How To Measure Horsepower Without A Dyno
1. Why own a dyno?
Every racer understands that without horsepower the kart goes nowhere. As dynamometers are the just tool specifically designed to measure engine horsepower, it's no surprise that tiptop racers desire their own dyno. This article examines things to consider before selecting and using this expensive tool.
Like near test equipment, a dynamometer (or dyno for short) helps isolate and quantify a particular parameter (in this example the engine's ability output) from overall vehicle performance. Why do you demand to practise that? Racers (that don't dyno) often rationalize "I only test on the track …where it counts"! They infer that power output is good if lap times are low. But, that fails to isolate the contribution of a sharp driver from a strong engine! Want a doctor that, instead of checking blood force per unit area with instruments, determines patients are ok if they survive between visits?
Many hop-upwardly modifications only help at loftier rpm, actually reducing power downwards depression. Even with days of rails testing yous might condemn some new high rpm pipe unless you lot test a agglomeration of sprocket changes likewise. What if you demand to friction match the fuel mixture too? Add upwards those exponentially increasing combinations, and thoroughly rails testing stretches to years! Dynamometer owners get pointed in the right direction with simply a couple of 20-2nd "pulls".
Using a dynamometer also helps you avoid discounting "insignificant" 1-% gains from modifications. Just because you can't "feel" asingle 1-% power increment does not mean you want to forego ten such tricks! Combining pocket-size improvements is how pros win trophies.
2. What do I demand to dyno?
I'll presume you are a serious engine builder and want to start in-house dynamometer testing. What do yous need? First, to measure out engine torque, your dynamometer system must provide a load. Automotive engineers refer to this loading device every bit an absorber or a "brake" (since early on dynamometer absorbers used a drum and ring restriction to load the engine). Absorbers do not actually absorb the power. Rather, they convert it to another form of energy, like heating h2o or air.
Currently in that location are several commercially available absorber choices for kart engines. Professional person engineers, with Fortune 500 budgets, often apply electrical DC generators with calculator controlled field excitation to load and regulate their engines. The engine'southward power is typically prodigal as heat in the armature area or wired to remote heating elements. If the test engine'south operating rpm is low enough, information technology can be directly coupled to the armature with a brusk driveshaft. 6,000+ rpm kart engines volition need a gear reduction drive to match them to these low rpm generators.
The principal reward of electrical generator systems is that they can exist readjusted anywhere from zero load to full load in microseconds. This allows the engineer to regulate engine speed within a couple of rpm (even while changing throttle settings). Unfortunately, the cost of an acceptable chapters generator, excitation controller, and support hardware meet the tens of thousands of dollars. So yous nonetheless need to buy the data-acquisition system. If your kart engine runs at high rpm, you need the required gear reduction. Reduction transmissions add together still more, cost, complexity, and parasitic elevate.
The DC generator dynamometer has another shortcoming. It has besides high a polar moment of inertia. That's a fancy manner of saying that the generator's armature feels like a giant flywheel to the tiny kart engine. High inertia means a lot of horsepower is required to accelerate the armature. Besides, a lot of stored horsepower will exist returned when dropping downward in rpm. This really skews the test data whenever rpm is irresolute. And then, while generator dynamometers are great for steady state command, they are nowhere for testing rapid acceleration transient weather.
MAX – How Eddy-Current Absorbers Piece of work – Animated look at how boil-electric current absorbers create load(MAX narrated).
Boil current brakes are similar in operational characteristics to electric DC generator absorbers. The principal difference is that the boil current brake does not actually generate electricity. Rather, you use an electrical power supply to accuse its electromagnetic coils. The brake's input shaft spins a metallic rotor within that resulting magnetic field. When the dyno operator increases the current supply to the coils, the rotor shaft becomes harder for the test engine to turn. Like the DC generator, an eddy current brake'south advantage is its lightning-fast response to the controlling computer's loading instructions. Unfortunately they likewise come at the DC generator dynamometer'due south hefty cost.
These eddy current brakes dissipate the engine'due south power equally rut input to the rotor. This rotor must be cooled or it will eventually cook. Air-cooled boil current brakes take cooling fins on a large fe rotor, making them look like automotive disk brake rotors. These big rotors have too much flywheel mass though, and dominate the rotating inertia of a typical kart dynamometer installation.
