Understand AFR
 

I just bought an '88 rx7 Turbo II, and it has an AFR gauge. I need some help understanding if the reading i am getting on the gauge is good/healthy

at idle gauge sits at 11.0-11.5

it has downpipe and rb exhaust.

not sure if it is rich or too lean.

It's a little rich if the engine is warm, but stock engines tend to run that way.

See this video for a quick general overview of AFR values:

However, keep in mind that these values are generalized rather than specific. AFR readings have errors due to calibration, heat, and other factors, the stoichiometric ratio of pump gas can vary between 14.1 and 14.7 depending when and where you buy it, and each particular engine may run differently even if they appear to be the same.

Hey thanks for the info. helped out alot.

I was able to drive the rx7 around, and its running a bit rich. which i am ok with. under load the afr values are under 14.5.

the idle AFR is the least of your concerns with a boosted engine.

At max load it should be around 11 or so.

True. sorry. only started monitoring the gauges yesterday. yes under load the are 11-12, at cruising speed around 13-14. i am comfortable with these numbers, thanks for all the help and insight !

But since the car has a Rev TII turboback exhaust, im seeing significantly high boost numbers which are worrying me. climbing to around 10psi, i let off the throttle before it reaches critical numbers. thinking of going with an ecu upgrade. nothing drastic, vehicle is in pristine condition with only 90k original miles.

So your car has a fuel cut controller?

For a simple ECU upgrade, I recommend the Rtek Stage I.
Rtek7 ECU Upgrade Detailed Information

it has a FCD.

FULL MOD LIST:
Rev TII Turboback Exhaust
FCD
Wideband
short shifter
Boost gauge
Fuelpump voltmeter

essentially it is a stock vehicle. original owner sold it to a guy who modified, who in turn sold it to another guy, who sold it to me (4th owner).

Yeah, that's a really nice car. If you install the Rtek then you can sell the FCD.

ty
 

Im glad someone explained this for me lol

Keep in mind that the target AFRs should be taken as a guideline. On my Supra, I idle a little richer than I need to because, as I lean the mixture out the car will start to vibrate more than it needs to.

It is a pretty modified setup running 1000cc injectors that are not as precise at lower duty cycles.

T