ADD ON FUEL CIRCUIT

Practical experience

MCMOD's Bracket adaptor by Thunder Allee

What is it? How does it work? HOW MANY ADDED HORSES WILL I GET? In simple terms DIAL-A-JET is an add -on fuel circuit for carburetors. No carburetor is perfect most come with two jets to cover the entire power band of the motorcycle. If we ran at a single RPM all day it would be easy to tune the carburetor , but most of us don't hold the throttle open all the time while we are riding. Manufactures have to balance reliability, repeatability, maintenance, and cost of production so their products are in specs and most of the customers will be happy. I did say most Customers, the rest of us are not happy with the stock performance and choose to modify the weak points on our rides. Engine aspiration efficiency is usually one of the most modified week points. With EFI (DDFI) engines the ECM is constantly adjusting the fuel/air and ignition timing through mapping and with the feedback it gets from the multitudes of sensors that are all over the chassis. The ECM in carbureted models adjusts only the ignition advance using curves based on RPM (some use input from an engine temp sensor).
  The added fuel circuit that Dial-A-Jet provides fuel to those parts of the power band that the engine goes into a lean condition as it operates on the borders of the carburetor jetting settings. The Dial-A-Jet is like a parent that responds to a hungry crying baby, it feeds it. In the same way the noise of the hungry baby's cry evokes the response of the parent to feed it so, Dial-A-Jet responds to the noise that a lean (hungry) engine produces. The Dyno results are marginal as only a few (less than 5hp typically) are gained with the installation. What is noticeable is when the bike is being ridden (under load) as gains in the solid response through the transitions of the entire power band.

History

Dennis Dean, Ph.D. (Doctorate in acoustics) and holder of over 120 world motorcycle drag racing records as well as several Bonneville records is a man of many talents. As an experienced competitor he was well familiar with the challenge of constantly tweaking the carburetor for optimum performance through the different powerbands throughout the racecourse regardless of the constantly changing ambient environmental conditions (temp, air density, etc.). He felt he had to develop something that would compensate for the dynamic conditions and would allow for fine adjustments. Dial-A-Jet was born.

Image to left shows installed "Duely kit" (Two Dial-A-Jets installed on a single carburator).

New bikes come factory jetted on the lean side. Competitors in an effort to jam as much air/ fuel down the cylinder as possible, often replace their O.E.M air filter for a high flow type and install custom exhausts that usually have lower restriction. These modifications take a already lean condition and make it worse resulting in taking the time and expense of re-jetting the carburetor to get proper performance from the engine without burning it up. The Dial-A-Jet system can usually be installed at home in approximately 1 to 1 1/2 hours and because the carburetors don't have to be removed for disassembly most people with average mechanical ability and a few inexpensive tools can handle the job.

Dial-A-Jet allows you to externally adjust the rich/ lean setting in seconds by a simple turn of the dial. There has been no change in the basic concept in Dial-A-Jet from the start except to make it more user friendly.

OK so how does it work?  Three conditions trigger the Dial-A-Jet;

1. Engine pressure drop (vacuum or fuel signal)

2. *Acoustic sound signal, which either amplifies or de-amplifies the reversionary pulse waves of the intake tract.

3. Air flow and velocity

4. Engine load. The engine must have a load on it, merely revving the engine will not trigger Dial-A-Jet to function, since there is no increase fuel requirement. This is normal.

*The acoustic signal is generated when gasoline is ignited in the cylinder. This signal amplifies the pumping action created by the reversionary pulse waves that occur naturally in any engine's intake tract. Most experienced riders can hear the difference in the rich/ lean condition as they accelerate. The acoustic signal along with  normal engine vacuum or fuel signal causes fuel to be delivered to  the engine. Because Dial-A-Jet is in the close proximity of the acoustical signal it uses it as a trigger. Detonation is an extreme  lean condition that generates a sharp reversionary pulse wave. This excites the Dial-A-Jet causing additional fuel delivery. Remember that Dennis Dean, Ph.D. has a Doctorate in acoustics.

