What does Dyno do?

[JET]

Does it just read the horse power & torque or does it do anthing to enhance the cars performance?

:confused: :alone:

[TAF]

It's a way of measuring HP & TQ. You can also measure the Air/Fuel Ratio.

Think of it as more of a diagnostic tool rather than a tool that makes corrections.

O.K. there's my "laymans" attempt to explain....you smarter guys can give the more detailed explaination.

[Marauder57]

Since we are discussing this....did Mercury "Lie" about the 302 HP on the MM? Because when I hear the Dyno numbers and HP at the Rear wheel...the numbers start at like 240 and bump up to 260-280.....where is the 302?

Maybe I just don't get that part.....

[RCSignals]

302 HP is at the flywheel.

[Bigdogjim]

Yes all numbers for HP are always flywheel. They all state it that way.

[RF Overlord]

^^^what TAF said^^^

A chassis dynamometer is a measurement device that allows you to see "before" and "after" any changes or modifications have been made...it measures the actual HP and TQ the rear wheels are delivering to the ground, not the output of the motor...the accepted driveline loss is ~20%...

Here (http://www.dynojet.com/autospecs.shtml) is a link to one of the more popular units


There is also an "engine dynamometer" which will measure the actual output of the motor at the flywheel...
linky-linky (http://www.superflow.com/xtest/default.htm)

[engine23ccvfd]

RF good info from the links...thanks

[Warpath]

There are three different types of chassis dynos 1)Inertia type (dynojet) 2) Eddy current (Mustang) 3) and water brake.

Here's my limited knowledge on the subject. The inertia type measures hp by how fast it turns a large, heavy drum. If you ever see pictures, its the roller in the ground. The inertia of the drum is known. Therefore, it can calculate hp from its rpm and acceleration. I think torque is calculated from drum rpm and hp. Dynojet is the most popular inertia type.

The eddy current dyno is basically a generator. The rear wheels are placed on two rollers which spin the generator. Hp is measured from the generator's output. These dynos are more accurate. I haven't found proof yet, but I trust my sources. I believe Ford only uses these. These dynos will measure lower hp than a Dynojet. So, don't think you lost hp if you go from a Dynojet to an eddy current. I am only aware of Mustang brand of eddy current dynos. The advantage of eddy current dynos is that they can supply any load you want. An inertia dyno cannot. Therefore, on an eddy current dyno you can simulate your car going up hill or part throttle performance. It is much more useful for tuning.

The last one is a water brake dyno. I don't have a good understanding of this one. But, basically, the dyno is a big water pump and hp is measured from that - maybe through water flow and change of temperature. Many engine dynos are water brake dynos. These waterbrake chassis dynos work the same way except the hubs are attached to the dyno directly and any losses between the tires and rollers is eliminated. Water brakes is where the term brake horsepower (bhp) originated. They are not as popular. So, I don't know a brand name.

My personal oppinion is to use the Eddy current dyno since it is more accurate. You might want to use a Dynojet though since they are more popular. It will give you a direct comparison to most other people because they will likely use it also.

[Marauder57]

Ok....so 302 is at the Fly Wheel......when they say 345hp on a Chevy Pickup...that is at the Fly Wheel as well....

Is there a set ration that you can estimate Fly Wheel horsepower if you know the RWHP? For example 265 RWHP means 330 at the Flywheel?

Just curious.....

[RCSignals]

It's all at the flywheel

There will be different % of loss for different drivetrain assembles, so there isn't really a blanket way of converting measures RWHP to engine HP without knowing the drivetrain power loss.

[RF Overlord]

Warpath:

Thanks for the expanded version... :up:

[SergntMac]

Originally posted by Warpath
There are three different types of chassis dynos 1) Inertia type (dynojet) 2) Eddy current (Mustang) 3) and water brake. My personal oppinion is to use the Eddy current dyno since it is more accurate. You might want to use a Dynojet though since they are more popular. It will give you a direct comparison to most other people because they will likely use it also.

Typically, people tend to look at a dyno numbers as they do an time slip from a race track. That's not what it does, here's a link to a primer on all the styles. It's got a lot of pages, but the real 411 is easy to extract.

http://www.mustangdyne.com/ChassisDyno/50mustang/50mustang-article.htm

I agree, the DynoJet is the accepted industry standard. It operates on measuring the movement of a 3400 pound drum, or roller if you will, and the computer does the rest. It's best feature is it's popularity. The machines are precisely built and carefully installed, with the latest in refinements in AFR measurment and user training. It's also available in a trailer mounted portable version for trucking to meets. Some might say if it's not a DynoJet, it's not a dyno. That's up to you.

