Hey guys,
Just hooked up my wideband and noticed once the car warms up the A/F ratio at idle is in the 17's. If I remember correctly I used to see mid 14's in my previouse cars. Under wide open throttle the A/F go to between 10.5-11.5 so thats fine but when I let go of the throttle it goes super lean (seen in the 20's) and then when I get to a stop I see between mid 16's and mid 17's again?

Is this normal for an RX-7? Guys with these mods..... What A/F do you guys see at warm idle.

K&N Drop in
Downpipe
Midpipe with highflow cat
Catback
Profec B Spec II Boost Controller
Pettit ECU

PS, When I hold a constant speed the A/F go between 13 and 15 so that seems normal. It is just idle and deceleration.

Thanks!, Jason

 

The only one not normal is your idle. Do you have your air pump hooked up? Honestly I dont think a rotary engine would idle at 17. They need more like 12.7-13.5

 

Yup the airpump is hooked up to the aftermarket cat.

 

well theres the problem...whenever your air pump is running and the acv is directing air to the exhaust your Afrs are going to go silly lean.

 

Ditto, at somewhere between 13.3 and 13.6, my car dies. I think your unit is misreading the actual AFR. Mine idles smooth between 12.8 and 13.2. any richer and it lopes, any leaner, it quits running.

 

Hmmm, The wideband O2 sensor is on the downpipe a couple of inches down from the stock 02. Will it still get odd readings when the airpump is running?

 

Air is also injected in to the exaust ports of the intake manifold.

 

Well the unit was working when I took it out of my last vehicle so either it is actually running that lean (which doesnt seem likley from what you guys are saying) or there is something messing with the readings. I guess there is also a chance the unit is messed up now but I doubt it.

 

Ahh, I didn't know that. So would this be the cause of my lean readings at idle?

Thanks!

 

Yes!!

 

Thanks man!

 

Just wondering if this is a good place to tap the wideband O2 sensor into.

And if anyone can remember, what size tap do i need to do this?

TIA

 

Just fyi on my Zeitronix kit ( and alot of others) they recommend at least 16 away from the turbo. It is pretty common to put them on your midpipe which is safe so your 02 sensor doesnt get too hot. And about the tap, its pretty easy to order a bung and just weld it on. On mine I didnt even have to drill a hole, I just got burned a hole straight through with the welder and then welded it on and it works perfectly. gl.

 

So if i have the stock cat, do you think its ok to put the bung there?

What would happen if i use put it in the downpipe, say right before it meets the main cat? I wouldnt get accurate readings?

 

Generally a good place for an A/F bung to be welded is near the end of the down pipe or the beginning of the midpipe (where mine is). afr's at idle are usually in the mid 13's unless of course you have the airpump connected. Lean afr's after letting of the throttle or cruising are normal.

 

Yeah, as far a placement of the bung, I'm going with the beginning of the midpipe only because it's so much easier to take on and off than the entire downpipe.

 

I've ordered the PLX SM-AFR and planning on installing it in the original O2 sensor hole on the top of my HKS 3" downpipe. As I can read from this thread, it should consider blocking that hole and making a new one closer to the midpipe?

Friend of mine said that the APEXi Power FC has some issues (maybe it's the auto adjusting) with the AFR when you remove the air pump, but from what I can read on this thread it's the other way around? Anyhow, I will probably run with the standard O2 sensor for a week or two after I start the engine (just been overhauled and installed) as I don't wanna bother waiting for the PLX unit. The PLX should have 2 connectors, narrowband and wideband so I can hook it up to the existing connectors and have the ECU work normal, while running an extra gauge and perhaps logging inside the car.

 

So drilling into the main cat is not a good idea??

I dont have a midpipe because i still have the stock ecu in case you're wondering.

 

The O2 sensor is normally located upstream of the cat.

You may want to consider installing it in the downpipe.

Mine is installed in the downpipe next to the tranny.

There's more room there than you might expect.

 

I just ordered the plx m-300, and Im wondering the same thing. I will be mad at myself if this is the way to go, as I bought this one specifically so I could use it in place of the stocker....

 

Buy a downpipe and ditch the stock pre-cat. Its a reliability mod anyway. Then just weld a bung to the bottom of the downpipe for your A/F meter.

 

Would a 4x4" copper heatsink prevent overheating a WB sensor in the stock location?

 

Eggie,
I've seen a thread about this idea, and I *think* the conclusion was that it helps only a little bit. (btw the bends on the one in that pic appear to put it in direct contact with the down pipe, defeating the purpose of the heat sink. It should be flipped over, but there may not be room...)

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Drilling into the cat itself is likely to damage the internals. Besides, I think any O2 sensor has to be upstream of the cats to get accurate readings.

 

I have an HKS downpipe.

I was just told or so i thought someone said that installing it in the downpipe is not recommended and people normally put it in their midpipe but since i have the stock cat still, i was wondering if thats good enough.

 

weld it before the cat and I wouldn't see any problem with that.