milesgk

88 na s4, just replaced plugs & wires. i have a turbo 2 exhaust on it. thinkin' the cat is clogged. could that exhaust be causing the problem? changing oil tomorrow and air filter, new cat...? maybe. what would be the best help?

farberio

iTrader: (7)

Causing what problem?

milesgk

well the line from the car to the engine where i suppose exhaust runs through or is recirculated back to the engine...the high temp hose near the cat burned up and fell off.

i've replaced it a few times and it keeps melting away. so i thought the cat would be clogged...also before that started burning up around 5k ~ 6K rpms i'd get a bit of a sputter, lack of flow through the exhaust(clogged cat)? new plugs(did that)? injection problem maybe(going to use some cleaner next time i get gas, using 87 octange btw.. i heard that was good)...

i put some royal purple and that feels great. i was just curious how well that would be for the engine considering it has 122k miles.

uhm..soo.. should i cut that cat? if i do.. i'm guessing i need to weld the 90 degree angle part that comes out of the cat into that hose and pipe leading to the enjoy?

just trying to figure somethings out about my fc. thanks for the help and checking it out.

Blitanicle99

You can take the cat off and hollow it out. Its very easy. The line running back to your engine from the exhaust is an EGR valve. Its overrated. Clamp that **** shut.

RotaryRocket88

iTrader: (7)

Do not cut it off. It is not related to the EGR. The metal pipe running between the cat and your intake manifold is the split air pipe. The air pump sends air to the cat through this (2 check valves inline to prevent the reverse), and more importantly: The backpressure in this line activates your auxillary ports.

If the line is not connected, the #5 & 6 ports on your 6-port engine will never open. What this means is you lose about 25 hp.

Go here for more information: http://mazdarx7.iougs.com/intakeair.shtml. This is a great page to learn more about S4 NAs.

To keep the rubber from melting off, weld the pipe directly onto the cat, and keep enough length so you can keep the rubber as far away from it. Rubber will last much longer if it's away from the cat itself, since the combustion reactions taking place there produce extreme amounts of heat.

Blitanicle99

Jesus. Rotaries are completely different. I have done this for years and never messed with one but I am becoming surprised on quite a few things.

milesgk

well.. i'm thinking the cat is clogged and that is what was causing the high temp hose to melt?

so i was wondering how i could cut the cat off yet still have the split air pipe connected. after reading your post and a bit more on the link you provided, i've realized how much that pipe is needed. i'm assuming it would more effective to replace the cat..? and perhaps that will solve the issue of the meltin high temp hose and my exhaust leak.

thanks for the help, i've been really curious about this.

RotaryRocket88

iTrader: (7)

Your cat doesn't have flanges on either end so it can be unbolted & replaced? If someone welded the existing one in, have an exhaust shop chop it out and put a new one in.

If the cat really is clogged, you'll be able to tell easily due to the fact that your car will struggle to get past 4-5k rpm. It will be choking the motor. So, if you can make it to redline, the cat may be fine...just not the location of the rubber hose. A working cat can reach 1600 degrees, so the melting doesn't necessarily mean it's clogged.

farberio

iTrader: (7)

You can also look at the Bonez cat from www.rx7.com, it will connect from the exhaust manifold to the catback.