RSR Air/Fuel Ratio Gauge (2023)

RSR Air/Fuel Ratio Gauge (1)

RSR Air/Fuel Ratio Gauges

Whether your bike is carbor efi this is the best way to tune...By riding and observing, not on astatic dyno. Dynos are not exactly real world in terms of loads,airflow, or transitionals, and even if you had a million dollar ACTransient dyno room, you would still have to do real worldtesting. We have the most sophisticated Motorcycle Dyno, aSuperflow CycleDyn, with integral speed-based dual fans, but we stillride, test and observe in the real world and we have for nearly 40 years.

Thegauges are dead accurate and are millisecond fast responding whichmakes it very simple tointerpret or remember, even at a glance, while you are dodging carswatching for cops. No spooling digits just a four color bright displaythat illuminates a single LED for a dead accurate AFR feedback. A PDF explains it's use. You do not have to remove the gas tank to do the installation.

The Single and Dual gaugesship with eight feet of MIL-W-22759/32 wire. The first 24" is RaychemDR-25 sealed on both ends. The Green Wire breaks out at 24" for yourfront cylinder Bosch O2 sensor. Secondary wiring is sheathed in RaychemDR-25 where it passes under the gas tank. The harness and the gaugesare completely waterproof. Late model 12mm Harley exhausts requiresecondary 18mm x .5 bungs as Delphi/Harley throws additional voltageson top of the O2 voltage.

Anyone who tells youoptimizing tuning is easy is full of shit. Engineers at Ford say theyspend two years just perfecting tip-in or initial throttle openings.Ride, observe,..then change or edit with TTS MasterTune. No add-Ongizmos. Keep your Delphi and OEM sensors. Do not be tricked intochanging your Delphi ECM and using wide band and throttle angle basedsystems. Real world. Get your mileage and performance optimized.

Dead Accurate

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Here we are comparing ourRSR Single O2 Display versus the latest Bosch ADV 5 wire WidebandSensor (Pre-Turbo) sensor, not the common Bosch LSU4.2/9 sensors. OurSecond Orange Light being pointed at by the white faceplate arrow showsthe maximum torque and power value of 13.2-13-4 AFR (.9 Lambda). Testedunder heat with regulated propane-air mixture.

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Shown above: Into the First Red Light: Widely used 12.5:1 (into the 11.0 range) as a targetfor temporary acceleration enrichment or a slightly rich full powerratio and or a safe turbo boost target.

Second red light to thefar right is simply too rich 10:1 or richer if the engine is at normaloperating temperature. The second Red Light can show on initial warmup.

Ride in the real world and find out if your tune is right or not 20:1 AFR (RSR lights Out) to dead rich (Last Red Light).

Fuck It... My Bike Runs Fine

Ignorance is bliss as theysay. Don't look at your spark plugs. Don't monitor your bike's AFR inthe real world. Don't try to get your mileage back to what your stockbike got. Don't compare 40-60 and 60-80 mph roll-ons before and afterwith a stop watch. Don't monitor your oil temperature readings.

You should really read this PDF from a Champion Spark Plug Engineer...And get out your torque wrench and lighted 10X magnification spark plug reader.

All of the above plus monitor as you ride. The only way.


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Whenever you look at anexhaust and see it caked in black soot you know the bike is not runningor tuned correctly. Back in the mid 1980's we did a carburetordevelopment program for Keihin Corporation for their 41mm CR Race carbson both Shovelheads and the new Evolution motors. When we were finishedthe bikes got 56 mpg cruising and 46 mpg if you ran them harder...andafter 500 mile tests the pipes were perfectly clean inside and theexhaust ports were dead clean.

If you take the exhaustsystem off a modern Closed Loop BMW, as we have, you will find themdead clean or whitish inside. Harleys should be the same. We took theOEM exhaust off a 2014 Indian Chief and the exhaust ports wereperfectly clean.

We always ask what mileagepeople get from their "tuned" or modified Harleys after "Dynotuning"....The universal answer is 37 mpg or less. If they don't know,we ask them if they have to gas at 100 miles. Most do.

Once a customer bought anexhaust from us and took his bike to two different dynos in search ofthe "117 Hp" he was looking for for his 103...He got 110Hp. Afterpissing and moaning we told the guy to give us our exhaust back and wefound it caked in soot. So much for tuners and their tail pipe sniffersthat see lean reversions...They just kept adding fuel. You tell thecustomer to put on our RSR Air Fuel Gaugeto monitor the mixtures F/R in the real world...No, they want a "DynoTune". We have dynos...we know what they do and can't do.

Pictured above is theexhaust port from a 2017 Dyna Low Rider S with about 100 miles on it.No soot. Delphi engineers seem to have done a very good job. Looks likethe port you would see on a BMW. Now, when your "Tuner" gets finishedwith it, it will most likely be full of soot. Logic plays no part inpeople and their toys. EFI is complex...put in different cams, changeair cleaners, port the heads and all this goes out the window. Bravenew world.

