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Fooling the Computer
Posted 16 July 2004 - 02:30 PM
Posted 16 July 2004 - 05:19 PM
The issue is temperature. As incoming air to the engine is heated, it becomes less dense, occupying more volume. So, your engine ingests less oxygen when it is fed air at 150* vs 50*. Thus, it makes less power.
The general rule of thumb is that for every 10* intake air temp increases, you lose 3% in power, ceteris paribus.
As the motor heats up, the motor proceeds to transfer the heat into the incoming air. Thus making the motor run cooler, and limiting the engines ability to transfer heat improves performance.
I would look to improving your cooling system and looking at using a lower thermostat. Adding an intercooler will make tons of difference as well.
Posted 16 July 2004 - 06:45 PM
Now, as far as the above post, this is true of the intake air temp. Your solution to that is to make a free flowing intake that draws air from outside the engine compartment.
Posted 16 July 2004 - 09:05 PM
btw, if there is only 1 wire on the sensor, connect the other end to ground.
what you really might wanna think about is adding a switch to the wiring to be able to switch between the computer reading from the ECT, and your "modification"
anyone that doesnt know anything about electronics and wants to be able to do this PM me and I can help further.
Posted 16 July 2004 - 11:20 PM
Posted 17 July 2004 - 08:51 PM
The reason it cant precisely obtain around that mixture is because first off your computer doesnt pay attention to your oxy sensor when it is cold. also your oxygen sensor isnt designed to give you a reading like that. The oxygen sensor is sorta an "approximation" for the computer. Its designed to give around .2-.3 volts when lean, and .8-.9 volts when it is rich (comparing to stoichiometric 14.7 to 1). so it doesnt have a very large range. basically anything richer than 13 or leaner than 16, isnt really measured. the computer just sees it as "rich" or "lean".
Modern OBD2 fords or GM's, I cant remember, use a new type of oxy sensor that is more precise, and is measured by the computer in current, not voltage output
So after all that. your problem might actually be your oxy sensor. Hook up a volt meter to it and a good ground when it is hot. at idle it should read .8 volts-ish. rev the engine up to around 2500 and hold it, and you should then see the voltage start to bump back and forth between .2 and .9 volts. if it doesnt, or the voltage is low, persay around .4 at the most, then something is wrong.
Posted 19 July 2004 - 12:49 AM
oh yeah a good o2 should cycle at idle when hot as well as off idle.
Posted 20 July 2004 - 12:51 AM
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