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Discussion Starter · #1 ·
I have a 1982 na that I just had the exhaust system replaced with a Flowmaster muffler and 2.5" pipe from the cat on back (other people in the forum have complained about how loud this muffler is, but I think it's very reasonable). The guys at the shop told me they could go ahead and cut out the cat converter for $50 more. I guess my question is how many of you Z dudes have had this modification done and could you give me some feedback. I can tell a big difference just from the muffler replacement. On my way to work this morning I had the speedo at 80mph and the tach at 3000rpm, before the change the tach was reading 3200rpm. Should I expect that much more gain from removing the cat. conv. or should I leave well enough alone.

Thanks,
Newbom
 

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Discussion Starter · #2 ·
>>On my way to work this morning I had the speedo at 80mph and the tach at 3000rpm, before the change the tach was reading 3200rpm.


No offence but how did the muffler and pipe change manage to change your gear ratio?
 

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Discussion Starter · #3 ·
I am not sure, could it be that the engine was not making all of the power it would normally make under a more efficent setup and hence required more rpm's to make a speed? I am not a mechanic/engineer, just a guy who likes to drive my Z and I guess that would be a question best answered by someone more knowledgable than myself. I was looking for advice from others on their experience on removing the cat. converter. Do you have any input on that subject?
 

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Discussion Starter · #4 ·
Changing the exhuast won't change the rpms at a given speed. Removing the cat will probably give you more hp., but it will affect you emmisions. I took mine off and hollowed it out. I don't need my emmisions done for another year so I will see what happens then. I do feel a little more power, like the turbo spools up faster. And it sounds cool too... :)
 

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Discussion Starter · #5 ·
I passed smog in Phoenix with flying colors on my 78Z /ca "WITHOUT" a catalytic converter and they didn't catch it!!! But I have a glasspack that looks kinda like a cat...

Got away with one.

Steve G
 

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Go with a low restriction cat, Jegs sells one for about $120.00

Don't take off the cat if you want to pass smog. If they take one look under the car and see there is no cat they won't even inspect it, unless you insist, then they will just fail it, and take your money as well.

Like Trevor said, what you see would take a gear change. Remember this is a stick not an automatic (correct me if I'm wrong about the tranny), there is no native slippage in a manual tranny, it's gear to gear. In an automatic there is a % of slip, reduce the slip and the car will go faster at a given RPM. Stall converters usually add additional slip at final drive, but it would take 3500-5000 stall or something in that neighborhood to create appreciable slip, which would give the opposite affect that you are seeing.

Ken
 

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Discussion Starter · #7 ·
<b>How difficult is it to change the header.</b>

After the back side of my muffler rusted through I guess it is time to replace the exhaust. I want to replace the entire thing.
How do you remove the stock header? It is hard to see the bolts, plus the ones i see are rusted.
Any suggestions.
I will probably get the exhaust system from Motorsport with a -2 header and super turbo muffler.
If you have any other suggestions on different system let my know.
Web
83zx
 

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Discussion Starter · #8 ·
RE: Took my cat off after adding 2.5" and...

It really made a diff in the output of the car! Serious difference, but that doesn't mean you will see the same kind. Mine may have been clogged more than yours. It did make the car louder. It is still livable with the same boominess inside at 2.2k rpms. It's noticably louder. I can live with it though. Did you get a two chamber or three chamber muffler? Mine is a 2 chamber.
 

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Summit has one for $80 if I remember right
 

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Trevors right. Your exhaust system will not change your RPM's at a given speed but what will change is your shift points. Your car will make a slightly higher useable HP and torque so you can and probably do shift higher. Gas mileage will be better if you keep your foot out of it. Most don't due to the cooler tone. I wouldn't hollow the cat, I can't even believe the shop offered to do it since it is a Federal crime. I would get a Random Technology Hi Flow Cat and get the head pipe from MSA that comes off the exhaust manifold and ends in a 2.5" pipe. The Random Technology cat loses NO HP to a hollowed Cat. By the way, the 78 with no cat is not illegal unless it was a CA model. Federal models had no cat.
 
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