Wideband AFR sensor location
 

Guys,

What's the consensus for locating the sensor's boss on the exhaust system?

On PET, the 964 turbo has the Lamda sensor located somewhere on the exhaust pipe the 'wastegate' is mounted. I've seen a couple of guys here position the sensor on the top of the turbo-muffler coupling (but it's particularly hot here and I've seen some relocate to the muffler's bottom pipe).

Which is reckoned to be best? (Does one need a heat shield to stop the sensor baking in the turbocharged-exhaust-pipe sun?)

tj,

The general opnion will pobably tell you 6-10 inches from the turbo outlet at the 2 or10 o'clock position and preferably with a heatsink and shield.
Also your configuration will depend on your exhaust system , zork or
muffler and tail pipe.

Cole

+1 as Cole stated.

For my application, there was too short a space between the muffler and turbo outlet to get far enough away from the turbo and not cook the sensor. So, I installed mine in the tailpipe as close to the muffler as possible....probably 10 inches away from the tip. Works fine, the only risk being that at a standstill and stiff tail wind, you may get some ambient air getting in and causing a false high reading. But I haven't seen that happen.

This where Innovate tech support told me to mount mine.

http://forums.pelicanparts.com/uploa...1258152464.jpg

I get good stable readings and I also have a 2000 deg. heat shield on it.

Thanks, guys - so, close enough to the action (but WITHOUT getting melted)? ;)

Gsmith, my car's muffler is pretty similar to yours - I see that you've located the sensor nearer to the cold side of the turbocharger, but it's still going to be pretty, damn hot there! (I can see why a heat shield would be a really good idea.)

David and Mark - thanks and I hope you're both returning to full strength and peak physical condition very soon. ("Tiptronic?" splutter... cough.. Get well, Cole, and then help kick his behind for even suggesting such a thing! ;))

tj,

Innovate also makes a great heat sink for mounting to the bung. The EGTs on
a 930 are really brutal and sensors burn up fast without adequate precautions. I
ran my LM-1 hard wired in the car but only use it to power my digital dash display. When tuning or periodic AFR and system checking I reinstall the WB02 and run some data and then remove it. If your not doing track work that's the way to go.

Cole

They also suggested the 1 inch bung I'll see if I have a pic with the heat wrap. I found one.
http://forums.pelicanparts.com/uploa...1258154679.jpg

Yup, I've already burned up two sensors running them next to the turbo. One of my projects this winter is to get a bung welded on the pipe beyond the muffler. I have a RarlyL8 muffler so there is room on the right hand side where it will get more airflow and be away from the turbo completely.

^^^ +1. I've burned up several as well at the track. Happens a lot when I blast of out of the pits. It just goes into some error mode and it's no good after that. That's with a zork.

For the street, I need to move it to the outlet portion of the muffler like above and use my heatsheild.

I installed a catalytic converter bypass pipe for "test purposes only". I have already done the air injection delete so I don't need this threaded fitting. With some delicate drilling and tapping, I was able to get a WB02 sensor threaded inside the male M22x1.5mm fitting (so now it is a hermaphrodite fitting?) midway between the turbo outlet and the muffler. Here is a picture of the fitting on the bypass pipe:
http://forums.pelicanparts.com/uploa...1258169347.jpg

Mark

tj,

Thanks for the kind words and the "OLD ONE" is just great.

Cole

What if you're running a zork?

use a heat sink

g,

Great idea with the heat sock, Nice install.

Cole

thanks time will tell if I did good

Sensor placement reply
 

I attached my sensor at the end of the muffler and it is connected to a XD-16 gauge on the dash. This works well and was straightforward to connect.


http://forums.pelicanparts.com/uploa...1258266555.jpg
http://forums.pelicanparts.com/uploa...1258266597.jpg

When I bought my NGK wide band setup they recomend installing the 02 sensor 10 times the dia. of the exhaust system from the end (ie. 3' pipe = 30"), to insure false readings from air being sucked back in the end.

I'm thinking I will mount a temp sensor on the heat shield and run it then move it inside and see how hot it gets if it warm enough I might do this soon.

