New Caprice - Discussion forums

Got a CEL on the way home from church this morning. I could tell by smell that it had been running rich. But hadn’t looked into it yet.

Code was for no response from O2 sensor (B1S1). Logged it and it never moved from 450mV.

I had considered an exhaust leak at the manifold flange, sensor failure from silicon, sensor failure from getting knocked around, or who knows what else.

Just lifted it back up and found this. Will repair tomorrow. I have a new sensor ordered but probably won’t swap it right away.

Always something... I thought I was the only one with luck like that.

I'm usually pretty good with electrical stuff, but sometimes these things can really throw you through a loop. At least you saw the wire was physically broken. The wires that break inside the insulation are wayyyy more fun to track down.

I like the tips you have on there now... looks more factory.

As for the "howl", could that also be described as a drone sound? Small adjustments to the exhaust can sometimes fix that, including how far the tips protrude past the bumper. In the muscle car days, we had to make sure they were something like 3" beyond. While it won't look great in your case, you may want to try that just to see if it helps the drone or not. If it does, there are other tricks you can use to tune the system.

I pulled the sensor and repaired the wire. My solder job is just ok. It is just above freezing this morning and I didn't bother to put a jacket on to go do this job. I was starting to get a little shaky by the time I was set up to solder.

The sensor is back in. I'll go scan it in a bit to make sure it is now reading.

The noise isn't like typical drone. It is much higher pitch. You don't feel the pressure on your head/in your ears like drone. It is just a noise. The radio drowns it out enough that it isn't too annoying. I'm pretty confident it is coming from the expansion chamber. I'm going to try some things tonight to quiet it a bit more. It is good enough to drive - which is good since I want to use this vehicle for a several hour trip on Saturday.

I spent the last couple days logging and tuning and logging and tuning some more. I don’t have a wideband set up yet so I was just tuning from long term fuel trims.

I did several iterations of MAF tuning and then several more iterations of SD tuning. MAF calibration didn’t have to change too much, but the SD tuning was off by a bit.

I was surprised to find that when I was done, the idle was significantly smoother.

At any rate, I’d guess I’ve spent 6 or 8 hours driving with the new exhaust. It reminds me a lot of a Hemi Challenger rental car I had a couple years ago. For now it is going to work just fine. Down the road I might try to quiet it a little more.

Cool man! If the forum had a "thumbs up" button, I'd press it. Great thread and exhaust system build. Keep us posted with any updates.

We took the PPV for our vacation at the end of November. It was about a 4 hour drive. I did some more logging and tuning while on vacation and then drove back home. The exhaust kept getting louder the more I drove it and by the time we were close to home I was hearing rattle type noises at some RPM.

The car is back on stands. I found a cracked weld in the expansion chamber and pulled the whole system off again. Now that vacation is over I’m going to take my time and go over everything and improve fit in a few places. I was thinking about wrapping the existing chamber in insulation and a stainless shell, but I think I’ve decided to start from scratch with it. I’ll be able to do nicer work and a cleaner install. I’m not ready to give up on the chamber idea quite yet.

I picked up a sheet of heavier stainless that will be easier to weld. I’m going to pick up a batt of mineral wool to sandwich between a double wall. I’ll post up photos as I go.

Have you seen the X Pipe mufflers that are made by magnaflow and I assume others? Would seem to be exactly what you describe thinking of buildings yourself? A bunch of the guys who run Full headers on the SS sedan use them in the same location you are putting your expansion chamber and seem happy.

https://www.summitracing.com/parts/mpe- ... gKdvvD_BwE

I have seen/heard of those. I appreciate you pointing them out though! While I’m not going to rule that idea out, it isn’t exactly what I want. If my second attempt fails, that will get some serious consideration.

GREAT thread
Thanks for posting
And please don't stop posting.

Thanks!

I’ve been working on it a little here and a little there. So far I’ve just been working on massaging the 3” pipes to tuck up closer to the floor. I had them positioned close to the floor at one point but something must have moved/warped while welding and both sides were hanging lower than I liked. I tried bending one first, but it is just too stiff. Ended up slicing and welding it. I pretty much finished that yesterday and will get started on the new chamber. Didn’t take any photos since everything pretty much looks the same.

The flange gaskets to the manifolds didn’t show any signs of leaking, but I spent some time trying to flatten them out for a more reliable seal. The passenger side is good. I’ll spend a little more time on the driver side. Both are better than they were.

I found a weld defect in the passenger side flange weld that was allowing a leak. You can see the evidence of water running out of it in the photo. I went over the welds for both flanges and ground out any questionable spots and laid in better welds. Also touched up a couple spots in an O2 sensor bung. Doubt it was leaking, but this was the time to make sure.

Hoping to get started on the new chamber tomorrow.