RSR Air/Fuel Ratio Gauges

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

New Dual O2 Meters...For Sequential EFI

For EFi sequential injection our new RSR Dual Air Fuel Gauge displays the fuel mixture in both the front and rear cylinders separately. The gauge is housed in a hard anodized round enclosure in a standard 2" format with a 2.250" bezel, center back mount, with a 5/16" x 18 stainless socket head cap screw. The gauge will show fuel ratios from 17:1 to 12.0:1 (or richer). The gauge is visible in daylight and automatically dims 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 with four different compounds and take about a week to manufacture to allow for IP67 waterproofing. Mil-Spec 22759/32 wiring is used with Raychem DR-25 Heat Shrink. Full stainless and hard anodized finishes.

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

In 2010 FLT/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 these smaller sensors on all the newer models. The small O2 Sensor models have a floating ground voltage offset that has a complex scheme that varies the signal to meet emissions purposes. If you think you are going to trick these you are in for a surprise.

You must specify the year of your motorcycle when ordering the RSR Dual O2 Gauge. Models with the small OEM O2 sensors will require two 18mm O2 ports in addition to the 12mm ones to monitor your bike as you ride. Our RSR Dual Gauges will monitor the 18mm high temperature O2 sensors we supply. It is the only method to monitor both front and rear cylinders of your bike as you ride. Real world observations to perfect your tune. Better than a dyno which tends to overheat you motor quickly skewing your tune.

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

The above chart gives the response times of the 2009 and later 12mm Delphi Oxygen sensors. In actual dyno tuning you really have to hold one "site", i.e. the intersect of load and rpm to get an accurate feedback as the sensors are always "behind" due to their response times. That's why you see Superflow engine dynos doing step testing so things can stabilize. In a tenth of a second you could be at any location on the fuel map...Not to mention the eight surrounding sites that are being interpolated.

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

The white arrow indicates the maximum power mixture, the second orange light, which is 13.2:1. Transitory enrichments should not, if the engine is warm (>200F Oil temp), go past the first red light. Readings at the far right side of the scale, the second red light, are simply too rich. Proper closed loop operation will cycle back and forth from 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.

Compatible with OEM narrowband sensors. Can be supplied with new high temperature Bosch narrowband sensors. Far right photo shows gauge in dim light conditions at maximum power setting.

Dual or Single Gauge?

 Pretty simple. It depends on what you have.

If you are running a carburetor order the single display meter. All RB Racing 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. The rear cylinder runs a bit warmer as it is shrouded and it needs less fuel...True, whether you believe it or not.

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

Handlebar Mounts 06-1025 / 06-1024

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 mount 5/16" x 18 x 1/2" Stainless Socket Head Cap Screw and stainless lock washer. You can fab your own bracket for this anodized billet clamp or order the 06-1024 Mount Stainless Brackets. They are sold in a pair for either mounting on the horizontal (near bar clamps) or on the upswept portion of the handlebars 90 degree offset bracket. The two mounts are cnc laser cut 304 stainless steel. $9.95

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

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.

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

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

Internal Potting: Four Different Compounds

This does take time as each step involves a day of curing. The eight gauges above are being final potted with a two part epoxy after the previous three cures have been made. They will sit an additional few days to complete the curing of the two part epoxy. After that the Raychem DR-25 is heat shrunk and sealed. The gauges are then tested a final time, cleaned and packed with the installation hardware and billet mounts. The whole process takes more than a week.

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

Final Oxygen sensor simulation on our RSR Air Fuel Ratio Single Display Gauges before the hard anodized billet RSR Air Fuel Ratio Gauge cups are filled with a two part epoxy to make them vibration and waterproof. There really is no turning back at this point as three separate compounds have already cured inside the cups locking the electronics into place. This is the third electrical simulation/check with a fourth and final check made just before shipment to the customer.

Final operations to do: Heat shrink the Raychem DR-25 harness tubing and seal the harness ends with Raychem ES2000 tubing and package the gauges with billet handlebar mounts and wiring hardware. With fabrication, assembly, and curing times plus packaging this takes longer 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 air fuel 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 fuel ratios in the real world.

What do the strange lights in the sky mean? Are we about to be visited by Sculley and Mulder? Get a grip on yourself, we are talking about gauges not tequila sunrises. If the display gets to the 2nd red (far right) your situation is too damn rich. Further detailed information as to exactly what the air/fuel ratios are for each light and what your target points are for full power, acceleration fueling, steady state operation, idle mixture strength, maximum economy etc. are all contained in a eight page manual that comes with the gauge.

Put your bike on the dyno and....