That's a very innovative approach - I hadn't considered that! :cool:

Thanks, I have an LM-2 and can connect it to this and can log AFR's, boost and rpms.

John, I at one time considered doing the same with a direct-to-muffler mount, but my only concern was being able to keep the sensor vertical between 10:00 and 2:00...to keep the condensation from settling on and ruining it. So I opted with installing in (on top of) the tail pipe and snugged up against the muffler.

Fears about ambient air back-wash (10" for every 3" of pipe diameter...come on, who in a 930 has 30" of tailpipe available!?) are really only a concern at idle when not enough exhaust velocity exists. But we don't install AFR monitors to see what's happening at idle, so who really cares? With that said, mine reads just fine at idle regardless of being only about 10" from the outlet (maybe the fact that the pipe has about a 30 degree bend helps in this regard).

I think the location depends on whether you are using the sensor for control, or to just monitor AFR. For control the optimum location is as close to the cylinders as possible. This means mounting it before the turbo. The problem with this is that exhaust pressure throws off the reading, which is why it is usually suggested to mount it after.

For EFI with the capability for it, you can correct the AFR reading for the pressure effect using this formula:

AFR(corrected) = (AFR(measured) + B x P) / (1 + C x P)

where: AFR(corrected) = the AFR corrected for exhaust pressure.
AFR(measured) = the AFR output by the AFM.
B = 0.009140 for AFR < 14.57 (rich).
B = 0.012100 for AFR >= 14.57 (lean).
C = 0.000627 for AFR < 14.57 (rich).
C = 0.000830 for AFR >= 14.57 (lean).
P = the exhaust pressure in mmHg above the pressure at which the sensor
was calibrated (using the CAL POT on the AFM while the sensor is held in air).
Valid for -152 mmHg < P < 532 mmHg.

Mark ,I have over 30" of tail pipe on my 964 turbo and if you measure through that muffler to end you p;robably do also. I tune my afr @ idle as well @ higher rpm , as I am useing a digital wur and it makes a difference for me. I didn't say it should be 30" on a 930,just that is what the mfg. sugested to do . I had a zork on it for a while and had it mounted on top of it about 2" from the turbo as Brian Bodart sugested to do and it worked fine on boost but was not real reliable @ less than about 950 rpm.

My misunderstanding...I thought it meant 30 inches before the open end of the tail pipe. If I include the length of the muffler....starting at the turbo...to the end of the tail pipe then you're right I probably have 30" as well (on my non-stock straight thru muffler). I realize it's just the manufacturers recommendation.

I also tune mine at both idle and on higher rpms/boost, at idle using both the AFR gauge and the old standby Gunson Gas tester for %CO. My whole point is that we should not discount mounting sensors (for monitoring purposes only) post-muffler and relatively close to the end of the tail pipe. Each application is indeed unique.

Here is what we do for the zorks. Not much to work with. Idle readings can be iffy.

http://forums.pelicanparts.com/uploa...1258327849.jpg


I also have the O2 bung in the neck of the mufflers due to packaging and other considerations. A heat sink will protect your sensor while not affecting the readings.

http://forums.pelicanparts.com/uploa...1258328028.jpg

So hopefuly I can get some help here I've asked this quesiton on rennlist, I've got a B&B dual outlet which side do I put the sensor?

Post a pic you might be able to mount it somewhere on the muffler itself.

So it's ok to place it in the muffler?

You can put it in the exhaust any place you want so long as a few rules are met, one it must point up like at the 2 or 11 oclock position so moisture cant settle in the sensor it will destroy it and it must get full exhast flow no stagnant locations and it must be back from the exhaust oulet so outside air cant corrupt the reading. Thats why I said post a pic of your muffler and I am sure we can steer you in the right direction.

I understand I will post a picture, I just have to take off the bumper which is no big deal I'll have to do to install the sensor. I just thought someone may know because for some reason one side of the exhaust is hotter than the other which must be due to baffling and I wasn't ready to do the job right now but I thought while it was brought up I'd ask. I really do thank you so please don't think I'm being an ass, I try and ask allot of question so I'm informed when I make a decision. So anyway I'll post some pics this weekend.
Thanks Don