You at home may immensely benefit from our humongous 2003 YZ450F exhaust analysis but it must be duly noted: Knuckles bled, bolts stripped, tires wore, dynos worked and two test riders were beat into submission during our evaluation. To bestow concrete and all-encompassing information upon our readers, the crew went to great lengths to collect data. Each exhaust in our test was first inspected, weighed and measured on K&N’s dyno and then caned at Lake Elsinore’s motocross facility. Even though several units came equipped with spark arrestors, we removed them to even out the field because this was predominantly a motocross-only test. Spark arrestor or not, if you live in California, you’ll be restricted to a motocross track anyway because all of these silencers exceed the 96-decibel sound limit. Since motocrossers are never created equal, we gathered two diverse test riders, Jason “High Rev” Webb and Jim “Low-End Torque” Carley, to suss out which systems worked best for a particular riding style. As expected, the two did not always agree and often held opposing opinions.The YZ450F is a unique motorcycle created solely to kick some butt on a motocross track. The machine has even taken some heat for its overbearing, hard-hitting explosion of tire-spinning brawn. Before we embarked on this project, we recognized the target of this analysis wasn’t to unearth an exhaust that built a quicker-revving and harder-hitting power curve, but rather a broader power delivery that enhanced the bike’s ridability. During our track testing we discovered it was possible to build more ponies and still improve the overall power curve. Virtually every exhaust system in the test posted gains somewhere in the power curve, some just shined brighter than others. The dyno curves from a DynoJet rear wheel dynamometer reveal horsepower at 500-rpm intervals and the time between to reach those levels. Our overall grade scale is based strictly from on-track testing. Each aftermarket exhaust was judged off stock, which earned a grade between C+ and B. Comments were based on test rider feedback over the two-day test.Stock Material: Titanium header with stainless mid-pipe, aluminum canister and Ti end-cap Style: Complete system Decibels: 103 Fit: A Weight: 6 lb 12 oz Spark Arrestor: None Overall Grade: Between C+ and B Comments: After testing a plethora of exhaust systems, we realized the stock system is pretty darn good. Not that almost every aftermarket exhaust didn’t produce gains in one place or another, it was just that the stock unit produced a fairly strong and predictable power curve. Although the stock curve is not for everyone, it isn’t overly flawed in any one particular area.AkrapovicMaterial: Full titanium Style: Complete system Price: $659.95 Decibels: 104 Fit: A Weight: 5 lb 12 oz Spark Arrestor: None Overall Rating: A- Comments: Akrapovic isn’t a staple brand in American motocross circles, but the company has made quite a name for itself in the world of streetbikes. This unit was highly praised by both riders and boasted a smoother yet still more powerful curve that came on very early and kept going all the way through. It relieved some of the harsh, aggressive pull through the mid and produced an overall improved delivery over stock. The Akrapovic performed for all levels of riders and was favored as one of the best complete systems of this test.DEPMaterial: Aluminum canister, mild-steel mid-pipe and stainless header Style: Complete system Price: $435.90 Decibels: 103.5 Fit: B, mid-pipe was almost resting on the bottom side of the shock reservoir Weight: 5 lb 6 oz Spark Arrestor: None Overall Rating: B- for low-end riders, B+ for high-end riders Comments: The DEP is another product new to the U.S. market. The DEP received very mixed feedback from our test riders. On one hand, Webb adored the performance because it produced such a usable curve from the midrange and pulled really strong up top. He announced the DEP enhances the execution in the rpm zone where he rides. On the other hand, Carley, who prefers more bottom to mid, was not a fan because he felt the DEP took away from stock down low, where he prefers to ride. This is one instance where riding style and preference really play a part in determining if this system is better or worse than stock.DSP Stainless Slip-OnMaterial: Stainless mid-pipe and canister with aluminum