Smokey Yunick

An engine dynamometer, not a chassis dynamometer, is the proper research tool. Smokey Yunick sought answers for questions no one thought to ask and he outsmarted and outran the best through his own research, on his own nickel. The innovations he came up with are often now the accepted standard like reverse flow cooling, longer connecting rods, raised deck blocks,  28" standard for airflow testing, and many others. Many of the questions he asked were answered in thousands of hours of testing on his dynamometer at "The Best Damn Garage in Town".

Whether it was Smokey's water brake dyno or his Spintron machine the engine development was always done directly on the engine. You are looking for that "unfair advantage" that will give you the power to win. We have, for the most part, always relied on actual riding and racing to develop our products. This is where the art comes in because single-minded focus on hp numbers on dynos and "dyno charts" does not guarantee results at the track. You have to deal with the total system running in the real world, be it at the track or on the road.

The difficulty comes in where, at RB Racing, we have to deal with high horsepower turbos that have such an extreme performance envelope that riding becomes more and more dangerous and less and less amusing (to the authorities) as time goes by. In the late 1980's we did over 5,000 miles of street testing on our Suzuki turbos with many runs over 200 mph. The bikes were very succesful at Bonneville, El Mirage, and umpteen dyno contests due to all the testing and never an engine failure. How we stayed out of jail is a mystery.

It's better to do engine development on an engine dyno and use all of your experience to tailor that development based on your experience in actual real world, be it the Bonneville Salt Flats on simply wound out through the gears in the middle of nowhere racing yourself or the unfortunate fool that decides to take you on.

Ask the Right Question

What is the Right Question ?

Is an engine that produces 135 hp is better than an engine that produces 125 hp?..Well maybe it is and maybe it isn't. What is the definition of horsepower anyway? The common definition is HP = (Torque x RPM) / 5252. Everyone is so enamored of peak horsepower these days that they will trailer their hot rodded V-Twin from dyno contest to dyno contest searching for bragging rights as to who has the most peak horsepower.

We hate to burst their ego-filled bubble, but in the real world it's the rate of acceleration that wins races, not peak horsepower. Torque is the most important element of the equation and if you can't produce torque in the lower rpm ranges it will take forever to get to the upper rpm ranges where the dyno junkies worship the God of peak horsepower. Every time you grab the next gear your rpms fall and you have to climb that elusive mountain to get back to those so damn important peak power readings. The rate of acceleration from one point to the next is how we judge a vehicle's performance, not how much peak horsepower it makes. The right question isn't peak horsepower but is the search for maximum torque in the rpm band that produces the greatest transient acceleration.

The next time you need a definition of usable power take a look at all the diesels roaming the highways. They are out there for a good reason, they make a bunch of torque right now, not at the top of the rpm band. A typical diesel will crank out 90% of its torque by 2000rpm!

Chassis Dynos: Lies, Damn Lies, and Statistics

Put your bike on an inertial only chassis dyno and spin up a 900 to 1200 lb steel drum and pick up your dyno slip. This is a great method to impress your friends and to develop motors that you are designing to spin steel drums. How many people have called us that spent $10,000 on a "billet motor" that was slower than their stock motor when they did roll ons against their friends...Oh, the billet motor made a lot of peak power, and as long as you left it on the trailer you didn't have to worry about the pesky real world. The real world, however, is where we live and it's not a simplistic world like accelerating 900 lb steel drums.

Racing stoplight to stoplight and passing semis at 70 mph or banging the next shift headed for the traps is where the rubber meets the road not where the rubber meets the steel drum. Chassis dynos are useless for development but a great way for people to gather and see who has the most peak horsepower.

As the people who sell them will tell you..."They are a great way to build traffic by organizing dyno contests!". If you ever pay close attention to the time these dyno runs take and compare the time to the way you ride or race in the real world you will see there is no 1:1 correlation. Often these "dyno runs" last only a few seconds, not exactly the way we ride motorcycles.

If you'd like a bit of an eye-opener look up a Hot Rod Magazine article that did a comprehensive back to back test of chassis dynamometers. Results were all over the place.

