First appeared in Race & Rally Magazine, Fall 94
Get ready for changing jet settings quickly and easily. Get ready for having a sled that runs at peak performance all the time. Get ready for…DIAL-A-JET!
How many times have you heard a snowmobiler say, “You should ride my sled when it’s cold outside. You just won’t believe it. It just about pulls your arms off. Boy, does it ever run!” What he has actually said is that his engine is way over jetted the rest of the time. Such rich jetting is the factory’s insurance policy so the engine isn’t going to burn down on the first cold day. And, carburetor jets would certainly be changed to match the prevailing conditions of temperature and altitude much more frequently if it wasn’t so difficult and time consuming.
This is just the situation that the Dial-A-Jet was invented to take care of. With a Dial-A-Jet your sled can run like-its-cold-outside all the time. If that’s the way you want your sled to run, get Dial-A-Jet, because changing the richness of your carbs can now be done in seconds rather than an hour.
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.
Pre-atomized fuel is quite different than the raw, liquid fuel fed in by other carb circuits – which has to be atomized by the air flow into the carb. The Dial-A-Jet pulls in its own air (through small holes in the dial), independent of other air drawn into the carburetor. The fine pre-atomized spray can’t displace the heavier (poorly) atomized spray from the other circuits, so it takes the path of least resistance and fills in the lean mix areas giving you a consistent fuel flow pattern.
There are five manually set positions on the dial, ranging from richer to leaner. Each of the five positions has a corresponding air hole (the bigger the air hole the leaner the mixture) which directly affects the richness of the pre-atomized fuel mixture. This provides quite a range of easy, quick adjustments. Each of the five settings would take care of about 1500 to 2000 feet of altitude. That would take you up to 12,500 feet without having to change jets. When you noticed your engine starting to run rich from the thinner air, you would merely stop and quickly adjust the mixture to the next leaner setting and restore the engine to full power. Each click of the very same dial would also take care of a 15 degree to 20 degree change in temperature.
Adjustments are taken care of in two easy steps. The fuel delivery tube acts as a lock down for the dial. It has a screwdriver slot in its top. It has to be loosened so the dial can be turned with the very same screwdriver. A “+” (richer) indication of the right side, and a “-” (leaner) indication of the left side obviously leads you in the direction you want to go.
A slotted “arrow” in the dial turned straight up between the plus and minus indicates the dial is in the center position. This means there are two more settings richer and two more settings leaner for quick availability. A tiny detente leg in the dial indicates when everything is in proper alignment so the locking screw can be tightened. Each of the five dial settings adjusts the entire range from just above idle to full throttle. Again, the key to it working throughout the entire rpm range is because of the pre-atomized fuel used. Pre-atomized fuel is very light in weight and it will be drawn in at very low rpm under load. You won’t see any fuel drawn through the tube at idle or even when you rev the engine. Only when the engine is under load will the fuel be drawn in. It flows partially because of air flow and partially because of the acoustical level. At idle the position of the fuel in the tube indicates the level of fuel in the float bowl.
The Dial-A-Jet draws its fuel from the bottom (a hole is tapped through the bottom nut) of the carburetor float bowl. This is where the water, alcohol, and other chemicals would normally settle. As water droplets settle, the Dial-A-Jet removes them and injects them into the carb as a shot of hydrogen. This means that the Dial-A-Jet is continuously purging the float bowl of the nasty things which have a tendency to accumulate. It will never allow a glob of water to freeze and form an ice ball that could take off a piston skirt.
The Dial-A-Jet was invented in the mid-seventies by Dennis Dean. Dennis holds well over 100 world motorcycle drag racing records. Also in the mid-seventies he formed Denco Engineering to market motorcycle speed equipment. During this time he developed the Dial-A-Jet concept. He was looking for a quick easy way to adjust his carburetion. He was encountering widely varying conditions in air density, altitude, and temperature as he traveled to different competitive events around the country. That final, critical fine tuning he was looking for was the difference in winning and losing. The newly developed Dial-A-Jet made these very necessary adjustments quick and easy for him.
