Landracing Forum
Tech Information => Technical Discussion => Topic started by: DaveB on January 30, 2015, 01:49:48 PM
-
I recently found out about a company site that has a lot of dyno data for motorcycles. I apologize if I originally saw this on this site because I don't remember where I learned about it. http://www.factorypro.com/dyno/true1.html
It also has a very interesting discussion about dynos and presents the case that Dynojet brand dynos purposely inflate the numbers so they can sell more dynamometers. In all fairness the site I'm looking at has their own dynos but there are many who say Dynojet by design purposely causes their HP results to be inflated.
-
All dyno's read a little different. Factory pro read way low, I forget why. There is a factory Pro in Houston. Several people have been tuned on the Factory Pro and then gone to Johnny Cheese, my tuner, and they all ran faster after JC tuned their bikes. Of course JC is the best. The Factory Pro checks four gasses and, when tuning, all four are adjusted, I think. Johnny says the Factory Pro Is BS. :-D
-
The Dynojet brand dynamometers are inertia type as opposed to brake type. There is a serious problem with the inertia type dynamometer in that they rely on how fast your motor can speed up the drivetrain and rollers. This is reliant on the rotational inertia of the system which changes when you change gearing, tire size, internal transmission ratios, primary gear ratio etc. Brake type dynos directly measure torque and RPM then a straightforward calculation gives horsepower.
The Dynojet operator can fudge the numbers up and down because of the lack of actually knowing the systems rotational inertia. This variable is not needed when using a brake dynomometer. For comparing one dyno pull to another Dynojet might be OK as long as things like gearing,tires and dyno settings are unchanged but I would never trust one for actual HP.
-
DaveB,
http://www.landracing.com/forum/index.php/topic,14175.15.html
This is my thread: How do I make my engine better. Scroll down to my post titled "Validation of your data".
:cheers:
Fordboy
-
The newer dynojet dyno's are brake dynos.
-
Well this is odd ... My inertia dyno, which is a Dayton Dyno, could be considered a dyonjet clone but has a rotating drum that is about twice as heavy a the dynojet ones. However, unlike DynoJet, I have to calibrate the bikes based on their gearing on every session. Because of that (which I am assuming), horsepower readings are within 1.5 no matter what gear. I can do pulls in 3,4,5,6 and on sub 250 HP bikes the graphs are identical. Higher HP bikes, especially 400+ ones it does make a difference, but I do believe it is because of slip.
-
It sounds like your inertia dyno has a couple specific improvements over the Dynojet that relate to the rotational inertia situation.
The total system rotational inertia (I'll call R E) is a sum of what is a result of the dyno (mostly the drum) and the vehicle. The part of the R E that I am talking about that varies is from the vehicle (bike). The dyno R E is not a problem since its weight doesn't change. The bikes R E changes because of internal speed changes in the drivetrain. I am not talking about shifting gears, I'm talking about changing ratios in your drive train. An example is a Harley where you increase the primary ratio (common on Harleys) but decrease the final chain ratio so the overall is the same but the R E is different because some parts are spinning faster and some are spinning slower. Another example is a car where you lower the rear end ratio but put on taller tires. It's the same some would say, but no because the parts are spinning at different speeds so the R E changed. Another complaint may be "but Dave the dyno drum is much heavier than my bikes transmission parts. This is true but the transmission or crankshaft etc spin much faster than the drum so they have more R E than you think. The drum maybe has the most R E in the system but the engine still has enough (since it spins faster) that changes in its part weights or gear ratios throw off the readings if they are not very carefully compensated for. Man, this topic is hard to cover without resorting to equations.
Since you noted the drum is twice as heavy as the Dynojet drum you must understand that benefit. The heavier the drum the less the R E changes to the engine/drivetrain goof things up. More of the engine energy is going to the drum and less to the drivetrain so drivetrain changes have less affect on the resulting numbers.
Also since you calibrate based on gearing every session, unlike Dynojet, that calibration is a benefit. The gearing changes I am referring to are a result of drive train changes like I have mentioned and not which gear you are in, for a properly calibrated system.
I'm sorry if my discusion sounded like I was bashing all inertia dynos. With careful use, honest operators and a manufacturer that is minimizing the R E issue, inertia dynos are probably OK. Interesting to hear newer Dynojets are brake dynos.
I would like to point out the stated subject of this thread "Motorcycle (and car) dynamometer results data" If you go down their web page they have alot of peak numbers and notes on many different performance bikes.
-
the dyno debate is as old as the apple and ev story, :dhorse:,,
my approach since 2005 has been to use the same dyno for every session, i believe this gives me a correct perspective on changes made, :-)
there are so many variables out there on the salt on any given day, dose it really matter if your horsepower readings are spot on correct, :roll:,,
-
Sta'tee, I agree the dyno debate is old and if you use the same trusted dyno each time things are fine. There should never have been a debate in the first place if everyone would have gone back to the base engineering the truth is apparent.
In reading many comments about Dynojet I strongly suspect they use any variability to skew the results high in an effort to make the customer feel good. My rambling comments above were trying to make that point without getting too calculation based. The horsepower calculations used for inertia dynos have to take into account the vehicle's motor/drivetrain rotation inertia. Unless the inertia dyno is sophisticated, this inertia for each vehicle is just an estimate. An estimate companies could use for nefarious gain.
