Rx Punk

iTrader: (4)

Does it matter if u're running a vortech supercharger? Is it usually higher? And what's normal operating range for a Z. I just bought a AFR from aem, haven't installed it yet, but I don't even know what the normal is. I hear 14.7

Z1 Performance

iTrader: (564)

14.7 is stoich

Normal is a loaded word, because it depends on many factors..not the least of which is where you actually mount your wideband sensor, what sensor you have, etc. But putting those split hairs aside, assuming the sensor in the recommended place per AEM, you should see readings at idle at or near 14.7 (not unusual for it to oscillate a bit), and at WOT, down into the low 11's on a properly tuned setup. At cruising speeds (light throttle inputs just maintaining a speed), you'll likely see it oscillate a touch between 14-15:1 depending on throttle inputs. Your throttle inputs between cruising (light) and WOT (full pedal to the floor) will create different AFR's depending upon boost, rpm, and calculated load, and really should be evaluated by a competant tuner, under controlled conditions to ensure the tune is setup properly

Rx Punk

iTrader: (4)

So its not dangerous if its at 14-15? Its a wide band. I'm gonna put the sensor on the driver's side a few cm's from the collection area. I was trying to figure out what is dangerous.

rcdash

iTrader: (18)

I can maintain a steady idle at 17 for hours on end! No worries. Just pay attention to the rest of what Z1 posted.

ffwturboZ

iTrader: (2)

Will it be any different on turbo? I have a powerlab kit and have no gauges and are in the same predicament. Im going to be installing the AEM wideband and boost soon. Just would like to know ball park figure till I get the car tuned up.

Sorry for the thread jack.

tylerxfire

iTrader: (15)

under load boosted you want to be in the high 11's imo thats plenty safe..

i will ask this though, for a car that is n/a with bolt on's and untuned what is normal for a/f?

teamsprock

iTrader: (1)

A typical idle A/F ratio is from 13:1 to 16:1 depending on the modifications to the engine, larger cams or higher VE will require it to idle richer for a nice smooth idle.

As you add forded induction you will want to aim for 11:1 to 12.5:1 depending on fuel, timing, load and the amount of boost you'll be running. On a stockish or mildly built engine its best to stay around 11:1 to 11.5:1. This is for safety not for maximum power, to gain the most power and reach MBT you need to be on a dyno and have it fine tuned by someone who knows the system you are using. That all being said will you aim for 11:1 from the initial onset of boost? No your A/F ratio's will ramp slowly richer as you reach peak Tq, you want to be at your desired A/F ratio of mid to low 11's as you reach peak Tq as this is when the combustion chamber will see the highest pressure and best chance for detonation.

The same goes for NA applications however you will not need to run as rich for safety, however some cars depending on cams, combustion chamber shape and many other variable will make better power in the low 12 area while others will be happy in the 13's. For best safety and power its always best to verify everything and have it tuned on the dyno. I am new to 350's but from what I have seen in stock form they run a little on the rich side, but I hate to make a blanket statement about all 350's since as I said I am new to this chassis and engine. I hope to learn a lot more, however I doubt I will take the 350 to the levels I took my other cars.

djamps

iTrader: (1)

If you're boosted on a stock block you want to be somewhere in the 11's when boosting. Outside of boost you should be 13-15 depending on load.

Ziggyrama

iTrader: (15)

I think this is a bit of a generalization. Using positive pressure as a primary criteria is not a good way to gauge what AFR should be. Engine load is a good metric to go by. Boost or no boost, what matters is how much air is flowing into the engine at a given RPM. That is really the bottom line. The more air, the more load the engine will experience which will dictate how much fuel should be used. For many people that live in an area with 4 seasons, a car will experience different loads in August than it does in February. OP, it's actually difficult to say what your AFR should be outside of idle situations. At idle, it's generally OK to say that you should be at stoich ratio 14.7:1, but after that, it will change rapidly based on driver's input. There are several variables that determine the target ratio. Think of it as a map where x axis is the calculated load, y axis is the RPM and the value in each cell is the target ratio. Depending on the intake temps, and hard hard you're pressing the gas pedal, the AFR will vary.

djamps

iTrader: (1)

^^ Notice I said depending on load.

And yes you should use boost as a factor especially on a STOCK block. It would be silly to run a 13+afr under boost at any RPM, why risk it?

Rx Punk

iTrader: (4)

Well i have a vortech supercharger, I heard generally it runs rich, but my friend talked to guy who dyno'ed the Z before with the vortech kit. He was saying it actually runs lean. But there's a bunch of people on this forum who run that kit safely for years now. So I'm wondering, when i get my wideband aem afr gauge, what would be a safe range. And what to be scared of seeing?

Ziggyrama

iTrader: (15)

Not necessarily true. If you're in a hot place or at a significant altitude and you're pushing some boost, your flow may not warrant going into 12s. Which is a good prelude to my point

Ofcourse, you want to pay attention to boost but boost is not fundamentally what determines the fueling, flow does. People generally think of them as the same but they are not. It's easy to get this mixed up because pressure drives flow. In general terms, if you up the pressure (boost), the more flow you're going to produce...BUT this is only part of the equation because you're not accounting for density of air. 8lbs of boost in 0F will produce significantly more flow than 8lbs in 90F weather and the fueling will be very different. Associating X lbs of boost with a given AFR is technically not correct. If half the pressure produces the same flow (bigger snail) should you be running different AFR? Ofcourse not. So, this is why flow is what you really should be thinking about. All of this being said, boost is easy to talk about because we all have boost gauges so it's an easy reference point for people to mention. But, if one is getting into tuning and they're serious about getting it right, the fundamentals need to be solid.

Ziggyrama

iTrader: (15)

I'd say that that is a difficult question to answer. It really depends on your physical setup like exhaust, the timing that you have set up and the quality of gas that you're getting. In MA, we get really good gas with lots of alcohol so I can get away with a lot more than guys in CA can. I am sure guys with that kit can probably give you an idea as to you should see. But take everything with a grain of salt. One thing, when you had your car on the dyno, how did the guy measure your AFR? Did he stick a clip in the tail pipe? If so, that alone can give you inaccurate results since you can get backwash from the free air that will produce false readings. Do you have cats in the car? Reading after the cats will also give you leaner readings.

Rx Punk

iTrader: (4)

OO no, haven't dyno'ed yet, actually gonna get it dyno'ed on thursday, just put the afr in last saturday, seems ok, at idle it sits at 14.5-15.0. On boost it runs 12-13. Sounds like its doing what it's supposed to. I just wanna know what to look for if the car starts leaning out, make this gauge useful, lol.

Brett@AwesomeZ

If it's in the 13's under boost, that is too lean IMO and your in need of a tune. If your in the 12's at low boost it shouldn't be a problem as long as the timing is also being controlled and the AFR goes into 11's as boost increases.

tylerxfire

iTrader: (15)

i would take it easy..on boost at wide open throttle that is lean..

whitez33350ztt

iTrader: (4)

yea u shouldnt beat on it until u get it tuned. 13s isnt good at all . im all tuned up and at wot im at 11 to 1 basically all the way through boost. just take it easy till u get it tuned up and ull be fine