'magnaflow' catalytic converter

[ke70dave]

yeah with N/A cars you really need to keep the exhaust relatively small, because the smaller pipe will create more suction and "extract" the exhaust out, helping your motor along. if you go to big of pipe the suction force gets smaller, and thus not as helpful to your motor.

i guess easiest analogy you can think of is when you use a tube to siphon water. its alot easier to get the siphon running with a small amount of water in a small tube, it doesnt take much effort for the water to fill up the tube and begin siphoning the water through (essentially creating vacume in the tube, sucking more water through). (ie small capacity engine, needs smallish pipe)

now if you used the same amount of water for a tube that is twice as big, it will be alot harder for the siphon to begin, you would need physically need more water for the vacuum to start having an effect. (ie bigger engine needs bigger exhaust!)

[shorty]

ive had magnaflow mufflers and cats b4

a bit pricey but u get what u pay for

i had no problems with mine

but i recommend if ur keeping ur 20v N/A, go a 2.25 system

like those guys b4 me said, with N/A u want more back pressure

[Hen is a total nutcase]

I think you'd be bananas to run 2.25 exhaust out to a 3" valve and back to 2.25. The steps up and down and all the welding required will do no good for flow. Ditch the valve, or if you really want to run one find one that's suitably sized.

Hen

[Paw-DK]

<div class='quotetop'>QUOTE (medwin46 @ Mar 19 2008, 09:17 AM) </div>yes medwin this is what I'm trying to do for my zorst
[4into1 extractors continuing to a 2.25' piping to a CAT to a 3' butterfly switch back to 2.25' piping to a 2.25' hotdog and then a 2.25' straight thru pipe]
dunno if i should put the hotdog close to the straight thru trying to make it look like a muffler for the pigs lol
or close to my butterfly where i could use a 2.5' piping between the two and then back to 2.25 piping to MAYBE get better floww instead of jumping from 3' into 2.25' (same concept as using a 2.5' cat for a more gradual jump in pipe size5)???

but am still thinking what cat SIZE i should use!
its either a 2.25' OR a 2.5' OR a 3' cat??
any more say on increasing then decreasing exhaust size

and for ditching the butterfly switch thats a hell no.. I'm using no muffler and yes its uber loud but sweet groan hahha
i can only find it in 3' but i thought it would be a good idea exactly what medwin said above

sorry if what i wrote is confusing!
but thanks all for replying made me think alot

[Marco]

we use magnaflow at work we have had no issuses no recalls. but if i were you i would do a knock out job.

[PuGZoR]

I have a mate that works at an exhaust shop, and he told me they're pretty ordinary... Apparently are good for the first 3 months but go downhill after that? For cost vs. performance, yeah, just knock the internals out of an old cat, heh. Somewhat illegal though.

[gunbz-r]

you'll find most cats stop working effciently after 3 months

[Vezza]

Skyline GTR cats are apparently one of the best, otherwise a genuine metalcat are tops and actually have a "catalytic" effect to clean your exhaust gasses. However not cheap though at $650, but you get what you pay for.

Hmm.... and as for the gutted cat mod, as mentioned fairly common. BUT, considering ae86's have a general tendency for attracting unwanted attention, a trip to emissions with a gutted cat will set you back about $10,000. So I guess it's up to you to decide if a cat is worth a few hundred bucks.