OXYGEN SENSORS DO NOT MEASURE AF RATIO'S

[Srxspec]

Jim, here is one of the stock runs from my dyno tests a month or so ago. You will see that the Innovate gauge actually shows leaner than what the mechanical is except right at the initial start of the dyno run?

Red line = Innovate

Blue line = Mechanical

Edit: Added each test graph that had both sets of data in it.

 

[dynotechjim]

Art we only used your sensor plugged int my dyno LM1, same as we did with Alan's.

Alan your sensor sure looks quicker than Art's. You can see the quick lean spot on initial acceleration only lagged behind the mechanical by a few seconds, whereas Art's was way behind. Also my graph is average of two of Art's runs which smoothed out the mini jerks in mechanical fuel flow.

The only difference is Art had lead and you had none, could that be the issue? Also if that crude cardboard/ duct tape adaptor we made from your airbox to the dyno airflowmeter was not perfect, maybe our airflow numbers were low, maybe actual A/F ratio of your innovate O2 sensor and the dyno mechanicals were closer than shown. But surely the lag time on your Bosche sensor and Art's were vastly different.

Or, maybe there's some unburned charge getting out exhaust port during cam timing overlap as ex valves close, sending some unburned fuel and unused O2 past the sensor, maybe fooling it into thinking A/F is leaner?

The mechanical meters measure charge mixture lost during overlap accurately, and the A/F ratio of whatever mixture is trapped in the cylinder to be compressed and burned may be closer to what the mechanical meters say it is.

But either way, Alan's O2 sensor seems close enough to mechanical to be trusted.

When Art comes back to tune his Boondocker with larger capacity pump, it might be good, after tuning to a safe map, to install a brand new O2 sensor with some unleaded 100 octane and see if lead is the problem.

 

[TWIN TURBO]

Jim,
I have used new sensors that have NOT been overheated or lead fouled and on one automotive SBC the mechanical and the O2 sensor were within .5 of ratio. The very next engine was a BBC both pump gas 9:1 engines and the spread was 1.5 of a ratio. I'm still confused over that.

Would love to have "RunninRX1" come to Chicago and straighten me out. He sounds like the articles I've been reading on the internet. I have to read them 3 or 4 times to get them ,alittle, and still wonder sometimes but I think I'm correct when I said "oxygen sensors do not measure af ratio's" but can be a help in tuning the engine.

I wish I could type better but there is what they call the "switch point" where sensor millivolts change very quickly indicating ,I believe if I get it right, stoic point between rich and lean, which moves with different fuels, that you need to find in order to tune from there, and go richer. My fuel supplier told me I should merely look at millivolts and watch for the sudden change but thats like the guys that come to the dyno changing jets leaner to find where power drops and back up a size or 2, SCAREY to me at least for 2 strokes. Four strokes with better fuel maybe.

Thanks for all the help and comments especially RunninRX1. Would love to sit and listen to that stuff for awhile.

PS. Jim. New drive shaft working well Greg

 

[SPEED]

Jim, Boondocker box and pump on the way, I'll drain out tank and bring unleaded race fuel with me when I come back up ,Will see you at shoot-out and firm up a date to return.

 

[dynotechjim]

TwinTurbo Greg (he's an old aerocharger pal of mine who built a legendary 330 HP twin turbo Vmax 750 and has a Superflow 901 in his home garage) I wonder if the two engines that gave you different A/F readings just had different cam timing?

I recall maybe 15 years ago GM engineer Steve Boehm came to dyno test a then new non-US Yamaha 400 four cylinder sportbike with EXUP variable exhaust restrictor (U.S. models did not have EXUP then). GM obtained this new bike from Europe, wanted to see what this then-new technology did to help low end HP. The EXUP valve would choke off exhaust pipes at low-midrange then open at high revs. The choked exhaust increased low-midrange HP very significantly on the dyno compared to locked-open exhaust, preventing loss of intake charge during high overlap at low revs. Had we been using wideband I'm thinking that without EXUP we would have shown 17/1 A/F ratio instead of the 13/1 the mechanical meters registered at low revs. With EXUP operational maybe they would have been closer.

After the two day dyno session Steve brought that bike back to GM in Detroit where it had to be crushed and disposed of. Before he left I suggested he put the bike in my dumpster out back to save them the trouble, but he grinned and declined my generous offer.

