Topic: EGA results on dyno?

[evanphi]

What sort of exhaust mixture results should an Exhaust Gas Analyzer find on a properly tuned CB750?

I have a motorcycle dyno near me that only charges about 40$ to analyze, including exhaust analysis. I have a 4-1 exhaust.


Should it be the same as the 12:1 or 15:1 ratios for in the engine?

[Muckinfuss]

with a carburetor engine,  you will not see a very linear 'curve' that expresses an exact ratio.  What you will see is the range of mixtures that the carb system is producing since there are four carbs and as much as you try, they will only be 'close'.  Your objective?  Mine has always been to get them 'closer' than close at a minimum of four different RPM's...the transition points of the carb system as well as the power band of the engine design. To err on the rich side is prudent....something like 14.1:1 unless you are running to achieve a specific air fuel ratio.  This can get really tricky with pulling carbs to set needles, etc. but again, it depends on your goals.  If this is a street bike to be ridden like a daily driver....you will want to know what it's doing at idle, and at the two or three likely speeds you will ride at.  If it's to be raced.....well....it's going to cost you more than $40 for a tail pipe analysis.  Things to consider .....  how experienced are these guys or are you one of their 'first'.  What sort of report will they hand you.  Is set up and tear down of their analysis tool (s) on your dime?  And so on.

[evanphi]

Yeah basically I just want a more detailed analysis than a plug chop to see where my current settings are. It is a street bike, and when I go off on a twisty day trip, I usually run around 70-80KM/H in third and fourth gears most of the time.

I was thinking of getting an idle, 1/4, 1/2 and WOT throttle setting readings, as well as one in the peak tourque/HP range.

They are the only bike dyno place in the area. They get tons of business.

[fitzmotor]

14.0 is not optimal for wide open throttle, that would be light to medium cruising, a wide open throttle hard power pull should be 12.0-12.5, maybe 13.0-13.2 if it's lean, the dyno shop should be able to tell you where you need to be.

[Muckinfuss]

Fitz, I completely understand where you are coming from, but it really gets back to what Evan is shooting for and what the shop can actually tell him (for $40) with their equipment since all dyno/gas analyzer setups aren't equal.  I'm assuming (without any information to the contrary at this point) that the equipment being used is based on the cheaper automotive narrow band oxygen sensors which are really only set up to read 14.7:1 and will give an accurate reading not much on either side of that ratio.  The best I've seen for accuracy has been what I recommended to shoot for....which is basically .5 on either side of 14.7.    An honest tech can only tell you that you are rich, or lean, when the readings exceed .5 drift at each test RPM, but not by how much.  It's a basic limitation of narrow band sniffers.

Wide band is way more accurate, able to read 9:1-19:1 accurately, but I don't see that in too many of the M/C shops with dynos. If the shop with the dyno has an analyzer from someone like Innovate Motorsports, then they can do a bang up job of setting up the ideal power A/F of 12.8:1 up to 13.2:1. BUT: the gotcha is that there needs to be a bung in the pipes for one sensor...at least and more accurately all 4 if they aren't 4 into 1...... or they need a wide band sniffer!  To be really on target... up to 4 sniffers...one for each pipe..eh? There is some data tho that sniffer reads are consistently read leaner than the bung reads due to in pipe exhaust gas changes that are the result of fresh atmosphere entering the pipe below certain RPM and contaminating the sensor.  In non cat autos without a bung and that are on a chassis dyno, the sniffer is usually put on a stick and shoved way up the pipe as close to the collector as they can get it...and still the readings are suspect. 

The Ideal for fuel efficiency will be more like 15:1 at part throttle.  Some water cooled EFI bikes have been tuned to 16:1 at part throttle to get max mpg with a downside of lazy response and some hiccuping.....and un-rideable in altitude!

[brewsky]

Here are my results from both on-board wideband meter and one dyno pull summarized:

These readings gave the best feel under actual riding conditions as well as confirmation the mixture was not way off.

You want to be richest on WOT and at max rpm.

I found that the mixture leans out at any given throttle opening as the rpm increases (at least on PD and PW carbs)

My thinking on the ratios:

Idle-a little rich to help keep the engine cooler when not moving and help smooth the throttle transition.

1/8 - 1/4- leaner, since this is the majority of the time spent cruising at constant speed under light load.

1/2-WOT richest for full power under max load.

These readings result in 41MPG in town and short trip riding, and around 50MPG on a long trip.

After installing the meter and marking the throttle positions, I was surprised at how little throttle is needed to cruise along at highway speeds.

[evanphi]

Thanks guys. This gives me a starting point for when I go.

I just want to see where my bike is currently. Everything "feels" right. No popping, no hesitations off idle or other transition zones, good response at WOT. I can pull to 150KM/H in 5th no problem on all stock components.

[fitzmotor]

That looks about right, WOT is richer, which is where it will make the best safe power, and cruise is close to stoich.

[scottly]

WFO should be about 12.8-13, although a leaner mix, such as 14 *may* produce more power, but is less safe. Evan, if the dyno is of the inertial type, you may not get good readings at part throttle operation, although they may still provide useful input if you can relate throttle opening to the graph. Put a strip of masking tape on the throttle body on the handle bar, marked at 1/4, 1/2, 3/4, and full throttle, with a taped-on pointer on the throttle tube. In the heat of a dyno run, it's hard to keep track of, but it's better than nothing.

[PeWe]

 It would be better to have an A/F gauge mounted on the bike. They cost some if readings should be logged with RPM reference and analysed afterwards.  http://www.daytona-sensors.com/wego3.html

Sensor to be mounted in an insert that is welded in the exhaust system which is easier with a 4-1.

Other variant with LED gauge only that can be difficult to read in higher speed when the focus must be on the road.
https://www.rbracing-rsr.com/rsrgauge.htm
LED's might be a good way to have constant control of the fuel mixture and be alarmed when its too lean.

I have Dyno run measured at WOT. It's not the same when driving the bike in the city and common roads, often low throttle lifts and various loads (gears)
I have richened up the carbs after this was measured, pic below.  Pilot jets one step up, needles richer, main jet 1 step up as well. Bike runs much better, now smooth starts without hesitations, jerks or pinging

The richer ratio in the beginning is the carbs acc pump at WOT, not jetting.

I have not checked dyno after rejetting. It's easier to direct see the AF ratio when I hear pinging so I can verify too lean or ignition too advanced. I had pinging with pilots and needles too lean. The gauge from rbracing might ba something mounted on the bar or beside the other meters.

[Deltarider]

No one measures in CO anymore?

[brewsky]

No one measures in CO anymore?

The government does!