I'm getting pretty confused over the how tuning works on the sc3800 especially on incorporating a wideband sensor, so I am having trouble figuring out what all i need to buy and how to hook up for the wideband. I'm planning on using sinister performance to tune it. I think he is on the forum, but can't remember who. As I understand it (I'm sure i'm misunderstanding something) the ecm has a table and controls how much fuel is put in the engine at a given rpm, throttle position, and manifold pressure (in addition to all the other things the ecm controls like spark timing.) The stock O2 sensor lets the ecm know when it is richer or leaner than 14.7:1 due to environmental conditions, and the ecm will temporarily adjust how much fuel it puts in to make it 14.7:1. If we want to run different fuel ratios, we need to install a wideband sensor to help us determine our initial ecm table adjustments, and to make temporary adjustments in the same way the stock O2 sensor does. How does a wideband controller interact with the ecm to allow for the temporary adjustments? I've seen that i need to keep my stock O2 sensor, Why would i need it if i'm not interested in that air/fuel ratio anymore? As for logging, how do I log data from my wideband and ecm at the same time? Just using two usb ports? What is the purpose of a gauge, other than having another fun gauge to look at? In general, i'm having trouble finding resources for quick basic learning about this stuff.

For clarification: Stock 1997 ECM to be tuned and used. 1997 series II L67. Mods: cam, headers, pulley.

[This message has been edited by johnnyray401 (edited 01-18-2016).]

If you use a wideband O2 sensor it can only be used for a separate accurate measurement of the A/F ratio. You can only use the narrow band sensor wired to the 3800 PCM.
In simple terms the narrow band is for running and the wideband is for tuning. The stock narrow band O2 sensor only adjusts the A/F ratio under normal running conditions . At WOT the A/F ratio values must be set in the program. The stock O2 sensor will do the job only if you have made zero changes and no modifications to the engine, If this is the case the PCM program should be close.
To use a wideband you need a separate A/F gauge. The sensor can be attached via a welded bung to the exhaust downpipe or you can buy them with a bracket that goes into the tailpipe. My 3800 has a few mods and the PCM needed many changes. Those change can only be put in place by monitoring with a wideband O 2 sensor. Most of the fueling changes were done via an adjustment to the new LS1 MAF curve that I am using. If you use a smaller pulley, different cam or up-sized injectors then tuning will also be necessary.

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quote Originally posted by johnnyray401: I'm getting pretty confused over the how tuning works on the sc3800 especially on incorporating a wideband sensor, so I am having trouble figuring out what all i need to buy and how to hook up for the wideband. I'm planning on using sinister performance to tune it. I think he is on the forum, but can't remember who. As I understand it (I'm sure i'm misunderstanding something) the ecm has a table and controls how much fuel is put in the engine at a given rpm, throttle position, and manifold pressure (in addition to all the other things the ecm controls like spark timing.) The stock O2 sensor lets the ecm know when it is richer or leaner than 14.7:1 due to environmental conditions, and the ecm will temporarily adjust how much fuel it puts in to make it 14.7:1. If we want to run different fuel ratios, we need to install a wideband sensor to help us determine our initial ecm table adjustments, and to make temporary adjustments in the same way the stock O2 sensor does. How does a wideband controller interact with the ecm to allow for the temporary adjustments? I've seen that i need to keep my stock O2 sensor, Why would i need it if i'm not interested in that air/fuel ratio anymore? As for logging, how do I log data from my wideband and ecm at the same time? Just using two usb ports? What is the purpose of a gauge, other than having another fun gauge to look at? In general, i'm having trouble finding resources for quick basic learning about this stuff. For clarification: Stock 1997 ECM to be tuned and used. 1997 series II L67. Mods: cam, headers, pulley.

I'm Ryan from Sinister Performance.

The 3800 Series 2 SC PCMs cannot directly use a wideband o2 sensor. They can only understand and use narrow band o2 sensor signal inputs. The narrow band o2 signal can be used to do ALL tuning, but it does not offer good accuracy outside of stoich (14.7:1 AFR for gasoline). That being said, the narrow band o2 sensor voltage signal can sometimes be used to determine AFR's outside of stoich, but such readings can't really be trusted due to the design of this particular type of o2 sensor. The wideband o2 gives us a true AFR reading everywhere, not just at stoich.

There are a couple of ways to get a wideband o2 signal into a scan data log. Some connect the wideband 0-5v output to the PCM's EGR position input so it can be set up to be recorded in a scan log along with the rest of the data. The only problem with doing it this way is we must calculate AFR based off of voltage, so it requires an extra step. The preferred method of getting wideband AFR into a data log would be using a vehicle interface cable that has an external input that can be configured to accept wideband o2 signals, such as the HP Tuners MPVI Pro interface. Their standard MPVI interface does not have external inputs.

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