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Discussion Starter · #1 ·
So, I am looking at the insructions that came with my Mopar A/F gauge (Thanks Performance Dodge!!) and I notice that it shows the stoich range to be approximately 14.7:1 Air:Fuel Ratio.

This can't be right can it? That seems awfully high to be stoich.

Under WOT, the car runs about 4 LEDs into the Rich range on the gauge, I want to know if anyone knows what A/F ratio this would correspond to.

According to the chart in the instructions, it looks like 12:1 or so, but I am pretty sure that the gassy smells and the nice black exhaust tips indicate more richness than that!

BTW, car is running S2 w/ toys, CAI, Big FMIC, 3" turboback exhaust.

Thanks!
 

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I dont think that the led's correspond with an actual ratio. It is really more of a light show. I'm not harping on you because I have one too! I figured that I would beat all the guys who are going to tell to buy a wideband and not the "lightshow"
 

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Discussion Starter · #3 ·
I just was wondering if the graph that they provide in the instructions had any relevance at all. I am sure that the gauge provides some sort of reference, but the numbers on the graph do not seem correct.
 

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Discussion Starter · #8 · (Edited)
hang on, I might have an idea.... picture coming soon...



OK, my idea... the sensor is heated, so as temps go up, maybe the blue 'photo-painted' curve is close to where mine is reading. my high voltage is around 0.850 - 0.900

Think this could be it??
 

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Discussion Starter · #10 ·
Rydiak said:
Should have gotten the AEM UEGO. The Mopar gauge is just simply for show.
It is not as accurate and there aren't numbers, but it does at least give you an idea of where you are at.
 

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Ok engine calibrator here. I could talk about O2 sensors and A/F gauges until you were bored to tears.

From what everyone has said here, the MOPAR gauge is simply tapped into the factory oxygen sensor. This will tell you jack Shat about A/F ratio. Unless the factory sensor is a wide band (seriously doubt it) or you got a new/second sensor with the gauge, YOU GOT HOSED!!!

If you are lean at say 14.8:1 the gauge will not likely read any more lean than if you were 16:1

Also on the rich end 14.0:1 will be almost untelligable from 9:1 on a narrow band sensor rich is rich, lean is lean, there is NO inbetween as it is an avalanche type sensor.

Please get yourself more informed before buying anymore "cool" gadgets for your car.
Every single product in the aftermarket advertises better mileage or higher horsepower and torque. They are usually shiny anodized and/or have pretty blue LED's but many of them don't do anything but lighten your wallet.

The "TUNER" market is both incredibly ingenious (ie map clamps, injector control attenuation and waste gate control) and incredibly naive.

Hopefully the gauge didn't cost you much. be more careful next time

BTW stoich IS 14.7:1 this is the only way a vehicle can pass emissions laws.

Going rich has a few benefits and fall outs.

1. Increase fuel vaporization decreasing the intake air temperature slightly thus reducing the tendency for the engine to knock and allowing more spark advance yielding more power. This effect is usually only slight and sometimes non existant. It all depends on the engine heat transfer and knock sensitivity. In addition it produces a slight increase in air density, more air = more power

2. Going rich up to 13.0-13.5:1 on a NA engine produces roughly 10% more power due to improved thermal efficiency per unit oxygen

3. It lowers the EGT's protecting the valve train and catalytic converter as a result EPA and CARB allow enrichment for "catalyst protection" at WOT while manufacturers get the added benefit increased power.

Drawbacks
CO Emissions go increase roughly 1000 fold
fuel economy drops
 

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since were on the subject where are the oxygen sensors wires and which do i tap into?
 

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Discussion Starter · #15 ·
NGIN EAR said:
Unless the factory sensor is a wide band (seriously doubt it) or you got a new/second sensor with the gauge, YOU GOT HOSED!!!
It came with a new sensor. I had the bung welded before the cat...

BTW, I got it from Performance Dodge when they had the big Labor Day sale so it wasn't too much. I was just looking to see if anyone knew within reason what LED on the gauge corresponded to a certain A/F ratio.

I understand that a wideband is easier for people ot read and is more accurate, but if you look at the picture up a couple of posts, does that seem to make sense (the blue line)?
 