H2o cooled eddy current brakes are available that have significantly lower rotating inertia (at to the lowest degree compared to air-cooled eddy current and DC generator systems). Unfortunately, the cooling system adds complication, making the price tag even harder to consume. Yet, if you have a $50,000+ dynamometer budget, give them a wait.
Before you get frightened abroad past these high priced status symbols, let's examine lower cost absorbers. The simplest and earliest class of brakes were only that, brakes. A rotating drum with a friction brake pad was used to apply drag at the engine'due south output shaft. These looked like old truck brakes. To measure torque, some sort of calibrated scale linkage was inserted at the brake pad anchor points to display the applied drag load. Issues with friction brakes included much difficulty in accurately regulating the load and brake pad cooling.
A more controllable load device is the hydraulic oil pump. These are occasionally seen on depression rpm, moderate horsepower engine dynamometers. A positive deportation oil pump acts as the restriction, and an adaptable oil discharge orifice valve sets the load. They can have a lower inertia than the DC generator and boil current units if the pump is modest, but sometimes required gear reduction units and coupling adapters push it support. Like many absorbers, the oil pump units convert a examination engine's power into a fluid'southward temperature rise. Since the oil can't exist but freely discharged, a cooling system (typically an oil to h2o heat exchanger) must be used to keep the oil's temperature within rubber limits.
MAX – How Water Brakes Work (page) – Animated look at how water-brake absorbers create load (MAX narrated).
When low cost, depression inertia, high rpm limits, and race engine horsepower capacity are all requirements, the about prevalent choice for an absorber is the h2o restriction. These accept been the favorite of professional automotive engine builders for decades. Water brakes are another form of hydraulic pump absorber. These pumps typically have one or more vaned rotors spinning in between pocketed stator housings. Load is controlled by varying the level of h2o in the brake with adjustable inlet and/or outlet orifices. Raising this water level increases the rotational drag of the pump'due south rotor, applying more resistance to the engine turning it. Interestingly the h2o brake is, past blueprint, a very inefficient pump. It uses up your engine's horsepower output by making "instant hot water"! Since the discharged hot water is clean, information technology tin either be allowed to simply run off, or it can be air cooled and recirculated.
The ability capacity vs. size of water brakes is startling. The 8 pound h2o brake in the photo on folio 15 handles over 65 continuous Hp at 12,000 rpm! By comparison the 300 pound eddy current brake shown next to it has the aforementioned continuous power rating and is only skillful to 7,000 rpm. Information technology is no wonder that water brakes are virtually the only choice for testing 2,000+ horsepower drag motorcar engines. Modern water brakes similar the ane pictured a low enough weight and inertia that they can be directly mounted on the kart engine'south output shaft. Direct mounting eliminates the inertia and parasitic elevate of driveshafts, u-joints, pillow block bearing, etc.
All of the above absorbers can be controlled manually by the operator (with a simple knob), or under reckoner control. Manual valve water brake load control is not as responsive as the electrical DC generator or eddy current controls but, with good electronic servo valve controls, you can close the gap a lot.
iii. Flywheel energy issues
In discussing the pros and cons of various absorbers I keep mentioning bug with high inertia. To illustrate merely how much power flywheel energy can mysteriously "captivated" let's "build" a rough, dirt-inexpensive dynamometer with no brake at all! This will be an "inertia dynamometer" because the engine'southward power output will become into "winding up" a heavy flywheel.
This instance uses a flywheel that is large, in relationship to the engine, and then accelerating the combination from idle to peak rpm takes several seconds. A fast data-conquering system logs the time periods and rpm changes. From that data we calculate the torque and horsepower the engine supplied to accelerate that known flywheel mass. The formula for determining the torque is:Torque = JM* rpm per 2nd / nine.551
where JM represents the Polar Moment of Inertia of our inertia dyno's flywheel.
If we don't know the Polar moment of Inertia for the flywheel (and our flywheel has a abiding thickness cross-section) nosotros can summate it with the formula:JM = (West* r ^2) / 32.16 / two
where W represents the flywheel weight in pounds and r is its radius in feet.
