From Autometers website
http://hp.autometer.com/techtips/faq.../air_fuel.html

The A/F Ratio Meter is a voltmeter with a range of 0 to 1 Volt. The meter displays the output voltage of the vehicles oxygen sensor through 20 LED's. The first LED will come on at a voltage of .050V, the second at .100V, the third at .150V, etc.

LEAN RANGE:
Four red LED's
(.050 to .249V)

STOICHIOMETRIC RANGE:
Ten yellow LED's
(.250 to .749V)

RICH RANGE:
Six green LED's
(.750 to 1.000V)


The stoichiometric (STOICH) air/fuel ratio is the chemically correct ratio, theoretically all of the oxygen and all of the fuel are consumed. The mixture is neither rich nor lean. However, due to the fact that combustion is never perfect in the real world, there will always be a small amount of oxygen left in the exhaust. This small amount that is left is what the oxygen sensor measures. The smaller the amount of oxygen that is left in the exhaust, the richer the A/F ratio is, and the higher the oxygen sensor voltage is. The on-board computer or Powertrain Control Module (PCM) monitors the voltage from the oxygen sensor. If the PCM sees an oxygen sensor voltage greater than .450V, it immediately starts to reduce the amount of fuel that is metered into the engine by reducing the on time to the fuel injectors. When this happens, the A/F ratio starts to go in the lean direction, and the oxygen sensor voltage starts to go down. When the voltage drops below .450V, the PCM immediately starts to increase the fuel metered to the engine by increasing the on time to the fuel injectors to produce a richer A/F ratio. This occurs until the oxygen sensor voltage goes above .450V. This repeating cycle happens very fast (many times per second). The PCM is said to be in closed loop. It is constantly monitoring the oxygen sensor voltage and adjusting the on time of the fuel injectors to maintain a stoichiometric A/F ratio. This A/F ratio produces the lowest harmful exhaust emissions, and allows the catalytic converter to operate at peak efficiency, therefore reducing the exhaust emissions further.

Since the oxygen sensor output is non-liner and very sensitive at the stoichiometric A/F ratio it will cause the A/F meter LED's to bounce back and forth rapidly. A very small change in A/F ratio causes a large change in oxygen sensor voltage as can be seen on the graph. This causes the A/F ratio meter LED's to rapidly cycle back and forth, and is normal operation when the PCM is in closed loop and trying to maintain a stoichiometric A/F ratio.



The oxygen sensor is very accurate at indicating a stoichiometric A/F ratio. It is also very accurate at indicating an A/F ratio that is richer or leaner than stoichiometric. However it can not indicate what exactly the A/F ratio is in the rich and lean areas due to the fact that the oxygen sensor output changes with the oxygen sensor temperature and wear. As the sensor temperature increases, the voltage output will decrease for a given A/F ratio in the rich area, and increase in the lean area as shown on the graph.

During wide open throttle (throttle opening greater than 80% as indicated by the throttle position sensor) the A/F ratio will be forced rich by the PCM for maximum power. During this time the oxygen sensor outputs a voltage that corresponds to a rich A/F ratio. But the PCM ignores the oxygen sensor signal because it is not accurate for indicating exactly what the A/F ratio is in this range. The PCM is now in open loop, and relies on factory programmed maps to calculate what the on time of the fuel injectors should be to provide a rich A/F ratio for maximum power. The A/F ratio meter should indicate rich during this time.

During hard deceleration the PCM will command an extremely lean mixture for lowest exhaust emissions. This may cause the A/F ratio meter not to indicate anything. The A/F ratio is so lean that it is outside the range that the meter will indicate.

 

hemis are so slow i drove one the other day...

 

o **** here goes a batttle . your kidding right ? im a die hard chevy guy but the results these hemis are doing are amazing me . im gonna go check this black one out at my buddys dealership next week

 

hmmm Hey Metal! Are you still running 15.40's ??? and Hemis are slow???

You just experienced the "Where's the Beef" test drive, A Hemi's PCM is very detuned for about 5,000 miles. Yep! my Hemi is sooooo slow, really wish I could do the headers and a complete exhaust.... perhaps I could drop another 5 tenths off of my slow time.

TJ

 

Careful BadAss you may slip off into the dark side!

TJ

 

Thats was an uncalled for statement. Like MrDestinE, I also own a slow hemi that only runs 13.9's with less than $1000 in mods. I haven't run with the 125 shot yet, but you can expect a 12.5-12.8 when I do.

 

well i love there looks , but ive always stayed away from them because of there transmissons problems and how slow they always were , all torque but went no where . even my buddys 02 360 was that way with intake exhuast and hypertec . but after readin what yall can do with a hemi , idk your top secret but i kno i kill them all the time around here . but if i was to get one id enjoy knowing some your secrets u kno since i dont live by u guys we can keep the name up lol

 

There is no big secret to get thes etrucks running fast...I ran 13's with just a cold air intake, hedman longtubes, an electric cutout, and a superchips tuner...thats it. I have nitrous now, so I plan to easily dip into the 12's, but it doesn't take much time or money to make a hemi run 13's N/A!!

 

Does anybody know what this is?

It kinda Looks like my stock exhaust pipe heh? But what is it really?



It's a Hemi Driveshaft

Plus some people have problems with the Axle braking at the wheel. The only drive shaft that i saw break was on a camaro runing 800rwtq on stock drivetrain with stickies the thing twisted and finally broke. Not to bash your trucks but i think they need kinda of a stronger driveshaft.

 

Until your truck runs as quick as even a stock hemi, you have no room to talk . There will always be someone who breaks a part or a defective part here and there, but that doesn't mean that every dodge is made poorly. I dont like to start **** between my dodge is better than chevy blah blah blah...and you know that 5.3...I always stood up for you on DT until you started talking like you were on a chevy site. That kind of talk isn't needed. If you have a problem with dodge, then go find one and race him, but dont go on every internet website talking **** about a truck you no nothing about. If you are ever in Texas, then drop me a line, and I will run you. I know that I will never be the fastest truck, but I am very happy with what I drive, and wouldn't have it any other way. I am jealous of the ford/chevy guys though because of their available aftermarket...I cant even imagine what the hemi would do if we had half the parts available that you guys have...yet we still manage to spank some *** every night at the track in our SLOW hemis.