gunlover05

Well today I installed a stainless Bursch cat by-pass and an M&K 1 in 1 out muffler. Thought I'd share some of my experiences. I had my car jacked up pretty high with my wheel off of course. I bought my M&K and new straps (3 stainless bolts/nuts and muffler gasket came with the straps for $40) from Euroeast and my cat by-pass, new oxygen sensor, and gaskets (generic, just spliced wires) from Vertex.

First is removal of the cat. Was kind of a PITA. I left the oxygen sensor on there and cut the wires right above it. My advise here is to COMPLETELY forget any heat or oil soaking on the bolts/nuts. I wasted about 45 minutes here. Go straight for the dremel tool with several cutoff wheels and cut a slot in the nuts and use a cold chisel and hammer to split the nut off. A few were a bit hard to get to, but not bad. Don't worry about cutting a few mm into the cat bracket, just don't go too deep. I had one bolt at the bottom of the cat bracket that seemed rusted in even with the nut off. Got it off easily buy twisting the cat a little once the muffler bolts were free.

Removal of the muffler. My bolts/nuts on my old straps were rusted and I couldn't get a wrench on the square nut, so I got out the dremel again and cut the straps. I had bought new stainless straps with the M&K. I highly recommend new straps for this reason. The muffler was easy to remove then.
Removal of the cat and muffler took about 2 hours. The cat took 80% of the time.

Installing the cat by-pass. Was easy. I bought 8X40mm stainless bolts, nuts, washers, and lock washers from Lowes. Put washers on bolt head and nut side.
Put the bolts on, gaskets, the position the cat-bypass. Get a few nuts/washers/lockwashers on to hold together. then get the rest on loosely.

Then install the muffler. I put the new straps in the same place as my old ones. The one furthest from the exhaust tip went on fine, but the other was too big. I had to add improvise here. I added a 1.25" socket up top and a 1" dia X 1.5" piece of copper pipe on the bottom, both wedged in by an existing muffler bracket. This is the only problem I had really, but improvising worked. Snug up the spring loaded bolts on the straps, but not overly tight. Both the by-pass and muffler should have a little slop so you can align the cat by-pass and muffler. Once these are lined up evenly, semi-tightened down the 3 bolts there. Now go back to the cat by-pass and position it evenly and tighten the bolts there. Then go back through everthing and snug them up tight.

Oxygen sensor. Cut the plug off. The sensor screws down a few turns easily, then gets tough. I checked several times as I thought I was cross-threading, but no, it just takes a lot of torque to get it snug down. Then splice the wires. There a 2 whites ones, one black just like original. I had no idea which white went to which white, so I just guessed.

Weight - I think I lost about 30lbs with the new setup.
Sound - idles a bit loud, but past 2K it sounds awesome!!!
Extra horses? - I think i do feel a few extras, definitely feels "Free'r" when it revs.

Would I do it again? YOU BET!

I do have a steve wong chip on the way, and will let you guys know what that feels like next week.

Naitove

Make sure you put some antiseize on your stainless bolts. They will gall overtime and be very difficult to remove.

gunlover05

One other thought. I do have a little popping when I let off the gas sometimes. Not sure why though, any other people have this same thing? Didn't do it with the old exhaust. Does it go away with the SW chip? It isn't bad like loud backfiring, just a little popping. Any idea why this happens and can I fix it?

More thoughts on the exhaust note - I said it idles kinda loud, but not bad imo. It sounds like a big block engine lopping. As soon as I go up past 1500 rpms, it quietens down to a low-bass purr and purrs louder on up. When you are in the car it sounds great. Where it really sounds great is going up through the gears up past 3K. I mean this is the music of the gods (greek).

My car is (was) a stock 85 Carrera with 86K, other than the recent stainless brake lines, this is my first "upgrade". As I said, I would do it again in a heart beat. Muffler, straps, by-pass, oxy sensor, and gaskets was around $800 and worth every penny so far. Anxious to see what the SW chip will "unleash" now when it gets here next week.

gunlover05

ohh, good point on the anti seize! I didn't do that. I think I will take one bolt off at a time in a few 100 miles and do that. Need to retorque them anyhow at that point anyhow.

Joel Lester

I installed the SW chip recently and love it - big difference. I am going things in reverse of you as I plan to do the CAT and muffler next. Thanks for the info! Joel

gunlover05

Joel, You probably know this, SW has chips specific to an exhaust setup. I know there is one specific for a cat by-pass and sport exhaust vs without a by-pass. If you have the one for without the by-pass, imagine steve will reprogram yours (don't know if there is a cost for that) when you do your exhaust upgrade? Steve is a really nice guy, chatted with him on the phone a while when I ordered my this week.

Chris57

The decel popping did go away on my car with steve wong chip installed. I am running a cat bypass and a sport muffler

rscredon

Great information. I am planning to do the same upgrades to my '87. I'll be interested in your review after the SW chip.

Naitove

My SC w/ SSI and M&K 2 in 1 out pops plenty on decel.

gunlover05

My SW chip came in on Saturday! I installed it that night and drove it of cours. My "seat of the pants dyno"tells me it does have more power. Idles smoother (bit higher too @ 880 rpms), has noticeably more "pull" under the normal driving conditions up to 5k. I haven't run it past 5K yet to see the top end, but I'm sure I will be impressed there too as this is wheremore gains are supposed to be (although harder to guage on the road maybe).

If you want a bit less "loudness", I guess you could leave the cat on or go with a pre-muffler I suppose, but I like my setup fine. Seemed loud at first but definitely not now.

Overall it was worth every penny for this upgrade of cat bypass, M&K, and SW Chip...I do not spend my hard earned money frivilously either. I can whole-heartedly recommend this upgrade. Total bill for all was around $1200. I'm a happy camper.

Corrales911

Unless the Porsche O2 sensor is unique compared to US domestic ones, you can't just cut and splice the wires. One wire (usually black) provides a source of ambient air that the computer uses to determine correct A/F ratio - splicing it will destroy that function.

JV911

any pics or sound clips?

Naitove

Update:

Since I had my motor rebuilt by Dan Jacobs, there is no popping or backfiring.

gunlover05

Naitove, any ideas why it is not popping now??

vacume leak that was fixed maybe?

mine still does it occasionally, but really runs great i have to say...

panchosouth

Gunlover
I suspect a vacuum leak, as I have the same issue (usually at pedal blip/rev matching/downshift.) I know that I have to replace some lines, and am upgrading the plug wires/cap/rotor monday. Will let you know ( I have the SW chip and CBP)
Glad to hear your upgrade is working out. Post pics sound ?