AFR Info

[posplayr]

Edit 5/20/2012
Bike is GS1100ED 1166, ported head, K&N pods, 36mm BS36, GSXR 4:2:1 Yoshi, 0.340 Webcams, Accel coils, coil mod

The final jet setting I arrived at are as follows. You can compare this with the various descriptions

Exhaust____4:1__________4:2:1
Type
Main jet_____140__________ 135
DJ needle__3 or higher_______ 2
Pilot jet_____47.5___________45
Pilot Air____stock?________stock?

A more normal jetting would probably be a 140 main (v.s. my 135) with the needle jet at 3 or higher (v.s .mine at 2). I'm attributing the leaner main and fatter needle setting to my 4:2:1 v.s. the more traditional 4:1. The 4:2:1 flows better at mid range but not quite the flow at the top end as compared to the 4:1.

http://www.thegsresources.com/_forum/showpost.php?p=1303763&postcount=12

As A guide, this is what I saw near my optimum tune point.

• 1 notch rise in needle ( e.g. 4 to 3 from bot) at 1/2 throttle will lower AFR 1 full point (e.g. 14.0 to 13.0).
• A drop in Main by 2 sizes (e.g. 140 to 135) at 1/2 throttle will raise AFR 1 full point.(e.g. 13.5 to 14.5)
• A drop in Main by 2 sizes (e.g. 140 to 135) at WOT ------- will raise AFR 1/2 a point.(e.g. 11.0 to 11.5)

SUMMARY: @ 1/2 Throttle: 1 needle notch = 2 jet sizes

Optimum tune (for my setup) seems to be about; (In other words I'm not sure it will get any better than what it is ):

WOT is AFR 11.5-12.5
1/2 throttle (high RPM) is AFR 13.5-14.5
1/8-1/4 throttle AFR is 11.5-12.5 (75 mph at 4500 RPM)
Idle AFR 13.5

http://www.iwt.com.au/mikunicarb.htm

I have been looking for references to guidelines for AFR.

How does this sound to everybody? tejasmud (Eric) has been helping through interpreting the AFR's but I was looking for more descriptions.

http://www.portablepct.com/fastlarry/banditfaq.htm

• 14.5-14.7 air fuel is maximum fuel mileage.
• 13.2 air fuel is maximum steady state rpm power.
• 12.7-12.9 is maximum acceleration power.

Air/Fuel Ratios
Carburetors can only be tuned for maximum power or mileage at a given RPM. 14.5-14.7 air fuel is maximum fuel mileage. 13.2 air fuel (richer than 14.7) is maximum steady state rpm power. 12.7-12.9 is maximum acceleration power. If you set the carbs for maximum power in the mid range and top end it is not going to get fuel mileage. Lowering the needle and adjusting the idle circuit will help. If you set the idle circuit lean, and lower the needles to 14.7 air fuel ratio then adjust your top end to 13.2, your bike while riding in the mid range/lower RPM's will get mileage. on full acceleration at high rpm you bike will have power. But if you set the carbs this way you will not have maximum mid range power. Also, one full clip movement may be more than what is needed to go from lean to perfect 14.7 air fuel ratio.

Mikuni suggests an increase of one full jet size for every 25 degree drop in temperature

Temperature/Elevation Effect on Air/Fuel Ratio
Changes in ambient temperature and altitude affect richness of your air/fuel ratio. This is because air gets more dense as it gets colder. Air is also denser the closer you get to sea level. Therefore; more fuel is needed to maintain proper air/fuel ratio in cold weather or near sea level than is needed in hot weather or at high altitude. If you set your carburetors for perfect air/fuel ratio in San Francisco on a 50 degree day, your bike will be chokingly rich in Denver on a 90 degree day. Obviously, you will be best served by jetting your engine to run best at the average temperature and elevation you will normally ride. Mikuni suggests an increase of one full jet size for every 25 degree drop in temperature.

My setup (more or less), I see the pic is missing SPEED, and I only used the slow RPM on the LMA-3

Additional Jetting info can be found here.

http://www.motorcyclecarbs.com/Motorcycle_Carburetor_Jetting__W7C240.cfm

[posplayr]

http://webcache.googleusercontent.co...&ct=clnk&gl=us

This is not for a CV carb but AFR should be teh same.

