acgreen

So i bought a 1986 944 Turbo like 3 days ago and i thought it already died on me today. Long story short driving down the highway and the cat send shrapnel through the rear muffler and now ive got fiber glass insulation coming out of a massive hole but the car sounds AMAZING and the acceleration is waaaaaay better now. haven't brought it to a mechanic yet but a guy my friend john recommended said over the phone he cant legally take out the cat even though my car is exempt from emissions but said i can drill out the inside of the cat myself to get the better airflow and to keep the acceleration (although he wouldn't recommend doing that wink wink if you catch my drift). I just wanna know if hollowing out the cat and straight piping it instead of getting a new muffler and cat would have any harmful affect to the car or my health (or my wallet) since when the cat imploded and bust open my muffler on the highway i could smell exhaust fumes and because i worry too much about random **** i dont wanna put on the sunroof with the windows up and die from carbon monoxide poisoning or something

V2Rocket

itll be louder with a straight pipe and itll STINK without a cat.
CO poisoning could be a serious risk if you have an exhaust leak without a cat, or even with a cat.

it should spool the turbo faster and make a little more power though.

acgreen

I dont care about the smell i just dont want to suffocate while doing 80 something down the freeway

Also the turbo went from pushing 1 bar to 2 bar consistently which definitely made a difference in acceleration

vandal968

Bought a Rx-7 years ago with serious power loss, discovered that the cats were clogged. Punched them out with a big chisel and reinstalled so that it looked stock. Performance difference was huge, sounded cool, had a little pop when I shifted it. No regrets.

c

harveyf

AC, just curious. How do you know the cat failed? Did you find "cat stuff" in the muffler? Is it possible that just the muffler failed? Whatever, if you are contemplating a modification, just make sure that the open end of the pipe is beyond the end of the car, just like stock, to get all that lovely exhaust out beyond the car.

You may want to look into getting a Supertrapp muffler. It has an interesting feature that you add baffle plates at the end of the muffler to increase/decrease the amount of "openness". In this way you can experiment with the power vs noise tradeoff. Trust me, you might get tired of all the noise from straight pipes after you've lived it for a while. If you go this route, be sure and get the end of the Supertrapp slightly beyond the end of your car. It shoots hot exhaust gases out in a radial pattern and can melt anything in the vicinity. Been there/done that. Not pretty.

acgreen

Well Harvey i suspect it was the cat because i heard a large CHUNK sound come from the front along with a puff of smoke that came out of the dash and when i got home and i called a mechanic who suggested it was probably the cat especially because i was experiencing a gain in power because there being a hole in the cat allowed the motor to breath more

harveyf

OK understand. Also understand the car is new to you. You might want to get it up on jack stands and do a careful inspection of the entire exhaust system. It is a little more complex on a turbo than a standard car. This is a good time to get familiar with the various parts and pieces. But things don't exactly line up here in that I couldn't immediately give you a reason for smoke in the cockpit if the only thing that happened was the cat internal matrix broke up.


You might also want to cross post over on the dedicated turbo forum.

V2Rocket

I had a cat disintegrate last year, only symptom was a rattling sound like a rock in the muffler (NA muffler is not straight through like a 951)...
imagine my surprise when, upon removing the muffler for inspection, several golf-ball sized chunks of cat matrix fell out

vandal968

On the Rx-7, the way I tested to see if I had a back pressure problem was to loosen the bolts on the flange in front of the cat almost completely. At rest, the flange was closed from the springy exhaust system supports, but when the engine was revved, the exhaust gasses pushed the flange open and gave the exhaust a second path out. Keeping the nuts on the studs ensured that the flange wouldn't pop off completely. I just went from a 2mi or so ride around the block and confirmed a massive improvement, then made a more permanent fix.

cheers,
c

jkotek

No technical comment but on first look I thought you hit a long haired blonde with your car

NelaK

OP is just establishing an alibi and plausible explanation for when the police come knocking about a missing long haired blonde.

On a different note - I'm kind of tempted to remove the cat from my car. We don't have inspections here so it wouldn't be an issue.

Dan Shea

Turbo car's it's not too bad with a straight pipe, spooling the turbo helps keep the noise down.

My car is an N/A, and it is unbearable without a cat/resonator in the cat spot.

raleighBahn

Get a sport cat and install with v-band - if you track it, you can swap it out easy - and I guarantee you'll be happy when you put it back.

Without a cat, it smells awful and there will be times you are sitting in a traffic jam or at a long light not feeling cool with the smell enveloping you and everyone looking around wondering what died. Not to mention the noise - the 951 is a car you need to keep in the high RPMs to have any fun at all. Without the cat on, the noise will more likely draw negative attention (blue lights) and make you feel more like a boy racer in a tricked out Civic SI and less like someone driving what is otherwise a very finely engineered vehicle

SloMo228

Yeah, I was coming in here to say that the downside of straight pipe is that the car will sound like rattly, raspy ***. Then I noticed it's a Turbo, so nevermind.

I bought my 944 with a hacked up exhaust and went through probably half a dozen different iterations of muffler combos before I found one that sounds good, doesn't weigh a ton, and isn't raspy.
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V2Rocket

random data point but years ago i weighed the complete exhaust system of my NA, from the flanges where it connects to the headers, to the muffler tip.
stock muffler and piping, but aftermarket cat...28 lbs.
stock cat is probably a few lbs more but the stock system aint that bad...just feels like it when you drop the whole assembly onto your chest under the car