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Nothing. I have this guage also but I have not installed it. It does come with a new sensor. My theory is the best way to tell if our cars are running properly and safely is to get an EGT guage. Our cars are based primarily off of EGT's atleast that is what the PCM really takes into account. I had both guages but never installed them and got rid of the EGT guage for an intake(mistake). I will be getting S3 and placing the Probe for a new EGT guage in the manifold and I will also hook up the lightshow as well. I am not going to be doing any fine tuning myself because the S3 PCM has already taken care of that. I just want these guages installed for peace of mind and not for tuning since I hopefully won't need to tune anything. I would feel much safer w/ an EGT guage than an AFR guage for our cars. If you are into tuning everything yourself then a wideband is the way to go since you will be controlling things and not the PCM. But I would also say you need an EGT guage as well to keep things monitored properly.
 

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Ok KUDO's to mopar for doing things right. If they bothered to include a new sensor than they would certainly have made sure it was a wideband.

If it is a wideband you are correct in assuming the LED's should correspond to a particular A:F ratio.

If you are planning on using this to tune the engine at all I wouldn't worry. the LED"s would work well. Just tune to the # of LED's that give you the best power but consider the following.

A/F is not the end all of tuning, EGT's do not tell you everything you need either. If you know your EGT's, what spark advance is doing, and what your knock sensor is telling the PCM and you are not knocking the engne or causing excessive spark retard due to knock, You're safe to jack the power using anymeans necessary until your head gasket blows. Then back her off a little bit from there and you got yourself the best damn SRT-4 on the block.

It would take some talent to blow your engine due to excessive power. Knock and over revving will kill her real quick. Also high egt's don't usualy melt piston's knock melt's pistons. High EGT's wear out catalysts (if you care) and burn out exhaust valves. I've made some headers turn yellow hued shades of orange and burnt out my share of exhaust valves but have never melted a piston. (cuz I always got a scope on my knock sensor and know what my spark is doing)

For EGT's I have no idea what "controlled" temperature is on this engine. On some of the older technology I've worked on usually 1650 F or 900 C at the manifold is a good maximum guidline.

However, valves and seats have become much more durable over the last 10 years and I wouldn't be suprised at all if this engine actually exceeded those temperatures during highway cruise. I would be interested in knowing what the max EGT's you could get at the manifold when running totally stock. Personally I would use the higher of 1650 or whatever max temp the vehicle sees when tuning.


And go_blue that blue line you were refering to does not make any sense in the way you were hoping it did.

That is the voltage output curve for a narrow band (factory) O2 sensor. (Your MOPAR gauge should be wideband) and a decent wideband should have a somewhat linear output. meaning that if you changed your air fuel ratio by .5 the change in output voltage would be the same whether you went from 8:1 to 8.5:1 or from 14.5:1 to 15:1


Anyways that's my essay for tonight. Hope everyone learned somthing.

BTW
If someone knows the criteria under which the engine goes open loop under high load I'd be interested in knowing. It likely wouldn't be too difficult to get additional fuel via throttle body injection, spark control by intercepting map and controlling map to a desired value, then you could juice the turb till your gaskets went.

However this system should work only while the system is running open loop thus retaining fuel economy and driveability until you pin er to the floor.
 

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Discussion Starter · #19 ·
NGIN EAR said:
And go_blue that blue line you were refering to does not make any sense in the way you were hoping it did.

That is the voltage output curve for a narrow band (factory) O2 sensor. (Your MOPAR gauge should be wideband) and a decent wideband should have a somewhat linear output. meaning that if you changed your air fuel ratio by .5 the change in output voltage would be the same whether you went from 8:1 to 8.5:1 or from 14.5:1 to 15:1
Not quite... The Mopar gauge is not a wideband. The voltage ranges for the new O2 sensor are 0 - 1 volts. The graph (minus the blue line) is from the instructions that came with the new O2 sensor kit.
 

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As long as you let the PCM control timing you won't have to worry about damaging knock since the knock sensor will pull timing via the PCM. Take the PCM out of the loop by running a piggyback or stand alone and when detonation becomes more severe there is no way for the pcm to retard timing when it is not regulating anything. Mopar tuned this car based off of EGT's and that is what the staged upgrades run rich and safe. Might not be the most power that route but atleast with the PCM controlling everything you don't have to worry about an accidental overboost situation causing detonation and blowing a rod through the block.
 
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