SECTION THREE – ADJUSTING FOR MAXIMUM PERFORMANCE
In Section Two you did three tests. Tests One and Two checked to make sure your machine did not run too lean. Test Three checked to make sure your machine didn't run too rich. Typically the Japanese motorcycles produced in recent years can function with minor modifications without any noticeable flaws at air/fuel ratios ranging from 14:1 to 11:1. Adjustments in carburettor jetting that fall at either end of this range are referred to as “fringe jetting”. Fringe jetting is responsible for the common myth that performance jetting must constantly be altered for normal temperature or differences in altitude. If a machine is operating in the rich fringe jetting range, for example at a air/fuel ratio about 11:1 at sea level at 70 degrees, it is likely that a difference of 2500 feet elevation and a +20 degrees could change the air/fuel ratio to perhaps 10.5:1 thus causing a slight carburetion problem during hard acceleration. The same thing can happen on the other end of the scale although it is not as common.
You can use the following procedure to make sure your bike is not jetted in the rich fringe area.

Motorcycle Carburetor Theory 101

http://home.everestkc.net/malsin/Mot...theory_101.htm

[tejasmud]

Here you go Jim.

I would say that the data you quoted holds weight, and is correct.

The Mikuni VM Tuning Manual is what I have always used as a reference in regards to AFR.

http://www.mikuni.com/pdf/vmmanual.pdf

Then here is a Print Screen shot of what Mikuni says.



I would have to look in the Sudco tuning book as well, Basscliff has a copy on his site, but pretty sure it will echo most of what can be found.

Air cooled/oil cooled machines like a little more fuel to keep them cool. Liquid cooled machines can get leaner.


Although I'm more of a maximum power type.

Fuel mileage is less, but I also run the final drive ratio around 3.6, which is even less.

I have found that this occurs in the 12:1 to 13:1 range as well from just feel. Too rich, power drops conciderably. When measuring in the summer, like now it is 100°F + here, I tend to jet it closer to 12:1 or 12.5:1 knowingly that when the temperature drops in the winter The AFR will lean out a tad. But this is not a bad thing, and no need to jet for different temps as they change on a street machine. The cooler outside ambient temp helps in cooling. In the cruise throttle positions the AFR can run a little leaner as the loads are not so dependent on the fuel for cooling.

My guess is with the $ you have in your engine, you are not worried about fuel mileage though.


Eric

[posplayr]

Here you go Jim.

I would say that the data you quoted holds weight, and is correct.

The Mikuni VM Tuning Manual is what I have always used as a reference in regards to AFR.

http://www.mikuni.com/pdf/vmmanual.pdf

Then here is a Print Screen shot of what Mikuni says.



Eric

Thanks Eric,
That is what I wanted. I found the manual as you did here.

http://www.mikuni.com/pdf/vmmanual.pdf

I has a Sudo catlog, I'll go look in it as well.

I'm not real concerned about gas mileage ,but at the same time don't want to be washing down the cylinders.
I did notice my temp came up[ maybe 10 degrees yesterday (but I was running pretty hard at times). So I'm probably closer to the lean side of where I want to be. Not going to try and draw too many more conclusions without seening some more steady state data.

Nice to know the AFR is not supposed to be constant; seems like how mine in acting.

Jim

[posplayr]

Found another good link

http://www.daytona-sensors.com/tech_tuning.html

Air/Fuel Ratio (AFR)

Higher AFR values correspond to a leaner (less fuel) condition. The practical operating range for most engines using gasoline fuel is from approximately 11.5 to 14.7 AFR. Combustion of a stoichiometric mixture (exactly enough air to burn all the fuel) results in 14.7 AFR indication. Automotive engines with catalytic converters operate near 14.7 AFR during cruise and idle. Air-cooled motorcycle and automotive race engines require a richer mixture to limit cylinder head temperature and prevent detonation. The table below lists recommended AFR values for engines without emission controls.