For a bit of Dynojet history we suggest you read this document.

Method 1: Superflow CycleDyn...Testing a Running Motorcycle..Inertia and Load

If you are going to use a chassis dyno it has to be a tool and not a toy. At RB Racing we use the Superflow CycleDyn as it best emulates the real world. We use it for development and not for publishing "dyno charts". Most of our work is with Pectel SQ6M controllers which have extensive internal datalogging and playback capabilities up to 2000Hz sampling rates. With the Superflow we can program specific tests and transient sweeps with our turbocharger systems up 750 hp in inertial mode or 500 hp in Eddy Current controlled accelerations.

Steve Cole (TTS MasterTune) who has spent untold thousands of hours on every dyno imagineable has this to say about CycleDyns:

Steve Cole: "In the development side what I can say is the SuperFlow when setup properly emulates the real world much better. As an example the only way to get a DynoJet to give you HP and TQ is a WOT unloaded run. The SuperFlow allows that plus just about any other combination you like with real torque output. So what does any of it buy you becomes the question. I can tell you that if we tune to a DJ and get the best we can, then repeat on the SuperFlow using real world acceleration rates for the engine being tested the results are very different. Take the final calibrations and run them in both dyno's unloaded and the DJ developed type calibration will show the most HP and TQ in those conditions, on both the SuperFlow in DJ mode and the DJ. Then take the SuperFlow controlled condition calibration and load it in the bike the power will go up when tested in the SuperFlow mode again which can only be done on the SuperFlow.

Now the hooker, take the bike and put one of the finished calibrations in it and give it to the customer and say go ride it and come back after you've ridden it well, to know how it feels/runs. They come back after an hour or so then load the other calibration and ask them to do the same riding over and come back again. Each and everytime we have done this every customer has picked the calibration that was done on the SuperFlow under the controlled acceleration modes! So pick what works for you but there is a difference. Does it take longer, does it end with a measurable difference............. YEP!"

Wind Tunnel Dyno

These optional $5,900.00 internal "High Pressure Blowers" provide cool airflow to match road speed 1:1 up to 200 mph. The CycleDyn is calibrated at Superflow at the time of manufacture to measure and account for this additional drag. Like tuning in a wind tunnel. Far more accurate results this way.

Tuned by Shane T

Shane Tecklenburg tuning a Motec M130 on Tom Bookhamer's 120 Inch Bonneville bike on RB Racing's CycleDyn. We use 30 feet of 8" stainless tubing for exhaust extraction with an 8" Blower. The blower draws in 1725 CFM of free air mixed with the exhaust and extracts it far away from the operators and the building. Carbon Monoxide is not an issue with this evacuation. Shane has more time on dynos in more places all over the world than about anyone we have ever met. Shane is the "go to guy" when you get serious about Motec electronics.

Shane stepped off the airplane after a 25 hour flight from Bahrain ...tuned a Harley and headed home. He lives close by so it was a tight but convenient schedule for Tom and Shane. Tom all the way from Florida and Shane all the way from EKanoo racing in Bahrain. Strange world of racers.

Dynamometer Exhaust

Exhaust extraction on a F1 engine. Clean air is positively fed to the inlet and the exhaust is extracted from the Dynamometer Cell. Figure millions of dollars just for the test cell.

RB Racing's CycleDyn


2020 Road Glide 128 on RB Racing's CycleDyn

Carbon Monoxide is a killer. It has to be positively scavenged and discharged away from the building. All exhaust fumes must be vented so the operator and the engine cannot re-breathe spent gases. Carbon Monoxide is odorless and flat-ass dangerous. We have a CO meter on the dyno operators console.

We have 8" diameter stainless steel extraction ducts for both left side turbocharger and right side LSR 2-1 exhaust development.

Two shops managed to make this 2020 bike unrideable with the bike bucking violently at 2000-2500 rpm, forcing that RPM range to be avoided. This ruined a trip, two up, fully loaded.

