last week i had to throw my stock header and car back in my 924s so i can pass the dreaded DMV. i had a msds header and cat-delete on it and found that the 1 and 4 head pipes where raddling together like a mother so i am going to wrap up the header but now i am thinking about getting a high flow cat to drop in my delete pipe maybe like this http://www.summitracing.com/parts/MPE-59956/



what i want to know from the brains of rennlist is will the cat help or hurt the performance of the exhaust system as far as back pressure etc.?

 

You won't notice any change in performance with these new small aftermarket cats... The sound may change a little, but probably for the better.

*If anything thing the back pressure may help with your low end power, and hurt your top end power... But again, i doubt even a dyno would show much of a difference....

 

there is no real difference powerwise for the NA with or without the cat, you'd gain more just by removing the weight of it and that isn't much.

may as well just have one to keep DMV out of your hair, and it will help us all "breathe a little easier"

 

I removed the cat and fitted a pre-muffler. There was definitely a seat-of-the-pants low end improvement but that could be because my old cat was 26 years old. Only other mod on the car was a maxhp chip and that chip might have liked the cat delete better.

 

low end would be nice ever if it is a Minute amount but i think i might wrap the header and see how much sound that gets rid of before going with the cat i sure do love the sound at WOT

 

What size cat and brand did you guys go with? This is something I need to do. Did a search and there's all kinds of different info. Couldn't really come to a consensus after reading through all of it.

 

I deleted my cat and while upper rpm improved lower end did decrease. Thinking about adding a high flow resonator...if I can ever decide what muffler to switch too. Is there a thread that just has exhaust sounds on it around here? Would be a great thing to use as a exhaust 'data base'.

 

There have been dynos which have shown as much as 10hp improvement from deleting the cat.

Granted this is well up in the revs and on a 30 year old cat there is no telling how clogged it could be.

I got $110 for my old cat at a scrap yard.. just sayin.

 

I like DIY projects and I don't have state inspections in my county, so here's what I used: (Summit part numbers)

JEX-A3516S-5 GLASS PACK MUFFLER (in place of the cat)

FLO-942450 2.25"CNTR/CNTR DELTAFLO MUFFLER (in place of stock muffler)

I felt a positive difference all through the RPM range although more so in the upper RPMs. The Flowmaster alone is way too loud for me and had the Honda Civic type raspiness. The Jones glasspack took 90% of that out. At cruising speeds it's nearly as quiet as the stock muffler.

 

i used that same muffler and hated the sound with no cat so i switched to the magnaflow oval type and love the sound other then the rattling headers but i like your glasspack cat idea



+1 to scrapping i am about to make a huge haul of copper and steel from a renovation i am doing....every cent is going to the car or shop

 

Wow, I have find my old cat and take it to a scrap yard! Why so much?

 

If they don't scrap them I bet they turn around and re-sell them. CATs are worth a lot. There was a rash of people here cutting them off of Toyota trucks and SUVs last year. They literally crawled under peopled cars in the street and driveway, cut them out and were gone. Those Toyota ones go for about $600-700 used. Pretty good profit for 3 mins work.

 

i have an 86 n/a . i want a change is stovk exhaust note. could i cut the cat out and add a piece of pipe??

how would that sound

 

it would sound like crap.....

 

but for better results......