I don't think it's the most accurate test available, but it's close enough for what you need to learn about your particular car. Like running the quarter mile, no car will produce duplicate figures in back to back pulls. But, the differences will be minor, I would suggest you do three pulls and average your numbers. Again, it's the machine of choice and I think because of it's reliability. As a diagnostic tool, a DynoJet in Dallas will give you the same 411 as one in Chicago. It is S.A.E. corrected.

The eddy current style is probably the oldest technology in use today, and is marketed by Mustang. Here is where I have to disagree with Warpath. My first dyno experience on the MM was a Mustang, and it reported 363 RWHP, and 1336.6 RWTQ (remember, that thre pulls averaged). Oh really...From just 4:10s and a chip? I cannot support the Mustang because of it's lack of S.A.E. correction and AFR data. It does not S.A.E. correct, and your 411 is useless.

Both the Mustang and DynoJet take measurements from rollers or drums, and IMHO, tires, suspension, and stretching tie down straps have a lot to do with skewing the facts. I prefer the DynaPack 5000 dyno, which is probably in the "water brake" style mentioned above, though in more "up to date" technology.

The DynaPack removes the question of tires, suspension and tie down stretch from the measuring by side-stepping these distractors. The DynaPack attaches directly to the powered axles, you can read up more here, and there are pics in the photo section.

http://www.grdperformance.com/dyno.aspx

I've had a dozen or more dynos on my first MM while building her, all of them on the Dynapack 5000 and it performed quite consistently. I was able to duplicate pulls and not have to average my data. In fact, I was able to come back the next day and get data within 1.0 of the day before. My max power came in at 275.4 RWHP and 301.6 RWTQ.

I had one more dyno test after this, on a DynoJet for my Team Ford power tune. Before the tune, my numbers dropped to 261.1 RWHP and 283.2 RWTQ. That a significant difference between the DynoJet and DynaPack and it serves to show what loss can occur from tires, suspension and tie-down straps. After my tune, the numbers came back to 271.7 RWHP and 293.7 RWTQ.

In light of how well my MM performed, I wasn't disappointed by lower numbers, they are just numbers. The real 411 is in the graphs and charts. At 1900 RPM into the pull, I was pushing 233 pounds of torque to the ground. By 2500 RPM, torque rose to 275 pounds. That is one azz kicking hole shot for a 4200 pound beast, eh?

That's what you need to know from a dyno test and why it's a great diagnostic tool, and not a high performance poker game.

Just my .02c, from my personal experience.

[MitchB]

Whatever dyno you use, it is important to understand that you need to be able to fully load the engine in order to accurately tune your car for WOT. There are a lot of guys with tuning hardware using dynos who are not as knowledgable as they think they are or need to be. You cannot impose a full load with an inertia dyno. You can with an eddy current. Someone really knowledgable (like the guys many of you use) can compensate for this on a dynojet. I know of many guys who ultimately lost an engine due to poor tuning by someone with little experience using a dynojet. The ultimate way to tune a car is to actually drive it while datalogging. Since this is mostly impractical, the next best thing is an eddy current dyno.

Mitch

[TAF]

Well...there you go marauder2306...

If you STILL have any questions about Dyno-machines...I'm afraid you may never get it. J/K

Is this place GREAT or what??!!!

[jgc61sr2002]

Warpath - Very good explanation. Thanks:up:

[MitchB]

I have a question...for all of you: what do you think absorbs the most power on a chassis dyno? In other words, what is the biggest factor that accounts for the difference between crank and rear wheel horsepower?

Mitch

[JET]

Wow, thank you all for sharing your knowledge with me.

[CRUZTAKER]

I needed to know all that as well.

Thanks

[TripleTransAm]

Originally posted by MitchB
I have a question...for all of you: what do you think absorbs the most power on a chassis dyno? In other words, what is the biggest factor that accounts for the difference between crank and rear wheel horsepower?


Any surface in the driveline that sees friction, or some sort of exchange of power through different media (ie. oil-to-metal, etc.), or anything with a sizeable mass that has to rotate, etc.

Starting from the engine back, you've got the torque converter which, while unlocked, will soak up some of the torque being transmitted as heat through 'slippage' (ie. there is some shearing of the oil between the turbine and impeller blades).

Then there's the tranny. Inside it, any bearing-supported surface will soak up some energy. Then there's the small surfaces of the gear teeth, grinding away at each other with just barely a small film of oil between them. And all these planetary gears and bands have mass which soaks up some energy as it gets spun up to speed. The tranny shaft is also supported by a bushing/bearing as it leaves the tranny rear... more friction.

