The reason I'm wondering about a swap is I have a 99' CARB compliant cat system I got for free and my 97' is absolutely SMOKED.
It's hard to beat "free".
(edit: The best part of this story begins the 3rd to last paragraph)
Try to follow along. Whether any of the following "makes sense" in Cali is TBD; I'm in IL, not Cali.
On my 1998, I believe I can tune it to operate with two O2 sensors in front (prior to the cats) and one O2 sensor in the rear (after). This configuration (two front, one rear) jibes with that 1999 exhaust system you've scored for "free". As I noted in my earlier post, my 1998 system at present is the same as yours, two O2 front, two O2 back.
The image below shows the tuning parameter I'm referencing (see the YELLOW arrow,
ignore the RED arrow) to re-configure the ECU to expect the two O2 front / one O2 rear system. That parameter, and maybe the other parameter adjacent "Single/Dual Exhaust System", would need to be altered.
You must be registered for see images attach
So it appears the "tune" can be tweaked to accommodate the O2 sensors present on the "free" system.
Also, the "tune" can be tweaked to disable error indications (i.e., it won't turn on the "SES" light or set a code) for the O2 sensors, if that becomes an issue, e.g., see the parameter list below:
You must be registered for see images attach
How can you "tune" your ECU? I use JET's Dynamic Spectrum Tuner (p/n 14005), which reportedly works on 1996 and later ECUs (
@df2x4 has used JET on his trucks' ECU(s) from... 1996 or 1997). I see JET's DST selling for ~$400, but maybe less if you look around.
Perhaps there are other options for tuning.
I don't have an induction heater and don't wanna risk it with a torch.
I know the feeling.
Maybe it's just a "muffler shop has to just weld it all back together and put on stainless nuts" situ
Consider solid brass or copper plated nuts, not stainless. Stainless can gall easily and essentially lock itself to the mating fastener. Ask me how I know.
I used brass M10-1.5 nuts on my L31's exhaust manifold studs.
I can do many things, but adding learning to weld would be overwhelming at this point
Welding is a craft I've wanted to learn myself. Supposedly it's much easier with the TIG/MIG systems available now instead of the old "stick" welders.
as I'm in the midst of a career change into mechanical engineering.
Congrats!
I'm EE. You can't spell beer without "EE"
It's the first time I've had to work on exhaust and I'd rather just pay someone than spend a month of what little time I have getting it right.
Roger that, understood.
If I can just have someone remove the bolts and bolt in the new y pipe and a muffler myself I'd rather do that.
Keep in mind... that 1999 Y-pipe will work just fine. Hook up the front O2 sensors, that's mandatory to make the engine run properly as you likely know. You might ("might") be able to install another O2 sensor in the rear, so there are then two in the rear, and connect each to the existing O2 wiring. Thus, the O2 sensor expectations of the ECU's factory tune will be satisfied. I'll assume it'll also yield "no SES light".
You also might ("might") be able to connect the single rear O2 sensor's signal line to BOTH existing ECU connectors. Didja get that? The rear O2 sensor(s) aren't critical to the engine function, so if you can spoof the necessary signals for the
two rear O2 circuits, using only
one O2 sensor, then you're done.
I hate that there is a regulatory problem too; that's part of why I didn't just 4L80 swap.
I just would like to have everything skookum vs being kluge-fixed as the interior of the car is immaculate and everything else is pretty well done and ready for another 100k-200k miles.
You're preaching to the choir