No soot.

Customer Comments: Dyna FXDX T124 S&S

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Customer writes: " Hi, First feedback for the RSR AFG:

Why did I wait so long to get it and saving money to theDyno Jet? First issue, I dropped the pilot / low speed jet to thecorrect size on my Mikuni HSR48. It was way too rich. Now witheverything dialed in, the ‘warm’ idle will flicker between the orangeand red light, cruise is at the left orange light and hard accelerationtoggles between last orange and first red.

Now I got no issues to do tunings on the air filter or exhaust.

Thanks and best regards Ingmar"

Customer Comments

Customer writes: "Justwanted to reach out and thank you for making a superior product withthe afr gauge. Taking the guess work out of carburetor tuning andfollowing the color, I was able to really dial in my bike. It nowgets 52mpg, makes more power in all rpm ranges, doesn’t gas/smoke outmy buddies behind me, doesn’t decel pop and the pipe is clean inside!

As a shop owner I felt I had a decent ability to tune a carbureted bikeespecially with the staples of the industry but I found with your gaugethat it’s simply not possible to know if your lean or rich in only acertain spot in the rpm range without that O2 sensor feedback. It notonly helps me learn to see the very small signs that tell me somethingis off with the tuning but to allows me to use this as a way to givecustomers a truly ideal tune in real world riding conditions.
Awesome product!!

(Video) harley fxrs, RSR AFR test

Thank you,
Chad Mooney
Steady Rolling Motorcycles"

Customer Comments

Customer writes: "I can’t thank you enough for the great product. I installed the O2monitor as soon as I received it. It made tuning the carb so mucheasier. It also gave me a better understanding of what I have donewrong with other carbs in the past. Thanks you again for your productand your advice. Happy New Year
Sam Allen"

Customer Comments

Customer writes: "When the gaugearrived I knew itwould be of a very high quality, it has far surpassed my expectations.I was very eager to get this installed and take a look at mytune. Amazingto see how little adjustments on the carb effect the AFR. As a resultof this gauge, I have dropped one size on the low speed jet, raised theclip on notch and confirmed the main jet on my Mik48. Thank you, I really like this gauge. Ed"

"Just wanted to follow up with you. This AFR gauge is a game changer. Ithink the tune on this bike is just about perfect, or as perfect as aone can get with a carb. I have every needle, main and idle jetavailable for the Mik48 and think I used everyone of them chasing thetune. Now with everything dialed in, warm idle will flicker between theorange and red light, cruise is at the left orange light and hardacceleration toggles between last orange and first red. Plugs lookterrific, bike starts first thing in the morning without any choke,while riding around town the lights are relatively stable, some movingaround but not much. Again, I couldn’t be happier with how this gaugeworks.

I am building a 124” TC to put into another FXR that I am building.This gauge is already on the build list, can’t imagine not having thisgauge on any of my bikes. Thanks, Ed"

Follow the light to fulfillment

TheMother of all gauges! Not a gauge, but a precision tool that will tellyou exactly what your engine is doing in real-time. Gives youinstantaneous read-outs of air/fuel ratios from 17:1 to 10.5:1 andindicates maximum power ratios. Four color display is easily read indirect sunlight and automatically dims at night. Waterproof,billet aluminum construction. Your significant other will cheat on youbut this gauge will never lie! It won't keep you warm at night, but aperfectly running engine will look and sound the same when you wake upnext to it the morning after.

New Dual O2 Meters...For Sequential EFI

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ForEFi sequential injection our new RSR Dual Air Fuel Gauge displays thefuel mixture in both the front and rear cylinders separately. The gaugeis housed in a hard anodized round enclosure in a standard 2" formatwith a 2.250" bezel, center back mount, with a 5/16" x 18 stainlesssocket head cap screw. The gauge will show fuel ratios from 17:1 to12.0:1 (or richer). The gauge is visible in daylight and automaticallydims for nighttime operation.

Scale is, left to right, lean to rich: three greens, three yellows, two orange and two red l.e.d.s.

Gauges are fully encapsulant sealed withfour different compounds and take about a week to manufacture to allow for IP67 waterproofing. Mil-Spec22759/32 wiring is used with Raychem DR-25 Heat Shrink. Full stainless and hard anodized finishes.

New Small (12mm) and (18mm) Narrowband O2 Sensors

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In 2010FLT/H series went to the new small heated O2 sensors. The Dynas and Softails went to these in 2012 and the Sportsters in 2014.

Our LSR exhausts are tooled for thesesmaller sensors on all the newer models. Thesmall O2 Sensor models have afloating ground voltage offset that has a complex scheme that variesthe signal to meet emissions purposes. If you think you are going totrick these you are in for a surprise.

