400EX Pipe Test

We've done exhaust-system mods before, removing a stocker unit for a fancier, more powerful aftermarket pipe. But we'd never done a huge exhaust system test with the same machine, using close to 20 different setups.
   Bolting on a silencer is one thing, but bolting on complete systems — each with their own unique design features — can become grueling. Tests like these can get really ugly when you mix in radar runs, seat time, dyno time and uncontrollable forces like weather, mechanical problems, and more to each specific test.
   We chose the Honda 400EX as our test bike. Why? Because it was so popular, at the time. That was then, this is now. When we started this shootout, the 660R Raptor hadn't even been released yet!
   But that doesn't matter now. The 400EX is still the most popular high-performance quad out there. And just about every aftermarket exhaust manufacturer has some type of product for this ATV. Above all, exhaust systems seemed to be the most common product available. Exhaust systems for this machine were so numerous that the most frequent question we'd get from our readers was, "Which is the best 400EX pipe?" or "Which 400EX pipe should I run?"
   We've been working on this story and trying to find answers to those questions for more than seven months now. Seriously! In fact, during that time frame, we've managed to melt one silencer to its header pipe — someone forgot to use anti-seize — put the test on hold three times and had another magazine publish its own 400EX silencer "shootout." It truly is a long story, one we don't want to bore you with. The worst part about the whole thing is you may find the results disappointing.

In The Beginning…
Everything started out rosy! We had all the exhaust systems (some complete with header pipes, while others consisted of a silencer alone), and a finely tuned Honda 400EX. It was simple, we started by testing the stock exhaust. We did our radar runs and our seat-of-the-pants "feel" laps on our MX test track, we even weighed each unit. Next, we bolted on pipes and silencers and ran the 400EX that way. We were conscious to examine the machine and its parts before each test. This included replacing those copper-colored gaskets each time we added a new header pipe, and checking the oil, etc.
   We also tried to go with the stock jetting when we could, or if the pipe manufacturer didn't recommend a change. You could spend a century changing the jetting for this many pipes, trying to find the right setup. If the pipe manufacturer did send jetting guidelines or requests, we made them. We even tried the test with the stock 148 main jet as well as a 155 main jet. And for good reason.    
   For example, Curtis Sparks suggested we use new exhaust gaskets, anti-seize on the header bolts and at the header pipe-silencer junction, and a rerouting of the clutch cable before riding. Big Gun, on the other hand, said to swap the pilot jet for a 42, increase the size of the main jet to a range of 155 to 158 and lower the clip on the needle one position, remove the airbox lid and add a better air filter.
   Now, you can understand the difficulty with testing so many exhaust systems. And we are not just picking on these companies; each manufacturer's suggested setup was different. Even some of the silencer-only setups (Ritter) requested we make jetting changes, while others (SuperTrapp) did not.
   After we had tested almost every pipe, including recording radar runs, we honestly couldn't feel that much of a difference in our seat-of-the-pants riding time. Sure some of these pipes were louder than stock and seemed to provide more torque and power over the stock system, but from one system to another — including bolt-on silencers — we couldn't really "feel" a difference.
   The radar numbers backed us up on that. We used our Stalker radar system with acceleration testing software. Sure, there were minute differences, but nothing shocking. There was no drastic speed horsepower differences between the competitor pipes.
   Finally, we decided the best way to test these pipes was to run them on a dynomometer. And since there are no ATV dynos near us, we bought our own Dynojet Research dyno.

The Dyno Difference
Getting dyno numbers is certainly not the only way to test performance projects. In fact, we often prefer to get more real results; you know, actual riding reports, on the dirt, etc.
   But for comparing power-modification products that are very similar, a dyno is a great way to get real comparison results. You know we swear by our radar gun. But for testing these products, which, on the dirt, provided little difference, the radar gun didn't do it.
   Mike Cory — Dynojet research and development — flew to Minnesota to help us on dyno use. To ensure we wouldn't have any more delays, we also had Honda hook us up with a new 400EX.
   For the dyno runs, we based the proper jetting on the correct air-to-fuel ratios — measured with a special Dynojet sensor that inserts into the silencer — and left the stock airbox lid in place.
   After properly breaking in the Honda, we finally got the test under way. We could finally see the light at the end of the tunnel. What took more than six months for us to do, this dyno took care of in two days. Wow! (Note: Dynojet jets are different from other types. They are shaped differently, and measured different than other jets.)

