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If you are serious about squeezing top performance out of your snowmobile, then one tool you should have is the RacePak Avenger system by Exhaust Gas Technologies, Inc.

The RacePak systems come in several models from a single exhaust gas temperature gauge (EGT) to triple EGT gauges with multiple inputs for rpm, temperature and other analog sensors. The Avenger systems have a digital numerical display and come in three main models: Avenger I, II and III. Prices range from a MSRP of $314 for a basic Avenger I (p/n EGT0100) up to $927 for a top-of-the-line Avenger III "Gold" (p/n EGT0106). The difference in models and price is how many display windows and inputs the unit has. For any serious tuning, there is no choice but to get the Avenger III. Even if you have a two cylinder machine, the III makes the most sense because you can display RPM, EGT1 and EGT2 all at the same time. If you try and save a few dollars by getting the Avenger II, you'll only be able to see two displays at a time. (Changing displays will require reaching to the Avenger unit, or installing a handlebar mounted switch designed to plug into the Avenger unit. Neither are real convenient when you are bouncing down the trail.) At that, the Avenger III is not that much more in cost than the Avenger II, so it's worth the initial investment to go right to the top setup.

You can purchase just the Avenger instrument itself and all input probes separately, or there are packaged levels available. The base package "Avenger III Red Kit" includes three EGT probes, one water temperature probe, a remote switch, an e-clip shim kit and the Avenger instrument itself. With this kit you will be able to display and record engine rpm, three EGT values, water temperature and elapsed recording time. The Avenger will also store the maximum value for each of these inputs since the instrument was last powered on. You can recall the maximum values at any time by pressing the "max" button. Moving up to the "Gold" kit provides the addition of an alarm light and a second rpm sensor (for the jack shaft). With the "Gold" kit you have the added capability to display and record jack shaft rpm, clutch ratio, jack shaft revolutions and MPH. (Mph being calculated from jack shaft rpm and a "factor" that you program in, more on this later.)

If you plan on using the Avenger on a race machine, the one additional accessory you should have is the battery charger. The Avenger comes with a non-user replaceable internal battery. Normally, when connected to the sled, the sled's electrical system runs the Avenger. However, when you shut the sled off, the battery takes over and keeps the unit powered for a user definable period of time. On a trail sled, the batteries are constantly being charged while the

Photo 1

machine is running, but on a race machine, you'll find yourself using it long after the engine has been shut off. Eventually, the batteries will run down and the unit will only function when the engine is on. A race machine does not run long enough to fully charge the batteries. Use the battery charger to charge the instrument the day before a race.

The Avenger not only displays all the data in real time, it can also record it. It can record up to 25 seconds of information at .2 second intervals. This data can then be "played back" by stepping through the data with buttons on the instrument.

Installation of the Instrument:

Photo 2	Photo 3

Photo 1 shows the Avenger III installed on the handlebars of a '97 Ski-Doo Mach 1 set up for asphalt drag racing. The data collected by the Avenger system is invaluable for engine and clutch tuning. Installation of the Avenger III on a '98 Ski-Doo MXZ 670 and on a '00 Ski-Doo MXZ 700 are show in photos 2 & 3. These installations are typical of all makes of sleds. Photo 4 shows the numerical display of the Avenger instrument. The large display is easy to read at a glance at any speed whether you are on the trail or the race track.

Photo 4

When you pick a location to install the instrument, you should consider exposure to the weather, exposure to damage and theft, and interference with the cowl and/or handlebars. If you mount it on the cowl, you will have to have access for the wires. There will be holes to drill for the mounting plates as well. Some people are squeamish about drilling holes in their cowl. For those of you like that, the handlebar installation may be the solution.

The "Gold" kit comes with a remote thumb switch to operate the sensor display. When ordering the kit, you'll be asked if you want the "short" or the "long" thumb switch setup. The "long" kit includes a wire harness long enough to mount the switch on the handlebars and run the wire down through the engine compartment and back up to the dash on the cowl. The "short" one only has an 18" long harness. Since you cannot cut the long wire to make a short one, you need to decide where you want to mount it before you get it, or get the long wire and coil up any excess wire somewhere out of the way. The unit has mounting hardware to clamp to a 7/8" diameter bar (standard size of most handlebars) or it can be mounted to a flat surface.

The instrument itself is sealed and is weatherproof. However, on my trail sleds I've always mounted it to the cowl, under the windshield. This limits exposure to rain and snow as well as keeping it discrete. No sense in advertising it by having it sticking up off your handlebars in the hotel parking lot!

The unit is powered from the sled's electrical system.

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It has an inline fuse to protect the instrument. There are 2 wires: red & black. The red should be connected to the lighting coil, the black to engine ground.

The EGT and water temp probes plug into the back of the Avenger in sockets labeled "EGT1", "EGT2", "EGT3" and "EGT4".

The remote switch and "2^nd RPM" plugs connect in the back and are labeled as well.

Photo 5 shows the back of an Avenger III with power, remote switch, 2^nd RPM sensor and 4 temperature sensors plugged in.

Installation of the Jack Shaft Sensor

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The jack shaft sensor is an aluminum split ring with a magnet inside of it. It is clamped to the jack shaft and a pickup sensor is installed within 1/8" of the ring. See photo 6 for installation as done on a '97 Mach 1. Each time the jack shaft revolves, the pickup senses the magnet and sends an electrical pulse to the Avenger instrument.

