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[Twolanerider]

You might be or not be concerned about the numbers generally.  That's a different question.  But don't be concerned at all that one dyno is different as compared to another even though nothing on the bike's hardware changed.  Environmental differences have a significant impact.  Warmer day versus cooler for denser air.  Humidity.  Everything matters.  So don't let a few % difference between separate dyno runs (especially on different machines) worry you at all.  Granted, SAE smoothing is supposed to take all those factors in to account.  But not in the real world.....

[JCZ]

I wouldn't agree that the air/fuel ratio is good, unless you're talking about after 3,800 rpm.  You can also get better with the HP and TQ with the right tuner.  Take a look at some of the previous dyno sheets in regards to A/F ratio and HP and TQ.  Take a look at mine, or hd-dude's or Erniezap.  We're all from Northern Calif. but all three of our bikes were tuned by different tuners on different dynos and we're all above 100 in both HP and TQ and our A/F ratio is much closer to 13 across the board (for ideal tuning).

[Fired00d]

Ok, with all the talk on another thread about STD vs SAE dyno numbers it made me look at mines to see what they were. In doing so I found that my numbers were neither.

[Twolanerider]

If somebody could explain to me what "DIN Torque" and "DIN Horsepower" compare, or what they are I would appreciate it.

[Fired00d]

D00d,

DIN is just another measurement standard.

[110tHunDer]

Off topic replies have been moved to [link=http://flhrsei.org/cgi-bin/yabb/YaBB.cgi?num=1136574508]This Thread[/link]

[BaggerDad]

Hello everyone.

[BaggerDad]

Continuation of post #471

ECE -- The ECE standard is based on the European Directives. Power is corrected to reference conditions of 99 kPa (29.23 InHg) of dry air and 25

[BaggerDad]

Continuation of post #472

Beat the Drum The crooked dyno operator can reprogram the weight of the drum, which will allow the dyno to create anomalous power numbers.

Change Load Changing the load by tightening or loosening the tie-down between runs can compromise any comparisons made with the dyno testing.

Messing With the Weather This is where the dyno operator has to be extremely devious. If you mess with the readings that the computer uses to calculate the correction factor, you can alter the corrected output significantly. The one reading that the built-in sensors do not take automatically is humidity. The dyno operator has to enter the humidity correction themselves. Since the humidity is manually entered into the computer it is the easiest to alter. While humidity numbers are obviously suspect, the temperature can be faked pretty easily as well. Another good way of bumping up the power figures is by "playing about" with the air temperature and pressure corrections. If you dial in your own "standard" conditions as being freezing cold with the barometer going off the scale, or you put the temperature probe near the engine, you can get the system to add huge amounts of power to what was actually measured. So make sure you know if such corrections were made or not and to what standards they were made if any. We actually decided to try this one, just to see how easily it could be done.

Jackson Racing's Dynojet is set up with the weather data box mounted on a perpetually-shady portion of the dyno room wall. The temperature probe hangs under the box in the open air about two feet off the ground--right where most air intakes pull their air supply. Oscar Jackson pointed out that he has seen these boxes mounted where they were more easily accessed, and has even seen the temperature sensor hanging on a divider wall next to the computer, or in a drawer on the dyno bench. In the drawer, an unscrupulous dyno operator could put his or her hand around the sensor before doing a run, bumping the ambient temperature reading up into the 90-degree range. With it hanging on a well-placed wall, the sensor could be flipped from the shade into direct sunlight, where it could slowly bake up to a nice, warm temperature.

The wire on Jackson's sensor was only about two feet long, so we couldn't get it into the sun, and a shield prevented holding the sensor in a warm hand from having much effect. Instead, I cupped my hands around the sensor and blew on it. Within 30 seconds the dyno was reading 95 degree ambient temperatures even though our baseline run made a few minutes earlier had been in 66-degree air. We made another run with the engine breathing 66-degree air, but the dyno correcting for 95-degree air. Our corrected power jumped from 136 hp to 143 hp.

Correction factors between 0.97 and 1.03 are pretty normal. Outside that range, you should be on the lookout for large differences between the runs you are comparing.

