SW exhaust - replace resonator w/pipe

[rlaggren]

JIC somebody else is looking at a similar problem:

The resonator (first can aft of the engine) on my 82 wagon more or less fell off and since the pipe from the manifold appears OK for a while and I need to get this fixed quick, I installed a piece of 2" ID electrical conduit (EMT). 2" ID x 21" or so long seems to work perfectly provided the existing pipes can be cleaned of lumps and or other problems. Oh, and the new pipe needs to have the cut(s) de-burred. There is a straight section of about 12" toward the motor and a straight section of about 6" toward the rear. The 2" ID pipe sleeves over my existing pipes easily; you can move the rear pipe to allow installing first on the pipe from the engine, then reposition the rear pipe and slide the piece back over it. 2" exhaust clamps worked fine; the clamps I bought from Kragen were annoyingly tight, but the clamps from a local independent were perfect; I did use one of the Kragen clamps.

I may have to revisit this some time because I forgot to use that exhaust caulk paste and the rear joint is "puffing" slightly. But it was late and I don't wrench at home so I had to get the thing on the road. The specs on the OEM pipe is 1-3/4, but after trying various couplers and adapters from the FLAPS, 2" ID was the best fit; it was nice that it sleeved over since that didn't reduce the exhaust size any.

There is an added low frequency sound (hum) when driving that's hardly noticeable and some steady very low level vibration at idle. It may have to do with not connecting the hanger at the rear of the tranny yet. I had installed skinny bolts and nuts, but to use the OEM welded nuts II need to drill and tap new threads - apparently they weren't used for a long time and rust took away the threads. 3/8" should get me clean metal w/out using up the nuts too much.


Rufus

[kassim503]

...There is an added low frequency sound (hum) when driving that's hardly noticeable and some steady very low level vibration at idle. It may have to do with not connecting the hanger at the rear of the tranny yet...

Ill bet that that hum and vibration is coming from that tiny leak at the end of the pipe. I had a similar leak just foward of the cat (gasser) and it was resolved after 10 seconds of the MIG.

Try gunning it and see if it hisses, mine made a little hissing at really high rpms

[rlaggren]

I'll try putting some silver tape around the joint when I install the hanger in the next couple days. I'm not going to pull it apart for a while at least and I'm definitely not going to weld it because I'm still looking for a small "can" to install instead of the straight pipe.

I may be able to use one of the performance mufflers. I _think_ I can find a 4"x9" can that will fit up there and if I can get one w/2-1/2" pipes I'll use a couple of adapters to make it look like an open pipe to the engine - try to get some exhaust extraction going here! <g> Assuming that Nissan had _any_ performance reason for putting that resonator there, that is.

edit: The original can is 3-1/2" x 5-1/2" x 13. I think I got the "x9" by assuming an offset-in offset-out style of can.

Anybody know how to (cheaply) test an existing exhaust system to see how much it flows? I'm wondering what the pipes and muffler from there back will actually flow...Something like pressurizing a box w/a 1-3/4" (size of the OEM exhaust) hole with a blower and then hooking the hole to the exhaust and seeing what the pressure rise is...Hmm. That would be back pressure at that flow. Well, something like that anyway.

Rufus

[kassim503]

Mount a low pressure gauge on the egr inlet and open it up hard!

Im guessing that would show any high rpm restriction, but i do know the oem 1 3/4" exhaust does restrict the motor at high rpms on the gasser. I would say the optimal size for high rpm power is 2 1/4"

[asavage]

For completeness, pics of that headpipe & resonator are in this thread.

I had the resonator rust out on my '82 Wagon in 1997. Bought the headpipe from the dealer, I think it was $140 or $180. Changed it in 10 minutes, everything fit perfectly. It's still on the Wagon.

On the diesels, the rubber supports (rubber bands) crap out, and the headpipe cracks from vibration, but I've yet to hear of the rear section rusting out or cracking.