Dial-A-Jet will only add fuel to the system, it will only function with a lean condition and will not function with a rich or adequate fuel condition. "Dial-A-Jet will automatically fill in the lean  areas of the fuel curve giving you optimum performance. The fine emulsified fuel charge can't displace the heavier poorly atomized fuel from the other circuits so it takes the path of least resistance and fills in the lean mix areas eliminating fuel spiking and giving you a consistent fuel flow pattern producing stable temperatures and horsepower. The only way Dial-A-Jet can fail to perform is if you do not get the carburetor within range of the Dial-A-Jet. This usually means that the main jet is too large. You must create a slightly lean condition so the Dial-A-Jet has a working range. This is typically about three or four jet sizes below  a properly jetted machine. A single Dial-A-Jet will deliver 10% to 15% of your overall fuel curve in an emulsified state. There are five automatic fuel ranges you can select from on each Dial-A-Jet.  Simply rotate the dial to raise or lower your fuel curve. " - Lonn Peterson.

Because Dial-A-Jet is mounted on each carburetor individually, it can be adjusted independently to maximize the full potential of each cylinder. The Dually Kit consists of two Dial-A-Jets per carburetor and delivers 20% to 30% of your overall fuel needs. This kit was designed to service highly modified or large displacement engines  that have high cubic feet per minute of airflow. Dually Kits are also used for extreme temperature/ altitude changes.

Other Uses

"Dial-A-Jet has even been successfully installed on fuel injection machines by installing an 0ptional Fuel bowl. One Arctic Cat dealer wanted to run performance pipes on a 580 EFI. The existing fuel map worked fine on the bottom end and  midrange; however, the top end was extremely lean. Dial-A-Jets wereinstalled on the throttle bodies. Fuel was pulled from a remote float bowl (available from Thunder Products) attached to the return line of the fuel injection. Dial-A-Jet cured the top end lean condition. The set-up worked great, yielding a crisp broad power band! The Dial-A-Jets could be adjusted for temperature, altitude, engine load, or fuel quality. The installation was simple and effective. More than 3,500 trouble free miles have been logged on this machine. " - Lonn Peterson

The Snorkel kit is a fitted rubber cap that goes over the Dial-A-Jet body. A vent line is inserted into the rubber cap and routed up the handle bar shaft, exiting just outside of the hood. A foam filter is attached to this end of the vent line. Cold clean air is fed to the Dial-A-Jet. This also eliminates belt dust, snow, ice or other debris from plugging the air correction circuit in the Dial-A-Jet making it run rich. Problems with under hood pressure are eliminated. The snorkel is a must for ATV's and dirt bikes equipped with Dial-A-Jets Each kit comes with a complete installation and tuning manual. Thunder Products provides full time expert technical support for all of their products. The above information was from Lonn Peterson's article " Dial-A-Jet Automatic Fuel Induction System and our own personal experience. To read Lonn's article in it's entirety click on the text link.

Practical Experiance

Why did MCMod choose Dial-A-Jet?
We ride a variety of machines, Buells (we have 7) mostly, but we also have a Harley-Davidson 883, and an old Cafe`racer, and family has a Yamaha Star. We have both EFI models in our X1 Millenium and S2 Thunderbolt and Carburated in the M2 Cyclones (4 total). In our own search to cure the changing mixture requirements on the track we first armed ourselves with an assortment of jets for our carbureted M2 Cyclone and the EFI X1 got the latest greatest high-tech electronic controller (real name withheld). This caused us to cut down on our socializing time at the track, as we were constantly tearing down and re-jetting the carburetor and tweaking the electronic controller on the EFI on the X1. We waded through all the paper work for the EFI controller and installed it then spent all summer long downloading different maps trying to get it to function right,  the results proved frustrating. The mixture monitor was still reading a dangerous lean condition at times. We ended up using the back up Cyclone on the track more times than not. By the time we were done with that summer we had one very expensive clay pigeon. The X1 was pulled from the track and is now retired to road duty and the Thunderbolt is morphing to a carburator model. Then we found out about Dial-A-Jet, leery we gave it a try on the Cyclone. To say we were impressed on the ease of installation and its performance would be a serious understatement. The end result was the Cyclone is now our main race bike, a happy mixture monitor and happy rider and the Dial-A-Jet is going on all the carbureted models.