Dial-A-Jet’s first snowmobile applications were in the winter of 1989-90. It’s exposure over the following three years was very limited, mostly a one-on-one spreading the word. Lonn Peterson (then of Recreational Engineering) sold a few Dial-A-Jets along with his other snowmobile related items. The feed back he received was always very positive. One day Lonn asked the owner of Dial-A-Jet if he wanted to sell the company. He did, and Lonn ended up as the present owner of Dial-A-Jet, (now part of Thunder Products, Inc., 21676 Deep Lake Road, Richmond, MN 56368).
Lonn Peterson’s background in snowmobiling extends back 20 years. That includes being a manufacturer’s rep before his activity in Recreational Engineering. After he took over the project in October of 1993 he immediately began to look to important industry experts for their evaluation of the product. He had been excited about Dial-A-Jet and the fresh feedback told him his impressions were right on track.
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 proven 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.”
Dial-A-Jets are also rapidly building a reputation for curing lean mid-range burn downs. They are load sensing with a built in window of automation at every dial setting. This happens through acoustical (sound) waves which the Dial-A-Jet responds to. A Dial-A-Jet can sense detonation from these shock/sound waves that occur in the carb intake track during detonation (pre-ignition). When this happens it automatically supplies more fuel to reduce the “pinging”. When the engine gets enough fuel, detonation diminishes and the amount of fuel delivered by the Dial-A-Jet is also reduced. It’s hard to explain why it works, but evidence indicates that it surely does.
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.)
Installation and proper setting of a Dial-A-Jet is relatively easy. Its add-on design means you don’t even have to take off the carb. However, it may be easier to remove the carb in some cases. It comes with complete instructions. Typically it takes less than an hour to install.
It is necessary to create a window of range for the Dial-A-Jet to operate within. This means that you’ll probably have to reduce that size of the main jet two or three sizes, and possibly change a needle jet position. Jetting is correct when the engine runs the way you want it to with the dial in the center position. This allows for two settings richer and two settings leaner. When you find the right jet sizes and needle position you are set for the winter. Any other jetting adjustment can be taken care of through the Dial-A-Jet.
If you are using exhaust gas temp gauges it is easy to jet until it is right on target. It is also relatively easy to figure out conventionally. Let’s suppose you set the Dial-A-Jet in the mid-position and go out and try it. You find it too rich. You back off the dial one click and try it again. Better, but still on the rich side. So you turn it to its lowest position and it runs just right. This means you should drop one more main jet size so you can return the dial to its mid-position and restore the plus two/minus two adjustability.
The approach is a bit different for those of you who run at altitude. Here you want your sled to run just fight at parking lot altitude with the dial set at the richest position. This would allow five easy settings (for every 1500 to 2000 feet). As you climb the mountain and the air gets thinner you back it off one click and restore your engine to full power.
Dial-A-Jet works very well on modified engines. Pipes, porting, and raised compression are all fuel flow sensitive. Power jets should not be confused with Dial-A-Jet. Power jets still dump in raw fuel, and only kick in from 7/8 throttle on up. Again, a Dial-A-Jet feeds in pre-atomized fuel from just above idle all the way to the top. The only comparison that could be made is that they both sit on top of the carb.
Savings in jetting time can be visualized by how long it might take to rejet a Vmax-4. Half hour to an hour? With a Dial-A-Jet it can be done in about a minute.
There are probably more sleds out there equipped with a Dial-A-Jet than one would expect. Racers have tried to keep it very quiet, trying to use it as a “secret” tuning weapon. Questions come to Thunder Products on how to install them in air boxes so no one can tell the sled is so equipped.
Riders who would benefit from installing Dial-A-Jets would include: The high altitude rider, the trail rider, and the racer. Put them altogether and that includes just about every snowmobiler we can think of.