Installation of the EGT probes

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Here is a tip; when you purchase your kit, you will have a choice of clamp on or weld on style EGT probes. Weld on fittings will work the best and last the longest. Also, when buying the kit, order some caps for the weld on fittings. This way if you ever remove the probes, you can just screw a cap on the fitting and it's sealed. Photo 7 shows the probes installed on a '97 Mach 1. Photo 8 shows two probes installed on a '98 MXZ 670. Photo 9 shows them installed on a '00 MXZ 700. In each case, take note of clearance around the pipe for installation and removal of the fitting and for vibration or interference while in use. Also make sure the fitting isn't blocking access to any of the hardware for the pipe flanges or variable exhaust valves (if your sled is so equipped).

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Make sure when you route the wires that they are not chaffing on anything. Measure twice, cut once !!!!!!!

Installation of the Water Temperature Probe

The water temperature fitting comes with a 1/8" male pipe thread fitting. This should screw directly into the fitting that your current temperature probe is installed in. See photo 10 for an example of this on a '97 Mach 1.

Photo 10

With all the probe wires, avoid sharp bends, hot surfaces and sharp edges. Chaffing wires won't last long. If you are installing your Avenger on the cowl, CAREFULLY measure the length of wire provided on the probes to where you will install the Avenger BEFORE drilling holes to install the instrument. Generally, there should be sufficient wire length on the probes to reach the front of the cowl. However, this may vary by model. You'll have to play with the location of the Avenger and routing of the wiring.

The temperature probes are factory calibrated to be accurate using the length of wire provided. DO NOT cut the wire length on any of the probes.

This is where it gets a little confusing for the first time user. When you first set up your Avenger, there are some parameters that need to be input. When the unit is powered up, press the "setup" button on the left side of the unit. You will be prompted through several setup steps. The number of steps varies based on how many optional inputs you have. Use the "clear" and "max" buttons on the right side to change values up or down.

An Avenger with the "Gold" kit accessory package will prompt for the information shown in the following table. Take note that the LCD display only displays three digits. Therefore when working with RPM and EGT, the display is showing the thousands, hundreds and tens values. For example, on RPM1's display, 9500 rpm will appear as "950". On an EGT display a temperature of 1320 degrees will be displayed as "132". However, water temperature of 205 degrees will be display as "205". Don't' let this confuse you!

The Avenger has up to 10 display "sets". Each display set is user programmable. A "set" consists of whatever three values you want to display at one time. For example, setting the instrument to display "EGT1, EGT2, EGT3" is a "display set". By pressing the "display" button on the side of the unit, it would then display whatever the user has defined as "set 2", and so on up to 10 sets.

The data types that can be displayed with the "Gold" kit are:

After setting the alarm limits, the instrument will start to cycle through the display setups.

It will start with display set 1 and the left window will show "d1". There are three things to display. The center display shows which LED window you are setting up. "L1" is LED1 or the left display, "L2" is LED2 or the center display, "L3" is LED 3 or the right display. So the setup program cycles through:

At the top of each window the "data type" code letters will cycle as you press the "clear" and "max" buttons on the right side of the instrument. When you are done programming your display sets, press the "replay" button to go to the next step of the setup. You do not have to have 10 display sets. Typical display sets used are:

After doing the display sets, there are a few more prompts:

But wait, that's not all!!!!! There is also an "Advanced Setup"

In advanced setup there is one value that you may want to change. It has to do with data recording. The default setup is that recording starts when you press the record button. However, you can set a record "threshold". That is, you can set an rpm at which recording will begin. By doing this, after you press the record button, recording will not begin until RPM1 exceeds the record threshold. I use this on my asphalt drag sled to get a more consistent playback starting point to correlate all my data. I set the record threshold to 6500 rpm. I usually run my engagement speeds between 4800-5800. After I roll through the water box, heat and clean the track, I'll press the record button. Then I'll bump up into the stage beams. When I leave the start, recording always starts when the engine hits 6500 rpm. That way when I record my data onto paper after the run, my charts and data sets all start at 6500 rpm, AND most importantly, the recording elapsed time always starts at zero. Now I can correlate my elapsed time and miles per hour from the tracks timing system to my data. I know from the race tracks timing slip that it takes me 1.57 seconds to break the 60ft beam, I can then go back to my Avenger data and see exactly what the clutch ratio was between 0 and 1.6 seconds to see what my clutching is doing in that first 60 feet. Same with the 1/8 and 1/4 mile ET and MPH. Otherwise, if recording started with I pushed the record button. I would have a difficult time trying to compare data from any two runs because I would not be able to lock down to the nearest .2 seconds when my sled actually started moving. So using the record threshold RPM gives the same starting point for recording all of the time.

Now you are all programmed? what do you do with this powerful tool??? Well this instrument is invaluable for clutch tuning; probably more valuable for that than it is for carburation. After all, the actual exhaust temperature as reported by this gauge is secondary to proper evaluation of the spark plug tip color and the piston wash. You don't' need the Avenger to read your plugs. However, without the clutch ratio data, how do you really know what your clutches are doing????

Stay tuned for the next installment of this story. I will provide a variety of setup sheets you can use to create a log book for racing, including spreadsheet templates that you can use to crunch all the data coming off your Avenger. There is a "data download" option for the Avenger III that will allow you to dump your recorded data onto a laptop computer. The software is very nice for storing, retrieving and analyzing, BUT it costs $450 or so and requires a Pentium class 500mhz computer. I don't know about most of you but I can buy a lot of paper and pens for that much money. I have developed a form that I use to "record" data from the instrument after each run. After the race when I get home, I punch it into a spreadsheet I made up and it automatically builds the graphs for me of elapsed time vs EGT, elapsed time vs mph, and elapsed time vs clutch ratio. I have several other spreadsheet templates that I've been using and I think you will find them very handy for keeping your race setup records, or you can modify them for your own use.

For more information on the RacePak System, contact EGT:

1-800-348-4678
1-714-997-5360 (fax)