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AS TIME PERMITS, we will be using this site to explore computer modeling and simulation to improve engine design and overall vehicle performance.

We will also explain various engineering formula and engine theory to help racers develop better engines and bikes.

We would like to point out that while we are in favor in some technology, we prefer to race older bikes, without breakout or delay boxes, air shifters, extensive electronics and the like. We are in favor of rev limiters to help prevent damage to older bikes. However, we do like to use computers and technology to help us design and test our bikes. We are also in favor of data-loggers to help accumulate information for future enhancements.

Why the seeming contradiction in using technology to model bikes but not using technology to run the bike? The answer to that is simple. It is much cheaper to model and test engines and bikes using a computer than it is to build an engine, race it, tear it down, make changes, rebuild it, race it again, etc. Let's say you have a choice of 3 different cam profiles. Which would you prefer to do? Purchase all 3 cams, spend hours installing, uninstalling and testing. Or let a computer do the grunt work? And on the riding end, it's MUCH more fun to actually have to ride the bike then to let a bunch of technology do it for you. I'm sure you can see what we mean.

This is not to say that any computer program will give you an EXACT representation of how a certain component will perform. There are entirely to many variables. But a computer simulation WILL give you an idea of how a component change will affect the overall performance. It will do this by providing a view of RELATIONSHIPS. If you establish a baseline, computer simulation and analysis will allow you to see what the result of a change would be. Not in terms of exact figures but in terms of the overall effect. You will not get an exact NET effect of the change but you will get an idea of the PROPORTIONATE effect of the change.

In all of our examples, we will be using the values for a 1971 Triumph TR6 650 cc with a Morgo 750 kit installed as that is what we are currently racing. Other than being in being in a hard-tail frame, using a modern solid state regulator/rectifier and a capacitor ignition, it is stock.

Below you will see a copy of the Horsepower and Torque curves for a stock Triumph 650cc engine that we developed using engine simulation software.

These figures are NOT exact but remember, we are dealing with relationships here, NOT exact figures. For example, if we take the graph below as a baseline and change, let's say, the carb. If regraphing shows a 12% increase, we could assume that no matter what our ACTUAL torque and horsepower that our bike actually produces versus what the graph shows, we should expect roughly a 12% increase if we change the carburetor.

To show you what we mean, if you notice on the graph above, you will see that horsepower peaks at 6000-6500 RPM at 45 HP. This is in line with the figures published by Triumph for a '71 650 TR6 (Please note that the published figures were at the crankshaft, NOT at the rear wheel! The software we use also bases it's output on output at the drive sprocket on the engine, not at the rear wheel. Additional computations must be made to compute the value of torque and horsepower at the rear wheel). However, the software we use will only allow a bore as small as 2.8". A stock Triumph has a bore of 2.795". A small difference, true, but a difference none the less.

Another important point is that the program will only allow a minimum flow of 100 CFM (Cubic Feet per Minute). Based on accepted formulas, the TR6 with a stock Amal will only flow about 86 CFM at 4500-5500 RPM (where peak torque occurs). So initially, these are the limitations we are dealing with.

Below you will see a copy of the Horsepower and Torque curves for a stock Triumph 650cc engine with a Morgo 750cc kit that we developed using engine simulation software.

When you then factor in the different bore on a 750 kit, which is 2.985", do you increase the lowest allowable bore of 2.8" by the percentage difference between the 2.8" and the 2.795" (actual stock bore versus smallest allowable bore), the percentage of which is 99.82% and then increase the 2.8" by the percentage difference between 2.795" and 2.985"? Or do you simply increase the allowable bore by the difference between the two, 0.19"?

We have opted to take the easy road. If we start with the assumption that 2.8" and 2.795" are basically equal, when we model the 750 kit, we will use 2.99" (2.800" plus .190" for the Morgo kit, a difference of .005") for the bore.

We should also point at this point, that the formulas and information presented on this site pertain ONLY to drag racing. Any engine analysis applies only to a narrow RPM range. As drag racing involves higher RPM only, we will only be looking at that RPM range.

Using the "PREV" and "NEXT" buttons at the bottom of each page, the sequence we will be following is as follows. First there will be a section on some basic math formulas that are useful in working with bikes and performance, then some information and formulas relating to basic engine dimensions. Then we will follow a typical "charge" through the engine, that is through the intake, combustion chamber, exhaust, and through the drive line. Next we will touch on the physical aspects such as weight, center of gravity and weight transfer. The next subject will be some formulas pertaining to torque and horsepower. Lastly, we give some formulas and explanations that are directly related to performance. So, by following the links, you can be well on your way to designing your bike, or you can click on the "Site Map" link at the bottom of the page and jump around to what interests you.

If you are running Windows, you may want to open the calculator, set it to "always be on top" and use it while running through this website. Most other operating systems have a calculator buried somewhere, you just have to find it.

Also, until I can figure out how to make this @#@$%# script save answers, it might help for you to write down the answers to any computations as they may be used later. Also, you may want to keep a written record of all the answers to develop a file on your bike design.

If you would like to explore using this technology to design or analyze your engine and/or bike, please contact us at the e-mail address below.