Thread: Why I tune to 12.0:1 A/F ratio (0.82 lambda) and why you should too. (all welcome)

Top speed is also power dependent. You could do top speed runs.
Or use 1/4-mile trap speed...

I guarantee you you're not starting ignition TOO EARLY. To do that and not detonate takes over 100 octane fuel or equivalent for N/A cars and over 110 octane for boosted applications. Assuming sane compression ratios, etc.
Your engine would have destroyed itself within seconds at WOT by now.

^^ Is your knock sensor hooked up??

Another way to tell is simply to listen for it (although very primitive and not all too precise as you have to have a good ear for it)

Thanks for the quick response that top speed idea is great, although I'd have to look for a highway that's long enough

The final set started at 12.5 3000rpm (WOT) slowly descending until it hit around 11.9 at 8200rpm. Does it sound like a good AFR for a NA SR20VE?



Actually it is, and we are reading it through an SAFC (the most it hit was 72).

And I got quite good at catching detonation just by listening after I had my SR16 piston setup.

N/A stuff should be 12.76:1 at WOT across the entire rev range. That's the standard. Deviate from that at your own discretion.

@BenFenner : I still don't fully understand all of this, but I think I just need time to review this thread in more detail.

Maybe if I find some time I'll make some animations to help.

What part are you really confused about? Maybe a chat on the phone can help

I think I get 90% of it, but I'm still missing the 10% if that makes sense.

Ben I have been reading this post on tuning to 12.0 AF ratio, and I would like to know if this applies for all boost levels or not? Many tuners I know are suggesting that 12.0 is only good for moderate boost levels of about 15 psi, any more boost will require a a lot richer mixture. Whats your opinion?

Most of the time we like to see anything between 11.5 to 11.8 for high boost apps. It's like a safety blanket. In most cases 12.0 will be ok but it's boarder line if anything goes wrong. I prefer mid to high 11's on any car I do.