Once you have the torque, it is like shooting fish in a barrel to calculate the horsepower with the standard formula: Hp = Torque* rpm / 5252
Keep in mind that the rpm in the last formula must be the boilerplate rpm during the sampling menses.
Say our example uses a 10-pound flywheel, 8″ in bore (thus it would take a Polar Moment of Inertia of .017 foot-pounds-2nd2). If the engine was able to accelerate this flywheel from say four,800 rpm to 5,200 rpm in ii/10 of a second (a rate of 2,000 rpm per second) that would represent a torque of 3.six pound feet. Since our above example had an average rpm of 5,000, information technology produced 3.four Hp during the test. That's all hither is to information technology. Unfortunately, inertial dynamometers alone are useless for doing the steady country testing needed for methodical evolution of porting, pipes, etc. You can non adjust the load to hold the engine at a given rpm indicate, information technology must always be accelerating. All the same, inertial testing is handy for working out acceleration and drivability bug.
The real reason for the above math exercise is to illustrate how much ability it took to advance that pocket-size flywheel. If you buy an absorber with a polar moment of inertia in the same rage as our flywheel example to a higher place, don't expect to perform sweep dispatch testing. Even accelerating at just 200 rpm per 2nd would eat x-% of our sample engine's power! Fortunately, high end computerized data-acquisition systems provide composition algorithms to back out the furnishings of cushion (and crank-railroad train) inertia from acceleration data. On a high inertia dynamometer, compensation is required even for adequately low rate sweep testing.
four. Measuring Power
Bold you settle on a overnice depression inertia brake to load the engine's torque output, how practice you lot mensurate that torque? Some DC generator and eddy current dyno'southward apply in-line rotary-torque transducers because they measure engine torque earlier the influence of the high inertia rotor! However, the rotary transducer alone may add together $3,000 to $x,000 onto the toll of your data-acquisition system. Luckily, the low inertia of a h2o restriction makes a rotary transducer unnecessary.
To get torque data without a rotary transducer, the restriction's outer housing must be mounted gratuitous floating (i.e. in trunion bearings). Housing rotation is then prevented with a form of "torque arm" protruding radialy from the housing. Some stationary back up linkage holds the end of the arm. The arm is called a torque arm because it "feels" 100% of the engine torque trying to rotate the loaded brake. Inserted somewhere in this anti-rotation torque arm linkage is a calibrated calibration or "load cell transducer". This transducer converts any applied strength into a usable torque bespeak that it supplies to a gauge or data-acquisition unit.
Beware that, some oil pump "dyno'southward" skip the expense of a load cell and endeavour to use belch oil pressure (ordinarily in conjunction with a look-up chart) as a crude estimation of power output. This is unsuitable for performance engine testing. No matter what type of cushion yous select, get a transducer which tin directly and accurately measure torque, not "guesstimate" information technology.
An electronic brandish or information-acquisition system expects to interface with an electrical strain judge bridge load cell. This type load cell has a metallic cross department with a hairline electronic wire filigree glued to its surface. Every bit this cantankerous section is compressed, tensioned, or bent (depending on the linkage and load cell design) the attached wire filigree is likewise deformed. The nearly minute deformation of the wire grid changes its electrical resistance some tiny corporeality. The electronic circuit acts similar an ohmmeter to read the resistance change, only it is calibrated in pound-feet. This same principle is used in everything from $500,000 dynamometers to $nineteen.95 digital bath scales.
Calibrating the torque display for accurateness is usually straightforward. Typically a certified weight is hung off the end of the horizontal torque arm while you observe the torque brandish. Multiply the altitude from the heart of the brake out to where you hung the weight, and it must friction match the pounds-feet of torque displayed. If the reading is off, the data-conquering system will provide some ways to recalibrate it for the deviation.
One time you have a system that is accurately measuring running torque, you only need a calibrated tachometer to calculate horsepower. Horsepower specifies the rate at which your engine is capable of producing a given level of torque (meet the earlier horsepower formula).