You must specify the year of yourmotorcycle when orderingthe RSR Dual O2 Gauge. Models with the small OEM O2 sensors willrequire two 18mm O2 ports in addition to the 12mm ones to monitor yourbike as you ride. Our RSR Dual Gauges will monitor the 18mm hightemperature O2 sensors we supply. It is the only method to monitor bothfront and rear cylinders of your bike as you ride. Real worldobservations to perfect your tune. Better than a dyno which tends tooverheat you motor quickly skewing your tune.

LSR 2-1 Exhausts can be ordered with thedual O2 ports ( 12mm and 18mm) at no extra charge.

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The above chart gives the response timesof the 2009 and later 12mm Delphi Oxygen sensors. In actual dyno tuningyou reallyhave to hold one "site", i.e. the intersect of load and rpm to get anaccurate feedback as the sensors are always "behind" due to theirresponse times. That's why you see Superflow engine dynos doing steptesting so things can stabilize. In a tenth of a second you could be atany location on the fuel map...Not to mention the eight surroundingsites that are being interpolated.

The problem with "holding things" on and eddy current dyno is that is things heat up in these aircooled engines and the hidden code in the Delphi ecm starts changingthings. You can really only do one wide-open throtte pull on a dyno at one rpmand load site before the engine heats up too much.

Best do real world datarecording with the TTS while you ride and then evaluate, in real time,your map with the RSR milli-second fast RSR Fuel Ratio Gauge withgenuine 18mm Bosch O-Sensors. Realtime monitoring when you ride is the only way you can evaluatetransitionals, acceleration additives, and wide open throttle...all inthe real world moving through the air and on the road like you donormally. All LSR 2-1 exhausts can be ordered with both 12mm and 18 mmO2 sensor bungs.

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Thewhite arrow indicates the maximum power mixture, the second orangelight, which is 13.2:1. Transitory enrichments should not, if theengine is warm (>200F Oil temp), go past the first red light.Readings at the far right side of the scale, the second red light, aresimply too rich. Proper closed loop operation will cycle back and forthfrom green to orange around the center of the display.

It is simply the best way to evaluate the tune of your motorcycle and saves valuable dyno time. Mounted permanently. Waterproof.

Compatiblewith OEM narrowband sensors. Can be supplied with new high temperatureBosch narrowband sensors. Far right photo shows gauge in dim lightconditions at maximum power setting.

Dual or Single Gauge?

Pretty simple. It depends on what you have.

Ifyou are running a carburetor order the single display meter. All RBRacing LSR 2-1 exhausts have had a front O2 port for over 30 years.You want to monitor the front cylinder as it requires more fuel. Therear cylinder runs a bit warmer as it is shrouded and it needs lessfuel...True, whether you believe it or not.

Ifyou are running an 2006 Dyna or any of the later year dual O2 port,sequential injection models, order the dual display meter.

(Video) How to tune without guessing

Handlebar Mounts 06-1025 / 06-1024

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06-1025 Hard Anodized Billet Handlebar mount with two degrees of freedom stainless mount. Available for 1"or 1 1/4" handlebars. $49.95. Shown with three degrees of freedom mount for on upswept portion of the handlebars.

06-1025 Hard Anodized Billet CNC machined Handlebar Mount. Available for 1"or 1 1/4" handlebars. $49.95.

The gauges have a center back mount5/16" x 18 x 1/2" Stainless Socket Head Cap Screw and stainlesslock washer. You can fab your own bracket for this anodized billetclamp or order the 06-1024 Mount Stainless Brackets. They are sold in apair for either mounting on the horizontal (near bar clamps) or on theupswept portion of the handlebars 90 degree offset bracket. The two mounts are cnc laser cut 304stainless steel. $9.95

Installation Instructions for both gauges can be downloaded in PDF format.

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Here the RSR Dual Gauge is mounted on 1.250" bars on a CVO 110" Road Glide with one of our LSR 2-1 Pro Stock RaceCat Systems.

Dual O2 Switchable

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A Bonneville Racer asked that we make thegauge switchable from his Bonneville racebike to his Dresser. The RSRDual AFR Gauge has eight wires, two for the O2 sensors, and 6 forpower, ground and the two L.E.D. warning lights (Red & Green). We added a Deutsch 6 position DTMconnector and supplied him with two secondary harnesses with matching 6position DTM Connectors and Weatherpack O2 disconnects.

With the Bonneville Salt Flats about gone we guess this may stayon his Dresser come next August. He races long course with a 120"Harley.

Internal Potting: Four Different Compounds

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This does take time as eachstep involves a day of curing. The eight gauges above are being finalpotted with a two part epoxy after the previous three cures have beenmade. They will sit an additional few days to complete the curing ofthe two part epoxy. After that the Raychem DR-25 is heat shrunk andsealed. The gauges are then tested a final time, cleaned and packedwith the installation hardware and billet mounts. The whole processtakes more than a week.