end-cap Style: Slip-on Price: $289.95 Decibels: 103.5 Fit: B, rear bracket can be a pain to hook up Weight: 4 lb 14 oz Spark Arrestor: None Overall Rating: C+ Comments: With its ties to FMF, it was hard to believe the DSP slip-on was not on par with its relatives. The slip-on did produce power gains, though the delivery was not formidable and felt a little ratty. It revs quicker–but that’s not necessarily a good thing with the YZ450F. Some may enjoy that sort of delivery, but both our testers relayed they would probably stick with stock even though the DSP created power in some areas.DSP TitaniumMaterial: Full titanium Style: Complete system Price: $649.95 Decibels: 103.5 Fit: B, rear bracket can be a pain to hook up Weight: 4 lb 12 oz Spark Arrestor: None Overall Rating: B Comments: The DSP is a nice-looking unit and does shave off a tad of weight compared to stock. On the track, the DSP Ti developed some power over stock down low, the mid was a little better and up top it was about the same. Power delivery is very similar to the FMF system but with less gains throughout. The distribution is enhanced but not blatant compared to several other units in this test.Dubach RacingMaterial: Stainless mid-pipe and end-cap with aluminum canister Style: Slip-on Price: $378 Decibels: 102.5 Fit: A Weight: 5 lb 6 oz Spark Arrestor: None Overall Rating: B+ Comments: Dubach is one rider who knows the YZ450F. The Dubach slip-on almost rivaled some of the best complete systems in our test. Dr. D boosted overall performance all across the board. The delivery is more robust than stock yet still smoother and easier to ride. The power is tractable and seemed to work well when the dirt was moist or hard-packed. The Dubach is a value-plus exhaust.FMF Titanium 4 Slip-OnMaterial: Full titanium Style: Slip-on Price: Ti mid-pipe $174.99; Ti muffler $199.99; Ti anodized muffler $224.99 Decibels: 103.5 Fit: B, rear bracket can be troublesome to attach Weight: 3 lb 3 oz Spark Arrestor: None Overall Rating: B+ Comments: The slip-on proved to be one of the best in its class, right there with the Dubach and White Brothers units. The power comes low and pulls into a heady mid. It is aggressive when the throttle is stabbed but obedient when applied with a steady wrist. The top isn’t as good compared to the FMF AMA-Legal, but it is still as good as if not a tad better than stock.FMF Titanium 4Material: Full titanium Style: Complete system Price: Ti PowerBomb header $274.99; Ti mid-pipe $174.99; Ti muffler $199.99; Ti anodized muffler $224.99 Decibels: 103 Fit: B, rear bracket can be troublesome to attach Weight: 4 lb 13 oz Spark Arrestor: None Overall Rating: A- Comments: The difference between the two FMF Ti 4 exhausts lie in the canister length and core diameter, the standard having a shorter can and larger core. Both FMF combinations positioned themselves in the upper quadrant, even though testers split their call to which was better overall. The standard produces more bottom and mid in comparison to stock and created a very potent yet rider-friendly power curve down low. This was one of the favorites for Carley, who preferred more authority down low. Webb enjoyed the output but leaned more toward the FMF AMA-Legal.FMF Titanium 4 AMA-Legal Slip-OnMaterial: Full titanium Style: Slip-on Price: Ti mid-pipe $174.99; Ti muffler $249.99; Ti anodized muffler $274.99 Decibels: 103 Fit: B, rear bracket can be troublesome to attach Weight: 4 lb 4 oz Spark Arrestor: None Overall Rating: B+ Comments: As a slip-on, the gains aren’t as great as with the PowerBomb header, but the rear set is still a nice addition to stock. The AMA-Legal broadens the stock power delivery and is more user-friendly. The FMF AMA-Legal is superior to the standard Ti 4 as it pulls from the mid and into the upper ranks with added vigor. This is another split-decision system that caters to a more aggressive riding style compared to the standard FMF. Of the slip-ons, this ranked among the top four.FMF Titanium 4 AMA-LegalMaterial: Full titanium Style: Complete system Price: Ti PowerBomb header $274.99; Ti mid-pipe $174.99; Ti muffler $249.99; Ti anodized muffler $274.99 Decibels: 102.5 Fit: B, rear bracket can be troublesome to attach Weight: 5 lb 4 oz Spark Arrestor: None Overall Rating: A- Comments: The FMF AMA-Legal is a rock star and emits a nice boost of ponies all around