New Caprice - Discussion forums

The section up to the expansion chamber is almost done. Had trouble getting a good weld on the driver side flange and eventually called it a night. I’ll attack it again today.

I expect to get this installed with O2 sensors and fire it up to hear the noise tonight.

Lookin good! Really curious to see how [you perceive] it sounds. These cars (at least with a stock engine configuration) seem to be slightly more challenging to get a good exhaust sound.

Thanks!

I installed what I have so far and fired it up last night. It was actually not as loud as I expected at idle. Revs were plenty loud. No question that this car is cammed when running low idle speed and open exhaust.

I slipped some 2.5” sections into the expansion chamber and then slipped on some flex joints, 90’s, and the Borlas this morning to get an idea how it would sound. Tough to tell for sure since the slipped together parts are rattling and there is significant exhaust leaking at the expansion chamber outlet, but I think it will be ok. Trying to decide if I’m going to weld the pipes into the expansion chamber to seal it up and then mock up the mufflers again... or just tack everything in place and weld it all at once. Taking the whole system out to weld it isn’t terrible, but it does get old.

Nice! If your engine is cammed, then the sound profile will be very different than a stock engine. That changes everything (for the better, LOL). I assume you have no AFM to deal with either (also for the better).

For the expansion chamber, are you tuning the pipes as they enter the chamber? Meaning sliding the pipes in to a certain depth to achieve the best sound?

storm9c1 wrote: ↑Wed Nov 04, 2020 12:50 pm Nice! If your engine is cammed, then the sound profile will be very different than a stock engine. That changes everything (for the better, LOL). I assume you have no AFM to deal with either (also for the better).

Yeah I have a TSP 220R cam and an AFM delete. I've got the idle set about as low as I can get it to without it getting too rough (around 610 rpm) to try to minimize the amount it pulls against the converter. Trying to come to a downhill stop in the snow with the engine still driving the rear tires is... well, just no fun. A looser converter is really the right way to go, but getting that expense approved by the accounting department is not going to be easy. But anyway... the idle is rough enough at that speed that I don't think the new exhaust is going to do a very good job of hiding the cam.

storm9c1 wrote: ↑Wed Nov 04, 2020 12:50 pm For the expansion chamber, are you tuning the pipes as they enter the chamber? Meaning sliding the pipes in to a certain depth to achieve the best sound?

I'm not. I just put the chamber where I could get it to fit and let the pipe length fall where it would. I know the pipe length to the chamber will change power and torque, but I do not know how much it changes sound. It would be fun to play with, but this project is moving too slow already. I'm just going to hope that it is quiet enough and does not have drone.

I almost finished welding the outlet pipes into the expansion chamber last night. The extreme expansion/contraction of welding stainless caused them to move all over the place, so I'll have some work to do to get them pointed back in the correct directions. Really wanted to finish those welds last night, but just could not make it happen.

Fandango wrote: ↑Fri Oct 09, 2020 4:37 pm Cool.

I wonder about those flat sections vibrating from the exhaust pulses and causing some noise. I think that's why most exhaust stuff is oval/round. Either way, looking forward to the progress.

You hit the nail on the head.

I welded some 2’ pipes into the outlet of the expansion chamber and installed what I have so far. I slipped on 2 more feet of pipe, then the Borlas, then a 90 degree bend to point out from under the car. Now that the leaks are gone, the exhaust volume seems to be quite low at idle, but anything off idle causes a terrible buzz/rattle from the chamber. It seems to go away if I apply some hand pressure to the bottom and sides of the chamber.

So what to do? I’m planning to push ahead with fitting the rest of the pipe and the mufflers. When I drop the system to weld everything, I’ll try welding some ribs to the chamber.

Here’s a shot of the system after adding the expansion chamber outlet pipes. They moved ALL OVER THE PLACE when welding. Had to flex them back to position as I installed it.

CapriceX2 wrote: ↑Sat Nov 07, 2020 9:04 am

Fandango wrote: ↑Fri Oct 09, 2020 4:37 pm Cool.

I wonder about those flat sections vibrating from the exhaust pulses and causing some noise. I think that's why most exhaust stuff is oval/round. Either way, looking forward to the progress.

You hit the nail on the head.

I welded some 2’ pipes into the outlet of the expansion chamber and installed what I have so far. I slipped on 2 more feet of pipe, then the Borlas, then a 90 degree bend to point out from under the car. Now that the leaks are gone, the exhaust volume seems to be quite low at idle, but anything off idle causes a terrible buzz/rattle from the chamber. It seems to go away if I apply some hand pressure to the bottom and sides of the chamber.

So what to do? I’m planning to push ahead with fitting the rest of the pipe and the mufflers. When I drop the system to weld everything, I’ll try welding some ribs to the chamber.

Here’s a shot of the system after adding the expansion chamber outlet pipes. They moved ALL OVER THE PLACE when welding. Had to flex them back to position as I installed it. 1333CAD9-40C0-4F41-9330-2CD44ABFD6DE.jpeg

Could you weld some stainless rod to the top and the bottom of the chamber to keep the panels from flexing? Welding ribs to the outside is probably easier, kinda like the bends I see in hvac plenums.

Fandango wrote: ↑Sat Nov 07, 2020 1:43 pm Could you weld some stainless rod to the top and the bottom of the chamber to keep the panels from flexing? Welding ribs to the outside is probably easier, kinda like the bends I see in hvac plenums.

Possibly. I thought about drilling holes through the top and bottom and running rods or bolts through and welding them top and bottom. Not sure if that is what you had in mind. I’ve seen that done before to combat vibration.

I got a few hours in the shop today. I’m one 90 away from having the passenger side muffler connected. Feels like I’m actually getting close.

It took quite a bit of time to get the routing right around the diff. It went well and I’m happy with the results, but it was slow going.

Hoping for a little more progress on Monday and will try to get some photos to share. Getting pretty excited to get this done, but I know it will take some time still.

Passenger side pipe is connected to the muffler. Started working on a hanger bracket for the muffler area. Stuck a 3” pipe on for a tip to see how it looks.

CapriceX2 wrote: ↑Sat Nov 07, 2020 9:02 pm

Fandango wrote: ↑Sat Nov 07, 2020 1:43 pm Could you weld some stainless rod to the top and the bottom of the chamber to keep the panels from flexing? Welding ribs to the outside is probably easier, kinda like the bends I see in hvac plenums.

Possibly. I thought about drilling holes through the top and bottom and running rods or bolts through and welding them top and bottom. Not sure if that is what you had in mind. I’ve seen that done before to combat vibration.

I got a few hours in the shop today. I’m one 90 away from having the passenger side muffler connected. Feels like I’m actually getting close.

It took quite a bit of time to get the routing right around the diff. It went well and I’m happy with the results, but it was slow going.

Hoping for a little more progress on Monday and will try to get some photos to share. Getting pretty excited to get this done, but I know it will take some time still.

That's what I meant. You worded it way better than me though.