Looking at RB's site they make sure to point out that their headers (or exhaust port tubing for the rotary elitists... ) don't have provisions for an 02 sensor. Will this cause a problem? Do they in any way influence performance in the 1st gens, or could I just leave it unplugged? I obviously wouldn't be able to pass emissions with that setup so I was wondering why else the ecu needs it?

Referring to RB full exhaust setup by the way.

 

i had rb exhaust on mine without the o2 sensor and it ran fine. i didnt notice problems. my friend that is a mechanic and races 1st gens told me they really arent needed.

 

O2 sensor is only used at light throttle for gas mileage and emissions

 

As stated above, the SE uses the signal from the O2 sensor to determine 'closed-loop' fuel injector pulse width and duration. What this means is that the car will normally follow an 'open-loop' fuel injection map under throttle to get best performance, but once you get to cruising speed and use cruise control, or light throttle, the ECU will use the O2 signal to determine how much unburned fuel is being run through the engine, and then make minor adjustments to the fuel mapping on-the-fly to reduce the O2 in the exhaust. Once it finds the correct stoichiometric balance of air/fuel (14.7:1 for ALL engines), then it will constantly make small adjustments based on the O2 signal - this accounts for better fuel mileage and better overall performance of the engine.

If you remove the O2 sensor due to not having a 'bung' on your exhaust system, your ECU will not be able to determine this setting, and will likely be running rich at pretty much all throttle settings. For the money, call up Mazdatrix and get their 'modified for SE' header that includes the O2 sensor bung and do it right. It's a RB header, but has been drilled for the O2 sensor, welded back up, and then chrome plated for durability. I'm very happy with mine, and glad that I'm still able to use the O2 sensor like Mazda designed.

While you're there, pick up their presilencer which includes the '6'-port feedback tube. This is necessary to correctly drive your '6'-ports. Installation of the correct Mazdatrix parts for your SE WILL NOT require you to remove the airpump or ACV valve that controls exhaust injection air - you can have the header, presilencer, and whatever muffler you want and still leave most of the emmissions stuff in place without negatively impacting performance.

I left all my airpump, ACV, etc. in so that when I swap out my exhaust every April for emissions testing, I have a minimum of work to do - car runs great, and continues to pump fresh air into the presilencer via the airpump which both reduces exhaust temperature, and further quiets the exhaust pulses. HTH,

 

my friend just had a bung installed on his racing beat header. he has the bung right where the two pipes collect.

 

Awesome. Thanks for the replies. I had planned on getting the full RB system. I will check Mazdatrix's site for the modified version.

As a side note: my SE passed emissions yesterday!! Now I can get tags, and order the exhaust system!!

 

So these are the parts I need?

The GSL-SE headers here.

The presilencer here.

The muffler here.

The pic on MT's site doesn't look like the road race/sp version of the header. Would I need to call them to specify?

 

I am thoroughly confused. I have an RB header I bought from RB (80% sure that is where I got it), and it has a threaded side port near the tail end (after Y) which is exactly where the O2 sensor goes.

My other car, which also has an RB header (vendor unknown) has the O2 sensor screwed into this same threaded hole.

Both cars are '84 GSL-SEs

Am I smoking something funny or isn't that for the O2 sensor?

Thanks,
BTC

 

Header pic:


CORRECT presilencer pic (Mazdatrix), notice that it has the correct '6'-port sensing tube installed:


Racing Beat muffler pic:


And, TexasGunRunner - you are correct that this is where the O2 sensor goes for the SE-cars. There are 2 things that you need to be aware of when purchasing these header parts for the SE; 1) O2 sensor 'bung' threading, and 2) '6'-port sensing tube in the presilencer.

Without #1, you won't be able to run 'closed-loop' fuel injection mapping under cruise and light throttle, and without #2, you won't have your variable port timing that's afforded by the '6'-ports, because you won't be able to actuate them unless you hook up some other system. IMO, the exhaust backpressure system works just fine as long as everything is in good condition. HTH,

 

Thanks Longduck. That is the info I was looking for.