The nine gauges above are in their second stage ofcuring waiting for additional assembly on the circuit boards. When the entire process is finished they are completely water andshock proof and are enclosed in corrosion proof hard-anodized billet cups.

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Final Oxygen sensorsimulation on our RSR Air Fuel Ratio Single Display Gauges before thehard anodized billet RSR Air Fuel Ratio Gauge cups are filled with atwo part epoxy to make them vibration and waterproof. There really isno turning back at this point as three separate compounds have alreadycured inside the cups locking the electronics into place. This is thethird electrical simulation/check with a fourth and final check madejust before shipment to the customer.

Final operations to do: Heat shrink the Raychem DR-25 harness tubingand seal the harness ends with Raychem ES2000 tubing and package thegauges with billet handlebar mounts and wiring hardware. Withfabrication, assembly, and curing times plus packaging this takeslonger than one week. They are Harley-proof at that point.

These single display gauges are headed for Harleys with carburetors. Our Dual Display Gauges are used on EFI bikes.

We have been making airfuel ratio gauges for well over 30 years and we still keep improving them.We make them in house. There is no better way to monitor your air fuelratios in the real world.

Road Toad...The Movie

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Harleys vibrate. Next time we'll make a better camera mount. Video showsthe gear indicator in action on a 5 speed 2004 Road Toad as well as ourRSR Dual Air Fuel Ratio Gauge. We made a few edits to the TC88 ECM forour LSR 2-1 Pro Stock Spyder exhaust. Gives you an idea of how we tunethings by actually riding them and how useful the Bonneville GearIndicator is.

O2 Meters and Tuning...Customer Comments

Customer writes: "When the gauge arrived I knew itwould be of a very high quality, it has far surpassed my expectations.I was very eager to get this installed and take a look at mytune. Amazingto see how little adjustments on the carb effect the AFR. As a resultof this gauge, I have dropped one size on the low speed jet, raised theclip on notch and confirmed the main jet on my Mik48. Thank you, I really like this gauge. Ed"

"Just wanted to follow up with you. This AFR gauge is a game changer. Ithink the tune on this bike is just about perfect, or as perfect as aone can get with a carb. I have every needle, main and idle jetavailable for the Mik48 and think I used everyone of them chasing thetune. Now with everything dialed in, warm idle will flicker between theorange and red light, cruise is at the left orange light and hardacceleration toggles between last orange and first red. Plugs lookterrific, bike starts first thing in the morning without any choke,while riding around town the lights are relatively stable, some movingaround but not much. Again, I couldn’t be happier with how this gaugeworks.

I am building a 124” TC to put into another FXR that I am building.This gauge is already on the build list, can’t imagine not having thisgauge on any of my bikes. Thanks, Ed"

(Video) AFR Gauge on FXR

Customer writes: "Can I useyour Air Fuel Ratio meter on Carburated V8 ford motor? I used onethat I purchased from a friend on my 124 S&S motor. It worked muchbetter than the dyno shop. I had my motor dynoed then took it home andinstalled my Air Flow meter. It was running pretty fat. I leaned it outa bit and to my surprise it was like adding 15 hp to my bike. Maybemore. The dyno came back with 156 hp to the rear wheel. Anyways Idigress. Back to my question. V8 Ford 302 Carburated motor. will thismeter work on a V8 motor."

RB Racing: "Yes".

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Customer writes: "Soundslike a FAST Harley! Revs quicker. Everyone that knows thebike immediately notices how the engine has better throttle responsenow. One blip of the throttle is all it takes to sparkenvy. It has a noticeable volume and powerful sound onacceleration complimented by a smooth deceleration growl.Cruising volume is somehow arguably quieter than the V&H slip-onsthat were on the bike previously. The chrome is flawless.Packaging was excellent. It’s amazing how spot-on the fitment ofthe slip joints are. The mounting bracket is perfect in form, fitand function. Everything eases into place with a slow methodicalhand. Don’t force or rush the installation and you will completeit without frustration. I bought the Dual AFR meter at the sametime as the pipe. I cannot imagine an easier way to tune with myTTS MasterTune! I was able to actually improve the tune and powerwhile maintaining 43 mpg. Thanks! Ryan"

00-1316 LSR 2-1 using RSR Dual Air Fuel Ratio Gauge.

Customer writes: "Ihad my TT 500 landspeed motor on the dyno the other day. Fuelingwas spot on thanks to your AFR gauge used on road tests. The dynooperator pointed out how the RB gauge was agreeing with his testequipment. You guys know this but we were both veryimpressed. I am still using Mikuni carbs so I use a marked twistgrip and keep my Sudco book handy. This gauge has now made about20 runs on the salt and covered many road miles with no problems.This 500cc single vibrated two of the K&N units to death in no timebefore that. Thanks, Tony."

