Gauges, Sensors, and Tuning Oh My

[Noodle]

Ok so I'm looking at getting my DD tuned. It already has a Catless Invidia Uppipe but otherwise stock aside from some suspension mods.

 

2005 Outback XT

 

First and foremost I want to keep it looking as stock as possible so I was looking at the CubbyPod from JCSPods or even just spending the cash on a Cobb V3 for the gauges and other perks that come with it.

 

1. My tuner is telling me to just get an AEM UEGO AFR sensor with gauge to use and while I know I need the wideband sensor and understand why its needed for tuning, if I'm looking at the Cobb wouldn't I just need the sensor? I see AEM has a version with an inline controller that doesn't have a gauge. Does the gauge in the typical kit have the controller built into the gauge? There is about a $100 difference with the gauge kit vs inline controller.

 

2. What kit to get. I see there are a few different AEM ones with 4.2 or 4.9 Bosch sensors. AEM 30-4110 for instance

 

3. Cost. since this is my DD I'm not looking to spend a ton but as mentioned was looking at the Cobb AP mainly for using it for gauges and then weighing the costs of multiple gauges and such. $600 for the Cob AP with a wideband sensor $80 - $100 would be about the same as a AFR gauge and sensor + Boost gauge kit +whatever else. (was initially looking at the vent gauge kit that would be another $200)

 

I'm planning on adding a downpipe down the road but will probably quit there. I won't be adding a bigger turbo, might try and setup for E85 but that's about it.

 

What am I overthinking or just plain thinking wrong about this. I guess I just don't quite understand the hardware aspect of the AFR and such.

 

I thought with the Cobb AP it could be just sensor replacement and plug and play basically.

 

Help please.

[solidxsnake]

You can't replace the stock O2 sensor (which, by the way, is already a wideband, but just doesn't read down past around 11.1AFR). You need to use the wideband in addition to the stock one. But for tuning, you don't need a gauge, really. Just need a way to log it.

[Noodle]

You can't replace the stock O2 sensor (which, by the way, is already a wideband, but just doesn't read down past around 11.1AFR). You need to use the wideband in addition to the stock one. But for tuning, you don't need a gauge, really. Just need a way to log it.

 

Don't most aftermarket wideband sensors go in the spot of the stock when dealing with stock exhaust and then have a controller that plugs into the stock wiring and the aftermarket sensor plugs into that?

[solidxsnake]

Don't most aftermarket wideband sensors go in the spot of the stock when dealing with stock exhaust and then have a controller that plugs into the stock wiring and the aftermarket sensor plugs into that?

 

It's possible, but I don't think it's particularly common (I may be mistaken). I'm under the impression most people who are tuning with a wideband likely also have an aftermarket downpipe with a WBO2 bung, or they just had a shop install a WBO2 bung on to their stock exhaust.

 

Mike @ Tuning Alliance put together a plug-and-play kit to replace the rear O2 sensor with a wideband, but you'll need to have AccessTuner Pro (with a Cobb AP) or know what you're doing with OpenSource to set it that up. It's not difficult to do, and it's real nifty when it's set up.

[Noodle]

So that's where I'm confused. What do people do then for a tune with stock exhaust. Stage 1 or so.

 

I have an Invidia Uppipe but wasn't planning on getting a downpipe just yet but still wanted a tune.

 

I was under the impression I could get a AEM UEGO AFR gauge kit and just install it in the stock location and wire it up. My issue is I want things to look as stock as possible so I'm trying to figure that out and thought I could just forgo the gauge but get an upgraded sensor for the stock location.

[NSFW]

Aftermarket sensors need to be mounted downstream of the turbo.

Exhaust gas back pressure throws off the readings of sensors mounted upstream.

 

In theory you could have the stock ECU read from an aftermarket sensor, but in practice basically nobody bothers. Keeping the two systems separate is just simpler. More parts, but no interoperability issues.

 

AFR gauges are very useful for troubleshooting, so I'm a big fan. They'll tell you right away if you have a vacuum leak (done that a few times), or a boost leak (only happened once so far), and they'll help you find fuel pressure problems (it's how I found out my old fuel pump was dying).

[Noodle]

Aftermarket sensors need to be mounted downstream of the turbo.

Exhaust gas back pressure throws off the readings of sensors mounted upstream.

 

In theory you could have the stock ECU read from an aftermarket sensor, but in practice basically nobody bothers. Keeping the two systems separate is just simpler. More parts, but no interoperability issues.