What did others have to say about Dial-A-Jet?
The Dial-A-Jet works equally well whether it's a round slide, slat slide, or butterfly carb in either stock or modified engines. The dramatic difference of the Dial-A-Jet is the little mixing chamber which shoots a pre-atomized fuel mixture into the main stream of the carburetor. This delivers smooth consistent HP at all engine speeds.Starting Line Products subjected the Dial-A-Jet to their usual new product routine of rigid testing for better performance, consistency, durability, and value. They rated the Dial-A-Jet very highly. They have been offering Dial-A-Jet to their catalog customers for the last three years. Their customers have been very pleased and their satisfaction is reported "remarkable". Snowmobile drag racer Pat Hauck not only uses them on his machine, but also reports excellent reactions from his customers.

Dennis Trabant of Fairbanks, Alaska reports that his two Dial-A-Jet equipped Polaris' markedly out perform his other two Polaris' with regular carburetion in Alaska's extremes of both temperature and altitude.A test by Jim Czekala of DynoTech on the snow with a Phazer (known to detonate in mid-range) showed that the sled was several lengths quicker with the Dial-a-Jet from 1/8 throttle on. He noted that the Dial-A-Jet had more dramatic affect on a stock Phazer than on one with a modified engine. DynoTech concluded their report (volume 1, No. 5, page 9): "The Dial-A-Jets have proved to be a great advantage in helping our air cooled engines remain at peak performance. We hear the engine ping when we're lean, and the ease with which we can "dial" the fuel flow is a welcome respite from the misery that normally accompanies winter field tuning - any automatic compensation that may be occurring during changing air density or detonation is an added benefit.

Randy Sturm of Bell Industries, (Brainerd, MN) began to hear about the 1994 Mach Z engines occasionally burning down. Having one himself, he cleaned up the cooling passages, added a Dial-A-Jet and avoided any trouble. Bell Industries sold a dozen Dial-A-Jet kit to Mach Z owners, or their dealers last winter. One dealer had already rebuilt an engine four times. After Randy's recommended "cure", he called Randy back and called Randy a "God".  A very similar problem also showed up last winter in the '94 580 ZR engines. This is another case where the Dial-A-Jet is expected to be a clear cut "cure" - as the 580 was also experiencing some mid-range burn downs. (We may only mention these two instances but all brands have similar or other problems.) "Dial-A-Jet" - Race & Rally Magazine, Fall 94

"** Reading plug color - the typical plug color that you learn to read is caused by the amount of unburned fuel in the combustion chamber. Since the Dial-A-Jet is supplying only the fuel needed, the amount of unburned fuel is less. Therefore, your plugs will look lighter than normal, and this takes some getting used to. If you use exhaust gas temperature gauges, trust your gage. Gradually lean down until you reach your desired temperature - and when you get there, the plugs will LOOK very light.

** The Dial-A-Jet provides crisper throttle response - the typical hesitation when you rip open the carbs does not happen. When a normal carb is opened fast, the amount of air going in is greater than the amount of burnable (atomized) fuel being delivered. The Dial-A-Jet responds to the condition providing pre-atomized fuel during this period, resulting in crisp throttle response. (It fill n the gaps left by the various stages of jetting that carburetors have.) We felt this to be one of the most noticeable benefits - our ZR 700 really woke up coming out of the corners and had a nasty holeshot. It not only ran crisp all of the time, but the quicker throttle response was an advantage.

** The Dial-A-Jet constantly purges the carb of water. Since the Dial-A-Jet pulls its fuel from the bottom of the carb, it is constantly removing the water and alcohol that settle at the bottom of the float bowl.

** The Dial-A-Jet has no moving parts or electronics - it is nothing more than a siphon device with a mixing chamber. The black box that mounts on the carb is the mixing chamber that meters the air (according to dial setting) and mixes it with the fuel, injecting a pre-atomized spray of the fuel and oxygen mixture. The finer spray of fuel ignites faster and more completely, helping to burn the heavier, denser fuel being delivered by the other circuits of the carburetor.

