lemonade

im going to be building a streetported 4 port 13b, NA, 48dhla dellorto carb, racingbeat headers, more in my signature......


i was wondering if putting a high flow cat would drain the power? say i was to have straight back exhaust, mods i have now, and a nice big streetport my mechanic claims will put me at about 220-40 at the wheels. if i turned around and put a high flow cat on, how much power would i lose?

would i lose acceleration? throttle response? basically, what are the set backs of a high flow cat.



i want one, because i want my car to stink less, be quiter, yet still be fast and hopefully sound good.

lemonade

bump

Zyrano

I'd think if you get an oversize bonez, you wouldn't loose much power, it's fairly high flowing, and you can see right through it(well, you can see light through it anyway), but i don't know exactly how much of a difference it will make.

purple82

I don't have any tested power comparison between with and without a cat on my SP 13b, but it definitely is more quiet with it. Although it's still loud.

Also, be warned, there isn't anywhere close to enough O2 in the exhaust of the rotary to oxydize the unburned hydrocarbons, without a correctly functioning air pump system, your exhaust will still be stinky.

lemonade

how does the air pump work? how would you go about reinstalling it? does it add to the restrictiveness?

lemonade

do you need to install something to the actual block?

purple82

Yes, the air pump is mounted to the engine and run off a belt, the air is metered by what's so affectionatly reffered to as the "rat's nest". You're not going to have any of the stuff you'd need for a proper emissions control system with a Dellorto. You can still run a cat without all that, but it's not going to oxydize the unburned hydrocarbons and CO in your exhaust very well.

mcnannay

you can get an electric one, i think the corvettes used an electric air pump

steve84GS TII

With a Dellorto carb,there wont be any way to hook up the ACV.The ACV is neccesary to properly distribute or cut off the cat's air supply under changing circumstances.Simply hooking up the air pump to the cat will get you by smog testing,but I would unhook it immediatley after or the cat will overheat and you could burn the car down.The ECU moniters engine load,throttle position,RPM,exhaust and floorboard temps and engine temps to determine where to send the smogpump air via the ACV.I goes either to the cat,the ports or back to the aircleaner to let the cat cool off if it gets too hot.
A 2.5" or 3" Bonez cat wont hurt performance and will cut some noise.RP Online sells them premade for first gen exhaust systems or you can get them blank for welding into custom or headered exhausts.I run a 3" on my ported TII and it doesnt hold me back from making power,even at 14psi of boost.

lemonade

if i install a highflow cat without an air pump, will the cat go to **** after a little while? will it burn up real quick? also, can you run premix through a highflow cat?