By Jason Witzeling

Introduction

"What’s the best pipe for the 250R?” How many times has this question been asked?  If you’ve been anywhere near ATVing for the last 15 years, you’ve likely heard that question posed countless times.  And each time it’s asked, a heated debate can break out.  Since the debut of the TRX250R in 1986, a myriad of different performance exhaust systems have been manufactured, each with the goal of boosting horsepower within a certain range of RPMs.  Some are low end oriented while others are top end screamers, and some even claim to do it all and boost power throughout the entire rpm range.  ATV Source decided to get the truth about some of the most popular aftermarket pipes around by dyno testing them.

Setup

ATV Source was fortunate enough to obtain the services of a Dynojet 200 dyno, owned by Jim Dralle of Rock River Powersports in Jefferson, WI.  Rock River Powersports is a full line Yamaha dealer with a large showroom and an excellent inventory of performance accessories.  Jim was gracious enough to let us monopolize his shop one Friday afternoon. The 250R test mule was strapped to the dyno for over 4 hours one Friday afternoon to take care of the testing.

In order to get a true reading for how each pipe affects engine performance, it was decided to use a nearly stock 250R for the testing.  The test engine configuration consisted of a 1986 stock head and cylinder with a 68mm Wiseco piston (long rod style) bolted to a 1988 lower end with a stock crank.  Fresh fuel and air entered through a Boyesen RAD valve with carbon fiber reeds fed by a K&N filter with an Outerwears filterskin, sans airbox lid.  Carburetion chores were handled by the stock Keihin 34mm PJ.

ATV Source was able to gather 10 of the most popular aftermarket exhaust systems available today.  Baseline horsepower was established using a stock 250R exhaust system.  For the average trail rider and motocrosser, we tested the Curtis Sparks MX, CT Midrange National, LRD Team B, Aaen, Paul Turner Midrange, and FMF Fatty.  For those with the need for serious high end power the CT TT National, FTZ in-frame hi-rev, Paul Turner Hi Rev and Eddie Sanders TRX 5 center mount pipes were run.

Results

Due to an oversight in setting up the dyno software, the RPMs on the X-axis of the graphs are half of what they should be.  For example, on the Sparks graph, peak horsepower occurs at 3300 rpm, which is half of the actual peak rpm.  On each individual dyno chart, the stock curve is in blue and the aftermarket pipe curve is in red.  Torque and horsepower curves for each are also plotted on those individual graphs.  On the multi-pipe comparison graphs, only the horsepower curves are shown.  It should also be noted on the Sparks and Paul Turner Midrange charts that the dip in the powerband can be attributed to an overly rich main jet.  Had the time been taken to fine tune the jetting, the dip would have disappeared.

Since the purpose of this test was not to determine the best available pipe, but rather to simply gather information, no winner will be declared.  That will be left to the reader to interpret the dyno charts and take that information into consideration when purchasing a performance exhaust system for their 250R.  With that said, the Curtis Sparks MX pipe peaked with the highest horsepower and had a very broad powerband, even considering the dip in the upper rpms due to fat jetting.  For motocross and general play riding, the CT Midrange National, Curtis Sparks MX, FMF Fatty and Paul Turner Midrange would all be good choices.  Each has it’s own specific area of strength and each has a broad spread of power.  For high rpm applications like TT and ice racing, the Paul Turner Hi-rev, FTZ in-frame and ESR TRX 5 center mount produce good high rpm power without giving a lightswitch powerband.  The two disappointing surprises were the LRD Team B and CT TT National.  Both produced unimpressive power curves when compared to stock.  All of the dyno charts can be found on the next page.

Dyno Charts for All Pipes

Conclusions

While dyno charts are informative tools, they are still just that, tools.  They do not represent exactly how the engine will respond to real world loads and conditions.  The dynamometer is an excellent tuning tool to use for comparison purposes, but the whole story isn’t known until the engine is used in the field.  It’s also important to note that the horsepower figures generated are only valid for the engine setup used and the exact atmospheric conditions of the day the testing was conducted.  Any change in elevation, air temperature and humidity will affect the performance of the engine.

A final item must also be taken into consideration when evaluating the results of this test.  The test engine was essentially stock, with stock compression and porting.  Changes in both compression and porting will change the horsepower curve of each pipe.  Alterations in port timing and duration will interact differently with each pipe, which is why it is best to use the pipe recommended by a particular engine builder.  For example, just because the LRD Team B produced a lackluster curve on this stock engine, while the Sparks MX built the most horsepower doesn’t necessarily mean that the results will be the same with a given port layout in a modified cylinder.

Results of this test should be used for reference only.  They are, by no means, absolute and exact.  As stated before, atmospheric conditions and porting will change how each pipe reacts and testing in the real world will ultimately reveal the true winner for a given application.

A big thanks to Rock River Power Sports
for helping with these Dyno Runs