Getting close to pulling the header in my 2002 to mount a wideband for carb tuning - hopefully I'll pull it this weekend. Before I start drilling and welding, I figured I'd ask if there are any things to avoid. I'm intending to weld the bung into the collector, with the body of the sensor oriented horizontally, roughly parallel to the floor. Is there anything more to it that that?
If you have the space, angle it down a little- just give an extra way to drain water off if it. And I can't remember how many diameters past the actual collection point- 2 or 3- so that it mixes enough to get a good signal from all 4 cylinders.
One interesting hint I've learned about for carbs- assuming there are two of them, make sure they are totally identical to each other. And double check them- if you can build them together at the same time next to each other. I've known more than one Alfa owner who went down a big tuning rabbit hole that was mostly caused by the two carbs not being exactly the same.
I've always put the sensor 4-6" after the collector outlet and it's seemed to work fine.
Alfadriver mentioned mounting it so moisture would drip off the business end. Typically that means putting the sensor between the 9:00 and 3:00 positions (e.g. above the halfway line) on the pipe. Lower than that, and condensation can damage the sensor.
The collector is a good place to sample from all four cylinders. Make absolutely sure there are no exhaust leaks anywhere upstream of the sensor, or even downstream near the sensor. Some headers can hide pinhole leaks and/or develop cracks that can invalidate your readings.
Other'n that, it ain't rocket surgery!
Widebands are sensitive to temperature and if you get it too hot you will cook it. This is mostly an issue with turbo cars (and rotaries!) and the collector is probably fine so long as you've got relatively long header primaries, but it doesn't really hurt anything to have it mounted further back. Just make sure it's in front of any cat.
Oh, and I would probably aim for closer to 12 o'clock on the pipe than 3.
Most of the aftermarket controller manufacturers recommend between 12-36" from the exhaust port or turbo, always pre cat, always as far away as reasonable from a joint or other potential leak point, always in the upper half of the pipe. LSU 4.9 sensors seem to like to be flush with the end of the bung. LSU 4.2 should protrude into the exhaust stream.
In reply to codrus (Forum Supporter) :
For the most modern sensors, they are not too bad with temp anymore. Past a collector, it will be more fine than not.
As for turbos- the temp is only a problem when the sensor is in front of the turbo- which is the way OEM's do it. But we deal with it really easily.
Thanks for all the input. I don't think there will any issues with heat - it's a long-tube 4-2-1 header. There is no cat, never was - this car predates them. Making sure I resolve any small leaks in the system post-header may require a bit of work, but I think the header itself is sound; I'll go over it carefully when I yank it out. Hopefully my welding at the bung won't be the weak point in the system.
One of my RX-7s has the exhaust collector at the rear axle, with multiple flanges and mufflers that can leak, so I just put the wideband in the header as far back as possible. It's only reading one pipe, but that doesn't worry me much. It's not like my computer can do individual fuel trims. The sensor is horizontal with the ground because there's a floor right there above the header.
On the other one, which has a collector in what most people consider to be a normal location and has room above it, I took the extended O2 bung that came with the kit, cut it at an angle, and welded it to the top of the collector with the wiring end of the sensor pointing forward.
Both are about 20" from the exhaust pipes. O2 life is not really degraded. The MTX-L eats sensors and they last basically forever with the AEM. My main concern is exhaust gaskets between the exhaust ports and the sensor, because leaks upstream of the sensor will skew the readings by a lot, so the sensors were mounted as far back as possible before running on the other side of a flange.
alfadriver said:As for turbos- the temp is only a problem when the sensor is in front of the turbo- which is the way OEM's do it. But we deal with it really easily.
It depends a lot on how much boost you run. 18-24" past the turbo on my Miata (24 pounds of boost) was too hot on track for my LC2 wideband. Finally had to use their wideband heat sink mounting solution to get it stay aalive.
That was likely an lc2 problem as the heater doesn't use the bosch chip. I have put them within 6" of the turbine with the 4.9 and ngk sensors with other controllers.
codrus (Forum Supporter) said:alfadriver said:As for turbos- the temp is only a problem when the sensor is in front of the turbo- which is the way OEM's do it. But we deal with it really easily.
It depends a lot on how much boost you run. 18-24" past the turbo on my Miata (24 pounds of boost) was too hot on track for my LC2 wideband. Finally had to use their wideband heat sink mounting solution to get it stay aalive.
Not discounting your problem, but I've run UEGO's in front of the turbo near 1750F, and they didn't fail. Turbos take out 100-200F in the exhaust stream. And another foot is at least 50F. So to get anywhere near a modern UEGO failing point, you would probably be destroying the engine first. So as Paul suggested, that's a LC2 problem.
Your issue would be worse if there wasn't a turbo in the way taking out a lot of heat.
I've run the ngk sensors about 6" off the port as well. Not sure how the Bosch ones do there but as alfa says likely not the sensor
alfadriver said:Not discounting your problem, but I've run UEGO's in front of the turbo near 1750F, and they didn't fail. Turbos take out 100-200F in the exhaust stream. And another foot is at least 50F. So to get anywhere near a modern UEGO failing point, you would probably be destroying the engine first. So as Paul suggested, that's a LC2 problem.
Perhaps, but this was fairly common knowledge amongst the Miata turbo community amongst a fairly wide variety of wideband systems at the time. Innovate sells a product specifically to address this:
https://www.innovatemotorsports.com/heat-sink-bung-extender-hbx-1.html
From the description: "For some turbo vehicles, rotary engines, and other specialty setups, this error message can be encountered with annoying frequency due to operating conditions specific to those engine types and configurations."
EGTs in the exhaust manifold were over 1600F (the max on my gauge). Engine ran just fine -- everything ELSE on the car broke at the track, but the engine handled it like a champ. This was with 100 octane fuel and plenty of timing (close to MBT).
In reply to codrus (Forum Supporter) :
So then the sensor system is indeed the problem. It's not running so hot to damage the engine, so the sensor should be fine.
The process I was working on was intended for production. So I know the sensor is capable of 1750, staying closed loop, and doing that repeatedly for 150k miles. The weak point of that powertrain were the valve seats.
There's no way you are getting anywhere near 1750 F downstream of the turbo, unless there's a massive leak and it's burning up post turbo. Even if you were 1700F pre-turbo, it would be sub 1600F past it.
In reply to alfadriver :
Innovates fry sensors no matter how you mount them. They are merciless with how they run the sensor heater.
I did have a lot of luck with an LC1, but this used the 4.2 sensor which may have been more robust. Or the LC1 may have had better heater control than the newer, less expensive controllers.
Pete. (l33t FS) said:In reply to alfadriver :
Innovates fry sensors no matter how you mount them. They are merciless with how they run the sensor heater.
I did have a lot of luck with an LC1, but this used the 4.2 sensor which may have been more robust. Or the LC1 may have had better heater control than the newer, less expensive controllers.
I've had an LM2 in the Jeep for years. Originally it had an LSU4.2 sensor and was less than perfectly reliable, it would flake out occasionally and I did have to run with the heat sink to avoid temperature related errors. Eventually Innovate gave a firmware update that supported the LSU4.9 sensors, so I upgraded and bought the new sensor. Since I did that, it "just works" and hasn't burned up a sensor yet. Sensor is at the end of the Y-pipe just before the catalyst. I don't think it has the heat sink installed with the 4.9 sensor, but I'd have to look to confirm.
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