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Quieting The Deztaz

About the only real complaint I've had over the past four years about the Dez is the noise level.
To put it simply, the Dez is LOUD!!!
Painfully loud. I wear ear plugs and request that anyone that rides with me wear them too. You can't fix hearing damage, but you sure can prevent it.

I've talked to Neil of ATV Racing in depth about the noise levels and where he feels it's coming from. He's identified three areas of the Dez's powerplant that the noise eminates from:
1) The Mufflers (yeah, yeah, an obvious "duh" on this)
2) The Expansion Chambers
3) The Carb Intakes
Other two stroke Tazcar customers have had the same issues with sound levels, so Neil's done a lot of research and experimenting trying to quiet down the Tazcars.

I'm guessing here, but I'd say that about 50% of the sound is from the mufflers while the other 50% comes from the combination of the expansion chambers and the intakes. So the first place to start is the mufflers!

Neil and ATV Racing have tried a few different muffler setups. They have one unit that looks like a small car muffler - like you see on the side of sprint cars every now and then. The muffler is about 8" wide, 14-15" long and about 4"thick. It has 2" inlet and outlets. It flows well, kills the engine sound some and, as I seem to recall, hurt performance a bit. He's also tried a few different types of individual mufflers, but with not a lot of success. After ATV Racing started putting the automotive engines in the Tazcars, not many two strokes have been sold, so the focus on quieting the cars was lost. I decided to pick up and work from there.

The expansion chambers and the mufflers that come on a two stroke Tazcar are made by Power-Pros. This company makes exhaust systems for a huge number of aftermarket companies. Develop a pipe, send them a prototype and have Power-Pros make it for you. That's what ATV Racing's been doing for years.

The mufflers that come with the system are a standard Power-Pros piece. Pretty simple. 4" diameter, 14" long aluminum tube with a 1.25"inlet on one end and a 2" outlet on the other. Perforated tubing connects the two ends and the packing is placed around the perforated tubing. Straight forward and, as I said, pretty simple. If you require the mufflers to be U.S. Forestry legal, you put a small stainless steel screen under the outlet end. As you can see in the picture on the right, you can see right through these mufflers, and to top it off, the perforated tubing is tapered between the two ends, so they have less packing closer to the outlet. LOUD! I had to do something.

Over the past few years (since four stroke motocross bikes have become popular), the major companies that make exhaust systems for MX bikes have started working towards making high performance exhaust systems that are quieter. They are using the latest technologies, materials and innovations to produce quieter systems, while maintaining or increasing performance. This trend, even though brought on by 4-strokes, has also trickled over to the 2-stroke market too. Sounds to me like the place to look.

Another thing on my side in the quest to silence the Dez is that one of the big gripes about the Honda Pilot (the ATV, not the SUV), when an aftermarket pipe is installed, is the increase in sound levels. A few of the more innovative people I know, that mess with the Pilots, decided to do a bit of experimentation with quieter muffler options. I watched and waited for results.

FMF is a company that's been around since 1973 and enjoys a reputation as one of the leaders in two stroke and now four stroke performance. FMF and the products it puts out are second to none. They've also been one of the companies on the forefront of making our wonderful motorized toys quiet. I run the Q pipe on my woods and desert bikes and love the way they work. Nice, quiet mellow sound, increased power, perfect fit - a damn fine product. Since the guys doing the Pilot mods were using the FMF two stroke Q pipes, I figured it was the place to start.

I've been seeing advertisements for the latest Q pipe. FMF is calling it the 'Turbine Core II Q-Silencer'. It's pretty much a combination of their Turbine Core and their Q-Silencer. U.S. Forestry legal spark arrester, repackable and a claimed 92db. Seems like this one is going to fit the bill.

You can see the outlet end of the turbine piece. It looks like a little bullet with angled fins running around it. It's held in with a screw.

Here's the inside view. You can see the "Turbine Core" and how it's wrapped in silencing material.

The perforated portion of the muffler only goes about 3/4 of the way into the muffler. The remaining part contains the turbine piece.

I called FMF and talked to the tech guys, explaining what I was wanting to do. They felt that the Turbine Core II Q-Silencer would probably work well. The muffler section of the Q is the same across the board for all applications, the difference among the muffler systems is the stinger where it attaches to the expansion chamber. The only issue I had was trying to find one with a shorter stinger. (I guessed wrong).