Leaving the tranny, there's a U-joint. There's gonna be some losses there, as the angle of the rotation is altered slightly. Then there's a sizeable driveshaft, that also soaks up some energy as it is spun up to speed (remember, rotation energy increases as the square of rotation speed). Then another U-joint at the rear.

The pinion is supported by a bushing/bearing. More friction. Then the pinion-to-carrier gear mating surfaces also soak up some more. blah blah blah axles and their bearings blah blah blah axles and their mass blah blah wheels/tires and their mass etc.etc.

That should give you a ballpark as to where it all goes, once it leaves the rear of the engine. :D


Oh yeah, some of it makes it to the ground as useable torque on the tire at the contact patch, too. :lol:

[MitchB]

Something (maybe one you mentioned, maybe not) absorbs significantly more power than anything else.

Mitch

[Warpath]

Originally posted by SergntMac
The eddy current style is probably the oldest technology in use today, and is marketed by Mustang. Here is where I have to disagree with Warpath. My first dyno experience on the MM was a Mustang, and it reported 363 RWHP, and 1336.6 RWTQ (remember, that thre pulls averaged). Oh really...From just 4:10s and a chip? I cannot support the Mustang because of it's lack of S.A.E. correction and AFR data. It does not S.A.E. correct, and your 411 is useless.

The Mustang dyno I used to get the stock numbers in my sig automatically SAE corrected it. You can also get A/F readings too. I think the Mustang dyno you used must have been really old. Like I said, I've been told eddy current dynos are more accurate than inertia type. But, I haven't found proof yet. This debate occurs occasionally with the Mustang (the car) guys too. Mustang guys seem to like Dynojets because they read higher and, thus, win the poker match. One thing to consider is the accuracy and repeatability of the dyno (or any measuring equipment for that matter). One may be more repeatable than the other. But, if its inaccurate, then the numbers are almost meaningless.

Sarge makes the best point though. Use they dyno to learn about changes and not absolutes. Measure your car stock. Then use the same dyno or at least the same brand of dyno after making a mod. Use these measurements to see whether the mod was worth the money and effort.

[SergntMac]

Looking back on this thread, I have to compliment on how well this web site works. It starts out with a "help me understand" question and answers flow, and without people getting in each other's faces.

The 411 is what it is, you have to draw your own conclusion. There is variety in the replies posted which reflects how each of us shape our own opinion from our own expeirence. To see any topic get fully explored to where it equals the "taste great-less filling" difference of opinion without getting ugly, is why this site rocks. Bravo!


Originally posted by MitchB
I have a question...for all of you: what do you think absorbs the most power on a chassis dyno? In other words, what is the biggest factor that accounts for the difference between crank and rear wheel horsepower?Mitch

I missed your quiz the first time around, Mitch, but I got it now. TTA posts an eloquent discussion of every possible power leak in the drive train, but I think he may have missed the quiz question too.

From front fan to rear rotors, everything is connected, one way or another. Pistons are physically bolted to cranks by connecting rods. Bolted together and allowing acceptable tolerances. From the tail shaft back, everything is likewise bolted together with acceptable tolerances. Acceptable or not, each connection leaks or taxes power.

As TTA points out, every connection has an inherrent loss to it, but the acceptable tolerances add up. One pound of power from the crank will not be one pound of power at the rear rotors, because of the collective power leaks and taxes.

The most leakage occurs in the torque converter, where things are not bolted to each other, but function in a "windmill" manner with trans fluid replacing wind. The second most taxing point of loss is inside the transmission, where gears slip, or, get suspended while shifting between gears. These two (if you look at them as separate components) have the most significant power leaks and pay the highest taxes. It takes a lot of power to make them function, and their parasitic "drag" is constant.

We can plug the leaks and reduce the tax with mods, but that's all we can do. A more efficient torque converter that's less taxing in function, and improvements in shift efficiency will allow more power to get through, but there will always be loss. You can cut your losses, but you cannot beat the tax man.


Originally posted by MitchB
The ultimate way to tune a car is to actually drive it while datalogging. Since this is mostly impractical, the next best thing is an eddy current dyno. Mitch

It's not impratical anymore, Mitch, this is exactly what's going on in a Team Ford power tune from www.FordChip.com It's done with computers now, not timing lights and distributor weights, and it's done live on a dyno. The results are later burned to your performance chip, or, your ECM. This is why I tell everyone here, mods or no mods, get a power tune. You'll be amazed at what you have been missing.