How about your own Apex SC on your SF901 dyno? did you compare Lambda vs mechanicals on that sled?

Also I know a guy who has a pair of brand new Aerodyne turbos sized and oriented by Gerhard like the ones on your Vmax4 plus a nearly new Vmax800 sled he was planning to turbo, but has shelved that project.

 

[TWIN TURBO]

Yes I'm sorry I sold that sled and you were supposed to ask him if he wants out of that project so I can replace the old beast, like I got lots of time to do it all over again.

My Apex was close mechanical to O2 like .5 ratio and I'm getting close to putting rings and pistons in it so I can try it again. By the way, my fuel flow problems were the same as you found on Arts Apex SC. NEED MORE FUEL PUMP.

Your also probably right on, as usual, with your suggestion about camshaft from the BBC and SBC. The BBC had a much larger cam than the SBC and it would have to affect the AF Ratio's with raw fuel and air in the exhaust except for the mechanical indicates leaner, should be opposite I think, thats why I'd like RunninRX1 to come over.

Thanks will talk soon, got 2 Ski-doo 1250's I can't make power with, need more of your help.

 

[Srxspec]

Jim, my sensor had 50+ grass drag passes on it between testing time and 9 races. Sometimes the 02 sensor was left on accidentally after a run for a few minutes, etc. There definitely has been no special care to my sensor! It has run 91 octane Amoco Ultimate and a few gallons of 94 octane Torco through it when it got cold, never any leaded fuel. My sensor is mounted at the 2 O'Clock position much the same as Art's and probably 2" before the stock silencer.

 

[Ted Jannetty]

RunninRX1, Thank You for all that information, It is an honor to have Engineers on here willing to share their Knowledge.

I work with Wide band O2 everyday on my Superflow chassis dyno although it is the primary tuning tool, I can't stress enough READ PLUGS to back up what The O2 is telling you.

And I like you understand that every engine has a Personality, and you must find what it wants.

So Rules of Thumb A/F ratios are just a starting point.

As long as everyone remembers that they will be OK.

Jim, I hope you purchased a new sensor recently, the one you had a year ago was shot.

 

[87gtNOS]

I have the Innovate setup (never used leaded fuel) and it is ultra-sensitive to even the slightest throttle input change, almost to the point that it's difficult to read, continuously climbing and falling in sync with the most minute throttle inputs, once the throttle is held in a steady state for 1-2 seconds it stabilizes... I cannot confirm that it is accurate but it seems to instantly recognize changes occurring in throttle position... My question would be: Can I take my sled to an automotive repair shop with an exhaust gas analyzer and verify my readings or would this be a waste of time and money ???

Interesting..I just sold a good customer of mine, and fellow Yamadood a 5 gas analyzer that he uses for emissions tests.....

Obsolutely.
Couple weeks ago I plugged a cell phone charger into a GT's 12V plug.. it didn't work until I fired the sled up.. so that's not a good choice on where to power your sensor.. unless you want to wait a bit after the engine starts in order to see A/F readings.

Mine is wired directly to the fuse box, and I have a switch on the dash to turn it on and off...it uses a 20 sec countdown also.
Here's video of mine quick reacting...however, I could understand that what it is picking up is a couple hundred rpms behind, as my sensor is just infront of the muffler...ignore the goofy filter

NGK WIDEBAND 5 wire O2
http://media.putfile.com/APEX-teaser--2

Good thread guys!!!

 

[Charger]

I was told that the o2 sensor output is supposed to be a analog signal. The Innovate o2 sensor controller chanes this over to a digital signal. It also samples at a rate of 60-100 times per second. I am trying a different one this year that uses a 02 sensor off or a C5 Corvette and samples 1000 times per second with a output to the gauge of 300 times per second.

It isn't the sensor that reacts slow on the Innovate, it is the controller for the sensor.

 

[Charger]

Shouldn't the A/F meter have to be free air calibrated according to elevation?

 

[BigDog05]

My instructions for my guage suggest calibration for large changes in elevation.

My garage is approx. 950ft and I ride at 2200-3000 ft elevation so I never bothered.

Probably would be more accurate to recalibrate though.