lean AFR
 

I know as well as anyone else on here that the rotary engine is different than piston engines, and a proper air to fuel ratio will yield the best hp. so what i want to know is what are the potential damages could be for running a slightly lean AFR. Im going to stay N/A, so i want my engine properly tuned to the best it can, and i know that the best AFR is 14.7:1. Now that ratio would be maintained at low to mid rpms, but then at higher rpms the ratio would slightly richen out to about 12.5:1 or around there. I will be getting the Int-x with an AFR gauge to monitor and maintain the best AFR. Is this ok for the renesis, or will it lead to disaster?

https://www.rx8club.com/showthread.p...ht=interceptor

lots of good info here..

good reading..

beers :beer:

Scored a 4BEAT modified ECU from KNIGHTSPORTS in Japan.

Have an 03-model 4AT so they modified it to suit the 4-port engine.

AFR is very lean for a rotary & at WOT pumps out at just under 14.0:1 until 5500rpm when the secondary shutters open for the additional port to open. AFR then changes to 12.9:1 until 7500rpm redline.

Good part to this is the excellent fuel consumption my car achieves (for a rotary) getting 10km / litre at a steady 120km/h (3000rpm-4th gear)

(no idea what that is in 19th century measurement)

Around town reaps excellent gains too with around 480 - 500km per tank as the wife is a cruisey driver.

Bad part to this is the lean mix under 5500rpm costs power as a rotary does combust differently as you state & the mix should really be around 13.0:1.

A few extra kW would come onboard around the mid-range zone if the mix was different. I'll get this fixed soon but for now am enjoying the fuel savings.

Just steer clear of anything over 14.0:1 as rotaries wont & dont like it

Thanks, i read all of it until page 38. Thanks for letting him use your car, how do you like the int-x now?

I ran mid 14 AFRs without issue for several months (unintentionally, made some mods that increased airflow more than was expected). However at the next tuning we put it in the mid-13s because the small difference in output didn't justify the risk. This was all NA. I wouldn't chance running over 13.0 for FI.

ITS MoTeC tune to .93-.95 Lambda with no issues. Have gone as crisp as .96 but found no changes so chose to err on the safe side. Please note: THIS IS NA!!!!! On FI I stayed on the fat side and my motor is still alive as far as I know. It is living under the hood of a first gen being used for drifting which I could not give a squirt of piss about. I stayed in the .80 Lamda range at peak torque. 13.0 would be Lambda of .89 and I would think pretty risky.

The "best" afr is not necessarily 14.7:1. That number will be different for each engine depending on it's volumetric efficiency and I have yet to see an engine make it's peak power at 14.7:1. NA will usually be in the 13.2 - 13.6:1 range but again, it depends on the engine.

What are you using for an AFR gauge?

MoTeC wideband.

where do you get motec's from, i havent been able to find them

Try www.motec.com or Speedsource is a dealer and I am sure they can help you. You want a PLM.

I have played around with this quite a bit and come to the conclusion that it does not make as big a difference power wise as at lot of people think . Anything over 12 and under 13.5 seems to be about the same power wise - however probably prudent to stay under 13.0.
Despite what Racing Beat say - I got more gains from playing with timing which is possibly more to do with our gas here in NZ.

here are lambda values from track day last friday (0.9=approx. 13.17 AFR ) - about 6mins of hard out driving ....

14.7:1 is considered the ideal stoichiometric for catalytic converter efficiency. In order to achieve this the computer cycles lean/rich based on O2 readings to form an average close to that number.

only for cruise and idle ...... way too lean for WOT

You're right, WOT is different. When you hit WOT the comp goes into open loop, until you let off and start cruising. The 14.7:1 is just an emissions thing for closed loop driving.

I read somewhere that the computer cycles between lean and rich because it is better for the cat. Any truth in this? I always assumed the cycle had to do more with the time it takes the computer to react to changing AFR...

thanks, but i read the huge thread that swoope posted, the leanest i would tune my engine at WOT is about 13.3 or 13.1. but for mid and idle rpms i would get it as close to 14.7 as possible. But i still have no idea how changing the timing curve or ignition can really help the engine, any highly informative threads on that?

Its not that its better for the cat, its just a function of how the catalysts work. In order to clean up HC and CO emissions oxygen is needed, so you have a lean mix. But in order to clean up NOx emissions there has to be a lack of oxygen, so you get a rich mix. The computer cycles rich/lean to get an average and to get the most out of the cat.

Cool, thanks for the info!

I'm not so sure that's true either, the computer actually cycles lean/rich because of the limitations of the narrow band o2 sensor- its so narrow that the computer has to hunt the mixture back and forth to actually know how lean or rich it is. A narrow band lambda sensor is almost a switch.

thats why wideband o2 sensors are much better.

I dunno about that. While you may be partially right, my information is what I was taught in school so until I see literature to the contrary, I'm gonna have to go with what I was taught.

agreeing with lone wolf. i was taught the same thing at universal technical institute.

good thing the rx8 doesnt have a narrowband, then is it?

yes it is . Corners should check my chart above - data is from factory 02 sensor