Advantage Performance: Had individual header pipes, a two-into-one design. This was a tad bit stressful installing, but nothing to get overworked about. This pipe looks cool, and is similar to the Duncan exhaust, minus the stickers.    During our dyno testing, this pipe showed improvements in mid-range and top-end power. At the top of the power curve, the DMC was better than stock by about two horses.
	Arrow Special Parts: This is Arrow's first ATV off-road silencer. It has had success in the street bike segment of the market. We found this system at the Indy Dealer Expo; we weren't able to ride test it.    On the dyno, the Arrow muffler required a bump up from a 148 to a Dynojet 150 main. It too produced better low-end gains, but very minor top-end improvements.
Big Gun Exhaust: This system fit like a glove, and it is also one of the most attractive. It sounded rather loud, but loud in a cool way! Felt powerful and torquey, but so did a lot of these systems.    The Big Gun exhaust didn't add significant increase at the top of the hp curve, but it did show pleasant gains versus the stock system in the midrange. Our jetting was right on, showing an air-fuel mix at roughly 12.8 to 1.
	Curtis Sparks Racing: The fit of the header pipe clamps was somewhat difficult. A little wiggle here and a pipe angle there and presto, it fit! This pipe felt strong throughtout the powerband. Screwed up the first pipe when we mistakenly forgot to use anti-seize on the pipe-silencer junction. We used the stock airbox lid and CDI box.    This exhaust system provided the biggest gains of any pipe in the shootout, barely edging the White Brothers system for the honor. With a Dynojet 142 main, this pipe had good gains throughout the power curve, including top-end increases. It was definitely the most impressive of the entire test.
DG Performance: This bolt-on silencer isn't light, but it's still lighter than the stocker. Rather loud, but can, like many of these systems, be set up with a quiet core and spark arrestor. Seemed to produce a solid four-stroke pull.    The DG system, with a Dynojet 138 main jet, was better than the stock system in both the low end and midrange, but dropped below stock at the max power level. Its hp numbers did surpass the stocker once the speeds hit close to 50 mph.
	Duncan Racing International: The Double Barrell exhaust itself, it looks wicked and we liked the sound of it, had a deceiving feel to it. One rider called it a "flat" feel, but its radar numbers proved that belief wrong, as it performed similar to the Sparks setup.    Using a 140 main jet, the Duncan setup really shines at the top of the power curve and when speeds surpass 35 mph. But it also showed adequate gains in the midrange. Overall, a good performer with stylish looks.
FMF Racing: We chose to test the PowerCore IV-2 silencer. First off, it was simple to install. It also has a nice slender, sleek appearance and a quality seat-of-the pants feel. Peformed similarly to other pipes in the radar runs.    For just a bolt-on silencer, we were impressed with the FMF pipe's numbers. Showed a steady 1.5 to two horsepower increase from bottom to top. The two FMF silencers produced similar results on the dyno using Dynojet 142 main jet. The only significant difference in these two pipes was their sound, with the PowerCore IV-2 being quieter. We probably could have gone leaner with these pipes, but they both showed full-range gains.
	HMF Engineering: We just discovered this silencer at the Indianapolis Dealer Expo in February. We weren't able to do a seat-of-the-pants feel, but did dyno it.    We inserted a 148 size Dynojet main jet. (This jet is different than the stock 148 jet. It has a different taper and subsequently creates a different way of measuring, etc.) It produced a nice gain on the bottom end for horsepower and torque. On the top end, the gains were quite small.
LRD: The header pipe was a little tight — without removing the oil cooler — when it came to installation and removal. But the sound it resonated was on the milder side. Its radar numbers were a close match to the Curtis Sparks setup. Nice job on the shipping and packaging.    Produced impressive power gains on the dyno with a size 138 main jet from Dynojet. At low- and mid-range speeds the exhaust showed improvements. It then leveled off prior to reaching peak hp, only to soar past the stock system as speeds hit 35 mph or more.
