Samurai Testing

By: Stephen Bess

A few months of testing has proven the ProTek Samurai 321B engine (first seen here: NeoBuggy’s Samurai First Look) to be a seasoned, and successful warrior.  As promised, this is the follow up, semi-long term report after over 2-gallons of fuel and multiple race outings here in Southern California.

I raced the Samurai in my TLR 8ight 3.0 buggy, and outfitted it with an OS 2090 pipe set.  I also tested with the 2060, which is a pipe ProTek has now released under its own label, but preferred the 2090’s smooth power band that favors low end torque, its exhaust tone and fuel economy.  I ran the 7mm oval carb restrictor and achieved 10-minute pit stops at our smallish test track, and felt no need to choke the engine further with a 6mm or 6.5mm insert.  Those small inserts are popular with racers wringing every last second of run time from the engine, but a 6mm insert creates a narrow tuning window that simply isn’t worth the trouble in my opinion.

Racers have asked me countless questions about the Samurai since I started running it several months ago.  How did the Samurai do?  How does it feel on the track?  What did I eat for dinner yesterday?  Slow down peeps, I’ll get to all (most) of that.

First, the Samurai’s construction—to repeat the tech specs, this engine is essentially an OS-based VZ-B Speed II engine in a XZ-B case, which means it’s a short stroke (16.6mm bore, 16.0mm stroke).  Like the previous gen VZ Speed II, its DLC-coated crankshaft is the crown jewel of this assembly, complete with orange epoxy ramping, a drilled and lightened crank, and a tungsten counter weight slug.  All told, it’s the engine AMain’s Kendall Bennett and his team designed as their “dream custom built engine.”  The short-stroke design allows the engine to scream at mid and high RPM, producing a distinctive and unforgettable exhaust wail on long straightaways.

Break-in went well, as expected, and I used a heat cycle method that has strangely filtered its way through the intewebz over the years as the “Bess Method.”  Look it up on RC Tech in the Nitro Engines section to see how I break-in engines, or check out Marty Korn’s break in article for this specific engine here: AMain’s Marty Korn Break In Article

After break-in, it was off to the races with OS P3 plugs, the 2090 pipe and smooth header (though I briefly used an OS square header from a 2050 until the smooth header arrived), and Byron’s 30% Worlds Blend race fuel.  Using this combination for the duration of my testing, the Samurai ran like a Swiss watch.  Reliable, buttery smooth power from low RPM to its 40,000 RPM redline.  I did not experience a single flame-out, nor did the engine have any durability issues.  Once the tight mechanical pinch was broken at top dead center, the engine began running to its full potential—and unlike urban legend may suggest, OS-based engines do run their best when you can turn the flywheel over with only a smooth “thump” at TDC.  The Samurai runs its best once that mechanical pinch is gone, and it should continue to provide reliable power well into or beyond the 6+ gallon territory.  My test engine is not there yet, but other VZ-Bs have reached that point regularly.

The Samurai made its first "big race" debut at a JBRL nitro race at Pro-Line's awesome test track in Banning, CA.
The Samurai made its first race debut at a JBRL nitro race at Pro-Line’s awesome test track in Banning, CA.

I set up a TLR clutch with 2 aluminum shoes and 2 fiber shoes, with green and black springs respectively.  The Samurai’s power delivery is classic VZ-B Speed II style, with a powerful but controllable low-end, a strong power ramp through mid-range, and explosive top end speed.  I would run this as a Truggy engine if needed, but to me 1/8-buggy remains the Samurai’s ideal fit.  Temps ranged anywhere from the low 200’s up to 250’s, depending upon ambient temperatures—and we had some scorching days during testing.  Like all nitro buggy engines, the Samurai runs its best when tuned to performance, not temperature.  It was not difficult to attain a steady idle and clean acceleration with only slight tuning of the low speed needle and idle screw.  I set the mid-range spray bar flush to 2-o’clock and never touched it again.

I did not blow a single P3 plug during testing, which surprised me due to the plug’s thin wire element and how hard I race this engine on “set to kill” mode.  I disassembled the Samurai after each week of racing (often 2 outings per week) to clean the piston head with 0000 steel wool and to inspect the parts for wear.  Based upon previous experience, the DLC coated crank will be good for at least 2 rebuilds before the pin begins to wear.  This is beyond excellent durability and makes the DLC coating price increase worth it.

Pro-Line's test track in the background--the ideal track to let the Samurai stretch its legs.

Pro-Line’s test track in the background–the ideal track to let the Samurai stretch its legs.

The Samurai isn’t the most powerful engine on the market, but it’s one of the smoothest and most controllable engines currently available for 1/8-scale buggy.  If you’re the type of guy who has to have the biggest, most badass engine at the track, the Samurai isn’t it.  Racers who appreciate consistent laps, consistent tuning and consistent fuel mileage upward of 9 to 10-minutes will find their way to this engine.  It’s not perfect, but for a nitro engine, there’s little to nitpick.  Perhaps a few extra carb restrictors in the box would be nice.  Priced at $399, you’ll be challenged to find a higher quality, better performing engine for less.

Check out that exhaust gasket before it was replaced; that's 2+ gallons of wear and tear.  Note: this is not the gasket supplied by ProTek, it was a cheap substitute.
Check out that exhaust gasket before it was replaced; that’s 2+ gallons of wear and tear. Note: my early production test engine arrived without a gasket, so this mangled one was a cheaper substitute.