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Customer writes: "Hello, Ihave installed your 2:1 LSR pipe (00-1122) with the AFR gauge. It's thebest money I've spent on my bike. The fitment of the pipe is great andit was not a wrestling match to install as are most other pipes. Thanksfor the great product. Kenny".

Customer Writes: "Ireceived my RSR Air/Fuel Ratio Gauge in October and installed it withinthe week. I am very happy with the Gauge, I have adjusted the Mikunibased on the gauge indication. I feel that the RSR Air/Fuel Ratio Gaugeis very accurate and repeatable. When I have the Mikuni adjusted justwhere I want it, then the engine temperature drops 20 or 30 degrees.The RSR Air/Fuel Ratio Gauge may be your greatest sales tool for yourRSR Efi. The fuel ratio gauge constantly reminds me of the limitationsof the carburetor.

I have continued to read and re-read the information on your website. It is informative, educational and often entertaining. Based on you recommendation, I ordered the Compu-Fire 40A 3-Phase charging system and I plant to implement all seven of your Recommended Procedures and Comments."

Customerwrites: " Thanks for the pipe and fuel ratio gauge. It was worth thewait. 116 inch with 2 inch pipe. The bike sounds really good. I havehad the Thunder Header before and did not care for the sound or theperformance. The pipe was too small though. This pipe sounds like aHarley should and it seems to rev quicker. Without the RSR Air Fuel RatioGauge I would have had different jets in it. { do not want to pay fordyno! } Thanks, Gregg." 00-1124 LSR 2-1 Turn Out, rotated 45 Deg,chrome w/ three heat shields."

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"Attachedis a photo of the pipe installed, just wanted to let you know the fitand finish were excellent, at first the sound was louder than Iexpected but probably because I had the slash turned down, now that Ihave gotten used to it I really love the sound . It also improved theperformance along with running smoother, the RSR fuel ratio meter madethe tuning a snap. This is on a 127" very happy motor. Bob". Part Number 00-1245.

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00-1236in chrome with heat shields. Joe used the two O2 ports to dial the efiin. You can't stick a sniffer up the rear of these pipes...all you aregoing to sniff is a bunch of outside air. Tuning has to be monitored atthe exhaust ports with O2 feedback. "Using your RSR Air Fuel RatioGauge is the way to do it."

Green, yellow, orange, red, colors swimming in my head

Thegauge is an industry standard 2" format and is unique in it's abilityto provide the driver/operator/tuner exact information that is easilyunderstood and remembered in stressful situations. Sitting on a 425hpmotorcycle with 24 lb. of boost you have little time to studyinstruments... It's impossible to read a numericdigital display...Running flat out at 200 mph plus you just can't takeyour eyes off the course!

The RSR Air/Fuel Ratio Gauge uses 10ultra-bright LED's in four colors: 3 green, 3 yellow, 2 orange and 2red. It's very easy to remember last yellow, second orange, first redetc. Designed to be permanently installed on your vehicle it willprovide you accurate data to perfect your engines fuel needs as onlyone light is lit at a time. Extensive testing has proven this to be theoptimum combination. In addition the gauge face plate is marked forStoichiometry as well as peak power Air/Fuel ratios.

Whatdo the strange lights in the sky mean? Are we about to be visited bySculley and Mulder? Get a grip on yourself, we are talking about gaugesnot tequila sunrises. If the display gets to the 2nd red (far right)your situation is too damn rich. Further detailed information as toexactly what the air/fuel ratios are for each light and what yourtarget points are for full power, acceleration fueling, steady stateoperation, idle mixture strength, maximum economy etc. are allcontained in a eight page manual that comes with the gauge.

Put your bike on the dyno and....

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Ifyou surrender your bike to the hands of another they are going to sticka probe up your pipe to see what's going on. Long rubber tubes, pumpsand gas analyzers. There's a lot wrong with this. First off, there isthe nasty secret of reversion where the pesky 15 psi of outside airrushes back up the pipe to skew the sampling data. Then there is thefact that you have blocked the exhaust flow with your anally fixateddevice. Thirdly, there is the time delay of the sampling which meansyou are always "behind", no pun intended. Lastly, the load on a dynodoes not reflect what you see in the real world.

Youare better off running the bike in the real world and watching the O2display which essentially operates in real time. It will reflect yourparticular riding style and will save you a lot of money compared tothose $200.00 to $400.00 dyno sessions. If dyno numbers are your mantrathen do all the tuning in the real world with the RSR Air FuelGauge...Then put it on the dyno. The dyno operators are usually amazedon how well the bike runs..."What did you do to it?" is the usualresponse.