If you surrender your bike to the hands of another they are going to stick a probe up your pipe to see what's going on. Long rubber tubes, pumps and gas analyzers. There's a lot wrong with this. First off, there is the nasty secret of reversion where the pesky 15 psi of outside air rushes back up the pipe to skew the sampling data. Then there is the fact that you have blocked the exhaust flow with your anally fixated device. Thirdly, there is the time delay of the sampling which means you are always "behind", no pun intended. Lastly, the load on a dyno does not reflect what you see in the real world.

You are better off running the bike in the real world and watching the O2 display which essentially operates in real time. It will reflect your particular riding style and will save you a lot of money compared to those $200.00 to $400.00 dyno sessions. If dyno numbers are your mantra then do all the tuning in the real world with the RSR Air Fuel Gauge...Then put it on the dyno. The dyno operators are usually amazed on how well the bike runs..."What did you do to it?" is the usual response.

Go back to the top of the page. That big red light is a 12V Dc event based warning light. Two of the wires on your RSR Air/Fuel Ratio Gauge activate 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 oil pressure sending unit the light will activate if you lose oil pressure. People use them to indicate all sorts of 12V Dc events such as nitrous activation, rpm shift lights, high gear indicator (Bonneville), electronic water injection activation etc. etc.

The Dual Air Fuel Meter has two 12V Dc event based lights...We have big plans for these. You may use them for whatever nefarious purposes you have.

Twin Cam amd M-8 Heat Conundrum

The impending beat of the water buffaloes hooves approaches. Behold the last of the air cooled dinosaurs, roasting your legs as if the comet of destruction had already hit ground zero with oil temperatures running 265 to 295 deg F. Ouch!

Oil temperatures in 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 cooler manufacturers scrambled to take your money. If you were stuck in the Hades of an Arizona Summer you might have been smart enough to run 70 weight Kendall oil. These days they tell you to run synthetic or your bacon will burn.

Those tiny little feed and scavenge gears didn't do much of a job pushing oil in any appreciable volume through a crappy little oil cooler so your scooter ran hotter as the years went by and as California pushed the limits of emission standards. "Cold" engines were dirty and needed more nasty hydrocarbons to keep them happy. Greasy, slippery lubricants like lead that reduced friction were sent to the aquifer and your liver but taken from your gas tank. More heat.

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

Catalytic converters that need heat NOW!

Brave new 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 of Goldwing tail lights in your windscreen. The heat you feel is not always power. The answer is complex and is often defined by the cards you are dealt. The heat you feel is not just the result of "lean mixtures". It's more complex than that.

Closed Loop and O2 Sensors

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

You decide you want to tune your efi so it runs at 13.2:1 instead of 14.7:1. There goes 11% of your fuel economy. The fact is your engine will have the most complete burn @ 14.7:1 and that is where it should run for the best economy and driveability, just like the car and truck you went to the dealer in. Programming and strategy for closed loop tuning is not the same as it would be for carburetion.

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

If you install some device that installs between the factory OEM sensors and the ecu/ecm and sends a phony signal ... that's headed back to electric carburetor instead of a sophisticated closed loop system. Remember that vehicle you drove down to the dealer in.

In any case we make RSR Air Fuel Ratio Gauges for our Bosch narrowband sensors . In many cases for bikes with 12mm O2 sensors we install secondary 18mm O2 ports on our exhausts.

The RSR Air/Fuel Ratio Gauge becomes your expert witness...there is no more guessing or having two operators with two different opinions. If you see your mixture going dangerously lean you can instantly back off and save your motor. For developmental purposes you need to have quick answers for full power, transient and steady state operating conditions. The RSR Air/Fuel Ratio gauge is the best tool to provide these answers.

We have included a calculator that shows the relationship of various fuels to one another in terms fuel ratios. At a Lambda value of "1" we have stoichiometry or the point at which the most complete combustion takes place. Values of Lambda less than "1" are richer than stoichiometry and Lambda values greater than "1" are leaner than stoichiometry. You can enter a value for any fuel and the calculations will be automatically made for the other fuels as well a calculation of the corresponding lambda value.

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

We use four-wire heated sensors on our RSR EFI systems and use the single display O2 meter with the O2 sensor in the front exhaust port. "Heated" simply means it gets up to temperature quicker. Four wire sensors consist of: one signal wire, two heater wires and a ground reference wire.  

Late model Harley Davidsons with sequential injection require our dual display meters and use the oem narrowband (two wire) sensors. If you throw away your sophisticated Delphi ecu for some aftermarket wideband ecu (LSU4.2 /LSU4.9etc.) these gauges won't help you as the voltages are completely different with wideband units.

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