Teryx Exhaust Test Results

[Hunterworks]

Updated 10/10/2008


Back in June I was going to start a exhaust test but had a motorcycle wreck the day I was due to start the test and did not get back on it until three months later due to the injuries. It is now four months later and the test I was going to do is over.

I didn't start this test and spend the $2800.00 plus on the four exhaust just so I could write a article about the test or just to pass on good info. At Hunterworks Inc. we test everything we sell before we will sell it. I did know from the Brute Force 750 that a exhaust on the Teryx would help in performance and just by pulling the exhaust tip which gave it 2.5 HP, gave me even more reason to do the test. At Hunterworks we don't think you should sell any product until you test what works, install it yourself, know you have a good product to sell and to be able to support it technically after the sale.

Yeah I know, get to the test results!! One more thing, you may find these exhaust at a cheaper price than us or maybe you won't but please remember we spent $2800 on exhaust and now we will have no use for three of them and we have a $30,000.00 dyno to make payments on too and most don't. Ok I will quit playing the sympathy card and get to the test. By the way, we have three exhaust for sale at a deep discount only been on a vehicle for one day.

The Test Set-up:

Our base test Teryx had a aftermarket CDI, our carb/air intake kit on it and the stock exhaust tip was removed. Why, because these items are the natural progression most people are making. No need in comparing it to a bone stock unit with no CDI or a jet kit of some sort because I can't imagine anyone spending $700 to $900 on a exhaust first and no need in comparing a aftermarket exhaust to the stock exhaust when removing the tip adds 2.5 HP and that is free HP. Also realize peak HP is not always the best way to judge anything. Look at the dyno charts below and watch how the power drops off differently for each system.

The test was not designed to test brands but styles. I wanted to test a slip-on, a two into one, a two into one and back to two and a true dual system. No matter which brand you buy any particular brand system will work as good as another as long as it is the same style.

We tested each exhaust in two ways, one was a traditional wide open throttle run to red line where you get a peak HP number and then I came up with my dyno test. Hunterworks has a load control on our dyno, that basically means we have a brake on it which can simulate any kind of load. Ours is called a Eddy Current Absorber. The test I came up with was to put the load control on 25% load, start the test at 10 mph and then run it to red line at wide open throttle. The idea was to simulate riding down a trail, rounding a corner and then nailing the throttle.

We were requested to test sound levels as well so we bought a db meter at Radio Shack to test the sound. Realize our results are not meant to match the manufacturers sound levels, they are designed to simply measure whether one system was louder than the other so don't put so much faith in the actual numbers of each system but how each number compares to another. Also a 10db gain means it is twice as loud and 20db gain is four times as loud. We tested each exhaust at 6000 RPM and under load from the same spot.

What We Tested and why:

First test was a Gibson Slip-On. Why? Because Gibson claimed 7HP for this slip on and others were asking me to test it so it seemed as good as any slip-on. Retail $350

Second Test: HMF Swamp Series and XL. Why? I thought the a two into one would be the best performer and HMF has a good system. The XL just adds a quiet core Retail $769

Third Test: Muzzy Dual two into one and back to two. Why? Muzzy has a good reputation for quality systems that perform. $899

Fourth Test: AC Racing True Dual Why? I only knew of a couple true duals for the Teryx and heard bad things about the Three Brothers exhaust. Retail $994

The Tests:

Our base line run with no exhaust tip on the stock system was 32.19 HP peak on normal test and 22.68 HP on the load test with a 6000 RPM db rating of 93.5 db

On the normal run test chart below I added the bone stock Teryx as a comparison what a the CDI, our Carb Kit and the exhaust can do for you Teryx, pretty impressive in my opinion. The gain was 8.55 HP which is a 31% gain over stock and that is at peak HP, a little further down the chart we got a little more about 10HP at higher speeds.