The Red Light District

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Goback to the top of the page. That big red light is a 12V Dc event basedwarning light. Two of the wires on your RSR Air/Fuel Ratio Gaugeactivate this light. One wire goes to a 12V Dc switched power source,the other goes to ground. If you hook the ground up to your oilpressure sending unit the light will activate if you lose oil pressure.People use them to indicate all sorts of 12V Dc events such as nitrousactivation, rpm shift lights, high gear indicator (Bonneville),electronic water injection activation etc. etc.

TheDual Air Fuel Meter has two 12V Dc event based lights...We have bigplans for these. You may use them for whatever nefarious purposes youhave.

Twin Cam amd M-8 Heat Conundrum

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Theimpending beat of the water buffaloes hooves approaches. Behold the lastof the air cooled dinosaurs, roasting your legs as if the comet ofdestruction had already hit ground zero with oil temperatures running265 to 295 deg F. Ouch!

(Video) AFR Gauge on my Buell

Oil temperaturesin the old, old, days were under 200 deg F. In the mid eighties the 80"Evo arrived and temperatures went to 210 deg F. Oil coolermanufacturers scrambled to take your money. If you were stuck in theHades of an Arizona Summer you might have been smart enough to run 70weight Kendall oil. These days they tell you to run synthetic or yourbacon will burn.

Those tiny little feedand scavenge gears didn't do much of a job pushing oil in anyappreciable volume through a crappy little oil cooler so your scooterran hotter as the years went by and as California pushed the limits ofemission standards. "Cold" engines were dirty and needed more nastyhydrocarbons to keep them happy. Greasy, slippery lubricants like leadthat reduced friction were sent to the aquifer and your liver but takenfrom your gas tank. More heat.

Alongcomes the TC88/96/110 etc. One extra cam forward and ten steps back.Tiny, tiny ports that trap heat, lean mixtures at or short ofstoichiometry that keep exhaust gases hot. Cylinder heads that havevirtually no fins save a few cosmetic slots and emission laws thatsniff your fuel lines and your air cleaner cover. Cam timing withlittle or no overlap and restrictive exhaust systems. It's no wonder anew 96" fuel-injected Twin Cam makes less horsepower than a decade old96" S&S engine with a carburetor and runs temperatures that scareyou to death and push the outer limits of tribology and chemistry.

Catalytic converters that need heat NOW!

Bravenew world. Buy a 900 pound $40,000.00 CVO Dresser and then dump another$10,000.00 into the powerplant so you can keep the faint glimmer ofGoldwing tail lights in your windscreen. The heat you feel is not alwayspower. The answer is complex and is often defined by the cards you aredealt. The heat you feel is not just the result of "lean mixtures".It's more complex than that.

Closed Loop and O2 Sensors

Youdrive down to the Harley dealer in your late model car or truck. Itstarts instantly, works perfectly for years, and it has narrowband O2sensors. You buy your expensive Harley and want to take off thesophisticated Delphi Closed-Loop Narrowband system and put on acompletely new system with Wide Band Sensors or, even worse, you wantto put on a Power Commander that eliminates the O2 sensors. Is theresome logical disconnect here?

Youdecide you want to tune your efi so it runs at 13.2:1 instead of14.7:1. There goes 11% of your fuel economy. The fact is your enginewill have the most complete burn @ 14.7:1 and that is where it shouldrun for the best economy and driveability, just like the car and truckyou went to the dealer in. Programming and strategy for closed looptuning is not the same as it would be for carburetion.

Yousurrender your bike to some "expert" who tunes your bike in open loop (closed loop disabled) with wideband sensors and then flips the bikeback to closed loop and the OEM narrowband sensors. Guess what...hecan't tune the bike at or below Stoichiometry but targets between 13and 12.5:1 so your sophisticated Delphi ECM is always trying tosubtract fuel to get back to 14.7:1. Every time you nudge the throttle aminute bit if extra fuel gets burned before it can be subtracted. Youend up getting less mileage that it did stock. Hey, he's andexpert...and it's your money. Never mind, he can get perfection in acouple of hours in a static non-controlled environment when Delphi orBosch will take thousands of man hours. Comfort in ignorance.

Ifyou install some device that installs between the factory OEM sensorsand the ecu/ecm and sends a phony signal ... that's headed back to electriccarburetor instead of a sophisticated closed loop system. Remember thatvehicle you drove down to the dealer in.

Inany case we make RSR Air Fuel Ratio Gauges for our Bosch narrowbandsensors . In many cases for bikes with12mm O2 sensors we install secondary 18mm O2 ports on our exhausts.

Fast, accurate, advice from a friend that doesn't ask for money

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TheRSR Air/Fuel Ratio Gauge becomes your expert witness...there is no moreguessing or having two operators with two different opinions. If yousee your mixture going dangerously lean you can instantly back off andsave your motor. For developmental purposes you need to have quickanswers for full power, transient and steady state operatingconditions. The RSR Air/Fuel Ratio gauge is the best tool to providethese answers.