Operating Mode
Recommended AFR
Cold Start (first 30 sec)
11.5-12.5
Idle
12.8-13.5
Part Throttle Cruise
13.0-14.0
Wide Open Throttle
12.5-12.8 (values down to 11.5 may be used to reduce detonation)

Where do these values come from and what is the effect of AFR on engine torque? The chart below provides some answers (ref: Automotive Handbook 2nd edition by Bosch GmbH, pp. 439). In the absence of other limiting factors, maximum engine torque occurs at about 13.5 AFR. Under wide open throttle (WOT) conditions, a richer mixture (12.5 to 12.8 AFR) is generally required to reduce cylinder head temperatures and avoid detonation. While the torque curve appears relatively flat from 12 to 14.7 AFR, the effect on cylinder head temperature is more pronounced. Please remember that the chart is based on lab experiments under carefully controlled conditions and with gasoline octane high enough to avoid limiting effects from detonation.
Engines with race camshafts exhibit large cyclical variations at idle - necessitating a relatively rich idle to prevent stalling.

[82Shafty]

http://www.jegs.com/i/Comp-Cams/249/170634/10002/-1?parentProductId=1222659

This will work just find for the street.

There's a real science to tuning for max power, but it's way more envolved than anyone would ever want to get for 2-3 hp on the street.

EGT's should be measured
Timing curves manipulated-ours are fixed
Peak torque timing should be pulled a few degrees than added back in going up towards peak hp..up to 4 degrees usually--when you can via a piggyback on a car or a tune through the comp--can't do it on our bikes

AFR up and down also works with timing...i.e. if you pull a few degrees in timing, it has the same affect as bumping the fuel up .5-1 on the AF ratio.

Then you should always follow up with dissecting the arc plugs; plug chops, but here's how to read them yourself.

http://www.4secondsflat.com/Spark_plug_reading.html

The mofo is that peak power today, won't equal peak power tomorrow.

[posplayr]

http://www.jegs.com/i/Comp-Cams/249/...ductId=1222659

This will work just find for the street.

There's a real science to tuning for max power, but it's way more envolved than anyone would ever want to get for 2-3 hp on the street.

EGT's should be measured
Timing curves manipulated-ours are fixed
Peak torque timing should be pulled a few degrees than added back in going up towards peak hp..up to 4 degrees usually--when you can via a piggyback on a car or a tune through the comp--can't do it on our bikes

AFR up and down also works with timing...i.e. if you pull a few degrees in timing, it has the same affect as bumping the fuel up .5-1 on the AF ratio.

Then you should always follow up with dissecting the arc plugs; plug chops, but here's how to read them yourself.

http://www.4secondsflat.com/Spark_plug_reading.html

The mofo is that peak power today, won't equal peak power tomorrow.

Thanks, I'm getting some real world experience with AFR. Here is the start of a thread but I still need to post up pics of the setup. I'm using an Innovate Lm2 and LMA3 configured for

O2 (tail pipe sniffer ut to the last Y in 4:2:1,
RPM (low side of coil working very well),
CHT (on the pipe),
MAP (intake vaucum),
G's (built into the LMA-3)
also have a start of wheel speed sensor but needs some better conditioning.

See example from Sunday, from rolling stop pulled to redline in 1,2,3 and slowed down in 4th going up 6% grade. The color legend is in the upper right

Yes there are alot of variable, fortunately I'm just looking to set jets and needle positions not win an NHRA record . It is very interesting. Right now trying to establish a base so I can more to Slingshot carbs. I have looked over so many plug reading charts I really can make much sense of it enought to trust it and the AFR seems to be a much better indication.

http://www.thegsresources.com/_forum/showthread.php?t=161402&highlight=innovate

[posplayr]

Timing curves manipulated-ours are fixed
Peak torque timing should be pulled a few degrees than added back in going up towards peak hp..up to 4 degrees usually--when you can via a piggyback on a car or a tune through the comp--can't do it on our bikes

AFR up and down also works with timing...i.e. if you pull a few degrees in timing, it has the same affect as bumping the fuel up .5-1 on the AF ratio.

.

Sound like you are refering to this section? (see stuff highlited in red) We talking about racing now or mods for a street bike?

Ignition Timing

We often receive inquiries about optimizing ignition timing during dyno tuning. Very sensitive and precise dyno tests are required to determine MBT timing. The chart below shows why (ref: The Internal Combustion Engine in Theory and Practice by C. F. Taylor, pp. 443). The engine torque curve is very flat near the MBT timing value. A useful rule of thumb is that advancing or retarding the timing 5 degrees from the MBT value reduces torque about 1%. You cannot reliably measure a 1% torque change on a chassis dyno. We have witnessed many dyno test sessions where attempts to optimize ignition timing generated strange results that were probably caused by measurement error.

