Earl H

iTrader: (1)

Tuned the A/F ratio on the dyno. I wanted to take the car out on the street to test timing under load. If I add timing, will it affect my A/F ratio? Thanks in advance for the help.

Slowhawk

iTrader: (12)

From what I've seen when you add timing it richens alittle.Take timing out and it leans out.

moehorsepower

iTrader: (3)

Actually it is the other way around,I tune on the Dyno and adding timing will lean the Air/Fuel a little........

Red01Chevy

id have to agree with him

foff667

iTrader: (2)

hmmm thats an interesting argument being slowhawk is a tuner if i remember correctly.

APeteSS

Yes, when you advance timing, you'll (theoretically) get a more complete burn of the cylinder gases, thus decreasing the amount of free oxygen in the exhaust tract which gives a leaner A/F reading.
In practice, this is true but AFR changes resulting from timing changes differ from car to car (probably due to different head/CC design/location of spark within the cyl/valve timing).

APeteSS

Slowhawk's smart. Is this an oversight, Hawk?

gonzo 6.2

iTrader: (8)

Here is what I noticed for me yesterday.Playing with a LM1 I was getting way fat like 10.2 A/F @WOT 28deg. westers tune running a KO box.disconnected the knock outbox running normal KSs,got 20 deg(lots of faulse Knock) WOT and 10.8 A/F.Installed my ED Wright PCM ,I get 28deg and 11.8 A/F @ WOT,Still to fat huh boys?

NoGo

iTrader: (2)

Ditto

Advancing leans, retarding richens. (as stated above)

It has to do with cylinder pressure and burn rate. Advancing timing increases cylinder pressure which results in an increased burn rate. The accelerated burn rate produces a more complete burn (as stated above). This will be true up until the point of detonation.