eventually go looking for the source, but I'm not in a hurry.
I think it sounds amazing at idle, low speeds, and WOT. I couldn't ask for anything better. I took my wife through an indoor drive-thru COVID testing facility and having a conversation with the staff with the engine running was a complete non-issue. The staff did not look annoyed at all and more importantly my wife was not annoyed.
At highway speeds around 65 or 70 there is a hum. Tone wise, it is basically a very quiet drone. It is quiet enough that I did not get any complaints from my wife on the 3 hour trip. It is quiet enough that you can still hear the tire noise and the wind noise. Hearing the radio is no problem. So it is really not bad and I'm OK with it.
I haven't taken any video yet, but will try to get that done and posted.