I found that the mufflers I was looking for were available from Dennis Kirk. I was able to go online and find three of the same application (Yamaha Blaster), so a quick call was made and two days later I had a box full of mufflers sitting at my garage.

The main reason I chose the Blaster mufflers was that when you order online at Dennis Kirk they have a little button that tells how many pieces are in stock. The Blaster's pipes were one of the only that had "Three on hand" and they were one of the more inexpensively priced pieces too. The Turbine Core II Q-silencers started just above $140.00 and went up, so I went with the least expensive that I could find.

Now comes the fun part. I have to make them fit!

The first thing was to make the new mufflers fit in the same place as the original mufflers. I wanted to be able to change between the two "packs" (picture above on left of Power-Pros muffler pack) with as little effort as possible. This meant removing two small bolts from the bottom rubber mount and removing the retaining springs between the end of each expansion chamber and it's muffler. Takes about a minute to do.

As I mentioned above, I choose a pipe for the Yamaha Blaster. Wow, look at the length of that stinger! It's longer than the muffler is, and it's only a 1" inner diameter, while I need a 1.25" inlet. Drats. Fabrication time was upon me. Naturally, I don't have any 1.25" id tubing handy, so I have to roll my own, weld them up and then turn them down in the lathe. Not a big deal, just extra work. I cut the stinger off one of the mufflers, welded the new inlet on and started trying to test fit the muffler. It's too long by about 4". Bummer. This meant I was going to have to modify the body of the muffler and the perforated tube too. When it was all said and done, my first pipe fit nicely. You can see in the picture to the right the three sizes. Top is the stock Q, middle is my modified Q and bottom is the Power-Pro piece.

After I got all three pipes made, I then had to mount them. A completely new mount was fabricated, retaining the rubber bumper that the Power-Pros muffler pod was mounted on.

Test fit

Top view of the mount

Finished view

Another finished view

After doing the muffler exchange, the exhaust note outside the Dez was drastically quieter, but the sound levels inside the Dez hadn't dropped much, if any. The majority of the sound heard inside the driving area comes directly through the three expansion chamber bodies. It's a very sharp, cracking type of sound that is reflected by the bodywork right into the driver's compartment. Once again, a sound that hurts at a level that hurts. Not a good thing.

To combat this problem many of the factories (Such as Honda, with the Pilot) will use a thicker material for the expansion chanmbers or make chambers that are two layers thick or have a quilted type of material that's bonded to the inside of the chamber, etc., etc. - all attempting to either absorb or contain the sound made by each pulse of the exhaust gasses leaving the cylinder. I took the quilting idea and decided to run with it.

The material decided on was header wrapping tape. It's a fiberglass based, two inch wide woven cloth that sort of looks like a light yellow, fine weave burlap. Each expansion chamber took right at 44 feet of the stuff. It's held on with stainless steel ties (similar to zip-ties) and is some itchy stuff to work with. I started at the engine end of each pipe and worked my way back to the stingers, making sure I overlapped each pass at least 50%. When it was all said and done I had three expansion chambers wrapped like mummies that had sort of a "works" appearance like you see on factory race vehicles.

The modifications made a HUGE difference! I can actually sit in the Dez w/o ear plugs and not have my ears hurt. I can even hear the horn now - never been able to before with the car in motion. I can also talk (scream at a lower volume?) to who ever happens to be in the passenger seat. In short, the quieting mods seem to work very well.

One worry I had with these mods was performance changes. I'd been told by one person that they had issues with quieter mufflers:
"I tried an FMF Turbo Core that fit a 500 Polaris two stroke on my old 600 motor and the turbo part was creating back pressure and couldnt get the motor to rev much past 7500. Once we took off the silencer it ran better."
I've seen nothing like this at all. As far as I can tell (with my highly calibrated butt dyno), the setup I'm running now has done nothing to hurt performance and everything to help sound levels. It actually seems like I have better low to mid transition, a more responsive throttle and the engine will rev freely to what ever it wants. I generally don't spin the Dez's engine over about 7800 rpm, but it's good for 8200 - 8500. I don't see the need to stress things if I don't have to.

All in all, I feel this setup is well worth the couple of hours required to do it. The combination of the Turbine Core II Q-Silencer and header insulation tape yeilded a much quieter, very well performing exhaust system on the Dez and I'm pretty sure it's adaptable to just about any two stroke application if you have the time, patience and desire to tackle it.

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