In order for dyno results to be comparable and universally understood there are a number of things that need to be closely controlled during the measurement process: Operating Conditions - air temperature, pressure and humidity affect the amount of power an engine produces. Cold dense air means a greater mass of oxygen per power cycle and thus more power is generated (provided of course that air/fuel mixture is properly calibrated for the conditions prevailing). There are formula that can be used to calculate how much the measured power would change if the test conditions were different. This enables dyno results to be "corrected" back to standard conditions to enable comparison with anyone else's test results. Sadly however there is no one universally accepted set of "standard" conditions because different automotive bodies in different countries use different standards to calibrate to. "SAE" power standards are used in the USA and sometimes in England. "DIN" standards are used in Europe and there are a few other oddball systems just to confuse the issue. So just because your car is rated at 100 bhp and a friends at 110 bhp doesn't necessarily mean that his engine is more powerful - it depends whether both measurements were corrected to the same standard conditions.

From Short Block Charlie 7/24/04 One of the big problems I see with dyno charts is the following. Was the dyno test performed in a dyno cell? A dyno cell is designed to input air and remove exhaust for proper tests. If not, you will see false readings. Very few dyno facilities have this, such as the traveling dyno tuners. The dyno has the capableness to compensate for humidity and elevation to record corrected information. The other problem I have with my own customers is they will get a dyno sheet that is not impressive, but bike runs like rocket ship. There is a lot of magic out there to fool the consumer.

[BaggerDad]

Continuation of post #473

An engine's output depends on the quality of air it breathes, and it is therefore essential to take into account variances in air pressure, temperature and humidity when measuring horsepower. Raw numbers are generally normalized to sea level conditions within a dynamometer's software using a standard correction factor. However, this does not mean you will get identical readings from two different dynos, or for that matter, the same dyno on two different days. While the dynamometer corrects the horsepower it reads to standard atmospheric conditions, it cannot account for jetting changes you should have made to account for the weather. For example, you could run your bike at the local dyno and see 100 corrected horsepower on a cold day and return--without changes--on a hot day for another run and get 98 corrected horsepower. Where's the two horsepower? To get back to 100 horsepower, you'd have to lean your bike out for the hotter weather. Because different weather conditions can result in different air densities and different oxygen concentrations, the weather can have a significant effect on power output. The SAE has a standard set of correction factors that can be used to normalize all power outputs to what they would be at sea level, on a 60 degree day, with 0 percent humidity. Every Dynojet has a small weather station built in to feed the appropriate temperature and barometric pressure readings to the computer so it can calculate this factor. The difference between 0 percent and 100 percent humidity is about a seven percent correction. A temperature change from 60 to 90 degrees, on the other hand, will have an effect of about a 2.8 percent. A difference in elevation from sea level to 5000 feet is worth a whopping 20 percent!

Operating Conditions Altitude, air temperature, pressure and humidity affect the amount of power an engine produces. The only thing to really worry about is the A to B changes on the same bike, same dyno, same day.
Sometimes you may want to know how much power you are really making on that specific day due to the temperature, humidity and pressure on that day; in that case, you should look at the uncorrected power readings.
When you want to see how much more power you have solely due to the new exhaust or the new cam, then you will find that the corrected power is more useful. It removes the effects of the temperature, humidity and atmospheric pressure and just shows you how much more (or less) power you have than in your previous tests.

Altitude As you increase your altitude the octane requirement decreases 1-2 octane per 3000 feet elevation. This is because the density of the air is reduced or there is less air available for your motor to burn. The higher the altitude, the richer your motor will run, making it necessary to re-jet the motor in order to lean it out. The fuel volume remains the same and the air volume goes down. If you have a vacuum advance, as the altitude increases, the motor makes less vacuum and the air fuel ratio becomes richer due to the decreasing air to fuel volume. Altitude and weather systems change the air's pressure. As you go higher, the air pressure decreases from around 1,000 millibars at sea level to 500 millibars at around 18,000 feet. Most of us race at less than 1000 feet of elevation. Weather systems that bring higher or lower air pressure also affect the air's density, but not nearly as much as altitude. Air density is lowest at a high elevation on a hot day when the atmospheric pressure is low, say in Denver when a storm is moving in on a hot day. The air's density is highest at low elevations when the pressure is high and the temperature is low, such as on a sunny but extremely cold, winter's day in New Hampshire. Humidity and air density Most people who haven't studied physics or chemistry find it hard to believe that humid air is lighter, or less dense, than dry air. How many times have you heard someone tell you to add more gear on a hot humid day because it is harder to push the kart through the hot humid air. The inverse is really true, the kart flows easier through the air but the pressure needed to fill the cylinder with the proper air fuel mixture is lessened by lowered air density.

