O2 sensors with dual exhaust?

[powerband]

O2 sensors with dual exhaust?

'talkin with a similar Offy Tri-Power forum member, his O2 sensor setup on his single out header was discussed and I was wondering about true dual exhaust setup ?

Switchable sensors?.. dual gauages?




Have Fun

 

[StrangeRanger]

If you're using an H-pipe, put it there

 

[MustangSix]

you might need a heated one if you put it that far downstream

 

[falcon fanatic]

Getting an average reading from three cylinders should be accurate enough for carb tuning purposes, specially if you do the occasional plug reading to be sure you don't have one cylinder that's gone wonky. Moving the O2 sensor too far down the pipe will likely give you less accurate readings due to inadequate heating.

 

[Anonymous]

For tuning purposes (getting cylinder-to-cylinder mixture relatively even), I asked around about the possibility of connecting one wideband air-fuel meter to four or six (we don't care about eight) O2 sensors, one in each header pipe, via a range-switch so that you could switch from cylinder to cylinder to compare readings on one guage. A tech man at Innovate tells me that it can't be done, that an uncontrolled sensor would very quickly be damaged by the exhaust. So the only way I'll be able to do such tests, without laying out a pile of cash for six complete A/F guage systems, is with pipe plugs in five of the six bungs in the headers, and move a single O2 sensor from one to another, and firing up the engine for each reading of the single gauge.

 

[falcon fanatic]

Totally pointless unless you have port FI and an ECU that can control individual injectors, methinks.

 

[Anonymous]

Ah, not pointless at all for tuning purposes, . . . mine, anyway . . . .

One of my enormous supply of half-completed projects is an older Clifford single 2/4bbl manifold that I modified for a 300 six that currently (YEARS after I started this) is STILL using the stock manifold and 1bbl. What I did to the Clifford was build a shaped "splitter" that is bolted to the floor of the plenum, effectively isolating the front three and rear three cylinders (another half-done project is a set of 3-2-1 headers that isolate front and rear cylinders). The Big Idea of the splitter was to have any one cylinder only have to draw vacuum on half of the volume of that big manifold, increasing velocities and sharpening the vacuum signal to the venturis. Should I live so long, I have three carbs and a Holley ProJection unit to try. Now, I shaped my splitter by mere intuition, by eye, guessing at what the airflow from the carb would like as it makes a 90-degree turn to either side of the manifold (half the carb feeding half the manifold. And of course the charge has to make further turns into the runners for each cylinder.

So, I ask you, Fanatic, what is the chance that mere intuition has led to making a splitter that will provide all cylinders with a fairly similar air-fuel ratio, all over the useful rpm range of the engine? A surpassingly slim chance, is my guess!! I'm expecting that I'll have to play with carb spacers, re-shaping the splitter, screwing little dams and diverters to the floor of the plenum, in order to see all cylinders get reasonably even readings on the meter.

And a great waste of time, to be sure. So, okay, you're right; on that basis, it is pointless. But the components have cost me nothing, and it ought to be fun to fool with.

 

[falcon fanatic]

Sounds like fun. I won't even begin to speculate on the physics of the pulses working in that manifold, but I suppose six 02 sensors would indeed give you useful data. I wonder how many sensors you could modify a megasquirt ECU to datalog...

 

[powerband]

...


Interesting question about "uncontrolled" (unterminated ?) sensor :

For tuning purposes ..., via a range-switch so that you could switch from cylinder to cylinder to compare readings on one guage. A tech man at Innovate tells me that it can't be done, that an uncontrolled sensor would very quickly be damaged by the exhaust. ...

If a the Voltage swing on an unterminated - "uncontrolled" sensor could damage it, I would think that terminating an "open" - uncontrolled sensor with ground or through a resistor would "protect" an "uncontrolled" sensor.

Thanks for the discussion on the dual exhaust O2 sensor question. Some useful info culled from it 8) . Dual bungs and sensors with terminating load switch will probably be next project. What's optimum location for steel headers?.



Have Fun

 

[Anonymous]

Powerband, I emailed the tech rep at Innovate with your question about grounding the unconnected sensors, or running each through a resistor, and he says there is no way to have the sensor not be damaged if it is not being controlled by the complete wide-band meter system. Dang!!

If anybody wants to ask about this, the tech guy's name is Felipe Saez

felipe@innovatemotorsports.com

I have also asked Auto Meter about my range-switch notion, and they also say it's no-go with the components they have now.

 

[kevinl1058]

I'm running a F.A.S.T. Technologies dual setup. I can read the front and back three cylinders or average them together for tuning purposes. Allow for more precise tuning with my Tri-Power set-up. Worth the money.

 

[powerband]

I'm running a F.A.S.T. Technologies dual setup. I can read the front and back three cylinders or average them together for tuning purposes. Allow for more precise tuning with my Tri-Power set-up. Worth the money.

Thanks Kevin,

The dual sensor setup looks good for the Hooker headers on my 250 although I did use an expletive when the pricing page opened...

Have Fun

 

[kevinl1058]

The F.A.S.T. unit is on the higher price range but it does give you a additional options. I like the fact that I can record up to 20 min pull over and make some adjustments.