	Powroll: Definitely not the prettiest pipe of the bunch, but effective nonetheless. Came with a new clutch cable to help fit properly.    Performed similar to the LRD system. A Dynojet 144 main jet was installed. The Powroll setup provides adequate low- and mid-range improvements. At about 40 mph, the Powroll system trails the stock setup in horsepower numbers. Once the speeds exceed 46 mph, however, the Powroll unit really starts to shine, showing good gains over the stocker.
Pro Circuit: The T-4 system has an attractively round, yet slender look. Our ride time, with this exhaust system installed, didn't supply us with any obvious improvements. And the radar numbers ranked it with some of the other pipes.    On the dyno, however, we were able to see a difference. The horsepower gains, using a Dynojet 138 main jet, were good, but nothing overwhelming. Did exceed the stocker throughout the entire power curve.
	Ritter Cycle Racing: The RCR bolt-on silencer had to be banged and pushed in order to fit the mounting hole to the fitting on the frame. Oddest looking of all the pipes. The ride "feel" was better than expected, yet not overly impressive. Produced a different type of sound, something close to the stock exhaust.    On the dyno, this pipe produced an ear-deafening, high-pitch growl. Even with all that noise, the pipe didn't really improve the 400EX's numbers over the stock system, except at peak horsepower, showing close to a one hp increase. The down-turned silencer cap may be a bit too restrictive.
SuperTrapp: Installation of this good-looking silencer was a snap, despite having to choose how many discs to use. We used 12 discs, which produced a nice throaty, but non-annoying, sound.    Good solid "feel." It still needed to go a bit leaner. Maybe removing the end cap — which would eliminate the spark arrestor functions — is the answer. We used a Dynojet 138-sized main jet and saw fair increases in the entire range. At around 25 mph, the SuperTrapp provided its best increase, offering three additional horses.
	TC Racing: TC's setup is a silencer that bolts on to a shortened stock head pipe. In order to fit the system on your ATV, you need to cut about five inches off the rear of the stock head pipe, and drill a hole in your frame to mount TC's modified SuperTrapp silencer. Looks and sounds nothing like a SuperTrapp. Short, almost hidden appearance. Very loud system built for racers. It did include discs for a quieter approach.    On the dyno, using Dynojet's 144-sized main jet, the TC system had the same peak hp as stock. This exhaust did supply relatively nice gains as the speeds surpassed 45 mph. This system is about three horses better in the mid-20s to the mid-30s speed range.
Trinity Racing: This pipe was rushed out to us, and we're thankful we received it. It was a snap to bolt-on, fitting almost perfectly. The pipe did produce a loud growl, yet of the good kind. And it felt strong, too.    It Performed well on the dyno. Biggest gains — near two hp — can be found in the mid range and at high speeds. Relatively nice gains were found throughout the curve.
	White Brothers: Installing the White Brothers E-series exhaust system was easy. Here's another one of those mufflers with discs. We went with 13 on this system. The WB setup "sounded" quieter than most of the units we tested. In fact, our test riders voted the White Brothers as one of their favorite systems because of its ease of installation, good packaging, softer sound and consistent power supply.    The dyno run backed up those beliefs. This system, using a 142-sized main jet from Dynojet — produced impressive hp gains everywhere in the power curve. Scores big at peak horsepower and when speeds exceed 40 mph. Easily one of the best, along with the Sparks unit. WB also makes its R4 exhaust silencer and a different version of the E-Series exhaust for the 400EX.
Yoshimura: This pipe was race tested! One of our test riders rode a stock 400EX (aside from this exhaust, handlebars, kill switch, nerfs and tires and wheels) in a local motocross and finished second. Installation wasn't easy, as the headers touch the oil cooler. Provides easy-to-use power. One of the lighter weight pipes.    With a Dynojet 138 main jet installed, had horsepower increases of about one to 1.5 near peak and beyond, respectively. Consistently had somewhat better hp numbers over the stock system.

What Do We Recommend?
If you know you want power gains at a certain point in the curve — low, med. or top — use our dyno charts to find just the right pipe. However, if things like price point, weight, overall feel and looks appeal to you, then you have to make your own choice. We see nothing wrong with using the stock system, but we also appreciate simple mods.
   If it were up to us, we'd select the most affordable exhaust system (call for pricing) that looks good, and performs better than stock.