 

AFR gauges are very useful for troubleshooting, so I'm a big fan. They'll tell you right away if you have a vacuum leak (done that a few times), or a boost leak (only happened once so far), and they'll help you find fuel pressure problems (it's how I found out my old fuel pump was dying).

 

But that's just it. I completely understand the use and reason for an aftermarket sensor and where it typically goes but that doesn't mesh with a stock setup I guess. in a stock setup then where does the sensor go regardless of if you want to use the gauge it comes with or not.

 

If I buy an AEM gauge with sensor but don't want to keep the gauge and use some other way to show the AFR does that mean I can't even use the sensor in a stock setup? That's what is throwing off my thinking on this setup.

 

This is where I'm confused on how to move forward.

[NSFW]

That's a fair point - if you're not going to be messing around under the hood a lot, then there's less likelihood of stuff going wrong.

 

With PLX you can definitely use the sensors without gauges. I suspect that's true for AEM as well but I don't take know.

[solidxsnake]

But that's just it. I completely understand the use and reason for an aftermarket sensor and where it typically goes but that doesn't mesh with a stock setup I guess. in a stock setup then where does the sensor go regardless of if you want to use the gauge it comes with or not.

 

If I buy an AEM gauge with sensor but don't want to keep the gauge and use some other way to show the AFR does that mean I can't even use the sensor in a stock setup? That's what is throwing off my thinking on this setup.

 

This is where I'm confused on how to move forward.

 

What do you mean "stock setup?" It's probably a bad idea to replace the front O2 sensor (in the up-pipe) with an aftermarket wideband, but you can replace the rear O2 with a wideband, disable the resulting P0420 code that you'll get, then play with the ECU calibrations to make the rear O2 sensor input read your wideband instead.

 

The reason you don't want to replace the front O2 sensor is because it's critical to your ECU's closed-loop fueling, and unless the tuner is familiar with recalibrating the front O2 sensor scaling, then your closed-loop fueling will be all over the place. The rear O2 is only used to monitor the catalytic converter (purely for emissions), so there's no harm in deleting it and disabling the codes besides emissions reasons.

 

Check out Tuning Alliance's plug-and-play WBO2 kit. There's no reason you couldn't do this with any other wideband (i.e. the AEM UEGO): http://legacygt.com/forums/showthread.php/tuning-alliances-wideband02-logging-kit-258451.html

 

One other thing... if you're on a stock setup (stock intake, injectors, fuel pump, exhaust, etc.), then you may not really need to keep an eye on fueling while tuning. The tuner can just trust that the fueling table targets are close enough (assuming the car's in good mechanical condition, this is a reasonable assumption), then tune a bit conservatively.

[Noodle]

What do you mean "stock setup?" It's probably a bad idea to replace the front O2 sensor (in the up-pipe) with an aftermarket wideband, but you can replace the rear O2 with a wideband, disable the resulting P0420 code that you'll get, then play with the ECU calibrations to make the rear O2 sensor input read your wideband instead.

 

The reason you don't want to replace the front O2 sensor is because it's critical to your ECU's closed-loop fueling, and unless the tuner is familiar with recalibrating the front O2 sensor scaling, then your closed-loop fueling will be all over the place. The rear O2 is only used to monitor the catalytic converter (purely for emissions), so there's no harm in deleting it and disabling the codes besides emissions reasons.

 

Check out Tuning Alliance's plug-and-play WBO2 kit. There's no reason you couldn't do this with any other wideband (i.e. the AEM UEGO): http://legacygt.com/forums/showthread.php/tuning-alliances-wideband02-logging-kit-258451.html

 

One other thing... if you're on a stock setup (stock intake, injectors, fuel pump, exhaust, etc.), then you may not really need to keep an eye on fueling while tuning. The tuner can just trust that the fueling table targets are close enough (assuming the car's in good mechanical condition, this is a reasonable assumption), then tune a bit conservatively.

 

 

What I mean by stock setup is I literally only have an invidia catless uppipe. Other than that my exhaust system is stock.

 

I'm realizing now that I can't do what logistically I thought I could. I thought I could just put an aftermarket wideband sensor in the stock o2 sensor location and run it off the stock wiring and such.

 

I'm understanding now that I need to run the aftermarket sensor in a different location and with it's own separate gauge unless I want to get really fancy with wiring and all that.

 

I didn't realize that the sensors were that different in location and how they worked with the car and ECU.