5. Logging the Data
On old-fashioned dynamometers, an observer must record thesimultaneous tachometer and torque gauge readings with a pencil and paper. Today, nearly dynamometers supplant the observer's notes with computerized information-acquisition electronics. Y'all would not believe how often everyone watching a test gets so excited by the racket and thrill that no one records the information! Or worse, the readings are "rounded up" by the biased engine builder. A skilful computerized data-conquering organization should be considered mandatory for whatsoever real testing, menstruum. Fortunately, today information technology is possible to get recording, control, and playback capabilities in a $2,000 hand held package that years agone would have cost the price of a house and filled a pocket-size room.
A suitable computerized data-acquisition system should have a fast sampling rate, especially for testing 4-stroke, single cylinder engines. By fast I mean at least 100 samples, of all sensor channels, per second (100Hz). A 200Hz logging charge per unit is a flake improve withal. Why? Understand that, between sparkplug firings at that place is a measurable drib in the instantaneous crankshaft torque and rpm. The crankshaft gets accelerated in the moments after combustion, then begins to deadening until most two revolutions afterward the plug fires again. You lot can't experience these rapid highs and lows when driving around the track (with all that vehicle inertia), but the dynamometer will!
If you sample at only 50Hz, that's only a unmarried torque and rpm sample everyother revolution (at 6,000 rpm)! Periodically, a series of samples will autumn in synch with the firings of the plugs, while at other times sampling volition fall in synch with the lower power compression strokes. Past using a fast acquisition system to read each firing cycle multiple times, enough information is captured to boilerplate out this phenomenon. The illustrations elsewhere in this commodity show the same data with and without dampening and averaging. While experienced dyno operators see the same power bend in both graphs, inexperienced operator's wait that smooth "publication-quality" line.
The ability of the conquering system to average and dampen the data is mandatory for other reasons. At 200Hz you're getting 2,000 lines of data for even a x-second dyno pull. Who wants to always wade through 40-pages of information for a few second run? Averaging both eliminates transient "noise" and produces more practical half-page printout.
6. Bells and Whistles
A estimator that only logs horsepower, torque, rpm, and fourth dimension may be all your testing requires. It will certainly put you several notches ahead of those without in-house dynamometers. Simply, for more advanced engine development in that location is much more you'll want to capture.
Weather data, significant air temperature, barometric force per unit area, and humidity is something that needs to be noted for each dyno exam session. Equally you are aware, lower barometric pressures, college air temperatures and humidity will lower an engines ability output (and vice versa). Without doing atmospheric correction, information taken under other conditions can non be direct compared. Dynamometers oftentimes come with the atmospheric correction tables found in many technology handbooks. These tables accept factors for the various weather condition conditions, which you multiply against your observed torque data. "Corrected" data is a closer judge of what the engine would have produced had it been tested under, for example, "standard" atmospheric weather condition. Adept information-conquering software should allow entering or recording these conditions and automatically calculate the correct data.
Exhaust and cylinder caput temperature thermocouples, identical to what you may already exist running on the rails, are practiced to have. They provide a condom check and insight into what is happening inside the engine. Monitoring the EGT readings is a nice security blanket when you offset leaning her out! On air-cooled engines, special sparkplug thermocouples are equally important. Some dyno software fifty-fifty lets you program condom limits that will close down the examination if things go to warm!
Block mounted thermistors let you monitor temperature variables that might inadvertently influence engine power. For getting repeatable test information you desire to test at consistent temperatures. Thermistors data as well lets you check the engine'south sensitivity to cooling system alterations
. Airflow metering turns the dyno and data-conquering system into a dynamic catamenia bench. Pocket-size turbine type transducers are bachelor that but clamp onto the carburetor inlet like an air cleaner. With the Static Cubic Foot per Minute numbers you tin can sort out combustion efficiency improvements from mass airflow gains. The software should combine the airflow info with horsepower data and provide a Restriction Specific Air Consumption number. Having BSAC data let's you compare your engine'southward efficiency with published dyno information from others. Such comparisons help guide you to areas where improvements are nigh likely to be had.
Like airflow turbines, a fuel flow turbine provides instantaneous fuel consumption and Brake Specific Fuel Consumption numbers. I like having BSFC numbers along with thermocouple temperatures to assist me isolate fuel mixture issues from those induced by spark timing, etc. This add-on pays for itself in shortened test sessions many times over. Combined with airflow data, software tin even rail the engine's existent-fourth dimension air fuel ratio. Keep in mind though that the Briggs engine takes some carburetor/tank retrofitting to allow reading fuel menses.
