Wideband lambda in primary - where ?

[Belgian1979]

Where is the best place to mount a WB lambda sensor in the primary ? The manual says at least 2 feet from the exhaust port. So that doesn't leave not much room. Some might end up close to the collector and my question is if this would be problem with reversion etc ?

[Brian P]

Are you trying to measure lambda of just that one cylinder, or are you trying to get an average? Usually these go in the collector to measure an average.

What does the exhaust system look like after the collector? If there is a proper exhaust pipe for some considerable length downstream as usual, the pulsations in the exhaust system won't matter. If it is open collector, then yes, you ARE going to have problems with air being drawn back in (reversion) and affecting what you are measuring.

[Warp Speed]

10" from header flange will be fine. Just remember to make them the same distance, as location distance of a couple of inches will change the reading slightly.

[Belgian1979]

No full length exhaust.

Placing them at the same distance is not so easy. Not enough room in all locations.

[F-BIRD'88]

Any header/collector/exhaust pipe gasket connection within about 20-30" of the O2 sensor that leaks will effect the reading of the O2 sensor. Even if you cannot hear the leak.

They want the O2 sensor located down the primary pipe to avoid excessive operating temperature as
if the O2 sensor gets just too friggin hot it will soon fail.

Running 8 individual O2 sensors on a street cars exhaust is pretty much impractical.
But using 8 exhaust temp probes instead is more practical and tells you a lot
by exhaust temp variance when combined with 1 or 2 O2 sensors with a wide band.

Excessive hot exhaust port- primary pipe temps are caused by incorrect AFR and incorrect spark timing. (fuel burning in the exhaust pipe).
I any case once the car is tuned you don;t want or need 8 O2 sensors.
A lot of $$$ to maintain 8 sensors that are going to have a short(er) service life if when exposed to higher than design temps.
Ok for short term testing-tuning.

I'd use 8 exhaust temp probes. They can handle the heat and will show you what you need to know.
1 O2 in each header collector is plenty.

[Belgian1979]

If you want to know what your engine is doing, you need at least something to measure. I'm redoing my exhaust so I could take of the headers. This means I have the possibility to weld in the bungs for the O2. Even if I use only one O2 and plug it in one or the other cylinder it will provide more info than what an EGO will tell. An O2 in the collector doesn't tell you any individual differences.

With an EGO you still won't know if your on the rich or the lean side of the curve for that particular cyl.

[user-23911]

The usual way is to read the plugs. You should at least know which cylinder tends to run the leanest.
That's the one that will detonate first.
So long as you know that , you can just put the o2 sensor in the collector, same with the EGT sensor.

If you don't know which cylinder runs the leanest........find out?

[Belgian1979]

Even so Joe, when at WOT it's not really handy to shut down an engine, coast to the side, try to pull a plug from an hot engine and read the plugs.

[dieselgeek]

It won't be super sensitive if you have to compromise on placement for a few holes Yves. Also, a couple corrections to the above advice, I have customers running O2 sensors at the outlet of the exhaust system to atmosphere, they're race cars but it works good under load/WOT. EGTs won't tell you nearly as much as O2s, period.

Just try to make sure no leaks at the exhaust flanges and do the best you can with placement to keep wires from getting melted. Those are the two biggest priorities I can think of. Even if you have O2 sensors at different lengths from the exhaust ports, you will see a world of eye-opening data and be able to get your tune sorted out, and know if your intake is working well or not.

[Belgian1979]

Well Scott, the ITB load was definitely a step in the right direction although I refrained from doing further tuning since I'm going to change to a 3" exhaust. The exhaust will change the tune as well and it's double the work so it will have to wait ...sigh...again.
I have the impression that the current exhaust was too restrictive, which was evident by the plugs color after my muffler blew up.

anyway, mean time I sorted out closed loop idle iac. Had to go that route because the linkage would vary tp from 2.0 to 2.6% at idle after heat soak and such. I'm close to having it under control except it won't spool down to idle rpm as fast as I would like.
The stop screws in each bank's linkage caused some uneven AFR's left to right as well. Very small changes there cause it to go up or down with .5 AFR or more. So this is a painfull exercise especially with the airboxes making them hard to reach.

The LS1 coils made a world of difference in ignition performance and reduced any misfires to almost 0.

As for the O2's. The 14point7's are not that expensive, so a couple of them would probably reveal a trend.

I'm in a world of small changes, but it's improving the overall engine's performance and feel (not that it was bad before)

PS : in the above I meant EGT and not EGO

[F-BIRD'88]

It won't be super sensitive if you have to compromise on placement for a few holes Yves. Also, a couple corrections to the above advice, I have customers running O2 sensors at the outlet of the exhaust system to atmosphere, they're race cars but it works good under load/WOT. EGTs won't tell you nearly as much as O2s, period.

This car spends 99% of its running life at far less than WOT. it idles more than it races.
Big difference between a street car and a "race car".
The When the O2 sensor is located at the end of the pipe it won`t read right at idle idle or any low throttle driving.
A street car can make a very good race car but a race car never makes a good street car.