In most engines (assuming compression ratio and other factors, such as air fuel/ratio, are within reasonable limits), the MBT timing value is a few degrees below the detonation limit. If you select a wide open throttle (WOT) timing advance curve that is retarded about 3 degrees from the point where detonation is detected, you should be close to MBT ignition timing.
The table below lists recommended maximum ignition advance at WOT for various V-twin engine applications. Twin Tec ignition and fuel injection controllers allow setup of ignition advance tables that meet these recommendations.

Engine Application
Maximum Advance at WOT
Stock Compression (less than 10:1 using premium gasoline)
35 deg BTDC at 2500-3000 RPM
High Compression (10.5:1)
30 deg BTDC at 5000 RPM
High Displacement (>120 CID or bore approaching 4 inch)
28 deg BTDC at 5000 RPM

Twin Tec Models 1005-1007 allow a maximum advance adjustment from 30-35 degrees using the switch settings. For use with high displacement Evo style V-twin engines, we have provided a custom advance table file that can be uploaded to the Twin Tec ignition with PC Link Evo software. When using this table, you can set the timing using a dial back timing light and the TDC timing mark.

[tejasmud]

Yes there are alot of variable, fortunately I'm just looking to set jets and needle positions not win an NHRA record .

Come on now........ lol

Hey, that chart looks really good. The lean spikes are only happening where you are shifting, and the MAP is dropping at the shift points as well, which corresponds to the AFR & RPM. The only thing I would say is it looks like you could turn the LMA3 180° and it would pick up G positively, but you know what it is doing so maybe not much of a concern.

If that chart was with the #140 mains, and your pics you sent of the spark plugs correspond, then looks like it is in good shape. To tell the truth not much difference between the plugs from the 145's.

Looks like it is time for the Slingshots.

E

[posplayr]

Come on now........ lol

Hey, that chart looks really good. The lean spikes are only happening where you are shifting, and the MAP is dropping at the shift points as well, which corresponds to the AFR & RPM. The only thing I would say is it looks like you could turn the LMA3 180° and it would pick up G positively, but you know what it is doing so maybe not much of a concern.

If that chart was with the #140 mains, and your pics you sent of the spark plugs correspond, then looks like it is in good shape. To tell the truth not much difference between the plugs from the 145's.

Looks like it is time for the Slingshots.

E

Well I'm pretty surprised that I got such a big change in AFR (8-10 up to 11-14) with little difference in what the plugs looked like. Kinda tells you you gotta be a real expert reading them or plug chopping is going to be pretty useless.

Also because the AFR at idle went from 8 up to 11.5 after pod cleaning and brushing off the plugs goes to show how much of an effect that DIRTY PODS can have. Mains should have little to do with idle especially only going from 145 to 140.

I'm guessing I must have perhaps over oiled the filters before the last rally and then got them plugged up with that NV desert dust. It was about 2K miles in a couple of weeks.

I doubt it was the 6" I took off the end of the sniffer or the jet change especially at idle.

I still plan on doing some steady state tests on the big hill pull later in the week if I can get out there.

As far as the LMA-3, I'm more worried about orientation on the tank (running wires) than the polarity of the signal. It is easy to "invert" the plot under "configure" signal.

Eric, Thanks for the help; I think I'm closing in on have a setup I can trust the measurements of.

One other thing that happened, I pulled onto a road doing a strong roll-on and the bike started to fumble, AFR was 16-18; I switched to reserve and it quickly dropped back to normal nice confirmation of AFR and the setup.

I would still like the wheel speed setup as it helps pin down what you are doing on the bike. The only other issue with the LM-2 is that it occasionally locks up so a method to cycle power is required. It is good practice to close a file rather than collect data for 1/2 hour and then have it lock up and loose it just at the end.

[tejasmud]

Eric, Thanks for the help; I think I'm closing in on have a setup I can trust the measurements of.

Not a problem.

Good to see it working for you. I remember you mentioning the LM2 locking up. I was looking at the Innovate site earlier, and it appears their forum is down for remodeling. It would be a good question to ask over there or at least read up to see if others have had the same issue on the LM2.

