Air Fuel Ratio Meter

[mayor]

NOW I have a question for you multi bike WEGO guys.

How many of you use the tail pipe sniffer? And for those of you who do, do you think the ability to tune within .1 is affected by the unit being in place? Does it affect the exhausting by .1?

If you don't use the TP sniffer what is different about taking the WEGO on and off vs the other instruments available?

If you do hook up the Tach, and MAP feature, is it even more complicated the a regular non data collecting unit?

well I haven't WEGO'd anything yet.    My WEGO is still sitting on the kitchen table.  I'm currently building a tail pipe sniffer set up, but I'm also going to be running O2 bungs on the head pipes of my TC's (both carb bikes). I hope to be able to comment on the comparison between headpipe and sniffer some time after the weather breaks.   If I followed (understood) the technical data published by the manufacturer correctly, exhaust design will affect the accuracy of a tail pipe measurement especially during certain throttle conditions (decel). 

[ederdelyi]

FWIW, I never had any good results with a tailpipe sniffer like Innovate or DTT shows. Most all HD's with an aftermarket cam with some overlap when combined with an aftermarket exhaust pull too much air in and it skews the readings. The sensor in the bungs placed close to the port will give the best results, IMHO and IME. Try it for yourself, you may have better luck than I did. I just got tired of F'n with the thing and getting questionable results.

[crazycalvin]

Able2222,

Check the plan on this website:  http://www.dbbp.com/    >click to enter>tech tips>Air/Fuel gauge.

A bud used this plan to built a dual gauge for me to monitor both cylinders real time, simultaneously.  I'll try to attach a pic.  The parts cost less than $50 plus the 02 sensors and connectors.  I bought the parts from a local industrial electronics distributor.  I adjust each cylinder independently, my bike has an individual runner intake manifold.  With a normal "Y" intake manifold, you could just as easily toggle between the front and rear 02 sensors.  It's kinda neat to see what's happening at any moment.  The smallest twist of the throttle shows up instantly, start up an incline and the a/f ratio changes.  The only way to get a steady a/f reading to adjust from is on level ground holding steady throttle.  I get close with jets and plug chops, then I fine tune the a/f ratio with the a/f adjustment screws at cruising speed.  The closer I match the two cylinders, the smoother and stronger the bike runs.  I can adjust real time for power or economy.  With a carb it doesn't make much sense to adjust for an rpm you don't use very much, it's not like closed loop efi.  Another point to consider is you're really only concerned with being in the a/f sweet spot, other than you don't want to be too lean for a long sustained run.

I was looking at that design at work on Thursday night.  What kind of O2 sensors did you use?  Thanks, Calvin.

[Sonny S.]

As for the sniffer..... what are the dyno tuner's using that is so different ?

[ederdelyi]

Dyno sniffer is most commonly a long tube that gets shoved up the pipe as close to the port as they can get it to reduce reversion and interaction with the other cylinder. Damn near impossible to do an individual cylinder map on a motor with an odd fire setup like the HD unless you do that.

PM Bob ... Oh, wait ... he's back :>)

I made a similar setup for 4 and 5 gas meters for the same reason.

[Jeffd]

http://www.knfilters.com/airfuelmonitors.htm

[Jeffd]

http://store.summitracing.com/egnsearch.asp?searchinresults=false&Ntk=KeywordSearch&DDS=1&Ntt=85-2441

seems cheap enough

[Sonny S.]

Dyno sniffer is most commonly a long tube that gets shoved up the pipe as close to the port as they can get it to reduce reversion and interaction with the other cylinder. Damn near impossible to do an individual cylinder map on a motor with an odd fire setup like the HD unless you do that.

That's what mine is. I made a long one to use on dresser's and a shorter one for all others.

[Sonny S.]

Jeff,

IMHO the K&N is not as good as the RSR. Not enough indication between 12-14:1, and that is the area that we are trying to tune.

[ederdelyi]

>>That's what mine is. I made a long one to use on dresser's and a shorter one for all others. <<

I believe that mayor was referring to the "clip on" sniffer (as was I) that just samples the exhaust near the end of the pipe. I never had any luck trying to get one of those to give meaningful readings on a HD exhaust. I got  it to work on cars and trucks. Nice idea if all you want is the average reading. I went to bungs on individual cyls on the cars and trucks for the "serious" stuff. Make each cylinder as even as possible ... neat stuff that one could not easily do prior to the advent of electronic engine management systems.

EDIT: Clip on as in "automotive sniffer" as shown on the Wego III web page. FWIW, I still prefer the bungs if at all possible, especially if one is road tuning and not using a dyno.

[Evo160K]

Crazycalvin,
One is a Harley the other is an Airtex, both are two-wire, both work fine.  I verified the gauge and system using cheap sensors from the junk yard, about $6 each, before I invested in new sensors and permanent wiring.  Believe me the cheap ones worked well.

If I were doing it again and didn't want to build a meter, I would go with the Edlebrock meter referenced above.  It's very reasonable and has everything you need.  Like I said, if you want to monitor both cylinders, you can buy a second 02 sensor and toggle switch between them using one meter and two 02 sensors.

Frankly, I'm not so sure accuracy with respect to a test gas is that critical.  As long as the sensor gives repeatable readings, you adjust for the best running engine for that rpm.  You know from experience when your engine sounds and feels happy.  For a carbed bike I wouldn't invest a lot of money.

[fuzznut5197]

I think I got the logger so I can post runs here and ask experienced people why the h*ll my engine is doing this...

