87racer

my local auto parts store carries two replacements, one is aparently for the rx-7 and it costs $37, the second is a universal sensor for $17. Other than the price, is there any difference between the two? i hate to be cheap but unless i have to i dont want to pay $37 for it.

ok, about the header, i got a RB header and i was wondering, does this replace two of the cats?? the damn thing is long!!! i didnt get the presilencer so should i just have some exhaust shop cut my existing exhaust pipe and put a flange on it that will fit the header? im not really worried about the sound so much but i was just wondering if it would work for a while.... thanks

Rotorific

iTrader: (1)

Im not too too sure but i think with out the presilencer it will bolt up to the main cat? I know for sure that the precats are gone because of the header. Pay 37 for the RX-7 O2 sensor its worth it. -Gabe

87racer

the problem is that there is no flange after the main cat. the only flange on the whole exhaust is the one right after the exhaust manifold. the damn shops around here want 100 bucks just to cut the exhaust and put the flange on!!!! can i just take a wire saw and cut the damn exhaust??? and then get a flange to fit it??? or is it worth it to just pay the $100?? Thanks

Mark S

iTrader: (1)

The RB header only bolts to their presilencer. You'll have to have a pipe made (or buy the presilencer).

Your profile says your car is an 87NA. You do know if you use a header without a presilencer, your 5th and 6th ports will not open. They rely on a pickup tube in the cat (or a tube on the RB silencer) to harness exhaust flow to open the ports. Do a search on 6 ports. You'll get the phone book, but they provide 15-20% of your HP up high so it'll be worth the read.

On the O2 sensors, just make sure they are both Bosche brand. If they are, the only difference is the Mazda specific on has a built in conector, and the universal one requires you to splice it in. Just cut the connector and wire off the old sensor and splice that in so you'll still have the plug if you need to remove the engine/exhaust.

87racer

well, about the 5th and 6th.... my exhaust is custom so the tube goes back all the way to just before the main cat, is this how it is stock? we held the header up underneath the car and it looks like i wont have to cut off the part with the little tube. will my 5th and 6th open if it is like that..... so it goes..... y-pipe, main cat, little pipe thingy(cool name huh?), header. will that be enough pressure? or do i really need the presilencer? thanks

87racer

bump bump

dr0x

Even w/ the silencer Id be wry of them opening. Read the sticky about 5/6th ports in this forum. That setup w/ the air pump isnt expensive.

ra ra rotory

"the problem is that there is no flange after the main cat. the only flange on the whole exhaust is the one right after the exhaust manifold." Its an s4, so it actually has a flange after the main cat, well, there is one at the exhaust manifold, one between the 2 pre cats and main and should be one at the y pipe.

87racer

nope.... its an S4 alright but it has a custom exhaust. its all welded..... i think im gonna try the air pump activation method. Any suggestions??

87racer

bump