Some other computerized data-acquisition software characteristic, one that buyers may not think of until after running the organization, is automatic triggering of data logging. Simply every bit observers ofttimes neglect to notation gauge readings, decorated dyno operators forget to toggle the information record push at the start and finish of important tests! It'south frustrating pushing the print push and getting nothing, or, ending up with hundreds of pages of engine idling data! Better systems allow setting rpm and horsepower trigger points which, once exceeded, automatically outset logging. Like algorithms should control the end of logging. This characteristic really makes a dyno operator'south life easier.
For long-term investment protection, make sure that your acquisition organisation tin can adapt to futurity applications. Information technology should handle numerous types of ignition system rpm signals, have provisions for other than one:1 gear ratios (you may dyno a bike someday), and it should handle a wide array of torque transducer types and ranges (when you kickoff building Formula-1 engines)!
By selecting a portable electronics package y'all tin can double your investment value. Merely add vehicle speed sensors, accelerometers, etc. and you have a professional on-lath data-acquisition organization. In fact, the DYNO-MAX for Windows dyno software goes and then far equally supporting Global Positioning Satellite mapping of the kart's location on the racecourse! I like using the same equipment in the cell and on the track because information technology makes comparing data much cleaner.
7. Dyno Installation Considerations
Once yous take delivery of the dynamometer you notwithstanding have to hook it upwardly. That means plumbing information technology to a skillful h2o supply (unless you have only take an air-cooled absorber). Thermodynamic laws dictate that water-cooled absorbers (including eddy electric current and hydraulic pump units) require one gallon per minute for every xx horsepower beingness loaded (assuming a temperature rise of 100 degrees Fahrenheit). Ideally the supply should maintain a steady pressure level in the 20 to forty psi range.
Most store's municipal water supplies meet the requirements for kart engine testing. In fact, you probably can get plenty correct from a ¾" garden hose. However, if y'all do come up up short on delivery, try replacing that restrictive garden hose sill-cock with a high flow ball valve. If you have a private well you may go wide pressure level swings as the pump kicks on and off. If so, stabilize things with a ¾" pressure reducing valve, set to most 25 pounds per square inch. You lot can also use something like DYNOmite Dyno's neat little 2-stroke powered pump and a bucket of water to even dyno test remotely at the rails!
Besides a water supply you need plenty of fresh air. Most dyno operators significantly under gauge the ventilation requirements for the room. It takes large area intake and outlet ducting combined with fairly large horsepower (three+) blower(south) to properly ventilate the room. This is especially true if yous are attempting to only run your exhaust out into the raw air of the cell. Fifty-fifty if you run a practiced muffler a lot of noise will go out the vent organisation. Insulated fiberboard ductwork tin can be used to add together sound dampening for the neighbors. If you practice non have the bucks to build a properly ventilated dyno cell, it may be best to just test outside on a breezy day.
If your absorber did not come with a stand and engine coupling, you'll have to fabricate 1 that is rugged enough for the loads of testing. 1-½" foursquare structural steel tubing with a 3/xvi″ wall works well. The frame must also provide vibration isolation and dampening to protect the expensive torque transducer, dyno hardware, and engine itself. Brakes remotely coupled to the engine require driveshaft couplings that let for some parallel and angular alignment errors that will occur. If you take a lightweight brake that direct couples to the engine, the job is much easier, but still brand sure that you have acceptable vibration dampening somewhere in the torque arm support arrangement.
8. Getting Consistent Results
No matter what type of dynamometer y'all select, controlling the test conditions is vital to getting usable data. Information technology's not enough for the dynamometer equipment itself to exist authentic; yous take to know that the engine's output is not beingness skewed past improper dynamometer procedures. For example, if you fail to start all your tests from a standard, stable engine and head temperature, there'due south no manner to tell which variable is responsible for any measured power differences.
Likewise, poor cell ventilation can allow exhaust gas to be inducted into the engine, drastically reducing its power. I've actually seen dyno operators, squinting from the hurting of exhaust fumes, trying to figure out why the engine suddenly lost 50-% of its torque!
