I've seen a 5-10whp difference, but also higher knock values the closer I get to 12:1(accompanied by plug reading confirmations). In short, 12:1afr is too much risk to stake my reputation on.
You'll more than make that power back on the street with proper airflow in and around the motor.
Ah, there you go, now you said it.
I only gave the mathematical number before. That doesn't mean everyone should run 12.5......but mathematically, this is where an FI motor will make the most power per burn cycle. *most of the time*
On my lotus I run between a 12.3-12.5 A/F value. I watch my gauges all the time, and monitor my car all the time. Not only that I have all the supporting cooling mods, and exhaust flow mods to be able to do that. I have TONS TONS TONS of time into my map, but I tune cars so my time is of course free to me.
NOW. What do I do on customers cars. Now that is a whole new ball game. All the cars I have ever tuned, I put there cars between 11.2-11.8 depending on the set-up. Meaning, depending on the size turbo, size intercooler, does the motor run cool, does the motor have a restrictive exhaust, what is the compressions ratio, and so on. There really is no magic number. I run 12.5 all day long with no knock on the ECU, and no knock heard through my knock muffs. Also the spark plugs show no signs of knock but are perfect because of the perfect burn A/F value, instead of on my customers cars that are usually a little black because I run them a little richer. Again though, there is no perfect number.
I figured the guy in the first post wanted a number, which is 12.5. There is the number....... but the reality is that many tuners are not willing to tune another persons car to that level and have there reputation on the line for it. I know I am not, and it looks like Cody is not willing either. And Cody is right. I am maybe getting another 15-20 whp out of the car running it the way I am. Is that worth it to a customer? I would hope not over a motor, but to me, its really no big deal so why not.
