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Discussion Starter #1
How can I know if my car is running rich?

I was told once you mod the exhaust system: eliminate Pre-cats and Cat and then install a DP and Catback: The O2 sensors will no longer read the proper A/F Mixture because of the difference in air flow, pressure and temp in the exhaust line, is this true?
( I was even told once these mods done, we will run much richer cause the O2 sensor is no longer reading correctly)

If so even an A/F gauge (that is connected to the O2 sensor) will give out incorrect readings as well as a datalogger that also uses the O2 sensor throught the ECU to read A/F mixture?

So if this is the case how do we read A/F? and set the proper fuel correction?
 

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I think the A/F guages like Cyberdyne, Intelitronix, Autometer, etc are good enough when you all you need to know is if you are running rich or lean.

Now if you need to know specific A/F ratios then you might have to step up to something that uses a wide-band 02 sensor like the Halmeter.
 

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The prehistoric way to detect richness is to look at your spark plugs. If they're dry, black, and sooty, then you're running rich. They should be a light tan colour.
 

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Discussion Starter #5
Here the thing, I have this Apexi AFC and I want to use it!! but I don't want to kill my engine by running to rich or Lean So I'm not sure what to use to read the A/F mixture so I can do the proper correction....
 

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Guages like the Autometer, Cyberdyne, Intellitronix are good for general tuning with your AFC. The worse that can happen is that you will run too rich which will not hurt your engine.

If you wanted to use a more precise A/F metering device, you'd be looking to spend a good deal of money ranging from several hundred to a thousand dollars.

Also they are bulky and are not for everyday driving. Meaning you don't just hook it up and leave it on the car. It's only supposed to be used only when you are tuning because the sensor will clog over time.

So you have to pull the sensor whenever you are not tuning.
 

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another question relating to this...

Without using an AFC an A/F gauge is pretty much useless isn't it? All it will do is bounce back and forth as the computer is trying to find stoich. When its WOT it'll be pegged at Rich and when decellerating it'll be down towards Lean.

So without a A/F controller (like the AFC) it's pretty much useless?

I only ask because I just bought one, without really thinking of that :rolleyes:
 

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Jagd, thats cause our cars are made to run rich... it shuold peg all the way to the right except for maybe one or two bars at WOT. If you max it out, then you are running 2 rich. If you look at all the options in an AFC such as the correction, it will pretty much tell u if your running too rich/lean. The AFC has alot of capabilities. I'd go with a more reliable Blitz, Greddy, or Apex'i a/f gauge.


-Ryan
 

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Not really...

It can act as a warning device. If something were to fail or was starting to in your fuel system, the A/F guage may be able to give you warning.
 

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Anthony said:
I was told once you mod the exhaust system: eliminate Pre-cats and Cat and then install a DP and Catback: The O2 sensors will no longer read the proper A/F Mixture because of the difference in air flow, pressure and temp in the exhaust line, is this true?
Nonsense. I have all that done (except have high-flow cat) and my two O2 sensors and the ARM1 meters monitoring them work just fine. How *fast* the exhaust flows past the meters makes no difference. Besides, O2 sensors are *not used* except at idle and cruising. When accelerating, internal maps are used.
 

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Blue'ish, white'ish smoke is usually an indication that your are burning oil somewhere and has nothing to do with A/F ratios.

White smoke is an indication of coolant being burnt which usually is accompanied by a sweet kind of smell.

In the case of white smoke after taking off from a light, that's oil burning fthat has leaked from worn valve stem seals, a problem I've had before.
 

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Jeff's right. O2 sensors don't start working differently because of exhaust or cat changes. The only one that succeptable to outputting "wrong" information with exhaust changes is the *post* pre-cat O2 sensors installed in the downpipe in the 96+ cars that are referenced to the *pre* pre-cat O2 sensors that are in all 3/S's. If you gut the pre-cats on a 96+ you run the risk of setting a check engine light because the difference in the readings between the *pre* pre-cat and *post* pre-cat O2 sensors to verify that the pre-cats are operating correctly. Personally I just cut the wires for my *post* pre-cat O2 sensors and left them off when I installed my ATR downpipe. There's no ill effects besides people asking about the check engine light. I just tell them not to worry about it and nail the gas to get their mind off of it. :D
You can tune by the stock O2 sensors. The resolution is not that great but it's not too bad. I tune my car to match the stock setup...O2 sensor output at 0.94-0.96V. Kinda rich but it's safe.
 
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