[Warpath]

I think what MitchB meant that it is better to tune an engine while on the road (have the fordchip guy sit next to you while you drive). That would be a real world tune. It would include aerodynamic drag, real world intake temps, real world engine cooling, etc. A car sitting on a dyno with a fan in front of it isn't the same thing. You can only simulate the real world to a certain degree. But, the dyno is the only realistic and practical way to tune an engine.

Just to add my thoughts to the power loss discussion: Power is lost by anything that makes noise, has friction, or makes heat (usually through friction). If you reduce any of these, you may see a power gain. There are exceptions. If you install a quieter muffler, it usually will rob power vs a louder one. That isn't what I meant about noise. An example of a reduction of noise which will increase power is a centrifugal blower. The older ones made a loud whine. The newer ones have different gears which are much quieter and much more efficient. That means it takes less hp to run them. The noise came from gear chatter/whine.

[SergntMac]

Yeah...that does sound like a neat way to tune a car, and quite possible I suppose, but wouldn't you worry about too much fine tuning? I mean, like if it was a perfect day and all, and traffic was real liight so your pulls don't get interrupted and all, and you lock down the tuning, how would you expect the car to run on a colder, or, rainy day? I think there is a "common sense" limit on how fine a tune should be, best leave yourself some elbow room if the car is still a daily driver, eh? At least on a dyno, a lot of essential settings are measured and reset in a controlled environment, and that allows for some elbow room in the real world.

With regards to your noise/power thoughts, thanks, but I'm not sure I'm following you. Noise means power leak or tax? Ummmm...Okay, better pulleys on a blower mean more quiet and less parasitic drag? Okay, I follow...

If you replace a standard muffler with a more efficient muffler, I would not expect to see a full loss of power. I would expect a shift in where the power can be tapped, meaning that most of the time, low end torque takes a hit, but high end torque and HP improve. I can see how this shift would be expressed as a loss when the low end torque is valuable, as it is in our MMs. However, a complete loss of power, even in minor numbers, is rare, and unacceptable. Unmod that mod right now.

I agree that friction causes heat and in any area where you fix the friction should improve performance. However, Mitch's question seemed to be looking for major leaks/taxes in the power train, at least I thought that's what he meant. Sorry if I misunderstood, maybe MitchB will stop back and clear this up?

[Warpath]

I think my noise explanation went beyond Mitch's question. But, the muffler example was very general. It may have been better stated that if you go from a stock muffler to a "high performance" muffler, don't think you lost power because the "high performance" muffler is louder. Noise can be created from something vibrating. It takes energy (or power) to vibrate it. I'm having a hard time explaining it more than that. I can't think of a better way.

As far as the blower, the old designs, as I understand it, used straight cut gears in the blower. The new designs use helical cut gears. Thus, gear chatter is reduced. Plus, the blowers are more efficient at compressing air - probably due to improved impellers. The more efficient compression process yields lower blower output temperatures, which leads to more power.

[MitchB]

I thought the question I posed was an interesting one and I was a bit surprised when I learned the answer. To be accurate, you would have to run the engine on an engine dyno and then add the driveline components sequentially while measuring output. It turns out the rear wheel/tire assembly(s) absorbs more power than anything in the drivetrain*.

Mitch

* Testing conducted and results compiled by John Ligenfelder using his on-site engine and chassis dyno.

[SergntMac]

Originally posted by MitchB
I thought the question I posed was an interesting one and I was a bit surprised when I learned the answer. To be accurate, you would have to run the engine on an engine dyno and then add the driveline components sequentially while measuring output. It turns out the rear wheel/tire assembly(s) absorbs more power than anything in the drivetrain*.

Mitch

* Testing conducted and results compiled by John Ligenfelder using his on-site engine and chassis dyno.

Yes it was an interesting question, but I missed your question twice, so, I won't try the next teaser you post. I do find your answer interesting too, seems the DynaPack 5000 is the most accurate diagnostic/test tool after all.

I felt it would be and that is why I used it for ten months of building my MM. I switched over to the DynoJet only because it was the tool of choice by the power tune dudes. This gets to be a matter of credibility within the community, people have said to me "if it's not a DynoJet, it's not a dyno." If that's how they feel, why bother to discuss it?

Thanks for the quiz Mitch.

[jrzygrl]

Sooo much information...GASP!! I, I think my head is gonna' explode!!!!!!!!

[Warpath]

Back to my sound theory... I thought of it a better way. Sound is a release of energy. Since energy is conserved, then eliminating the sound would allow that energy to be used elsewhere. But, for the most part, you can spend your time more wisely on larger gains than to try to eliminate a noise. You may not get anything measurable anyway.

[MAD-3R]

You've been losing sleep over that one haven't you :lol:

[mroder]

http://www.dynoperformance.com/search_details.php?ID=312