Gibson Slip-On:

At peak we got 32.86 HP on the normal test and 23.42 on the load test which is under a 1 HP gain on either test. The db rating at 6000 PRM was 96.5db which was noticeable louder. Funny part is Gibson advertises a 7 HP gain for this system and for every slip on or full exhaust on any and all UTV applications. I am curious how they got the exact same results with either system on any UTV. The truth is, their numbers are skewed somehow. I e-mailed them to ask how they came up with these exact numbers for all their systems and to tell them my results, guess what? No answer.

My opinion on the Gibson is this: Quality made system, good muffler design and installs in the least amount of time but provides basically no gain over removing the stock tip, therefore Hunterworks will not be selling this slip-on or any other slip-on as we feel the power is made in the pipes not the muffler. Why? Because the stock system has unequalled head pipe lengths and are on the small side when they should be the same tuned length which will take advantage of exhaust pulse timing which aids in keeping the velocity up and the aftermarket head pipes start with small diameter pipe and trend larger as they get to muffler which once again aids in moving the expanding exhaust gas.

AC Racing True Dual Full System:

Update 10/10/08 to this section about the AC. We found out we made a mistake on the loaded test and then retested but not the AC, we only have the normal run. This system won't be sold at Hunterworks so I didn't want to put it back on again for the load test. I know it would not have performed there like the others. My other opinions on this system are below.

This system is the last one I tested. I thought from the beginning this system would perform the worst of the full systems and I was right. Why? When you have a true dual you only have one exhaust pulse every 720 degrees of engine rotation in each pipe which will NOT allow these pulses to push and pull on each other where a two into one gets the exhaust pulses 90 degrees apart then 630 degrees with no exhaust pulse. Peak power was 33.97 HP on the normal test . What you need to notice is the Gibson slip on performed better above 40 MPH than the AC True Dual system did on the normal test. Looking at the chart below notice peak is less than the Muzzy and HMF and it falls off sharply at 40 mph which is where I really thought the true dual would do better than all, I was wrong again. Also notice on the chart where the AC beat the stock system was only between 18 and 30 MPH. Worth $900 plus? Nope!!

The sound level on the AC system at 6000 RPM 98db and 114db under load which was hideously loud.

My opinion: The system I had would not fit right and had to be held on with a welding clamp for the test. If I were going to use this system it would have to be returned for another system or have some replacement parts to make it fit right. There were no heat shields of any type and it really needs them. Hunterworks won't sell this system due to better performing systems, price for what you get, looked kinda cheap and way too loud.

HMF Swamp Series and XL Full System:

The difference between a the Swamp Series and Swamp Series XL is, one muffler is chambered and no packing and one is a straight thru design with packing. We tested the Swamp series which is chambered and has no packing to replace either can have the addition of the quiet core.. I tested with and without the quiet core with this system. With out the quiet core the db ratings are as follows; 92db at 6000 RPM and 102db under load with quiet core it was 92db at 6000 RPM and 98db under load which in my opinion neither set up was much louder than stock with no tip. HMF with NO quiet core peaked at 34.91 HP on the normal test and 24.99 HP on the load test. HMF claims no loss in power and if you looked at peak HP then you might agree but at 35 mph the curves start seperating showing a clear loss using the quiet core over no core with a net loss of about 4 hp at 52 mph. These numbers are less than 1.3 Hp difference in the highest performing Muzzy system on the normal test and less than 2 HP difference on the loaded test.

Install issue: I had to put the front head pipe on my belt sander to knock off a little of the length of the pipe where it went thru the flange that bolts to the engine and goes inside the exhaust port, it hit it before the flange got tight. Easy fix!!!

My opinion of the HMF: Hunterworks will be selling this system. Why? Because this is a good quality full stainless system with no packing to replace, performs basically equally as well as the Muzzy, cost about $150 less than the Muzzy, has the heat shields you need and not as loud. This system is a two into one system. Who would buy this over the Muzzy? The person who does not want to spend the additional money for the Muzzy, wants good performance and does NOT want a loud system. I personally would pass on the quiet core, I really could not hear a lot of difference and especially for the loss in power it caused.

