The Dyno-The Heartbreak Hotel
12:00 pm in Dyno Tuning by ScottCrawford
For about the 7 thousandth time someone asked me why after they installed a pipe or other mods to their bike, it only makes as much power as they thought it did stock. So I thought it would be a good idea to write a little on the subject. There are lots of reasons for this, and we will touch on the most popular in no particular order so hold on to your cranks and rods as we travel down this rabbit hole.
The magazines: Journalists get bikes from the factorys that are sometimes pre-production or maybe just a little bit “special”. They make just a bit more power than the ones in the dealerships. The more common issue is that they are using one brand of dyno at one place. There is no established standard between brands of dyno so horsepower is not the same as a pound of something for example, that would weigh the same on different brands of scale. There is an established formula for horsepower, just not of measuring it. Helpful isn’t it! The higher the number the more impressive the headlines so there is not much incentive to clean up the act.
The Internet (the forum experts): This is the most common source of bad information. There are forums for every kind of bike in the world. There is a bunch of good info out there. Unfortunately in is buried under lots of bad info. Everyone wants their bike (or kid, or dog, or car, etc.) the be the biggest baddest one on the block. Some shops cater to this by playing dyno games (more on this in a minute) and giving people the highest number they can legit or not. Don’t believe people on the computer just because they have a really bitchin high post count or posted pictures of their ex-girlfriend. That does not make them an expert on anything, it just proves they can type and log on to the internet (hell I can do that!!).
Dyno games: This is my personal favorite. Let us say that I dyno and tune your bike and get 100hp. Now you roll down to the the local bike nite feeling great, and some cool dude tells you that his bike of the same model made 115hp and I must suck. Well he tells you to go to his dyno guy. You make an appointment and take your bike to this supertuner. He plugs the bike in and makes a pull, slowly shakes his head, and tells you that I indeed do suck, and he can fix it for $300. Sooo, happy to hear this you pull out the Discover card and let fly. After an hour or so where he does his magic and you drink Dr.Pepper in the lobby, he comes in with a chart. As you can see here you came in with 100hp and now you have 116!! Wow, what a deal. Cyclewerkz does suck!! So now you come back to see me to tell me what for. As you try to stab me with the scissors on my desk. “WAIT!!” I plead. “Let me just dyno your bike so I may learn the ways of this master, this savant of the air-fuel ratio!” After putting the bike up and making a pull…. What is this! 100hp? How can this be? Where are my other 16 ponies? You didn’t get 16 more horses in your stable, you got a printout that says 116. That is all. It is all in the machine people. I can make the dyno read whatever I want, whenever I want. Sad but true. There is a correction factor to compensate for weather conditions. I use SAE corrections. That is the industry standard. If someone hands you a chart with a STD correction on it the difference will be usually 3-5 percent higher. If they change the mass of the roller in the dyno software it will read higher. Dynojet uses a known weight ( the drum) accelerated over time. If it thinks the mass is heavier it will read higher. If the bike is getting cooler air than the weather station on the dyno, it will read higher. If the tire has a 75psi it will read higher. There are a ton of tricks to pull this off and everybody that has a dyno knows how to do it. If they are honest they won’t. ALL THAT MATTERS IS THE DIFFERENCE!!! If your bike makes 95 and after a pipe and tune it makes 105 that is all that matters. It has to be measured on the same dyno with close to the same condtions.
Cyclewerkz has 2 Dynojet dynamometers. The one is an old DJ150, maybe 17 years old. The second is a six year old DJ168. It has every option that Dynojet makes, eddy current, strain gauge real time running torque, analog module sensor inputs, the works. They both read exactly the same. Within 1 horsepower every time. I have compared numbers and even run the same motorcycles as the race team I work for. They have a Dynojet in Athens, Alabama and it reads within 3 of mine. I could make my numbers higher but it is not a contest or a game, repeatability is what I am looking for. It is getting a little late so I will post up more on this subject in the next day or so. Keep checking back, we will get to the bottom of this matrix of misinformation.