With the stopping up air filters and change in AFR is one reason why I had mentioned in the other thread a while back about considering a LC1 and DB stand alone gauge for AFR up on the dash. You don't have much room up there, but a thought. Seeing the AFR would probably show when the filters need to cleaned. I have one on another bike, and it is nice to see what is going on. What I like about it is it really puts a definition to why a bike runs great when the weather changes. If jetted slightly rich when it is warm out, you can see the AFR drop when it gets cooler in turn the bike pulls harder due to the better AFR mix..

I'm sort of a miss on the plugs. They should have looked darker with the difference in AFR. Not sure why they didn't. Also the switching to reserve as the AFR went up is a prime example of what lean condition symptoms are like. Another thought is if there would ever be a concern that the fuel delivery from a petcock wasn't enough it would show up as well.

I may have to buy one of those prox sensors. I have one similar, but it is 24v. The hall sensor/magnet set up works well, but more of a pain to fit.

In all, the set-up really does help with tuning, and what’s best is it actually gives empirical values to what is happening with the AFR. Knowing this it becomes easier to relate to the documentation describing the AFR and its function. It will sure make fitting other sets of carburetors to an engine much easier. "Cheap Insurance" as they say, especially when some of these engines carry a heavy price tag. The set-up cost is pretty low in comparison.

E

[posplayr]

Found another good link

http://www.daytona-sensors.com/tech_tuning.html

OK This is an interim final report on the jetting of my GS1100. I'm using the 36mm GS1150 carbs and a stage III dynojet kit for the same bike. I have changed the mains though and have ended up with somewhat of a unusual situation but it seems to make sense and the bike is running well. I might just go down to the local motorcycle shop and have it dynoed just to see where it has ended up.

I rode the bike around with the mains at 145 and the needle at 3 1/2 notches from the bottom. After trying to read the plugs I went to 4 1/2 from the bottom. It ran well but rather than doing this by braille I decided to get the INNOVATE LM-2 and LMA-3. It was a challenge to get it all to work but I'm glad I did it rather than aimlessly trying to determine the jetting by reading the plugs.

I ended up moving from the 145 to a 140 and eventually to a 135 Mikuni and I'm still plenty fat (AFR approx 11.5 at WOT sea level).

With the main dropped all the way down to 135, the needle got lean and so it is now at the 2nd notch from the bottom. At 1/2 throttle high RPM I'm running about AFR 14.5, but as soon as I put on throttle it dives to low 11's. At 75 mph and 4500 RPM between 1/8 and 1/4 throttle I'm at AFR 12 .

When the throttle is just barely cracked, cruising at 20-30 mph it is a little rich at AFR 10.8-11, but it seems to run fine. When I tried to lean it out it would not idle and it bobbled. With the RPM input that I worked so hard on with the LMA-3, I now have a very accurate RPM (doesn't seem to jump more than about +/- 10 RPM) I can dial in the idle for max RPM pretty easily.

A more normal jetting would probably be a 140 main (v.s. my 135) with the needle jet at 3 or higher (v.s .mine at 2). I'm attributing the leaner main and fatter needle setting to my 4:2:1 v.s. the more traditional 4:1. The 4:2:1 flows better at mid range but not quite the flow at the top end as compared to the 4:1.

As A guide, this is what I saw near my optimum tune point.

• 1 notch rise in needle ( e.g. 4 to 3 from bot)at 1/2 throttle will lower AFR 1 full point (e.g. 14.0 to 13.0).
• A drop in Main by 2 sizes (e.g. 140 to 135) at 1/2 throttle will raise AFR 1 full point.(e.g. 13.5 to 14.5)
• A drop in Main by 2 sizes (e.g. 140 to 135) at WOT ------- will raise AFR 1/2 a point.(e.g. 11.0 to 11.5)

SUMMARY: @ 1/2 Throttle: 1 needle notch = 2 jet sizes

Optimum tune (for my setup) seems to be about; (In other words I'm not sure it will get any better than what it is ):

WOT is AFR 11.5-12.5
1/2 throttle (high RPM) is AFR 13.5-14.5
1/8-1/4 throttle AFR is 11.5-12.5 (75 mph at 4500 RPM)
Idle AFR 13.5


I'm going to take a break, do the dyno run and then next will be to move on to the Slingshot BST36SS carbs

If anybody wants to see the actual log files, you can go to the innovate website and download the LogView software ; then email me and I'll send some example logs for you to look at in detail.

