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1985 Dodge Daytona Turbo Z
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Discussion Starter · #1 ·
I saw a video of someone making roughly 30+ horsepower on a turbo’d first Gen miata by removing the cat. Would this hold true to a T1 car? I don’t have a cat anyways but I have 2 ways of thinking that it would effect performance. According to Legend Donovan, the cars ran good enough without it to pass emissions, back in the day.

(These are just my own thoughts, not fact)

1. The cats back then aren’t as efficient as they are now, meaning it would be MORE restrictive than that of a newer on.

2. The cat would be less restrictive as requirements rise, so ultimately the cat wouldn’t be as heavy duty allowing more air flow that that of a few years newer.

i could be completely wrong about all of the above. I didn’t live in the time so I have no idea what the standard’s were. I’m still a rookie.

my car in particular had 146 from the factory, (and while cars lose horses overtime, I’m still going to have it machined and completely gone through, so hopefully the normal target is achieved) I’m curious how much could actually be gained by its removal. If the car was super throttled back by emissions, I bet without it, it would’ve been a much more popular car.

In the big picture I didn’t get a cat with the car, I’m not ever getting one, and anything emissions related is getting ripped off. (Should get me a few months of enjoyment before it has to be converted to electric, thanks Joe Biden.)

(Semi-unrelated) For a Turbo 1 car, (85) there’s no cat right after the exhaust port correct? Just the one under the car?

just a topic for discussion, thanks.
 

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1992 dodge shadow es turbo
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Hard to say because it’s very uncommon to just remove the cat and not upgrade the exhaust pipe and muffler. I would say 5 to 10 hp but the gains would really be in spool time of the turbo.
 

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1985 Dodge Daytona Turbo Z
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Discussion Starter · #3 ·
Hard to say because it’s very uncommon to just remove the cat and not upgrade the exhaust pipe and muffler. I would say 5 to 10 hp but the gains would really be in spool time of the turbo.
Muffler is gone too. It’s literally a straight pipe directly from the exhaust port of the turbo
 

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How much power does a cat removal actually make?
It doesn't make any more power, it just loses less power;). You'll probably tire of the exhaust with no baffling at all. Well, either that or your neighbors, pets, and wildlife will. Seriously, you like loud, drony, obnoxious, ugly sounding exhaust? Nothing like the sound of compressor surge, when you let off the throttle. So soooothing... To each their own I guess...
The HP advantages will be at WOT pretty much only. Almost any street driven turbo car is in boost less than 5% of the time. To answer your questions, I've heard around 10 HP at WOT on typical performance 2.2/2.5. Turn up boost 1 PSI to compensate...And yes the T1 turbo car had just one converter in the middle of the car. Some models also had resonator in addition to muffler in back. Some people run a cat(s) without muffler(s). Did you consider that?
BTW, factory cats are a much higher quality than aftermarket cats. IIRC, Walker has like four different levels of quality of cats. Only the expensive one MAYBE approaches OEM quality. That is typically the only one that can be shipped to CA.
 

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1985 Dodge Daytona Turbo Z
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Discussion Starter · #5 ·
How much power does a cat removal actually make?
It doesn't make any more power, it just loses less power;). You'll probably tire of the exhaust with no baffling at all. Well, either that or your neighbors, pets, and wildlife will. Seriously, you like loud, drony, obnoxious, ugly sounding exhaust? Nothing like the sound of compressor surge, when you let off the throttle. So soooothing... To each their own I guess...
The HP advantages will be at WOT pretty much only. Almost any street driven turbo car is in boost less than 5% of the time. To answer your questions, I've heard around 10 HP at WOT on typical performance 2.2/2.5. Turn up boost 1 PSI to compensate...And yes the T1 turbo car had just one converter in the middle of the car. Some models also had resonator in addition to muffler in back. Some people run a cat(s) without muffler(s). Did you consider that?
BTW, factory cats are a much higher quality than aftermarket cats. IIRC, Walker has like four different levels of quality of cats. Only the expensive one MAYBE approaches OEM quality. That is typically the only one that can be shipped to CA.
The car itself isn’t too horribly loud, but I could see it getting annoying. I was thinking about getting a cutout or something. I kinda want something silent but deadly- quiet lows and loud highs.
 

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The car itself isn’t too horribly loud, but I could see it getting annoying. I was thinking about getting a cutout or something. I kinda want something silent but deadly- quiet lows and loud highs.
Did nothing for spool time on a 86 2.2 Log. Actually lost some off the line torque but the top end was a lil better.
 

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1992 dodge shadow es turbo
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Did nothing for spool time on a 86 2.2 Log. Actually lost some off the line torque but the top end was a lil better.
Interesting, I never had a log car but I know on a T1 mistu you can feel a difference
 
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