while producing a smooth delivery that still pulls very strong. It doesn’t have the bottom compared to the standard FMF nor the sheer dragster pull of the Jardine, but it accelerates and pulls from corners over stock. Our expert/mid to high-end test rider preferred this setup to the standard FMF.FMF QMaterial: Stainless mid-pipe with aluminum canister and end-cap Style: Slip-on Price: $329.99 Decibels: 100 Fit: B, a two-man job to get rear bracket mounted up Weight: 5 lb 14 oz Spark Arrestor: Yes Overall Rating: C for moto; A- for off-road Comments: Although the Q isn’t intended for moto, we still included it in our test. The Q produces horsepower; it just takes a while to get there. The delivery is down compared to stock but turns the mighty beast into a docile animal. If you were forced to trail ride the YZ450F, which we don’t recommend, this would be the ultimate exhaust.Jardine RT-FourMaterial: Full titanium Style: Complete system Price: $669.95 Decibels: 104 Fit: A Weight: 5 lb 4 oz Spark Arrestor: Yes Overall Rating: A- Comments: Boy, oh boy–if you want a top-fuel dragster, then the Jardine is the hot ticket. This exhaust produced nearly 50 horsepower on the dyno, and you can sure feel the hooves dig in at the track. It makes power from the low bottom and pulls like a stampeding cow as she starts to kick in. This exhaust is fun to ride. But it’s almost too much of a good thing and can prove to be a handful, causing more rider fatigue during a grueling moto. An added note, the Jardine also comes with a sweet heat shield on the header.M4 Ti Slip-OnMaterial: Titanium mid-pipe and canister with aluminum end-cap Style: Slip-on Price: $384 Decibels: 103.5 Fit: A Weight: 4 lb 12 oz Spark Arrestor: Yes Overall Rating: B- Comments: The M4 slip-on differs from the rear section of the M4 full system. The Ti mid-pipe and can is a nice addition to the stock header. The slip-on hits harder and quicker than stock. The rapid power gains are appreciated when soil conditions are superb, but there are times this unit delivers the power in a rough manner and not as smoothly as stock–not that stock is smooth. It tugs modestly stronger up top but just a tad.M4 TiMaterial: Titanium mid-pipe and canister, stainless header and aluminum end-cap Style: Complete system Price: $499 Decibels: 103.5 Fit: A Weight: 6 lb 6 oz Spark Arrestor: Yes Overall Rating: B Comments: The M4 is a stylish-looking all-titanium/stainless system with improvements from the mid to top. Down low it is about the same as stock and a little less than some of the other complete systems. Power gains are there, but the delivery feels rough and harsh, almost as if this system causes the engine to vibrate. There is no defined hit or rush, but the release is more potent than stock. The M4 wasn’t one of the leading full systems, but it’s not a total slug either.Power ProsMaterial: Mild steel with ceramic coating (tested) or stainless Style: Complete system Price: $419.95; stainless $459.95 (not tested) Decibels: 104.5 Fit: B Weight: 6 lb 13 oz Spark Arrestor: None Overall Rating: B- Comments: The Power Pros exhaust is like riding a moped–fun until your friends find out. Believe it or not, it works pretty well, producing a nice bottom and good mid before running into a top very similar to stock. It does go flat a little sooner than stock after peak horsepower. The quandary surrounding the PP is should you remove a titanium, stainless and aluminum exhaust for an all mild-steel ceramic-coated or a complete stainless unit? Power Pros is the only company to use older-school reverse-cone megaphone-style technology–not that that’s a bad thing. The PP is a price-effective replacement, but the quality and craftsmanship are not quite on par with stock or some of the leading aftermarket units.Pro Circuit Ti-4 and T-4Material: Ti-4 is all titanium with an aluminum end-cap; T-4 is stainless with an aluminum canister and end-cap Style: Slip-ons Price: Ti-4 $478; T-4 $378 Decibels: 103 Fit: B+, bracket alignment was slightly off but ours could have been an isolated incident Weight: Ti-4 4 lb 8 oz; T-4 5 lb 4 oz Spark Arrestor: Yes Overall Rating: B Comments: The differences between the two PC setups are solely material. The Ti-4 is a nice addition to the stock Ti header and does save more than half a pound compared to the T-4. The PC adds a little compared to stock, providing