Test pipe

[Leo]

I have bone stock 98 eclipse gst spyder. For my first mod I want to remove the cat and put a test pipe. Should i do it? Am i hurting the engine ?What are the good and the bad? Thanks

 

[99OZDSM]

The cat is the most restrictive part of the exhaust. You will have less exhaust back pressure, which means you will have a quicker spool. I also think it sounds a bit better personally. Most people probably wouldn't notice.

The bad is the toxins you release into the atmosphere. If you don't have a tuning solution you will throw a CEL as the rear 02 sensor will detect you no longer have a cat installed.

 

[bo0st]

You should feel a nice difference in power without the cat on the car.

Only downside, emissions.

 

[gst-turbo]

You might get boost creep with a down pipe because no back pressure

 

[PlanZero]

I wouldn't bother. You won't notice much difference, plus it will be a royal PITA getting the old cat off. If you don't care about emissions, and if your county doesn't either, just upgrade to a turbo back 2.5-3". Most aftermarket downpipes are designed to be catless and connect directly to the catback. You will feel a difference with this. If you go 3" you may want to port the o2 housing or get a tubular housing to prevent creep. Although I get bashed for it sometimes, I love my DNA 3" exhaust. Fit perfect, decent quality, sounds awesome, and cost $230 for the 02 housing, DP and cat back.
And you can buy a $5 spacer for the rear 02 sensor to prevent a CEL.

 

[bo0st]

I wouldn't bother. You won't notice much difference, plus it will be a royal PITA getting the old cat off. If you don't care about emissions, and if your county doesn't either, just upgrade to a turbo back 2.5-3". Most aftermarket downpipes are designed to be catless and connect directly to the catback. You will feel a difference with this. If you go 3" you may want to port the o2 housing or get a tubular housing to prevent creep. Although I get bashed for it sometimes, I love my DNA 3" exhaust. Fit perfect, decent quality, sounds awesome, and cost $230 for the 02 housing, DP and cat back.
And you can buy a $5 spacer for the rear 02 sensor to prevent a CEL.

If he won't notice a difference then there's a more serious problem with the car.

99% of turbo DSM's will be faster without the cat.

 

[simplejoe]

If you're having problems with your cat, then I'd change it out. I'd start out by intake and catback. Then work you're way up. Your taking the cat out but still keeping the restrictive muffler. An intake and catback will free up some hp and the car will actually breathe better.

 

[PlanZero]

If he won't notice a difference then there's a more serious problem with the car.

99% of turbo DSM's will be faster without the cat.

I'm only trying to save the OP the hassle of merely deleting the cat. Only because the differences I noticed between just replacing the cat with a welded in 2.25 pipe compared to replacing the entire exhaust with 3" were night and day. Not to mention much easier. Of course that's also assuming he removed intake restrictions as well.
On the other hand, if the OP has welding skills it should only take him a few minutes to chop out and replace the cat with a pipe. Then sell the cat and use the $ to snag a snazzy filter.
No matter what, replacing the 18 year old cat with anything is a good idea. But as we've all said, make sure you thoroughly understand your county's emissions criteria first. If its required, either look into a hi flow cat or just swap in the old exhaust when you need to, which is much easier said than done on a fwd.

 

[EvilGST]

I noticed a good increase in my mpg when I removed the cat. I also have a 3" downpipe with a 3" section of pipe with a Magnaflow straight muffler to a dump, my boost does not creep at all if your concerned about it. But to get the most out of removing the cat you really need a proper exhaust.