[Evo160K]

Well fuzznut, as I've never seen one of these charts in my life, I'll take a swing at it, and you should know I didn't stay at a Holiday Inn Express last night.  It looks to me like you're accelerating slowly through a gear, maybe first, you shift slowly to second after which you're moving along smoothly for 3-1/2 seconds when you quickly open your throttle (about 717.25 seconds at 3000 rpm), your accelerator pumps shoots raw fuel causing the a/f ratio to momentarily go rich at 717.4 after which your engine rpm quickly jumps to 6200-6300 rpm and since fuel is heavier than air and slower to move, the lean air rushes ahead of the fuel into the engine causing the a/f reading to go very lean, 19.5:1.  Then you throttle back and your a/f returns to 11:1.  I hope that was the question.

Now perhaps we can hear from someone who really knows.

[ederdelyi]

>>I think I got the logger so I can post runs here and ask experienced people why the h*ll my engine is doing this... <<

Sniffer or bungs? It sure looks like you are pulling air into the system from the plot.
If it's a sniffer it may not be long enough. If bungs they may be too far from the port(s). Open exhaust and cams with lots of overlap can be problematic.

EDIT: Also, consider this:

"Other things to keep in mind to ensure proper sensor function and longevity are exhaust back pressure, rich mixtures, and under/over heating.

A high exhaust backpressure forces more exhaust into the sensors pump cell which can cause an air fuel ratio meter to read richer than what the engines really running. Turbo engines run a relatively high amount of backpressure in the exhaust manifold before the turbine, making them a poor place to locate the sensor. 

Missfires due to a malfunctioning or underpowered ignition or an extremely rich mixture can cause false lean readings because unburned liquid fuel in droplets block the small hole leading to the sensors pump cell.

A wideband sensor should not be placed in the exhaust stream and left unheated. The hole to the pump cell can quickly become clogged and contaminated by exhaust byproducts, especially during a start cycle from a cold engine. The sensor can also be damaged by exposing it to temperatures above 700 degrees C, like those typically before the turbine in turbo engines. You never want to place a sensor there anyway due to the aforementioned issues with sensor accuracy and backpressure. Lastly you don't want to place the sensor so far away from the engine that its 10 watt internal heater cannot keep the sensor hot enough."

Excerpt from a AFR meter shootout --- I'd have to go back and get the URL and I'm too damn lazy!

[ederdelyi]

The trend is there for both mild and hard acceleration, more pronounced on the hard run. It's likely either reversion or an over rich condition that is giving a false lean reading. O2 sensors can be funny little beasts, they don't always do what you would expect. A fouled sensor can produce a reading that is off by .3 - .5 AFR or more and some meters will not be able to either tell you the sensor has a problem or be able to calibrate for an aging sensor. AFR meters are not all created equal.

First rule of data acquisition and test ... Question what you see, it may be bogus.

[Sonny S.]

Fuzznut,

Any chance you hit the rev limiter at that point ?
The only time I've seen a chart where there is a lean stall like that was when the ignition was killed or a bad sensor as Ed had commented on.

I deleted my earlier post because at low steady rpm's everything looks fine.

[mayor]

>>That's what mine is. I made a long one to use on dresser's and a shorter one for all others. <<

I believe that mayor was referring to the "clip on" sniffer (as was I) that just samples the exhaust near the end of the pipe.

I guess I should have been more specific.  I'm making one with a long sampling tube as well.  I'm making one similar to what Sonny is referring too (...very similar, since I'm using his pattern to make mine  ).  I wouldn't even try one at the end of a tail pipe, I just think there would be too much interferrence with outside air.

edited to show pic of components being used for the sniffer pipe I'm building:


more to follow once I finish the project..

[ederdelyi]

Look at the short accel/RPM increase in the 712 - 714 sec time range ... see the trend? Not as pronounced, and obviously less throttle was used.

[ederdelyi]

mayor,
Actually the "confusion" was likely more on my side ... when most folks say "clip on sniffer" I automatically think of the "easy" one that most will go for. Mia Culpa :>)

[Sonny S.]

Look at the short accel/RPM increase in the 712 - 714 sec time range ... see the trend? Not as pronounced, and obviously less throttle was used.

I believe that is a shift point where he let off the throttle.

[ederdelyi]

Maybe, kinda looks like a single gear run to me ... been wrong before, won't be the first or last time :>)

[Sonny S.]

Maybe he was sitting still and revving the throttle ? 

Fuzznut, will you get in here and tell us what's going on 

[Sonny S.]

similar set up as Mayor's .... interchangable probes.
Although I see he forgot the drywall screws.... 

[ederdelyi]

>>Maybe he was sitting still and revving the throttle ? <<

Dunno, about 2.5 sec from ~2000 RPM to ~6000 RPM and roughly the same for decel ...


The main thing I didn't like about the long sniffers was response time and having the dang thing hanging out of the pipe on the road. I'll go the bung route if I have the choice, but sometimes ya just gotta do what ya gotta do.

[mayor]

The main thing I didn't like about the long sniffers was response time and having the dang thing hanging out of the pipe on the road. I'll go the bung route if I have the choice, but sometimes ya just gotta do what ya gotta do.

I agree, both my TC's will have bungs on the head pipes.  I'm building the sniffer pipe for when I'm messing with bikes without the bungs. I've got a sporty with chrome pipe but without heat shields, so I didn't want to weld on those head pipes.