19 replies to this topic

[Radio Flyer]

I have a 85 GL wagon and everything is stock and running fine, but I'm thinking of gutting my catalytic converter for better breathing. Anyone done this on a similar vintage Suby? Anything in the design of the cat that makes it any more difficult than other cars? After done did you notice any performance or mpg gains? Did it sound any different? Lookin for a fun project for the weekend, but don't wanna waste my time if I won't see any dividends or worse if it'll run or sound like @&$;.

I know that it is illegal for on-road usage afterwards...blah blah blah.

Here is a pic. Sexy huh? ;-)

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Edited by Radio Flyer, 02 March 2013 - 06:54 AM.

[987687]

Unless your cat is clogged, you're probably not going to notice anything. I gutted my rear cat because I smashed it up against a rock and broke the stuff inside which caused it to clog. After gutting it, I didn't notice any difference from before.
I'm probably gonna go to jail now for ruining the environment.

Edited by 987687, 02 March 2013 - 08:24 AM.

[grossgary]

i've gutted 80's XT6 cat with no notable difference. 

[ivans imports]

it will take power away as the car is tuned to run a catt have seen very little proof that removing the catt helps power in anyway unless its pluged

[Radio Flyer]

But a genius friend of mine said I'd get an easy 50 hp and 10 more mpg! ;-). Good to know. Looks like I'll be shooting sage rats for fun this weekend instead of bastardizing the Suby. Thanks guys.

[monstaru]

On the contrary, IF YOUR vehiclee is carb'ed, It WILL help.Every one of the cars stated was FI.
I have gutted every cat I have had on carbed vehicles and noticed a difference.

When you gut the cat, start looking at the Intake next.more flow out can use more flow in.

Your friend is wrong , kinda.The numbers are TO high.But there are results.
cheers

[scoobiedubie]

If you leave the front cat alone, but install a 2 1/2" pipe running out of that to the muffler, and eliminate the rear cat, then you will notice an increase in horsepower of maybe 5 to 10 ponies.  Don't expect any improvement in gas mileage.

[NorthWet]

My Opinion (free of charge today, and worth about that) is that no single change will net you a noticeable improvement.  (With the exception of forced induction.)  The engine is a system, and changing one item in a relatively balanced system to remove a perceived bottleneck just tends to shift the bottleneck somewhere else.

 

In the end, you are dealing with an engine with siamesed ports, and that (quickly) becomes the ultimate bottleneck.

[MilesFox]

I gutted the cat on a 95 legacy and it ran super rich and got 18-20 mpg. I gutted both cats. Retrospectively, the o2's would have functioned better if i left them alone. Vs. hollowing the cats, o would try to eliminate them with a straight piece.

 

I have the idea of simulating the cat with by using a cherry bomb at the header and making o2 bungs on either end.

 

My argument here is that it fouled or misread the o2 sensors and thus ran rich. ou could fool the o2's with a resistor, but then again if you did that you could just eliminate the cats.

 

I would say leave them be with a mpfi using 2 o2's.

 

I think the argument for gutting the cats with a carb is valid.

 

I would only gut the cats on an mpfi if one was failed and i had to salvage it out of lack of parts.

 

The cat is worth more in scrap as a complete unit, vs the guts by themselves. I trued to turn in the debris at the scrap yard and only got 3 bucks for it. Otherwise the cat would have been worth about 30 bucks whole.

 

If you want to play with exhausts, take my example and put a glass pack muffler behind the donut gasket in the mid pipe, and straight pipe the muffler. You can literally chop the midpipe, install the cherry bomb, and use the leftover section to replace the muffler with.

[MilesFox]

I did gut out the cat on my 86 3door because the tail piece broke off at the cat and i had to weld it.

 

The first time i gutted the cat it was on an carb ea82 with the cherry bomb at the midpipe flange and a turnout 2" pipe and it had better midrange torque. I give this more credit to the cherry bomb than gutting the cat. The subaru header y-pipe itself does a good job and basically does all the work being tuned to the engine, and the rest of the exhaust is just to take it past the rear bumper.

 

just the y pipe and no other exhaust running open frees up a lot of upper rpm, but you do lose some torque. But it does breathe better. Then you put the glass pack at the end to restore the low end torque.

Edited by MilesFox, 02 March 2013 - 11:57 PM.

[r81gsr95]

very nice looking subaru 

[1 old hiker]

Let me know what you end up doing and how it works. I just picked up an '87 wagon. I love it and will use it as a daily driver, plus getting me to hiking / mtn biking destinations.

Any thing I can do to improve performance would be a help.

[ystrdyisgone]

I am interested as well. I was actually thinking about doing this to my wagon today, but woke up to snow and wind :-(. Woes of a driveway mechanic...

[Radio Flyer]

very nice looking subaru

Thanks. Check out the new summer look. She hasn't had a bath for months...still sexy ;-). Thanks to SuperBrat for the swank Enkeis.