Temperature When the temperature goes up, the air density decreases, thus you have less air available for combustion and your air fuel ratio becomes richer. The same works in reverse. As the temperature goes down, you end up with more air per cubic foot, and without re-jetting your carburetor, the engine will run leaner.

[BaggerDad]

Continuation of post #474

Air Density As the air density increases, your engine will lean out. As the air density goes down, the engine runs richer. Like driving up a mountain, at the top, the motor has less power because you have less air to burn. Cold dense air means a greater mass of oxygen per power cycle and thus more power is generated (provided of course that air/fuel mixture is properly calibrated for the conditions prevailing). Air density is a combination of two factors: barometric pressure and temperature. At 85 degrees Farenheight and at 29.92 inches of mercury for barometric pressure (at normal sea level) air density is considered to be at 100%. The horsepower and torque available from a normally aspirated internal combustion engine are dependent upon the density of the air... higher density means more oxygen molecules and more power... lower density means less oxygen and less power.

The relative horsepower, and the dyno correction factor, allow mathematical calculation of the affects of air density on the wide-open-throttle horsepower and torque. The dyno correction factor is simply the mathematical reciprocal of the relative horsepower value.

Air density is affected by the temperature, pressure and humidity of the air. On a hot day, or at high altitude, or on a moist day the air is less dense which means that there is less oxygen available for combustion which, in turn, means that there is also less engine horsepower and torque.

Vapor Pressure Humidity or vapor pressure is an important factor in calculating the corrected horsepower and torque values. An abnormally high vapor-pressure figure will inflate the torque and power numbers. Cool days typically produce 0.3-0.4 vapor-pressure readings. You'll likely see 0.6-0.7 vapor-pressure numbers only on hot, humid days; 0.9 or higher would occur only if it's raining cats and dogs.

Inputing the right barometric pressure is one of the most important factors in obtaining accurate corrected torque and power numbers. Traditionalists still rely on a wall-mounted mercury barometer, but its reading must be corrected for temperature and gravity.

Humidity When the humidity increases, octane requirements ease. The formula is something like... for every one gram of water increase per one kilogram of dry air the octane decreases by .25 to .35. WWII aviation engines used water injection and it worked well for a short time by cooling the cylinder temperature. As temperature goes back the effect goes away.

Many people think that the dyno is the "all knowing, almighty," last word. Nothing could be farther from the truth.

[BaggerDad]

IMHO

The best TQ curve is one where the TQ steadily and smoothly increases over the whole rpm range.  A long broad TQ curve over the rpm range where most riding is done....looks more like a mesa or plateau than one of the Alps.  For concern would be any dips or spikes in the curve because this will induce a feeling of flat-spots - areas of the rpm band where the bike feels lethargic or feels like bogging down.  When comparing runs it is important not to look at peak figures, rather it is necessary to look at the whole of the curve. The torque curve which will accelerate a bike the fastest is the one with the greatest area under the curve for the rev range of the engine, so this is a good method to compare torque curves.

Torque is what gets you started.  Torque breaks your wheels loose when you launch, and torque allows trucks to tow heavy loads.  Torque accelerates your vehicle.  Combine some measure of torque with speed and time, and the result is horsepower.  Horsepower is what gets you through the quarter-mile.  As far as which one is best, the answer is - it's best to have both.  High torque numbers allow you to leave the gate quickly and power out of turns.  High horsepower numbers keep the vehicle accelerating and give it a higher top end.  Just as important as the peak numbers, though, is what your curves look like, and where those peaks are.  An engine might have a high horsepower peak at a high rpm, and a graph that looks like one side of a steep mountain.  This means that in order to take advantage of the high horsepower, the rider must keep the engine at that high rpm.  This requires more shifting, which can result in lost time.  Flat curves mean that the rider can take advantage of the engine's power without as much shifting, but in order to obtain a flatter curve, an engine tuner must sacrifice some power.  

[fatboyse2]

Thanks Bagger, this has been helpful.

[BaggerDad]

Some more tidbits - just stuff I've found, may or may not agree with.

From "Harley-Davidson Bolt-On Performance" - Denis Manning, owner of Bub Enterprises.
 
In road racing, you can beat guys every time if you can beat them in the low RPM range coming out of a corner.

[BaggerDad]

Torque article by the late Jim Feuling.

HARD AS IT MAY BE for those of us brought up to think of horsepower as the ultimate measure of an engine