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Old 05-15-2013, 03:26 PM   #32 (permalink)
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Originally Posted by Phantom View Post
Unless you have two O2 sensors one for each bank more common on v8s and some v6s, the ECU will see lean and dump more fuel to get it to 14.7.
Unless I'm remembering some other thread, the OP has a header and the O2 sensor is only installed on one of the exhaust pipes, so it is only fed by a single cylinder.

Measuring AFR won't tell you anything about how much fuel is being burned, unless you also know how much air is coming in. And measuring it on a single cylinder's exhaust when you are disabling a different cylinder tells you even less about overall fuel consumption.

If you have an MPGuino, you can get a reasonable idea of how much fuel is being burned. You need to tap into the signal for a non-kill injector, then multiply the fuel usage by 0.75 because only three injectors are working when the one cylinder is killed. Chances are that the MPGuino raw readout will go up, but if it does so by less than 1/3, then you have a fuel savings.

The SG and UG options might be quite inaccurate for this usage, because they estimate fuel used from a bunch of other parameters. And shutting down one cylinder violates at least some of the assumptions made for this calculation, rendering is much less reliable as an estimate of fuel usage.

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