I have been looking through the forum and have saw plenty of discussion about Air/Fuel ratios.

My question is if mine is normal.

91 Mazda RX-7 N/A Auto converted to Manual.

At idle my A/F ratio is 12.5-13.1
At WOT at 8k rpm my A/F ratio is 10.1 - 10.3
Going downhill with no throttle my A/F ratio is 17.0+++

Are these normal readings for a stock car with just a header and eliminated cat???

 

yep.

 

rich side i'd say, the S5's i have tested usually run in the low 14's AFR under WOT past 4500RPMs. a little skewed by the air pump but that is still a bit rich.

when tuning i usually shoot for mid 13's under a high load with no cats/air pump.

 

those are normal, but if you want to lean them out that would be in your favor, you'd get a bit more power and better gas mileage. with an NA you can run cruise AFR of 18, and a WOT afr of 12 or 12.5, partial throttle should be around 14.5 or so.

EDIT:

Karack is right, those numbers look rich, but his numbers look a little lean to me. Like he said that's probably the air pump but I like to play it safe. Nightmares from having a turbo you know

 

rich is an understatement at those afrs for a n/a lol
even for a turbo car, thats a little rich.
On a n/a I try and aim for high 12s to 13.2 at WOT
idle is fine, at cruising a normal afr would be 14.7 but you can go leaner as long as the engine isnt stumbling around.

 

"...a little lean" ? Ha!
You can safely run 12.X afr on a turbo setup (in the lower boost areas obviously) so 13.X is nowhere lean for an n/a actually its pretty conservative for all but the highest load portion of the map. Cruise should be no lower than 14.X and really 15-16 would be closer to ideal (i cruise between 14-15 w/ a turbo). This is all assuming the OP has some way to adjust afr....Either way 10's and 11's are way too rich and far from ideal for an n/a. Whether its "normal" for a stock tune or not, I can't say, but leaning it out will only help.

 

i agree that leaning it out would net more power, but the original question was "is this right for a stock tune" and put a WB on an S5 NA and you'll see that the stock tune actually is that rich @wot and high rpm.

the idle number looks close for a car with no airpump/acv, with a working ACV it should read somewhere around 16-18:1, because of the air pump air.

 

Any kind of misfire or ignition related problem will affect the wideband readings

 

Well I guess that I will have to either invent a way to adjust the mapping to lean it out or get a stand alone. Either way it will be a while. Just hooked up my AFM and wanted to check. Also I did note that the AFM when I shut off the car goes 17+ because my car stumbles to a stop instead of immediately stopping when the key is turned to off.

Do I need new injectors or can I clean a good set I have and put them in with new gaskets to fix???

 

or you could just install an safc...
that takes like an hour and you could edit your afrs

your injectors seem fine, the car stumbling isn't related to that. and of course your wideband will read lean when you turn the car off, you turned off the fuel.

 

Thanks for the info....

On a side note I am working on my brother in law's rx7 and is there a trick to get the s4 **** off the lever because I am having a hard time removing it so I can put the lever back in with the new shift boot.....

 

My car is Exactly the same as yours as far as Afr's go, I thought there was something wrong at first but i've tested everything, fuel pump voltages, fuel pressure different injectors etc no difference

 

the chrome thing under the **** is a locknut

 

kk got it loose. Also my cruising A/F ratio is 12.3 - 12.8

Also what safc is a good choice for someone on a budget and still has good functionality???

 

Which model? lol....the cheap one.

Seriously they all do the same thing, so just get the cheapest best condition one you can find.

 

have you replaced your stock O2 sensor? an oldschool SAFC is the same thing as an AFC Neo. same ****

 

i just did an O2 sensor, and i think i will be doing more of them. my last car had 76K on it, and i put a wideband on it, and i noticed that the ECU had a bunch of latencies built in, there were delay times between it going in and out of closed loop, which i thought was just an S4 thing.

today i put a new O2 sensor into an S4, and while i didn't use the WB, i used an LED on the check connector, the latencies between the zones were almost gone. it'll drop in and out of closed loop with maybe a 1 second delay, VS about 3-5 for the 76,000 mile car.