P.S. Eric thanks for all your help.

anybody wondering what all this is about go here:

http://www.thegsresources.com/_forum/showthread.php?t=161402&highlight=AFR

[tejasmud]

Optimum tune (for my setup) seems to be about; In other words I'm not sure it will get any better than what it is :


WOT is AFR 11.5-12.5
1/2 throttle (high RPM) is AFR 13.5-14.5
1/8-1/4 throttle AFR is 11.5-12.5 (75 mph at 4500 RPM)
Idle AFR 13.5

Hey Jim,

I would say that is about a good as it will get. Looks good, and identical to the AFR to throttle positions I have set up on the GS700 with VM29s.
Jetting is different obviously.

So, you did have to move the needles after changing the main jet with the CVs. From your email the 1/2 throttle position leaned out quiet a bit.

That was something I didn't observe with the needles on the VMs as I changed main jets. Hmmm.. Different carbs, smaller displacment, different pipe, ect, ect... Different results are to be expected I suppose.

When I mentioned that I run just past redline when measuring the AFR at WOT this was on the street not on a dyno. I could see your dilemma with the higher gearing and larger displacment. I'm geared much lower, 3.6:1 on the drive, top out at about 105-110 MPH, smaller displacement.

But, looks like you have dialed in good.

From your emails I gather you started to litterally "feel" some of the differences as any given circuit was lean or rich. How things smoothed out, and the stumbles went away. Now having a good feel it will make setting up those BST36SS carbs a breeze.

E

[posplayr]

Hey Jim,

I would say that is about a good as it will get. Looks good, and identical to the AFR to throttle positions I have set up on the GS700 with VM29s.
Jetting is different obviously.

So, you did have to move the needles after changing the main jet with the CVs. From your email the 1/2 throttle position leaned out quiet a bit.

That was something I didn't observe with the needles on the VMs as I changed main jets. Hmmm.. Different carbs, smaller displacment, different pipe, ect, ect... Different results are to be expected I suppose.

When I mentioned that I run just past redline when measuring the AFR at WOT this was on the street not on a dyno. I could see your dilemma with the higher gearing and larger displacment. I'm geared much lower, 3.6:1 on the drive, top out at about 105-110 MPH, smaller displacement.

But, looks like you have dialed in good.

From your emails I gather you started to litterally "feel" some of the differences as any given circuit was lean or rich. How things smoothed out, and the stumbles went away. Now having a good feel it will make setting up those BST36SS carbs a breeze.

E

Eric,

Hoping to go for a ride this weekend and give it a try. Last weekend was dedicated to jetting .

Yea that is strange about the mid range. It is basically a 1/2 throttle deal. AFR went real lean after the 140 to 135 jet change. The LM-2 kept firing e8 errors which apparently relate to CO production from too lean. All cleared up after droping from 3rd nitch to 2nd notch. I did not want to move to the lowest notch.

Jim

[posplayr]

One final update on jetting. After ridding without the LM-2 AFR installed I started to get some low RPM sogginess. I assumed it was the needle so I dropped it all the way to the bottom groove. That was a mistake The plugs came out black after a few minutes of low throttle cruz'n.


I ordered 45 pilot jets, to replace the 47.5 Bill had installed for when I originally had the 4:1's installed. The new pilots had the holes while the old ones did not . Anyway went back to the original #2 grove position with the 45's and the bottom end is now very sweet and I got an inadvertent power rollown 2nd gear wheelie so it seems to be running crisp.


Final settings then:

Mains = 135 (down from 145)
Grooved DJ needle = 2nd grove from the bottom (down from 3 1/2)
Pilot jet = 45 (down from 47.5)
Mixture screws were set for max RPM = close to 2 turns (was 1.5)
Float height 22mm (unchanged)

I'm assuming that the fatter needle and smaller Main are to compensate for the 4:2:1 v.s. 4:1 flow characteristics. Dyno Time?


Just a note, After changing the pilots and checking the float heights , I reinstalled the carbs and the bike stumbled at idle and ran higher idle. I assumed it was the pilot change. After digging out the Balance gauges and calibrating them I realized that the chock cable was not seated and it was partially pulling causing one set of carbs to be more open that the others (Duh).

Anyway basically the pilots did not affect any of the carb throttle balance settings