Torque information dampening and/or averaging is vital if you are using a kart engine with the fuel tank doing double duty every bit a giant carburetor float bowl. This design, while perfectly adequate for running lawn maintenance equipment, is non noted for precise control of air/fuel ratio. As the engine shakes, the fuel sloshes around in the huge tank, changing the head on the metering jet. It'southward all-time to go on the tank level consistent and almost full to minimize this outcome. Depending on your rulebook, more than sophisticated cures can be implemented. Don't be turned off past problems similar this, they are your opportunities! Pinnacle racers apply their dynamometers to track down and plug these horsepower drains.
Even if yous select a depression inertia brake remember that the engine's moving components still accept there ain inertia. If you take readings while the engine is accelerating or decelerating, inertial energy is existence subtracted or added, respectively, to what your gauges indicate. Disappointingly, unscrupulous dynamometer operators use inertia to display impressive flash power readings by suddenly cranking on the brake load. Obviously such "inertial free energy augmented" numbers accept nothing to do with the truthful horsepower capabilities of the engine. Afterwards you lot run a dynamometer for awhile, y'all can spot such shenanigans in other'due south printed dyno information. This is another reason engine builders get their ain dynamometers.
The subject of inertial energy brings united states of america dorsum to the capabilities of the dynamometer itself. If you're manually controlling the brake with your wrist, you may be limited to steady land testing at unimposing RPM steps. It can exist near impossible to do a controlled low-rate sweep on some peaky race engines. Instead, settle for only adjusting the load valve to a stable rpm exam betoken, and collect enough data at that place to allow averaging out the inevitable modest inertial and transient spike influences. Once you lot accept collected this data, quickly move to the next desired rpm and repeat the process. By averaging enough data, this method produces very usable data for those on a upkeep.
If you have sprung for a system with a computerized load control, the rules modify. In a typical installation a servo valve, under the data-acquisition computer's command, adjusts the load rather than the operator trying to do it manually. Water brakes equipped with calculator servo load control routinely concur the engine inside one-% of target rpm. That is much ameliorate than you should wait to do manually. Reckoner load command allows programmable rate sweep testing and automated step testing (i.e. running the engine at each even 250 rpm for a few seconds of settling time and then automatically logging a couple of seconds information). In fact, with the additional electronic throttle command on top of the electronic load command y'all tin can really programme an entire racecourse simulation and sit back and spotter the dyno run the testify.
9. Your First Dyno Exam
Assume you lot've selected an appropriate dynamometer and properly installed it in a well-designed test cell. How should tests be conducted? If this is your first experience operating a dyno, it'south best to showtime with a fairly balmy engine. By that I mean an engine that isn't running with ultra-peaky porting, super loftier compression, or anything else that makes the engine finicky to run. Pull out some low-tech engine that's inherently reliable and which yous don't mind running frequently at peak power (or over-revving occasionally).
In one case you have that engine mounted, warm it to operating temperature. During the warm upwardly, practice by applying calorie-free loads to the engine. This speeds warm up too. Next, gradually open upwardly the throttle to total load while using the restriction's control valve to regulate the rpm. Notice that it's actually the throttle that controls engine load, while the brake'southward "load" valve actually regulates rpm!
One time you lot are at broad-open throttle (which is where about of your testing will be done) exit the throttle in that location while you movement between desired exam rpm points with the restriction's load valve. If yous're collecting data with paper and pencil system, its fourth dimension to kick one of those observers in the shin to remind him to start jotting things downward. Those with electronic information-acquisition system may need to push the record button (a tertiary paw helps). On a proficient computerized system, you can preset data collection parameters so that on future tests recording will offset automatically based on the horsepower threshold points you preset.
Once you've stepped through each rpm indicate (holding each long enough to get meaningful data) merely dorsum off the throttle while simultaneously unloading the restriction so the engine returns to idle. Stop recording data, your first test is done.
If it did not get well, effort over again. Learning to run a manually controlled dynamometer is like beginning to ride a wheel. Everyone thinks they will never "get information technology", or that the load valve, brake, etc. is defective. Really, with exercise, operators before long become to the point that information technology becomes a reflex activeness.