[dieselgeek]

It won't be super sensitive if you have to compromise on placement for a few holes Yves. Also, a couple corrections to the above advice, I have customers running O2 sensors at the outlet of the exhaust system to atmosphere, they're race cars but it works good under load/WOT. EGTs won't tell you nearly as much as O2s, period.

This car spends 99% of its running life at far less than WOT. it idles more than it races.
Big difference between a street car and a "race car".
The When the O2 sensor is located at the end of the pipe it won`t read right at idle idle or any low throttle driving.
A street car can make a very good race car but a race car never makes a good street car.

Quick question, how many EFI engines have you tuned STREET or RACE, with individual closed loop lambda sensors? so we can establish the experience level.

[F-BIRD'88]

It won't be super sensitive if you have to compromise on placement for a few holes Yves. Also, a couple corrections to the above advice, I have customers running O2 sensors at the outlet of the exhaust system to atmosphere, they're race cars but it works good under load/WOT. EGTs won't tell you nearly as much as O2s, period.

This car spends 99% of its running life at far less than WOT. it idles more than it races.
Big difference between a street car and a "race car".
The When the O2 sensor is located at the end of the pipe it won`t read right at idle idle or any low throttle driving.
A street car can make a very good race car but a race car never makes a good street car.

Quick question, how many EFI engines have you tuned STREET or RACE, with individual closed loop lambda sensors? so we can establish the experience level.

Your question is irrelevant to the fact that the O2 sensor will never read right when located at the end of the exhaust pipe when at idle and or part throttle.
I know this because I tried it.
I do not claim to know all that is knowable. But I know a lot about what DOES NOT WORK.
The wide band AFR meter-gauge manufactures also clearly advise just this in their install instructions.

[dieselgeek]

Your question is irrelevant to the fact that the O2 sensor will never read right when located at the end of the exhaust pipe when at idle and or part throttle.
I know this because I tried it.
I do not claim to know all that is knowable. But I know a lot about what DOES NOT WORK.
The wide band AFR meter-gauge manufactures also clearly advise just this in their install instructions.

No, my question is directly relevant to this post. If you haven't used EFI or his type of system, if you haven't implemented coilpacks, if you haven't used O2 per cylinder, then why do you feel the need to tell him how it needs to be done? Yves is plenty smart. I'm quite sure he's read the manuals already, and now he probably would like help from someone with *experience.* If that's you, keep posting. If not, then he's heard your opinion, how about letting someone whose done this a few times get a word in edgewise? Sorry, that's as polite as I can put it.



Yves, you'll be fine with varied placement per cylinder. Biggest thing is to try to keep wet fuel or condensation out of the sensors, so mount them pointing downward, or at least 90* to the horizon if at all possible.

In the end, you won't need the sensors in the exhaust stream after it's tuned, you'll be applying corrections to the Fuel Trim tables.

Also, don't expect to be able to hit your AFR targets in every cylinder at all times. The idea if to keep them in a range where each cylinder is safe. Then, at WOT, when the cam is in it's RPM powerband, it'll be easier to get each hole to the same AFR. Don't be surprised if it takes up to 12-14% difference between cylinders, we aren't Hendrick Motorsports here.

If you want, I can share some datalogs to show you how we ended up after tuning like this. Usually, individual O2s show a problem with valvetrain in a cylinder (you'll notice one hole needs 25% less fuel than another, indication of airflow problems). But you'll learn a lot. I think this is going to help your tune out bigtime.

[Belgian1979]

Yes, I'm sure it will help the individual balance and overal tune. No idea if it is way out or not in a specific hole. So far I've had pretty equal color on the plugs but it's doubtfull what I'm seeing is actual running conditions. If valve train...I keep my engine on a short leashe as far as intervals for checking the lash. The car itself doesn't run that much, maybe 700 miles in an entire year. However I do tend to push it from time to time.
I'm also not convinced there is more to be had from using 8 O2's at the same time. Like said I think it's finding a trend and then trimming them individually to get them in the ball park and then let the main O2's sort it out. So I could squeeze by with 2 O2's extra. One on the center cyls or the one that runs leanest and then one to check all the others and compare them to the one reference. An extra 2 WB's would be an investment of 250$ which seems well worth it, if not only for the fact that it will give me 2 spares at hand. I don't even need an extra IOX board as I can/could switch the left overs on the board to use them temporarily for the O2 setup.
Might even wire one of those in definitely as I found the LM1 I still have is way slow in warming up and more fluctuations compared the the LC1 I have on the other side.

As for placement : that's a whole other ball game. I'm aware of the condensation issues and position requirements, but it's not as easy as it may seem. I need to place them at least 2 feet from the head which is right where the space is tight. Going further, I end up at the collector, which makes it difficult to get them all at least at a 10° angle from horizontal and still have enough room to weld the bung shut or enough room for the sensor without hitting steering, oil pan etc.
Best place would be at about 5-6" from the head but that's taking a risk for damaging the sensor. That is if it can get damaged on NA and during the time needed for the test.