Exasperated, the client who also has a 2023 Road Glide pulled the 2020 bike and we asked him to bring both bikes to us...all the way from Wyoming. We don't work on customer bikes.

We installed our RSR Dual AFR Gauge to check mixtures when riding and rode the bike which showed the rear cyl going dead lean despite TTS VE  entries >100. Odd. We rode the bike down to see Steve Cole (TTS) to see if he had an idea. Steve said it made no sense and asked us to check for (1) manifold leaks (2) compression check and (3) a possible broken valve spring. We checked all three and it wasn't those.

We then put the 2020 bike up on our SuperFlow CycleDyn dyno removing our RSR Dual AFR Gauge and installing the two CycleDyn Bosch wideband sensors and did both WinDyn Road Load (frontal area load corrected to 200mph) and Steady State tests to see where other issues were.

We finally traced the rear cylinder lean condition down to some way out of bounds EGR entries which forced the AFR dead lean...Not to mention other issues throughout the TTS .MT9 file. Bizarre entries with someone was throwing spaghetti at the refrigerator trying to ship the bike. They even had the bike entered as a 148 Cubic Inch. We started over from ground zero TTS-wise. Steve Cole came up twice to check our editing as the bike was now operating. Steve suggested he zero out all the modifying non-VE tables and program known values as someone had edited about everything.

Above: TTS tucked away in Flight Recorder mode for an extended CycleDyn Road Load Test after full load editing...Recording Idle, all TTS RPM Points 700 to 6000 RPM, transitions and W.OT. without dodging cars and cops on the 405/110/60/605 and 91 Freeways. Cruising at way over 100mph. We have three additional fans in addition to the two SuperFlow 1:1 road speed fans. The CycleDyn allows you to enter the bike's frontal area and it will provide aero loading up to 200mph corrected by barometric pressure.

If you think you are going to make radical cam and displacement changes and not have to go to square one you are in for a surprise. This bike started out as a bone stock 107. There are no magic downloads in this world. The tuner is in the mirror. TTS MasterTune gives you the same tools as the OEM.

After the SuperFlow dyno calibration the RSR Dual AFR gauge was reinstalled and the bike was road tested. It agreed 1:1 with the dyno and had glass smooth closed loop drivability and spot on W.O.T. mixtures.

Steve Cole downloaded the flight recording we had done and after zooming in on the data said "It's 99% and we can chase a few things but it's good to go".

Customer picked up the bike and did two 500 mile test rides...He could not believe how drivable the bike was...saying it was "flawless".

Conventional Engine Dynamometers

Water brake Dynos (many manufacturers) like Superflow are routinely used in performance engine development. You program these dynos to hold or stabilize your engine for "x" number of seconds in a series of ascending rpm steps to measure the torque at wide open throttle at each step. These steps are then plotted to generate the "Dyno Curve" for the engine. Usually, depending on the software and flow controls, transient accelerations are not measured, only the torque the engine will produce at specific points while being artificially held there so measurements can be made.

Without going to million dollar AC Transient Dynamometers these dynos are the best type of dyno for both brief and extended testing. Water cooling and high rpm capabilities make them the engine developer's choice.

When was the last time you were racing that holding a particular rpm had anything to do with winning? A race vehicle is always accelerating not sitting at some particular rpm and the vehicle with the most torque will always beat the motor that sacrifices torque for peak horsepower...This is why an engine with 135hp is not necessarily a better motor than one with 125hp.

Races are won, not on one factor, like peak power, but on a myriad of variables like traction, driveability, a wide torque curve etc....and if you don't believe this then why did Honda struggle so hard in Class C AMA racing against the archaic XR 750 Harley-Davidsons and finally had to take out horsepower in their search for traction and driveability. Honda won the Championship 1984-1987. It's all XR's now.

Multi-million dollar dyno cells are pretty much going to AC style water-cooled dynamometers. The accurately control the rpm and load at lightning speed and pump power back into the power grid.

