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

Wow, I read all the info on that link Thanks a lot, I needed to read that timing section.

About fuel, you got a really good point about the 12:1. The cars I have tuned I try leave them at 11.8 just for the safe margin, but I'll see how it goes with my own engine, apparently the VE has a head with more resistance to detonation.

Okay, I feel like I should say some more here.

Some engines need to be richer than 12.0:1 to avoid detonation. It's not as easy as all that. You can't just go out and tune to 12.0:1 because Ben (or anyone else) said so. You might break something, and I wouldn't want that.

The thing is, a properly built turbo engine (basically as long as you keep intake temps under control) will do great with 12.0:1. That's the bottom line. And at the end of the day, 11.8:1 to 12.2:1, whatever. It's your car, and your ass on the line. If, however, you're in the 11.6:1 or lower area and can't go any leaner due to detonation I highly suggest you re-think your set-up.



That's what I keep hearing, and I don't doubt it. Lucky bastard. =]

i am running a calum basic board right now but i have used JWT ecu in the past with a emanage for fine tuning lol.On my 91 i have no IAT sensor so cant due that if i wanted.
i stuck with mid 14-15 Afr because that is what i have seen most stock ser or mildly modded run for cruising and get decent mileage

I have noticed that cars weren't much stronger at 12.0 afr, than 11.2-11.6 afr. My boss liked to tune cars at about 12.0afr's, and didn't have very good results on the dyno. Some times as much as 30whp lost at the same boost pressure. I have probably tuned 30 dsm's in this fashion, and always had very good results.

You still can't argue with the fact that timing makes more power than leaning the afr. So tuning at 11.2 on the street with a bit more timing makes the car feel better, for DD.

I still appreciated what you are doing for this forum, and extreme newbs. Keep up the good work.

On a side note, Are you OCD Ben?J/K

There's no arguing with this. Unless the wideband readings were off, but when they're off they usually read leaner, not richer...

Ahhh yes, the [in]famous DSMs... There's something about those engines and the people who tune them. Something very odd. They like to run 30+ psi, 0° timing, and rich. They make power though, so I can't say anything about it. Maybe a friend of mine could, he's a DSM guy (well respected in the community) who shares my tuning philosophy. Are we talking about the DOHC DSMs or the SOHC (non cross flow head) DSMs?

I'd simply argue that if you couldn't run that same timing at 12.0:1 then you should look for a way to keep the intake charge colder. You're going to foul spark plugs, O2 sensors, cause scoring in the cylinder walls, etc. with that A/F ratio in a daily driver.

Thanks. I think?

Not about cars or anything. I just don't like to do things half-assed. I don't like to do things unless I know why I'm doing it. I like to know things, and help other people know things.

I made the best power on a 12.0-12.2 AFR on the VET. On 24psi I leaned out as far as 12.3 at it's peak. This wideband reads a little bit lean though from my experience. I had an LM1 in the car for tuning and it never read over 12.1, but on the dyno it got up to 12.3. No biggie.

My timing maps are conservative. When boost hits at 4500rpm, timing gets pulled to 15*. Then timing gets added back in 1* for every 1000rpms or so. At 7500rpm the highest timing reading I have ever gotten is 20*.

I richened the mixture up for safety, and retarded timing by 2* or so. Car feels a bit slower, and doesn't react as hard. But I know it is safe. I will be re-tuning it soon, so I will bump it up again. I never got any detonation on 12.0 AFR. I will keep the 15* base, and lean her out a bit.

youve been sharing alot of good info in various threads ben, thanks.

ive read your theory and have a simple understanding of tunning and a/f.


i have never had to really look into it simply because on my previous set ups my a/f have been dead on. fully bolted cammed set up, af dead on, t25, tmic, cams af dead on.

t28 @ 16psi, tmic, s4, 740cc's @ 3 bar (give or take) cams a/f ratio is RICH. it made 285 whp 265 wtq at 6000rpm and then after drops off like a tank.

from 3500 rpm to 4500 rpm its below 11.0very choppy to about 5k were its about 10.2 after 6k it drops off the charts way below 10 (machine stops reading at 10) so who knows how lower it goes.

im running a jwt ecu as always but its super safe. ive purchased a safc2 in hopes of leaning it out a bit. i will eventually take it to a tuner and have it dyno tuned to 11.8.1 as this is a streat car and i dont need to make max power.

is that the right number i should be shooting for ?

what kind of power can i expect to extract and leaning it out to say a 11.8.1 a/f ratio.

tia ben.

stratton.

I would say that 11.8 is about right. You get a nice margin of safety, without being too far on the edge. It will depend on your setup though. Generally the engine will knock at peak VE. So have it dip a little richer when you hit peak torque, then bring the AFR back up a bit to keep power from dropping off too much.

I quit.

I quit.