Air/Fuel Ratio for Stock FRS @ High RPM
 

Trying to educate myself on this topic. Just purchased a AF gauge and will be looking into getting a tune soon.

My question... Does anyone know the AF ratio at high rpm for our cars?

What's the best ratio for power at high rpm?

I've read a bit and it seems like every car is different. Thanks for helping.

There is no real answer, AFR change all the time for each RPM and Load. It should be 14,7 most of the time.
It will go lower with load/RPM increase.

You want to stay as close as possible to 14,7 as long as you got no detonation or overheating exhaust valves.

Then your tuner will decrease AFR just enough to protect the engine. You don't want the lowest possible AFR, because you will loose at lot of gas and quite a bit of power.

The stock tune runs quite rich at high rpm getting down to 10.7 afr.

most aftermarket tunersnaturally aspirated will target mid to high 11 afr at upper rpm..



Stock tune Primary oen loop fueling table

http://www.ft86club.com/forums/attac...1&d=1437551990

:offtopic:.... but is that windows 98??

WOT high RPMs should be 12.5:1 on regular gas for optimum performance 14.7 is incorrect and will be too lean.
14.7 for cruising.
This is recommended for NA application.

I was not suggesting 14,7 for WOT :)

Perfect chart. Yes idle was was sitting at around 14.7.
At WOT above 7k I hit 10.2 and I thought that was really rich.

I'm going to ask if they can keep AF ratio between the suggested 11-12. Thanks for the replies!

The OFT stage 2 UEL tune seems to run rich at least mine does and I'm at sea level. Its low 11's. I'm sure I'm losing a bit of power.

Yeah but he was talking about high RPM so I figured I would specify. I don't know about you but I dont hover at partial throttle and 6000-7000 RPM

Looking at the journalists video on YouTube, they do that all the time. Which is of course stupid :)
But I have seen many post (around here) and video where people drive crazy part load road driving rpm. Like JF on Drive TV.

Anyway, sorry, I'm off topic :p

nope XP running cut down theme so it runs better on my old netbook :D

Ahh! I see haha!!

The AFR is that rich under high speed and heavy load to keep the cat from experiencing accelerated aging. It's to comply with EPA longevity requirements.

It's not a big deal if you do. It won't hurt anything although I would change my oil more frequently if that's something that happens regularly.

I'm partial throttle at high rpm all the time. Do you guys every see the track? Not to say it's a regular occurrence, but every time I'm in a canyon or on the track the engine sees a lot of partial throttle high rpm. Especially when I'm sideways.

you will need to look at the Closed loop fueling tables for partial steady throttle AFR then, as it likely you will be in closed loop not open loop fueling

here are the tables from a tuned rom (petrol)
note the closed loop fueling target is 14.7 + (closed loop target value)

eg for above 5600 rpm load say 1.0 target AFR = 14.7 + (-1.319) = 13.38 , other compensations may apply some unknown.

open loop = WOT and aggressive throttle movements 02 sensor not used only LTFT compensations applied that were learny on closed loop
closed loop = partial throttle with slow or steady throttle movements feedback loop using 02 sensor to correct AFR using STFT and LTFT

You're drifting all the time ? On the track I'm flat out or in fuel cut off. Part load is for a very low time.

If you drive fast canyons only, that's a different story. But that's not normal driving.