Eddy Current Dynos

RB Racing uses Eddy-Current Dynos to do load testing. It's the cheapest form of accurate control of load and rpm but still has variables. These type of dynos can perform automated tests such as roll-on times from one rpm band to another, quarter mile et and mph as well as other tests since rpm and load is all under computer control. We have our Dynos set up to do engine direct as well as chassis-mounted testing. Companies like Superflow use Telma retarders.

Eddy Current brakes or retarders were originally developed to provide frictionless braking on trucks and industrial equipment. They have been adapted for dynamometer use in both air cooled and water-cooled (vastly more expensive) variations.

With Chassis mounted testing you still end up with all the variables of gearbox, tire pressures, etc. but it still is the best way to do in-chassis testing. All those variables such as brake heating, tire heating etc are still present. It does afford you computer control of engine rpm and load. This allows you to examine specific areas. Without expensive water cooling these aircooled units rapidly lose effectiveness as the brakes heat up.

Companies like Dynojet use Frenelsa retarders in their eddy current dynamometers. Some companies re-badge Mustang Dynos as sell them under different names. There are some things that are pretty well defined, however, like roller diameter. Smaller rollers like 12" are only good up for brief tests into the low to mid 100mph range. The people who rebadge Mustang motorcycle dynos use a small roller under the guise that it has "low inertia". The fact is you need to get up to about a 20" diameter roller for 200 mph brief accelerations...smaller rollers place too much strain on your tire.

Rollers are round and you race on a flat road surface. No matter what you do any roller is a compromise, and don't forget you are dealing with gearbox loses, tire pressure variances, tie strap tension, and techniques of the operator. Lots of variables between the crankshaft and the roller.

When you get into serious high speed testing and the tire-roller contact surface area needs to be accurately modeled, rollers about 10 feet in diameter are called for. Like most things, the science and engineering was done a long time ago, now the compromises are the norm.

1980's Eliminate the Tires

We can run the engines direct to a 250hp Mustang Dyno Eddy Current Controller though a transmission without having to deal with the tires etc. Good way to run-in an engine befoe it gets stuffed into a chassis

Real World Testing, The Old Way

We spent thousands of hours measuring rates of acceleration trying to develop carburetion in the 1980's endlessly recording 40 to 60 and 60 to 80 mph times as well as quarter mile e.t. and mph readings. If we couldn't get three tenths to half a second improvement in these "roll-on" tests and six tenths and six mph gains in the quarter mile we wouldn't sell the carb and pipe packages we were developing. We took stock engined 750's and put them in the tens and took stock 1100's and put them in the nines with no internal engine work. As they say..wasted days and wasted nights and  pie a la mode and coffee at 2 AM at the long gone "Ships Diner".

When the Harley-Davidson Evo motors came out in 1985 we took a dead stock 4 speed California spec big twin and with only a RB Racing 2-1 and a 38mm "PowerMaster" flat slide carb we developed ran a 12.90 @ 104.37 quarter mile. We didn't use any dynos because we found the early chassis dynos like the Patraco and even the early Superflow SF-900 series to be useless for carburetion development...Our only recourse was to instrument the bikes and ride them to measure the transient accelerations to see if we were making progress. If you spend 2500 hours doing this, sooner or later you stumble on workable solutions and formulate approaches to tuning...like recording all the temperatures, barometric pressures, relative humidity readings and changes in altitude. It was an expensive and stupid way to insure we always had three to sixth tenths of a second advantage when we went hunting whether it was on the street or at the track. Real World.

It was also a process that had a lot of variables that were difficult to sort out like rider technique and road conditions and gradients. It was also dangerous because you were instrumented to high heaven and taking your eyes off the road made life interesting. Then there were the cops who took a dim view of 120 mph passes past Donut shops while trying to get exhaust gas readings with a tube stuffed up the exhaust. These days you have cameras and cell phones to worry about...

What are you measuring?

Take an inertial dyno that everyone is searching for bragging rights on. Take the oil out of your transmission. Put on the lightest rear wheel than you can. Put on a chain and can the belt drive. Regear the mother. Shave the rear tire. Put on a set of 20" stepped drag pipes. Shave the flywheels. You win. Do you really? Not in the real world.