driftmissile

Under a good-running '79 RX7 I recently bought, the new stainless exhaust headers glow red until they hit this also new stainless cylinder. ( see photo)


newer 79 RX7 exhaust, resonator or cat>


Afterward, it's old rusted pipe and a large muffler. Would that round stainless cylinder right after the headers likely be a resonator (pre-silencer) or catalytic converter? It's not wide, extra-shielded, or extra-air-tube like the stock catalytic. I know cat's can clog and reduce airflow; could a resonator also clog? Is it worth pulling it off and looking inside?

Lastly, what is the likely cause of the glowing red headers? I know it's burning excess fuel & air in there. The rear rotor's exhaust pipe glows a bit more than the front one. I know rotary's normally run rich and most likely this carburetor-and-points one does too since it doesn't have an oil-delete and I pre-mix 100:1. I know it gets air because the air pump works. It has new plugs and wires but I haven't done a basic tune-up yet like points, dwell, timing, valves, or idle. My guess is timing. Yours?

Thank you.

LongDuck

That's a Racing Beat header and presilencer, aka resonator. Its a hollow pipe through the center - as in you can see all the way through it - with a perforated section on the outside with stainless steel mesh to help quiet the exhaust. There's nothing in there to clog up.

Also, you RB header is glowing red hot because the engine is running LEAN, not rich. You need to check your Fuel flow (*volume and pressure), because running it that hot is going to lead to internal engine damage over time. The exhaust is carrying a lot of the heat out of the system, but that heat is inside your combustion chambers and will temper seals, springs, and other important parts due to excessive heat.

anderml1955

Also the air pump is not really doing much since the RB header deleted the thermal reactor.

LongDuck

The Air Pump would still be injecting fresh air into the exhaust ports if the ACV is still installed on the Lower Intake Manifold, but this is actually work against you because it's creating even more heat in the header alongside your lean burning condition.

From the aviation world, airplanes have exhaust gas temp gauges for exactly this reason. When the EGT goes up, you enrichen the mixture to save your engine. More fuel means a richer burn which brings temps down immediately. Continuing to run an engine very lean is a recipe for disaster.

Unless his is an afterburner setup we've never seen before,

driftmissile

Thanks for the direction, LongDuck

That's exactly what was happening. The air pump was still connected, pushing lots of O2 into the hot exhaust which started burning a few inches downstream and turning the headers red. I disconnected the hose from the air pump and now the air is blowing down beside the engine, over the headers sorta. I capped off the other end that leads to the engine/exhaust. No more red. Now it runs rich, at least from the smell of the exhaust.

Once warmed up it runs very well -- good enough for me to learn the suspension all around is shot. New rear springs, shocks, and bushings are my next project.

I read that it's best to leave the air pump in place and spinning due to how the belts are loaded. Correct?