Frequently Asked Questions


1. Q:  How much does a dyno test cost?


1. A:  If you have a 2WD vehicle and you just want to come in and see what your horsepower and torque is, the cost will be $60.  If you also want to see what your air/fuel ratio is (whether you're running rich or lean,) add $10 for a total of $70.  I will let you do a few minor tuning changes to your vehicle and I will throw in a few extra runs for no extra cost.  If you can make these changes within a few minutes, go right ahead.  If you are going to perform changes that take more time, i.e. swap jets or a carburetor, and you're going to be on the dyno for an hour or more, you need to rent the dyno.  I am flexible with the pricing.  If you want to bring some friends with you for additional dyno tests, we can negotiate a price.  See the PRICING page for details.  If you have an AWD vehicle, the price starts at $75 instead of $60.



2. Q:  How does the dyno work?


2. A:  Read these pages:

            DYNO 101




3. Q:  Can I drive my own car on the dyno?


3. A:  For the most part - NO.  I do let certain customers perform the test themselves, however.  Customers that have dyno experience, customers that are friends of mine, and customers that are testing legitimate race cars are some examples.  I will not let a customer perform the test himself if the only reason he can site is the fact that he "doesn't let anyone else drive the car," or "the clutch is tricky," or some other equally-lame excuse.  If you're worried about your vehicle, you should be happy that I am going to test it and not you.  Driving on the dyno is nothing like driving on the street, and I am the one with the experience.  I am much more likely to perform a safe test than you.  There can be some variability in testing certain vehicles on a dyno (those with high-stall torque converters, for example) and you are also much more likely to get a successful, repeatable test result if I do the testing.



4. Q:  Does the dyno measure wheel horsepower or engine horsepower?


4. A:  The dyno measures wheel horsepower.  Torque is a slightly different story, however.  Since gearing has a direct bearing on torque and 1st gear would obviously generate a great deal more torque than 5th gear at the wheels, to return a useable number, the dyno actually gives you engine torque as measured at the wheels.  It does this by factoring the engine rpm into the equation and negating the effect of the different gears.  If this hurts you to think about it, then stop - just trust me.



5. Q:  What is the difference between engine and wheel horsepower?


5. A:  About 15 - 20% is the general rule of thumb.  Engine horsepower is always greater as some power is lost through the drivetrain on its way to the wheels.  Most believe that standard transmissions are closer to the 15% number and automatics are closer to the 20% number.  People will argue about this number forever, and frankly - you shouldn't be concerned with it.  Once the engine is in your vehicle, you don't care what the engine's power is.  You only need to be concerned with the wheel horsepower, as that is the only one you can use now.  If you really need to know - most stock vehicles seem to be in the 20% range.  Higher horsepower cars have a lower loss, as it's not possible to lose a great deal of power through the drivetrain without burning it up.  The higher horsepower cars usually have racing (lightweight) drivetrain components, so that will result in a lower loss also.



6. Q:  What is the best kind of chassis dyno?


6. A:  Ask this question of a dyno shop owner with a different kind of dyno, and you will get a different answer.  I chose the Dynojet dyno (an inertia-type dyno) because it has the simplest design and it has proven itself in a wide variety of applications.  The theory behind each type of dyno is sound, and in theory, each dyno should return an accurate horsepower number.  Unfortunately, those of us with dyno experience realize that each type of dyno returns a different horsepower number, sometimes by as much as 10% or more.  Contrary to what some people would have you believe, this does not mean that one type of dyno is more accurate than another.  The more I learn about this, the more I believe that the different results occur because the dynos load the engines differently, and engines respond with different power outputs.  The most important thing for a customer to realize is that the dyno is a tool.  It is a tool that will give you an accurate, repeatable, relative number.  The exact horsepower that a vehicle is making is almost never important.  If you just want a number that you can brag to your friends with, then just make sure that your friends get their vehicles tested on the same type of dyno.  The dyno will show you the exact differences between the vehicles.  If you want to use the dyno as a serious tuning tool, then just make sure that you use the same type of dyno after each time you modify or tune your vehicle.  It will give you an exact difference in horsepower between the changes, and that is what is important.

