Author Topic: Fuel trims/exhaust temp monitoring  (Read 1537 times)

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Offline Valkyrie

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Fuel trims/exhaust temp monitoring
« on: December 15, 2015, 09:21:44 am »
Quick question. I'm suspecting I have an O2 sensor (namely the 2nd one on the downpipe) that's connected to a standalone unit. Have done some recent work to the car and am getting ready to do a Tactrix opensource tune. But I don't think I'm getting a proper AFR reading.

My question is; if the O2 sensor is faulty or on a standalone unit will data from the fuel trims even be accurate? Been monitoring exhaust Temps as well looking for signs of leaning but not seeing anything out of the ordinary. Have also heard the stock O2 sensors were garbage and don't read accurately anyway.

Kinda at a stop at this point cause I'm unsure of accurate ecu readouts. Pointers anyone?

Vehicle is 05 STI.

Edit : bit more info.
O2 sensor on DP is connected to an Innovate Motorsports module. Haven't followed the opposite end of the wiring, but ate these traditionally tapped into the ECU?

Offline RockThePylon

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Re: Fuel trims/exhaust temp monitoring
« Reply #1 on: December 15, 2015, 12:52:51 pm »
Sounds like you have a standalone wideband O2 sensor in the downpipe, where the OEM #2 sensor is usually located. Fuel trims should be accurate, assuming the #1 O2 sensor in your up-pipe is still present/working. How are you measuring EGTs?

Hard to say what's going on without crawling around and looking.

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Offline funk32

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Re: Fuel trims/exhaust temp monitoring
« Reply #2 on: December 15, 2015, 02:31:09 pm »
ok lets think about this... you have a o2 sensor in the downpipe that is connected to a Innovate motorsports module, to my knowledge they do no have a standalone ECU system.  You would not normally connect an aftermarket wideband to the stock ECU either, it would go to a gauge or bluetooth device.

what else has been done to the car?

if the system is standalone you would normally tune it via a port on the ECU itself and the tractrix is really not used.

The OEM wide band is not super accurate but is good enough to see if there is a major problem (hens why you get lean codes)

Offline Valkyrie

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Re: Fuel trims/exhaust temp monitoring
« Reply #3 on: December 17, 2015, 05:18:30 am »
Sorry was about delayed response.

K so question one: EGT is being measured by a defi sensor tapped into the headers. Please keep in mind that these guages and sensors were present on the vehicle when I bought it. So I haven't been able to trace everything yet but I'm getting there.
 Front 02 sensor is tapped into up pipe,  rear O2 behind turbo but before the cat.

Rear 02 sensor is connected to an AFR guage but I think somethings off cause it reads a constant 15.1 all the time. So I've removed that from my list of viable info readout. EGT reads between 300 and 400 C at warm idle. Hasnt gone over 800 C under any condition pulling or highwaty/freeway driving. The tool I'm using to monitor and data log is a real time OBDII Bluetooth module and the Torque app until I recieve the opensource tools.

Question 2: Current mods to vehicle are AEM CAI, process west tmic, full exhaust (Tomei EL to Invidia DP followed by HKS the rest of the way out) turbo was replaced with a blouch 18g xtr ball bearing (18 psi). Tune to vehicle is a stage 2.5 by Sunny (this came with the car). Because the vehicle was used I'm unaware of injector size at this point. DW300 series fuel pump, aeromotive FPR, turbo XS knock sensor/light.

I'm finding sensors and modules all over as I work on this thing and though trying to play safe, I'm trying to figure out at this point what is giving me data I can actually believe. Because of this I'm trying to look beyond for any other signs/ info I can get that may suggest leaning as at this point that's my major worry.

Edit: I may have worded it wrong earlier. By stand alone unit in regards to the innovate Motorsports module, I mean that I suspect the sensor, unit and guage are not wired into the ECU, not that it's a standalone ECU. It's a wideband sensor and the front one is an OEM narrow band as far as I know. Is rear 02 directly related to AFR monitoring or is it more of an emissions sensor? Do these ECU's calculate the fuel trims by
Info gathered from both or just the front one?

Offline RockThePylon

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Re: Fuel trims/exhaust temp monitoring
« Reply #4 on: December 17, 2015, 01:23:52 pm »
Front 02 sensor is wideband, it just doesn't give useful information for tuning. It's where the ECU gets info for A/F Learning #1 and A/F Correction #1. If the front O2 sensor is constantly and quickly moving around 14.4-15.0 during light cruise, I'd assume it's fine. A failing O2 sensor becomes slow to respond, and/or consistently reads too rich/lean. Your car will generally run like a bag of itshay if it's on it's way out.

The O2 sensor near the turbo is (should be) for your Innovate wideband. It will not be wired to the ECU.
Being stuck on 15.1 means it's dickered, or it might be physically disconnected from the gauge.

There should be a second O2 sensor (post-turbo) that you find crawling under the car, on a horizontal stretch of the downpipe. This is connected to the ECU, and is used to monitor the catalytic converter. On the MY08+ STI, it does affect fuel trims, not sure about your ECU in specific.

EGT's under 800C are considered safe. Nothing super scary there.
I may scream like a dainty lady, but I punch like a fairly strong 11-year-old.

Offline Valkyrie

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Re: Fuel trims/exhaust temp monitoring
« Reply #5 on: December 19, 2015, 12:11:17 pm »
Perfect at this point that's exactly the ifo i was looking for. Reason I'm a little worried is I did IC, headers and turbo all in one shot. Was watching for any leaning on the boost end due to higher flow rate. So far everything's looking ok but I'm not looking to grenade anything here so keeping it light, watching and listening like a hawk until I can beef the injectors and tune.

Cheers