We have included acalculator that shows the relationship of various fuels to one anotherin terms fuel ratios. At a Lambda value of "1" we have stoichiometry orthe point at which the most complete combustiontakes place. Values of Lambda less than "1" are richer thanstoichiometry and Lambda values greater than "1" are leaner thanstoichiometry. You can enter a value for any fuel and the calculationswill be automatically made for the other fuels as well a calculation ofthe corresponding lambda value.

RSR Air Fuel Meters available with O2 sensor, without, or all by its lonesome

RSR Air/Fuel Ratio Gauge (28) RSR Air/Fuel Ratio Gauge (29)

Ifyour vehicle already has one Oxygen Sensor all you need is the singledisplay RSR Air/Fuel Ratio Gauge. If you need to install an O-Sensor inyour exhaust we have the 18mm x 1.5mm weld-on, machined adapters. One wire sensors are unheated and must be installedclose to the exhaust port. Our Harley Davidson exhaust systems for 30 years have had anO-Sensor port in the front primary tube about 2 inches from the portitself and use one-wire sensors on carburetted systems.

We use four-wire heated sensors on our RSR EFIsystems and use the single display O2 meter with the O2 sensor in thefront exhaust port. "Heated" simply means it gets up to temperaturequicker. Four wire sensors consist of: onesignal wire, two heater wires and a ground reference wire.

Late modelHarley Davidsons with sequential injection require our dual displaymeters and use the oem narrowband (two wire) sensors. If you throw awayyour sophisticated Delphi ecu for some aftermarket wideband ecu (LSU4.2/LSU4.9etc.) these gauges won't help you as the voltages are completelydifferent with wideband units.

There will be a test on this at 2 o'clock.

Why EGT and Narrowband.... Not Wideband for Turbos

RSR Air/Fuel Ratio Gauge (30)

Asyou can see from the chart a Bosch LSU 4 wideband sensor has a 15%error if subjected to 2 Bar exhaust pressure. On turbos you have tomount a wideband sensor after the turbo which is a big problem becauseturbos, at least in race applications, use short dump tubes and this isway too close to oxygen-rich atmospheric air. On our race bikes we useour RSR Air Fuel Ratio Gauge which is not affected by exhaust pressure. On our Bonneville Bullettwe run two single wire high temperature Bosch O2 sensors in addition tothe dual egt ORCA Turbo Dash. Wideband LSU 4 sensors can be damagedwith egts greater than 1500 Deg F. We run above this. We use speciallycalibrated NTK L2H2 sensors with pressure compensation tables with our Pectel SQ6M engine management systems.

A second reason you useegt on turbos is that, if you are running leaded race gas, any O2sensor, narrow or wideband, will become contaminated, resulting infalse readings. This can happen very quickly or maybe 10 hours laterdepending on the fuel used. When fouled, they render false leanreadings. It is better to watch and record high egt temperatures whichare completely unaffected by either pressure or racing fuels.

Check out our ORCA Turbo Dashfor specialized turbocharger and supercharger applications. Used inconjunction with our RSR Air Fuel Ratio Meters these are the best wayto tune and monitor your high horsepower application. We also offer RSR Bonneville Gear Indicators to you always know what gear you are in.


How do you monitor air-fuel ratio? ›

How is it measured? The air/fuel mixture can be analyzed by looking at O2 Sensor data from your ECU. Another way to monitor your air/fuel mixture is with an Air/Fuel Ratio Gauge. Many AFR gauges also display lambda value.

Is 15 AFR too lean? ›

For optimum fuel economy 16-17:1 is usually best, leaner than that and the car will begin to misfire. Maximum power is usually found between 12-14:1, but this may be too lean for safety on many engines. For maximum reliability at full power, air fuel ratios from 10.5-12.5:1 are considered best, depending on the engine.

What should my AFR gauge read at idle? ›


With 14.6 being the industry standard stoich AFR value, we typically like to see these conditions run slightly richer. We are looking to fine tune an engine to get the smoothest operation.

What is the best AFR for Harley Davidson? ›

Real world inefficiencies result in an air/fuel ratio (AFR) of 12.8:1 to 13.3:1, for best power and 14.5:1, for best mileage. Keeping the AFR around 13.8 under load, get the best of both worlds.

What is the perfect AFR ratio? ›

In a perfect world, all gasoline engines would run the ideal air-fuel mixture of 14.7 parts air to 1 part fuel. This target mixture, which is referred to as the stoichiometric air-fuel ratio, is a compromise between optimum fuel economy and optimum power output.

Is air-fuel ratio gauge important? ›

An AFR gauge monitors the air-to-fuel ratio of your internal combustion engine. Having this information allows you to determine whether your engine is running at an optimal AF ratio. You don't want it to be too rich, as this hurts performance and fuel economy.

