DIY Intake Heat Wrap: $10

[Chinky420]

dayum, 16:1?!?!? i thought the stock NA a/f ratio was 10.5:1

sounds super lean

[CASTRO]

stock afr should be around 14ish. no real way to tell unless you've gotten readings with a wideband. stock 02 sensors are not correct readings and used to just adjust ratio.

[D-money]

I have an adjustable performance chip and i do the tuning with the live data data stream on my obd2 code reader

[sydemoid]

Ummm

no disrespect... but wouldn't you need a piggyback fuel management system to adjust AF ratios?.... the adjustable chip you mention.... what exactly is it?

[D-money]

none taken well im still fairly new to tuning i may not be exact on my calculations of the a/f ratio let me check into that

[CASTRO]

for real tuning you still need a wideband 02 sensor. stock is just for general arf adjustment and is grossly inaccurate for tuning purposes

[CASTRO]

also not trying to bust you out but just wanting to get more info.

also interested for the specific equipment being used.

[Chinky420]

stock afr should be around 14ish.

duh, that's right.

i forgot, "limp mode" with the CEL on is about 10.5:1, running a bit rich to prevent knocking/pinging.


yeah, 14:1 is stoich (ambient pressure)...i totally blanked on it.


still, 16:1 is pretty lean, no?

[panic]

running 16-1 AF Ratio

No reason not to - provided your knock sensor works well, engine has no temperature problems, and your spark advances far enough to make use of the leaner mix.

You're going to see "14.7:1 is the correct air:fuel ratio" posted all over.
The problem is that what happens in the combustion chamber is not a lab experiment, with controlled conditions.
14.7:1 is the ratio that yields no "left-over" air or fuel - exactly the right proportions to combust every fuel molecule and leave nothing on the table... except that it never happens.
There's always some fuel that didn't vaporize enough, or wasn't mixed enough, or cooled off too much from contact with the intake valve, etc. The mixture also never burns in a single complete chemical transaction but is partially burned several times. Guess what: if a fuel molecule isn't burned, what happens to it's oxgen partners? Right - they're left over, even with the correct ratio.
Remember that 14.7:1 is by weight, not volume (which would be far higher), and is air, not oxygen, so of the 14.7 only 2.94 is oxygen (11.61 is nitrogen, .15 is argon).
14.7 is not the best ratio for power - it's too lean. The assumption is that the engine is getting all the air it can use, and if more fuel is added the chance that all the fuel burns goes up (plus a slightly boost from cooling effect). The best ratio depends on how much cooling you need, typically between 12.0 and 13.5:1.
14.7 is not the best ratio for mileage - it's too rich. The assumption is that the engine is getting all the fuel you want to use, and if more air is added the chance that this fuel all burns also goes up. The best ratio depends on how hot the engine runs, how much load it's under, and how much spark advance is available, typically between 15.0 and 18:1.

[CASTRO]

stock afr should be around 14ish.

duh, that's right.

i forgot, "limp mode" with the CEL on is about 10.5:1, running a bit rich to prevent knocking/pinging.


yeah, 14:1 is stoich (ambient pressure)...i totally blanked on it.


still, 16:1 is pretty lean, no?

all good I blank out even at what type of oil we run sometimes. lol

16:1 is ultra lean and would soon start pitting the cylinderwalls. In addition to a wideband, I'd also get an EGT meter as the leaner you go, the hotter exhaust gasses get. Gonna be getting a melted cat soon

[Chinky420]

The best ratio depends on how hot the engine runs, how much load it's under, and how much spark advance is available, typically between 15.0 and 18:1.

wow, upto 18:1....that just doesn't sound right to me.

not that i'm saying you're wrong, it just don't sound right to me.

[CASTRO]

for newer motors its okay as I've read a lot about some that can do ultra lean burns but for an old dinosaur like the 1mz, im sure it'd explode rofl

[panic]

Diesel engines run at 30:1 ratio under light load, and 150:1 at idle.
Vizard has run gas engines at 22:1 for cruising - no harm done.

[panic]

Chrysler "Lean Burn" ratio was 18:1 in 1976.

[Midias]

Ummm

no disrespect... but wouldn't you need a piggyback fuel management system to adjust AF ratios?.... the adjustable chip you mention.... what exactly is it?

His adjustable chip is a potentiometer hooked into the IAC.