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Old 12-23-2014, 05:51 AM   #1
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Default Individual Cylinder Trim, AFR vs EGT

Because this is the best technical forum around I want to ask this here:

I'm ***** deep in a semi-money is no object (within reason) build and have a subject I'd like to breach: At what point are there just too many damn sensors?

The skinny: what's the best/most efficient/most realistic way to take advantage of individual cylinder trim? The way I see it you have 3 options:

1) EGT every cylinder pre-turbo, One general AFR post turbo

2) Both AFR and EGT all cylinders

3) AFR every cylinder, FUQ DAT EGT

To me, option 1 seems the most sensible, as if you have your AFR's where you want them across the map, you can use EGT to fine tune each cylinder and have a 99.99999% solution. Whiel obviously option 2 is the most robust, I feel that the benefits really don't outweigh the cost and complexity.

What say you oh experts? BTW, if it matters, the engine in question is an I-6, and I honestly think that 6 EGT probes and 6 o2 gauges would REALLy start to get stupid in terms of cost/clean routing, etc.
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Old 12-23-2014, 09:56 AM   #2
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Getting a good reading off a wideband pre-turbo is a bit dicey as they're affected by heat and pressure. I'd use 6 EGT probes and as many post-turbo widebands as you have turbos.
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Old 12-23-2014, 02:34 PM   #3
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I think that's the ticket as well, though I've done a little research and found some threads discussing (not necessarily on new o2 sensors with heat dissipating bungs making pre turbo mounting a viable solution. So I wanted to ask ya'll incase my knowledge had dropped behind recent trends (for instance I had no idea CAN-bus was widely accepted on an enthusiast level)
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Old 12-24-2014, 10:58 PM   #4
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Pressure is the problem. The exhaust manifold pressure is going to make the widebands read off. You might be able to get the graph of the skew due to pressure and measure it with another map sensor in the exhaust manifold... EGT is also way cheaper.
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