Is 14.7 AFR rich or lean? ›

So what is meant by a rich or lean AFR? A lower AFR number contains less air than the 14.7:1 stoichiometric AFR, therefore it is a richer mixture. Conversely, a higher AFR number contains more air and therefore it is a leaner mixture.

Is 13 AFR rich or lean? ›

When the air-fuel ratio is lower than the stoichiometric ratio, the air-fuel mixture is called rich. For example, for a gasoline engine, an AFR of 16:1 is lean and 13:1 is rich.

What is the best AFR for fuel economy? ›

A naturally aspirated engine, running on pump gasoline will normally make the most horsepower at an AFR of about 12.8 – 13.0. An AFR of about 14.6 will produce the best fuel economy.

Is 14 AFR too lean? ›

In a real engine, a 14.7:1 air-fuel ratio is a little too lean. To compensate for incomplete combustion, and to reduce NOx emissions, modern automobiles are tuned to run more rich, sometimes dipping as low as 12:1 or even richer during high-load situations.

What AFR is best for torque? ›

​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.

Does fuel pressure affect AFR? ›

The objective of changing fuel pressure is to optimize air/fuel ratio (AFR) for best wide-open-throttle (WOT) power. Tuning with the aid of a wide-band O-2 A/F meter is strongly advised. 8.) Adjusting the base fuel pressure of most modern, EFI engines will initially affect both the WOT and idle/cruise AFR.

What is the AFR for max power? ›

We mentioned the stoichiometric air-fuel ratio (14.7:1) that is the ideal ratio for lowest emissions, but this isn't the best ratio for power. It used to be that 12.5:1 was considered the best power ratio, but with improved combustion chambers and hotter ignition systems, the ideal now is around 12.8:1 to 13.2:1.

What is the best air-fuel ratio for a motorcycle? ›

Typically, at a steady cruise, an air-to-fuel ratio of about 14.8:1 to 15:1 provides the best compromise between economy and power. Unless what we're riding has an EFI system operating in closed-loop mode, this is as close as most of us will get to our ideal stoichiometric mix of 14.7:1.

Does octane affect AFR? ›

No, the stoichiometric ratio of gasoline does not change with the octane rating.

What happens if AFR is too lean? ›

An engine running a rich AFR mixture will result in terrible fuel economy and increased emissions, but a lean AFR can potentially be much worse! A lean mixture will cause a much hotter burn, potentially hot enough to melt pistons and spark plugs, and cause untold amounts of damage to the engine's internals.

Is a lower air-fuel ratio better? ›

Air–fuel ratio with lower numbers than stoichiometric are considered rich air–fuel mixture, which are less efficient, generate more power and mixture burn cooler, which is gentler on the engine.

What causes rich air/fuel ratio? ›

As mentioned, running rich is the result of a faulty combustion process, and this leftover fuel escapes into the exhaust in all of its stinky, polluted glory. Usually, our catalytic converters prevent the smell from appearing.

What is average AFR? ›

As of Apr. 2022, the IRS stated that the annual short-term AFR was 1.26%, the mid-term AFR was 1.87%, and the long-term AFR was 2.25%.

Do you get more power running lean or rich? ›

A rich mixture is more common and not necessarily detrimental to your engine. In the case of a slightly rich mixture, you may notice reduced engine efficiency and worse fuel economy, but the rich mixture will generate more power and actually burn cooler.

What is too rich and too lean? ›

The expression running rich or lean is in reference to the amount of gas that you have in the engine. If there is too much gas, then you will be running rich, and if there isn't enough gas, then you are running lean. Either situation can cause damage to the engine if not fixed quickly.

Is rich better than lean? ›

However, the key difference between lean and rich fuel mixture is that we use a lean mixture for maximum efficiency while we use a rich mixture for maximum power in an engine. These air-fuel mixtures are useful in internal combustion engines and industrial furnaces.

Does a ECU tune improve mpg? ›

Theoretically, an increase in torque means the engine revs reduce so under normal driving conditions, you should see an improvement in fuel consumption.

How do you monitor fuel? ›

Five ways to manage fuel consumption in the vehicle fleet
  1. Monitoring without satellite systems. ...
  2. Satellite tracking without additional telematics. ...
  3. Satellite monitoring using the CAN bus. ...
  4. Satellite monitoring with fuel flowmeters. ...
  5. Satellite monitoring with a fuel level sensor.
Oct 16, 2020

What happens when air-fuel ratio is too rich? ›

Too much fuel in the air/fuel mixture can make your vehicle surge, sputter, or even stall. For example, if the carburetor is set way too rich, it will push enough gas through to the combustion chamber and flood the engine. Your engine power might lag if the engine is being flooded while you're driving, as well.


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