Muzzy Full System:

This system is the overall performance winner. The two into one and back to two works well. Peak power on the normal test was 36.32 HP and 26.77 HP on the loaded test. Both numbers were the best of the bunch but only barely better than the HMF. Muzzy gets the cool factor too with the dual look without being a true dual and it is not overly loud either. The db ratings were 92db at 6000 RPM and 104db under load which is only slightly louder than the HMF single system.

The Muzzy comes with quiet cores and spark arrestors installed, without the the quiet core performance did not improve in either test and it got very load. Also when decelerating I got a lean pop that if you fixed it would mess up your idle mixture. To use this set up would not be recommend, leave the quiet core in along with the spark arrestor screen.

Install issue: The area of the flanges where they bolt to the engine are smooth instead of the pipe sticking thru the flange so installing the exhaust gaskets are a little difficult trying to get them in and lined up. The newest systems from Muzzy will have the pipe sticking thru the flange so it will be a easy install. The new headpipes are a running change in the system and Muzzy won't be able to replace previous headpipes as there is really no need to because one you get it installed, it is on and you shouldn't have issues.

My opinion: Hunterworks will be selling this system Why? The performance and quality are second to none as is the customer service for dealers at Muzzy. I really like this system if we can get the heat under control. I recommend using header wrap on at least the front pipe and replacing your plastic engine cover on the drivers side with a metal one off a Kawasaki 700 which will be available from us. I like the look of the system, the billet mounts and the sound is pretty cool without being overly loud. Who should buy this system? The person who wants the cool dual factor, cool sound, does not mind a little louder than stock and wants the most power you can get.

Muzzy liked our test so much they put a link to this article right on their ad for the exhaust on their site!!

Update 10/10/08 on the Muzzy:I wrapped my front header with header wrap and the heat does seem to be down. I won't really know until I ride some with it like this.

Update 1/7/2012 The metal plate or header wrap is no longer needed on the Muzzy for the Teryx. Muzzy has changed the fitment of the front head pipe.. They have also changed the gasket area, they include the gaskets as well.

Final notes:

Really study the charts below and pay close attention the results from about 35 to 55 mph and you will see some gains that are more than peak power numbers. This is the reason I say peak power numbers are not always the best numbers to look at. Also realize what a chassis dyno measures, it measures how much power reaches the ground.

You will need to re-jet your carb to use any of these exhausts, the jets don't come with the systems and you will have to change the settings on your slide needle and you can't do it with the stock needles. Best bet is to buy a jet kit and our kit cost no more than any other. Jetting with our jet kit will be worked out for you by the time we start selling these systems. Also realize you may have to tinker some with jetting especially in higher elevations and those who change elevations as you ride. Another reason to buy our carb kit will be the added performance it adds with the use of the TPI valves and the lighter diaphragm springs in our kit compared to others.

10/10/08 Jetting Update: On the HMF and Muzzy the idle mixture screw needed to be turned out 3 complete turns unlike our direction with our carb kit for stock systems which is two turns. The Muzzy also required one jet size up. Instead of 144 in front and 146 in rear I used 146 in front and 148 in rear.

We do NOT recommend buying any kind of aftermarket intake with the stock vacuum operated carburetors as they will most likely underperform the stock system with our kit in it. If you think I am just pushing our kit then why don't we just sell the same intakes everyone else is selling? We know they don't work well.

So if you buy your exhaust for your Teryx from Hunterworks you will simply have to decide whether you want the HMF or Muzzy with the largest difference being cost and sound levels. Which system will Hunterworks use on it's Teryx? The Muzzy and the reason is we already bought it, it performs better overall and I don't mind the slight extra sound levels.

Speaking of buying a exhaust, the links below go directly to the two exhaust descriptions on our site.

Teryx HMF Exhaust

Teryx Muzzy Exhaust

Now the charts!!

To see a close up of the Normal run go to the next reply page.




Loaded Chart

[Hunterworks]

Here is the graph of the normal dyno run up close.