** How does the Dial-A-Jet differ from a power jet? A power jet merely supplies heavier raw fuel in the 7/8 to full throttle range, where the Dial-A-Jet supplies pre-atomized fuel across the whole throttle range.Anyone who changes jets will benefit from installing a Dial-A-Jet. It is performance, convenience, and insurance in a single package. It could be the best money you will ever spend on your machine. The Dial-A-Jet is available through most major distributors or directly through Thunder Products, Inc." "Dial-A-Jet-Updated" - Race Rally Magazine, Fall 95

"The Vance & Hines dyno provided some initial figures. Mounted on a box-stock GSX-R750 Suzuki, the Dial-A-Jet kit produced impressive numbers. The stock GSX-R without the kit made 84.1 horsepower at 9500 rpm. With the Dial-A-Jet installed, the Suzuki made 87.8 horsepower at 10,500 rpm, a difference of 3.7 horses.  Peak torque also increased by 1.7 foot/pounds.  At 10,500 rpm, the point at which the stock motor's power drops significantly, the difference between the kit and box-stock machine was 14 horsepower.  Suzuki's GSX-R1100 was next on the agenda, and the numbers were equally impressive. The box-stocker made 12.6 bhp at 10,000 rpm. With a Vance & Hines pipe and a two-step-richer main jet, the optimum jet for power production with that particular pipe, the 1100 produced 118.2 bhp. The Dial-A-Jet was then installed, leaving the V & H header in place. This combination netted 123.7 bhp at 9500 rpm, a jump of 11.1 bhp over the box-stock machine. The testing impressed Vance Hines enough to become distributors of the system.

below Air boot installation of Dial-A-Jet

We then installed the Dial-A-Jet on two other test machines, Yamaha's FZ750 and Honda's Nighthawk S. Installing the kit was relatively simple.  Installation on our FZ was easy due to its carburetor placement.  The cramped quarters of a normal in-line four engine takes more time, however. Installation time ranged from 45 minutes on the FZ to an hour and a half on out Nighthawk S. To install the kit, you need a flat-blade and a screwdriver and wire cutters, along with the supplied cutting tool that cuts a small hole in the air boot. The Yamaha motor is phenomenal in stock form, and we weren't too surprised to find that the FZ with the Dial-A-Jet ran identical times to the stock version. The FZ's rideability, however, was improved with the Dial-A-Jet. Midrange power seemed stronger, and the transition from midrange to top-end was smoother and less abrupt. The Nighthawk S also benefited from the kit. The slight midrange flat spot nearly disappeared, and top-end power was stronger from a seat-of-the-pants point of view. Fuel consumption did increase slightly with the system, however.  Without the Dial-A-Jet, our Nighthawk averaged 42.7 mpg.With the kit installed, the mileage numbers dropped to 40.3 mpg.The Dial-A-Jet system does offer advantages. First, the dyno numbers don't lie, and even though the horsepower gains are near the top of the rev band, the increases themselves are significant. Secondly, the kit offers easy adjustability, a trait that's especially important for those who ride in varying altitudes. The dial, which is located on the face of the mixing chamber, can be turned with a screwdriver to any one of five positions. Turning the dial counterclockwise results in a leaner mixture. A clockwise turn richens the mixture. At higher elevations, the leaner settings worked best. Nearer to sea level, the richer settings were optimum.

Certain machines will benefit more from the kit than others, especially in terms of sheer performance, but the rideability of all machines we sampled improved, and our riders felt the system was a worthwhile addition to the machines.  The Dial-A-jet kit fits more than 230 models at this time."- "Dial-A-Jet" +Products tested by staff - Motorcyclist Magazine"Watch for further updates on our experiences with the Dial-A-Jet. Some of our staff is already using them with great success."- "Dial-A-Jet Fuel Induction - What the Heck is it? ATVConnection.com / SnowConnection.com Magazine April 99