My wagon is carbureted, so I may try it, but with a junk yard unit so I can switch back to stock if the move backfires.

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Edited by Radio Flyer, 18 March 2013 - 02:56 AM.

[spazomatic]

I gutted the cat on my 84. It only had one at the "Y". It was harder than most....usually on most cars you can just take a rod and knock out the catalyst, but no not on mine! I ended up cutting a 4x4 hole in the top with a torch (use a fan to keep the smoke away from ya) pried, picked and dug the wire mesh and catalyst out, then welded a patch on top. It is just a tad louder, but i did gain some extra power. At least, thats what my seat of the pants-dyno tells me. No backfiring....
But my motor is completely de-emissioned, running a weber and turbo muffler. It passed emissions even! And gets around 26mpg.

Id say though, that unless you have evidence that it is plugged, it may not be worth the effort

[ivans imports]

I put subaru catts on everything even my lawn tractor no unburnt feul smell and i dont breath hydrocarbons win win and it shoots flames when she backfires !

[mdcc2010]

I gutted the cat on my 84. It only had one at the "Y". It was harder than most....usually on most cars you can just take a rod and knock out the catalyst, but no not on mine! I ended up cutting a 4x4 hole in the top with a torch (use a fan to keep the smoke away from ya) pried, picked and dug the wire mesh and catalyst out, then welded a patch on top. It is just a tad louder, but i did gain some extra power. At least, thats what my seat of the pants-dyno tells me. No backfiring....
But my motor is completely de-emissioned, running a weber and turbo muffler. It passed emissions even! And gets around 26mpg.

Id say though, that unless you have evidence that it is plugged, it may not be worth the effort

 

A lot of cars don't NEED a catalytic converter to meet tailpipe emissions testing standards for their respective years (for example, Honda's CVCC engines were cleaner without a cat than most engines that had one), but they were federally mandated for all cars in 1983 regardless of an engine's exhaust stream content. If your car were tested to CARB and/or modern standards, it would mostly likely fail miserably. That being said, any car over 25 years of age is considered an antique and as such need not conform to federal NHTSA or EPA standards (though they may need to comply with state standards, especially in CA), so I'm not worried about restoring my XT's stock system from the aftermarket catless 2.5" turbo-back system installed before I bought it.

 

Really, gutting a cat is really only a good alternative if yours is bad and a replacement is unobtainable or unreasonably overpriced (as many things tend to be for these cars, sadly). You may see a small improvement from doing so, carb'd or FI'd, especially on mid-80s engines that weren't originally designed for them. You definitely don't want to do it on a more modern car with a post-cat O2 sensor because you'll screw up your AFRs. Also, reducing the cat-induced backpressure on a turbo'd system can cause boost creep and/or overspool your turbo, so you may want to be careful if you're running with boost.

[spazomatic]

A lot of cars don't NEED a catalytic converter to meet tailpipe emissions testing standards for their respective years (for example, Honda's CVCC engines were cleaner without a cat than most engines that had one), but they were federally mandated for all cars in 1983 regardless of an engine's exhaust stream content. If your car were tested to CARB and/or modern standards, it would mostly likely fail miserably. That being said, any car over 25 years of age is considered an antique and as such need not conform to federal NHTSA or EPA standards (though they may need to comply with state standards, especially in CA), so I'm not worried about restoring my XT's stock system from the aftermarket catless 2.5" turbo-back system installed before I bought it.
 
Really, gutting a cat is really only a good alternative if yours is bad and a replacement is unobtainable or unreasonably overpriced (as many things tend to be for these cars, sadly). You may see a small improvement from doing so, carb'd or FI'd, especially on mid-80s engines that weren't originally designed for them. You definitely don't want to do it on a more modern car with a post-cat O2 sensor because you'll screw up your AFRs. Also, reducing the cat-induced backpressure on a turbo'd system can cause boost creep and/or overspool your turbo, so you may want to be careful if you're running with boost.

Actually, '75 and newer are required to have cats, nationwide.
Mine was in fact, going bad. Which is why i went to the trouble of gutting it.
And it did pass colorado emissions standards, with a weber and without a cat. Granted, it took me 5 tries....but finally i had the weber set to pass....just baaarely it passed! And then i bumped the jets up a size afterwards, cuz it was running shitty, and way too lean.
Just sayin...

I agree that cats are for the most part, a good idea. The honeycomb design of modern cats barely restricts flow, if at all. And they do help burn off crappy emissions, so....

[NickNakorn]

EA82 Wagon UK spec; no cat, 200miles at 70+mph and nearly 40mpg - I'm chuffed!

[Uberoo]

I don't know if WA has a visual cat check but if they dont then cut the cat out and replace it with a straight pipe.Then take your old cat to a scrap recycler and get money for it.IIRC the last time I turned in a subaru cat I got $30.