an improved jump down low and a meatier midrange. As it shoots to the top, the delivery is a little rough and doesn’t pull as smoothly. It does build power up top, but that’s not exactly what the doctor ordered. The PC is better than stock, although not the best slip-on in our test.Pro Tec Mach 1Material: Stainless mid-pipe and end-cap with aluminum canister Style: Complete system Price: $449.95 Decibels: 105 Fit: A Weight: 7 lb 3 oz Spark Arrestor: Yes Overall Rating: C Comments: The Pro Tec lost some brownie points because the exhaust note is quite loud to the ear and the bike tended to backfire and pop during deceleration. Pro Tec does include a spark arrestor and an adjustable quiet block-off plate, but as a race pipe it can ring some ears. On the track this system is meatier down low and offers a robust surge right before the mid. From that point, the mid holds its ground compared to stock but starts to fall off and doesn’t pull as well up top. This exhaust is more suitable for really tight courses or riders who don’t prefer to ride much past the midrange.White Brothers R4Material: Stainless with aluminum canister and end-cap Style: Slip-on Price: $254.95 (filter included at no charge) Decibels: 103.5 Fit: A Weight: 4 lb 9 oz Spark Arrestor: Yes Overall Rating: B+ Comments: White Brothers’ R4 proved to be another worthy candidate. It created a smoother and broader power delivery, which equated to a more usable and easier-to-ride machine. The unit also boasted improvements in overall output from the mid to the top. This was another favorite among the slip-ons. It didn’t totally alter the stock curve; it just made the YZ better and easier to ride.Yamaha GYT-R Carbon and TitaniumMaterial: Carbon is stainless with carbon-fiber canister with aluminum end-cap; Titanium is full titanium with aluminum end-cap Style: Complete systems Price: Carbon/stainless rear exhaust $399.99; stainless header $125; Titanium rear exhaust $549.99; titanium header $229.99 Decibels: 104.5 Fit: A- Weight: Carbon/stainless 7 lb 3 oz; Titanium 6 lb 3 oz Spark Arrestor: Yes Overall Rating: A- Comments: Although Yamaha offers its GYT-R exhaust in titanium, we were presented with the stainless/carbon-fiber model. Yamaha assured us both units produce identical performance. This system fared well because of its impressive bottom to midrange gains. It builds more ponies down low compared to stock, but it doesn’t jerk the arms as some would suspect. Rather, the delivery is healthy and enhances the bike’s ease of riding. The pull up top parallels stock, but the gains down low created a broader and very usable curve. The delivery is similar to the Dubach unit. Our low-end rider raved about this unit, and our top-end rider liked the overall delivery as well.Yoshimura Tri-OvalMaterial: Full titanium with aluminum end-cap Style: Complete system Price: $745 Decibels: 104.5 Fit: A Weight: 5 lb 8 oz Spark Arrestor: Yes Overall Rating: A- Comments: As usually expected, Yoshimura manufactures one of the best-built and most expensive exhaust in the lot. The performance rivals its looks and earned it very high marks during our test. Power is improved across the board with a broad delivery and smooth, tractable roll-on. The highlight of its curve lies in the mid, but the delivery caters to all levels of riders and styles. This was another unit that made the top-five list. Yosh also builds its systems to accommodate the stock heat shield, which we think is a bonus.Zip-Ty Racing Signature SeriesMaterial: Internally ceramic-coated stainless header and mid-pipe with aluminum canister and end-cap Style: Complete system Price: $470 Decibels: 105 Fit: B, pipe section was a little too close to the clutch cover Weight: 6 lb 2 oz Spark Arrestor: Yes Overall Rating: B Comments: The Zip-Ty exhaust drew a power curve like nothing else in the test. On the dyno, it lost in overall peak horsepower but held its peak longer than any other unit here. On the track, the Zip-Ty, designed and sold by Ty Davis, comes on stronger that stock down low and wants to pull into the midrange. After that, the power holds its own and keeps revving, but the distribution feels flat up top and not as potent in comparison. We can understand how this curve could work for desert/off-road/GP racing, but for a moto bike, it wasn’t one of the class favorites. Like the Pro Tec, it is loud.