"Our second test took us up in the mountains to an elevation near 7500 feet. With the same internal jetting, our 400EX performed fair with the dial at a neutral position. However, when we turned the dial to full negative (less fuel) the motor performed as good as it did back at 2500 feet. For example, we turned the dial to full rich and the motor did as expected. It ran well in the mid-range then stumbled on the top-end and puffed smoke when we shifted. The new system allowed us to ride with nearly full power all the way to about 10,000 feet. The product comes with a complete guide to help tune your machine for any elevation. To turn the dial all we had to do was remove the seat, making it a much easier chore than actually changing mainjets. This system will also help when jetting for an aftermarket exhaust system as well, and can work with modified motors. The Dial-A-Jet does what it says and more. At $69.95 it beats rejetting every time you change riding locations. We suggest getting their $10 snorkel kit as well if you ride in dusty or sandy conditions. Dial-A-Jets can be used on any single or multi cylinder/carb ATV engine."- "Dial-A-Jet" - Dirt Wheels"At our usual testing altitude of 2500 feet, the biggest improvement we noticed was throttle response. Our stock EX revved up just as quick as if it had a free flowing exhaust system on. The revs hit the limiter noticeably sooner than before. Since the product only effects the main jet, idle was not affected. Out on the test track, we noticed a small increase in mid and top-end power. The makers claim it is about two horsepower gain. At this altitude, turning the dial barely made a difference. An average rider wouldn't notice a thing. Confused? We were, too. That is until we rode our Dial-A-Jet-equipped Raptor. Compared to stock, our Raptor's throttle response is much crisper on the bottom end thanks to adequate fuel atomization and the engine does not feel flat on top. It is like having fuel-injection instead of a carb. Power gains were nice as well. With some airbox mods and the Dial-A-Jet system, we increased power delivery by approximately two horsepower across the powerband, and noticed a significant smoothing out of the fuel curve. we've seen similar results on a 400EX.Many riders never touch the carb�s jets that is okay but those riders are missing out on as much as a 15-percent horsepower gain by leaving the stock jetting untouched. The installation was easy and straight forward. Single carb kits are $70, and twin carb kits are $110. Snorkel kits cost $10 each. Chaz Rice "Dial-A-Jet" - ATV Sport

"Even without turning the adjuster on the Dial-A-Jet, our initial test runs revealed that the Honda was running a bit better. That makes some sense; it was getting more fuel. It still didn't have the solid, even pull of a well-tuned stocker with it�s airbox lid in place, so we cranked the adjuster to position five, full rich.  It ran too rich, so we clicked to number four.  Still not right, but better than the stumbling lean response we had before we installed the Dial-A-Jet. We settled on position two and found ourselves with a crisp running 400EX.  The Dial-A-Jet is the easiest was to adjust jetting that we've tried. It can't replace re-jetting entirely, but it's great for fine tuning. It certainly beats the tedious, trial and error open-carburetor surgery we're used to. Rating:*****." "Dial-A-Jet" - ATV Action

"After installing the Dial-A-Jet, snorkel kit and TPI valve, it was time to see if we could get our coughing Scrambler whipped into top shape.  We went down slightly on our main jet size to help with some of our existing problems and would work with the Dial-A-Jet to work through the rest.  What we found our was amazing. Previously it would have taken us over 20 minutes to adjust the jetting' now it took less than two!  It was simpler and worked better than anything we had ever worked with before. In no time we had our Polaris scrambling around the fields with the crisp throttle response it should have had all along, and on days when the temperature and/or humidity changed, we are able to adjust things with simply little time or effort. Trying out this little device convinced us that we need one on almost every one of our carbureted toys to get the maximum potential and efficiency out of the motor.  The improved fuel economy alone will more than pay for the minimal cost of the kit (MSRP: Dial-A-Jet, $74.95; Snorkel kit, $9.95; TPI Valve, $19.95). This item is perfect for sport or trail enthusiasts alike; everyone with a carbureted ATV has a lot to gain by using a Dial-A-Jet!"- Andrew Smith "Dial-A-Jet" - ATV Illustrated Magazine

"There are more benefits to this technology than just cleaner throttle response. A side benefit is dealing with poor quality fuel problems. More and more pump gasoline is suffering from inconsistent added-in elements like benzene, alcohol and even water. These power restricting materials are constantly "settling in" at the bottom of the carb's float bowl causing varnish and guck. With a Dial-A-Jet constantly drawing from the bottom and purging the float bowl, there's no chance for these elements to build up and cause problems. They simply get sucked into the system, emulsified or converted to burnable fuel. Another benefit of the Dial-A-Jet is fuel economy. Because of the finer, leaner fuel mixture it allows, fuel consumption drops by 10 to 20 percent. Some of this is due to the smaller main-jet sizes allowed with the Dial-A-Jet."Although it looks like nuclear submarine plumbing, the Dial-A-Jet system is simple in design. It is powered by engine vacuum and draws its fuel supply from a fitting on the float bowl. The mixture is controlled by a ratchet-style rotary dial with five air settings. The fuel is delivered to the carb throat through an emulsion nozzle (in the carb's intake throat). Every MXA test rider described the Dial-A-Jet as a "supercharger," because fuel delivery through the nozzle is controlled by engine demand. The greater the load, the more fuel is dumped into the engine. It is not the same as a Power Jet, because the Dial-A-Jet doesn't squirt raw fuel, but instead sprays an emulsified fuel/air mixture that has been atomized for instant burn."- 36/39 Carb Mods How to supercharge your KTM two-stroke Dial-A-Jet" - Motocross Action Magazine