If you take an automated servo valve, program the belongings rpm and finish test point before starting the engine. Then just bring the throttle to full, letting the servo hold the rpm for you. Push the test and allow the estimator do the rest.
10. Examining the Data
On a purely transmission recording arrangement it'south time to grab the calculator and extend those torque and rpm readings into horsepower numbers. If you've got a manual electronic information collection it's time to playback or print out the data. On full-diddled personal computer equipped dynamometers you lot'll usually want to name the new data file and probably enter whatever pertinent engine data or special notation's most the test run just completed. Many software packages allow you to enter nigh every parameter under the sunday in predefined windows. That's helpful so you don't forget to log something important, plus it's all in one database for y'all afterward on. If your organisation is non equipped with sensors that automatically capture the weather atmospheric condition y'all should note them now.
Choosing the best output report format for reviewing the dynamometer'southward data is important also. In cases where I will only get to see the data presented one way, I find it more useful to look at it plotted vs. fourth dimension, rather than vs. rpm. Presented with fine enough resolution and/or appropriate averaging, a time printout helps one sort out valid ability information from bogus flash readings. When examining the data, don't rely on data captured during periods of rapid rpm change. Instead, look for ranges (during the menstruum of broad open up throttle operation) where the engine maintains a steady rpm for a few consecutive seconds. When you examine the recorded data vs. time like this information technology will be easy to spot the ranges where you held the rpm steady plenty that your torque data is valid, and not influenced by crank-train inertia.
Brand sure you average the data too. Fifty-fifty numbers with a bit of inertial error can be averaged out to produce usable information. Computerized data-acquisition systems allow you to set the averaging and dampening periods set to suit the blazon of testing you are doing. For our near steady country pull instance you would turn on about a second of dampening and nearly 1/10 second averaging.
If something is plainly wrong with your results, like the rpm appears off past a factor of two, you might accept selected the improper tachometer pulse setting. Or, if horsepower is just a fraction of what it should be, was the throttle wide open during the exam? Commencement fourth dimension operators have a habit of backing of the throttle, instead of cranking upwards the brake drag, when trying to regulate rpm. Don't forget nearly the problem of exhaust getting back into the intake organisation. Then again, if ability seems just a trivial depression, welcome to horsepower reality. Be glad it's a clunker motor your friends are seeing, non that "mega-power" engine yous've been exaggerating almost!
Do a second pull, repeating the aforementioned procedures as the commencement exam. Remember to bring the engine back to some consequent temperature first. Since we haven't fabricated any changes, nosotros're looking for repeatability, not a power increase. In fact, yous are really testing the repeatability of yourself and the engine, since the dynamometer does not modify betwixt runs. Whenever it's feasible, particularly when chasing small improvements, retest the engine in its baseline form. This extra reality check saves a lot of time in the long run.
11. Graduation Day
Just after you acquire some skill as a dyno operator and can demonstrate repeatability should you move on to changing things in search of ability. Merely as you shouldn't start testing new engine modifications on the track if you haven't run consistent laps in weeks, it's just equally pointless to do it on the dyno. Of course it almost goes without saying, make only one modification at a time!
Y'all should try a few modifications on that "beater" motor to gain still more dynoing feel. Something like a higher compression cylinder head and/or thinner gasket combination is like shooting fish in a barrel to examination. You can as well experiment with various combinations of spark advance and jetting. If you've equipped the dynamometer with exhaust temperature probes, etc., picket how they modify as you add together horsepower with modifications and run fourth dimension.
If you have other instrumentation, do with information technology too now. An engine that has strong airflow, the right air/fuel ratio, and appropriate frazzle temperature, simply which has than stellar horsepower output, points yous towards things like a low compression ratio. Seeing too loftier frazzle temperatures while you are indicating a correct air/fuel ratio hints of late spark timing. Endeavour watching airflow as you examination a few different exhaust pipes. If that new whiz-bang pipage sends both airflow and power downwardly, you lot will not likely bring information technology to life with tuning changes.
The beauty of having own dynamometer is it provides the opportunity to do the methodical testing everyone whishes they could. Become prepared to be surprised too. You'll be amazed how sure little things make an improvement while many over hyped tricks return nada.
Source: https://dynomitedyno.com/tech-corner/how-dynos-work/
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