            There are also a few more things to consider when choosing the best type of dyno for your needs.  A Dynojet (inertia-type) dyno places an identical load on every vehicle.  The only difference in load to the vehicles' engines will be from different gearing and/or if vehicles are tested in different gears.  Therefore, as long as similar vehicles are tested in the same gear, comparisons with the dyno results are perfectly valid.  The load that a load-type dyno places on a vehicle varies depending on the parameters that the dyno operator enters into the computer, namely the vehicle weight.  Some shops with load dynos weigh each vehicle and use that weight, others look up the weight on a chart.  There is an inherent issue with these methods that must be considered if one is to use a load-type dyno to compare results between vehicles.  For example, if two Mustangs have the same engine and drivetrain, but one weighs 3600 lb. and the other has been stripped for racing and weighs only 2900 lb., which method should be used?  If the actual vehicle weights are used, one engine will be loaded significantly higher than the other.  If the same weight is used for both vehicles, the load placed on the engines will be the same, but which weight should one use?  One may even argue that the actual vehicle weight must be used in order to duplicate real-world driving conditions, but that would inevitably return different results in cases like the one in the above example, even though the two vehicles have the same powertrain.  One could therefore change a vehicle's horsepower output by changing its weight.



7.  Q:  I noticed you have a large fan to place in front of the vehicles, does your setup accurately mimic street conditions?


7.  A:  Absolutely not.  The purpose of the fan is to provide enough fresh air across the vehicle's intake so that the engine is not burning stagnant air with a reduced oxygen content and to provide some air movement across the vehicle's radiator to help keep the engine from overheating.  There has been much discussion lately because some dyno shops have installed large, very powerful, very expensive blowers to "simulate" road conditions.  The horsepower results with these blowers are significantly higher (what a surprise) and these shop owners are now saying that everyone else is wrong, because they don't simulate road conditions.  The big problem with this attitude is the fact that the dyno was never intended to simulate road conditions.  Like I said in the previous answer, the dyno is a tool that will provide very accurate, relative results that can be used for tuning your vehicle and/or comparing your vehicle to others.  These giant blowers are ramming tremendous amounts of air into the intakes of these engines and are creating a form of forced induction.  This is fine if you want to see an inflated horsepower number, but it is useless if you want to compare numbers with someone that went to a different shop.  One also needs to take into account the fact that even a slight difference in the setup of the blower may create a huge difference in the horsepower number.  If the dyno operator points the 30,000 cfm blower directly at your intake one day, and points it slightly askew the next, you won't know if the modifications you made to your vehicle made the change in power or not.

    If you want to consider the math, let's do an example.  If a 4" diameter intake is mounted at the front of the vehicle with no filter on it, it will receive 461 cfm of fresh air when the vehicle is traveling at 60 mph.  Keep in mind that an engine with a properly designed intake will suck all of the air it needs out of the atmosphere regardless if the vehicle is moving or not, and that very few vehicles (no street vehicles) have an intake set up like the way I just described in the example.  Intakes are usually mounted inside the engine bay and rarely have a direct flow of air coming from the front of the vehicle.  So - ask yourself: "what is the purpose of aiming a 30,000 cfm blower at the intake of my vehicle when 461 cfm will simulate 60 mph?"  The 12,500 cfm fan I have is in place to prevent the vehicle's intake from sucking stagnant air out of the atmosphere and to help prevent the engine from overheating.  If you're still curious, it does simulate driving at approximately 20 mph.



8.  Q:  What should I do to prepare for a dyno test?


8.  A:  Read this list:

Make sure the tire pressure on the drive wheels is where you want it.

Make sure you have enough oil.

If there is a cover over the spark plug or coil wires, please remove it.

Make sure you have good spark plugs and that they are GAPPED PROPERLY.  DO NOT TRUST PRE-GAPPED PLUGS.

If you're going to perform some tuning, read THIS and become familiar with it.

If you're going to perform some tuning and you're not confident in your abilities, bring a friend that is.

If you're going to perform some mechanical work, bring the necessary tools.

If you're going to perform some mechanical work, you may want to bring a friend to help.

Call or e-mail me if you are not sure about anything - 860 282 2248.



9.  Q:  What is the air/fuel ratio, and what number do I want?


9.  A:  Read THIS.