BRACKET

We at MCMOD have experimented with different configurations of the Dial-A-Jet notably mountingand enhancements. Our machines are Buells using Mikuni HSR carburetors. One notable enhancement is the addition of the YOST power tube. We have found that adding a Yost Power Tube to a Dial-A-Jet system creates a synergistic effect; these two products really work in harmony. By adding these multiple fuel circuits will offer the optimum in fuel mist (vaporizes) that can be delivered to the engine. For daily road use, we recommend sock filter or snorkel kit (DJ-510). We have found that the Dial-A-Jet was an easy installation but we ride or Buells and Sportsters on the track and on the road and kept changing from the High-Velocity stack to a tamer air cleaner on our Mikuni HSR carburetors. With the normal installation location of the Dial-A-Jet we found that we had to hold our tongues just right to maneuver to the adjustment dial on the Dial-A-Jet. We like to socialize more than wrench (although some call it lazy) so we took a clue from the way sledders and 4-wheelers where mounting their Dial-A-Jets on the air boot. We knew we had to keep the mounting as close as possible to the carb throat so we designed a very nice bracket. The main thing about this bracket is that it will let you, the builder, mount different external mounted fuel circuits, like the Dial-A-Jet, to work as a jet-able third fuel circuit to the Mikuni HSR carburetor. The unique flat landing at the top of the bracket gives you the ideal location for mounting and operating conditions of one single external jet, located center, or two jets positioned side by side. This bracket on its own is a very well built accessory for the Mikuni carburetor/air cleaner adapter, whether the builder chooses to or not to run external jetting.

Our bracket with Dial-A-Jet installed With S&S velocity stack with air cleaner mount

This bracket is made by Thunder Allee of 6061 solid billet aluminum and replaces all existing stamped out metal brackets and carburetor/air cleaner adapter rings. This bracket makes for a sturdier and solid mount due to the precision fit of having a one piece mounting system. The allen head breather bolts are set up to flush mount in a very unique way that will give a mounting system with superior strength design, and good looks for both the High Performance Builder and Custom Bike stylist. The bracket to carburetor mount is held securely with a standard easy to replace fitted O-ring that works well to reduce vibration and gives a good seal. The backside on each end of the bracket is cut out for vent tube clearance. This gives the builder the option to work with stock air breather vent tubes, or custom makes such as Banjo style fittings that can be vented out in many different directions. The outer face of the bracket is drilled and tapped to adapt the standard HD - C.V. air cleaner bolt pattern. This gives the Custom builders a wide variety of production air cleaners to use. This bracket is also drilled and tapped to fit S&S velocity stacks for the Performance builders.This mounting bracket makes possible the combination of installing external fuel atomizing style jets like the Dial-A-Jet and internal fuel atomizing style jets like the Yost Power Tube to work together for obtaining exceptional engine tuning and maximum performance. Either for the High Performance or Custom builder, the combination of external mounted jets, overall clean appearance and solid mounting applications, this bracket delivers performance and style that any bike builder working with Mikuni HSR carburetors would want to use for total satisfaction. This Mounting Bracket comes in various sizes to fit Harley- Davidson and after market, Big Twin Evo, Twin Cam and Sportster/Buell style motors. Custom size brackets available upon request.The BUELL, SPORTSTER Mounting bracket air intake system support for external jets on the 42mm/45mm MIKUNI HSR carburetors comes with: 

2-STAINLESS ALLEN HEAD BREATHER BOLTS, 1-BILLET ALUMINUM MOUNTING BRACKET WITH O-RING, AND 3-STAINLESS SET SCREWS TO CLOSE OPEN JET HOLES.

**(Kit does not include any jets or air cleaner parts as shown in pictures)**.