project7s

iTrader: (5)

The exhaust on a gsl se I'm restoring is messed up som I'm decideing on what to put back on it. I'm really wanting the racing beat street port setup since I already have a rb sp muffler.
My question is on the collected header there's a place for the o2 sensor and the road race one does not have a place for one. Are you suspossed to just laeve it unhooked or weld your own bung in one of the header tubes? The engine in the car is stock with the stock fi setup. Thanks

j9fd3s

iTrader: (3)

the center section has an o2 bung

project7s

iTrader: (5)

oh ok that makes sense. ive never seen the rb center section in person and from the pictures on rb web site they don't show you the drivers side of the set up. so the rb center section has a bung and the six port tube already on it as delivered from rb?

t_g_farrell

iTrader: (1)

You should call RB and verify. I know for non-GSL-SE there's no bungs or tube hookups.

Maybe for a GSL-SE its there but the 6 port tube I'm not too sure it will be.

ioTus

iTrader: (5)

Get the Mazdatrix version of the RB street port exhaust. They have both he 6-port actuator as well as an O2 bung welded on:

https://www.mazdatrix.com/r-exh-85.htm
P/N: 16-MZTX-4230

project7s

iTrader: (5)

I noticed that mazdatrix modifiys the rb road race header by welding a bung in it for the 02 sensor. they put the aux. Port hook up on the header aswell stating to works better being closer to the engine than on the presilenser. So knowing that I'm going to get there header and some of there flanges and have a shop make me some pipe to connect it to the racing beat road race muffler I already have.

WalkerCaroll

For the GSL SE, the RB Streetport setup does not have an O2 sensor spot anywhere. (I've found my car runs better without it hooked up lol) and the center section should come with a tube that extends to meet the exhaust tube for the port actuators.

ioTus

iTrader: (5)

Correct the best place for backpressure pickup tube is on the bend of the front rotor header pipe.

WalkerCaroll if you're using the OEM computer then you need to have the O2 sensor hooked up. If it was running poorly with it plugged in, pick up a new one $40 Rotary Performance | FC Fuel (3/4 down the page)

project7s

iTrader: (5)

I'm going to run the header from mazdatrix that has the o2 sensor and pick up tube on it. Then I can just run some regular pipe to my road race mufffler. I will be useing the right flanges for the center section, so it will still be unboltable but I've found the racing beat road race set up is still a bit quite. That's why I'm going to use thin wall pipe in my center section, and if I get tired of it all I would have to do is get the 12a center section.

j9fd3s

iTrader: (3)

RB actually sells the thickwall tubing for a good price.

project7s

iTrader: (5)

Yeah I've seen that. I just wonder if it would still be quite with that? Right now I have another car that has a 12a with rb street header stright piped with thick wall pipe back too the 79-80 rb street muffler and its too quite. I know the long primary will be louder, its just a question of how much louder? That's why I was thinking of useing the thin wall pipe.

Jeff20B

iTrader: (13)

How would thin wall make things quieter? Or did you want louder? I'm very confused.

WalkerCaroll

Why do I need to have an O2 sensor? I am running a stock computer in the car. It's running better now that the O2 sensor isn't connected. I've got the correct backpressure tube for the ports but the header didn't come with a place to put an O2 sensor so I don't know why I should have to modify the header they gave me. I don't live in a place that requires emissions testing so I don't know any other reason.

ioTus

iTrader: (5)

O2 sensor isn't specifically in place for emissions testing - thats the catalytic converter. The only time an O2 sensor will be helping with emissions testing specifically is if there are two of them, one pre-cat and one post-cat, to determine how effective the cat is. Only the post-cat sensor is used for emissions here, the pre-cat is used for the ECU to determine air fuel mixture. GSL-SE do not have a 2-sensor emissions system.

Start here:
HowStuffWorks "How does the oxygen sensor in a car work?"

Then I suggest browsing through the Factory Service and Training Manuals which fully describe the electrical system to which the O2 sensor belongs, that should give you a good starting point of what the O2 sensor is doing and why you should use it:

Foxed.ca - Mazda RX-7 Manuals

You may not find anything directly relevant, but when modifying these systems you need to have a very clear and specific reason and understanding of the why and how to do it. This prevents odd "wtf!?" situations down the road. It may seem like a drag up front, and overwhelming at first, but its crucial to understand a system as much as possible before changing its variables.

If the car is running better without it that means the sensor is bad and sending the computer the wrong signal, throwing the A/F ratio off and making it run poorly. With it disconnected it's sending a constant, wrong signal to the computer, or erroring out and the computer is ignoring that input (not sure as i havent delved that deep). This constant signal is still throwing the tune of the engine off, but not as much as the variable incorrect signal of having it plugged in.

Many aftermarket header manufacturers for the 1st gen do not include an O2 sensor bung because they assume that if you're installing their exhaust system you have also "upgraded" to a carburetor. This is the case because for quite a while that was the only aftermarket upgrade available for these cars.

Any modern car, or any aftermarket stand-alone fuel management system, including full on race-track only cars, require an O2 sensor for a) initial tuning purposes and b) closed-loop burn ratio detection to micro adjust the a/f in real time.

Unless you're hacking into or re-engineering the OEM computer (like with a piggyback or separate standalone fuel system), i strongly suggest using the systems that the Mazda engineers developed.

Think about it like this - if a part goes bad the solution is not to throw it out - the solution is to repair or replace it. This is not the same as changing one system to another (swapping catalytic exhaust for straight exhaust), however its still the case that if the muffler were to go out, the solution is to replace it not just chop it off.

RX7.com even suggests that the O2 sensor is a 30k mile part, and I doubt many (if any!) one on here replaces them that frequently.

Another thing to do is replace the fuel filter - usually overlooked and undermaintenanced, and can throw off the entire tune of the car as well.

Jeff20B

iTrader: (13)

I've been told the S4 NA ECU doesn't really need the O2 sensor. So if a slightly newer ECU doesn't really need one, the slightly older one surely doesn't as well.

But hey, it's not my car. I won't lose sleep over whether it gets one or not.

ioTus

iTrader: (5)

My Haltech F9 did not use one - though it had the capability (if wire up your own loom for it) for closed-loop operation. Although it's not required for operation its a system to fine-tune the mixture on the fly. Personally - i'd keep the system in place, especially if its wired for it and expecting the input.

Jeff20B

iTrader: (13)

The MegaSquirt is the same way. I've never actually had an O2 hooked up to mine. Should I have? Yeah, but I didn't have one at the time. Now I have a wideband but it's going on the blow through carb setup instead. This actually needs one as you know. I just have to convince myself of this fact.

project7s

iTrader: (5)

Yes I'm wanting it the be louder, well raspy loud. That's why I'm thinking of going with the thin wall center section. I'm thinking if I use the thick wall pipe it would lose the raspy and be too quite.

j9fd3s

iTrader: (3)

the way that the 02 seems to work is that the ECU is set to run a little rich, and the O2 only pulls the ECU lean, so that when the O2 isn't hooked up the car runs fine.

you will loose MPG though

ioTus

iTrader: (5)

Thanks for the specifics J9!