When I see debates such on dyno accuracy, I have a hard time not going to the base engineering to cut thru to the truth. I have read many things about dyno function as well as the calculations used to come up with horsepower based on inertial acceleration (thats why we can estimate hp based on how fast a car can accelerate from 50 to 100).
Here are some good explanations and engineering with regard to dynos and rotation inertial acceleration:
http://www.newton.dep.anl.gov/askasci/phy00/phy00124.htm
http://en.wikipedia.org/wiki/Dynamometer
http://rcboat.com/dynotech.htm
http://www.factorypro.com/dyno/true1.html
http://hyperphysics.phy-astr.gsu.edu/hbase/mi.html
-
DaveB, I didn't take your comments as bashing anything, just as information. My comments were more of a reflection than a defense. I purchased a Dayton Dyno years ago because is was much cheaper than DynoJet and being a poor racer that was all I could afford. But over the years, I've noticed differences between my Dyno and higher dollar ones that seems that I get more consistent and believable results even though I paid less. Facts keep appearing that support my suspicions.
-
Dyno................the only way to go.......take out the rear wheel and hook up the chain to the Dyno .. build in the late 1950's early 1960's ......no stinking computors......check the clock and do the Math.....works everytime....free standing made with angle iron.....load the Dyno and watch it move acrossed the floor....some bikes it moves forward.....some bikes it moves back.....and for entertainment, put a strobe light on the rear chain under load, and wonder how a chain works as well as it does......scary to watch.......Old school....real horsepower....from 125c.c. to twin Busa drag bikes.........works for all
-
All dyno's read a little different. Factory pro read way low, I forget why. There is a factory Pro in Houston. Several people have been tuned on the Factory Pro and then gone to Johnny Cheese, my tuner, and they all ran faster after JC tuned their bikes. Of course JC is the best. The Factory Pro checks four gasses and, when tuning, all four are adjusted, I think. Johnny says the Factory Pro Is BS. :-D
"which is best" is a loaded question, both can be useful.
Over a 10 year period, I have had my bikes (drag & LSR) on:
1) JC's Round Rock, TX Dynojet (inertial & brake) dyno prob 20 sessions (many hundreds of pulls)
2) Andy's Houston, TX Factory Pro (load - eddy current) at least 52 sessions (many hundreds of pulls)
I kept detailed notes at every session, almost every pull.
Q: Which is best?
A: Dynojet, if you want a bigger number "hp" number.
A: Factory Pro, if you are developing a motor, testing component changes, need consistent data over a long period of time
Q: What about A/F & ign timing tuning for that big race coming up?
A: BOTH can be good IF:
- Dynojet: you MUST have an operator who is REALLY experienced, like JohnnyCheese
- Factory Pro: you MUST have your own A/F logging on yr bike (FP does not log A/F)
Basically: before "going to the dyno", 1) know your specific objective and 2) know your operator/equipment.
I "went to the dyno" before EVERY LSR event to assure the motor/drivetrain & all my subsystems were GTG.
I love JohnnyCheese like a brother, he is a great tuner, and i recommend him
But i gotta say that I really loved hearing my bikes on Andy's FactoryPro when he'd hold 11,000rpm under full load for 15 seconds.
This was supposed to simulate a 1 mile LSR pass, plus the sound is like nothing on earth when standing 5 feet away. :-D
Karl
-
....But i gotta say that I really loved hearing my bikes on Andy's FactoryPro when he'd hold 11,000rpm under full load for 15 seconds.
This was supposed to simulate a 1 mile LSR pass, plus the sound is like nothing on earth when standing 5 feet away. :-D
Karl
Ok, maybe I am going to have to swing by Houston on the way home :-D,
Sum
-
....But i gotta say that I really loved hearing my bikes on Andy's FactoryPro when he'd hold 11,000rpm under full load for 15 seconds.
This was supposed to simulate a 1 mile LSR pass, plus the sound is like nothing on earth when standing 5 feet away. :-D
Karl
Ok, maybe I am going to have to swing by Houston on the way home :-D,
Sum
hey Sum!
You know you are welcome ANYTIME!
but
I sold my bikes and anyway, Andy with his FactoryPro got tired of me & my obsession.
Too bad... He was my bud, i even paid for him to install a MOJO AC unit in his dyno room. Sadly, i don't go to his shop anymore.
15sec WOT pulls were a huge thrill for me. Standing right next to a high hp, screaming bike engine is better than sex, WAY better! :-D
Getting TFA's lakester to a dyno is problematic; we did it but the logistics are a lil complicated for me.
-
Engine life is a big, big, concern for this low bucks guy. The dyno jet inertial dyno we use gives us the info we need and exposes the engine to minimal time at full throttle. More data with less motor wear.
-
Engine life is a big, big, concern for this low bucks guy. The dyno jet inertial dyno we use gives us the info we need and exposes the engine to minimal time at full throttle. More data with less motor wear.
WW,
good point on less motor wear on a Dynojet :cheers:
Dynojet sweep pull lasts 3-4 sec; do 3 of 'em back to back = data at all rpm.
3 4000-11000 sweeps x 4 sec = 12sec WOT
tune - repeat -tune - repeat, etc
tuning can be fast if you have a very competant operator, like JC
dyno operator does tuning adjustments
whereas
FactoryPro, you do steps at 1000 rpm increments, each step is 3 sec+/-
e.g. 4000, 5000, 6000, 7000, 8000, 9000, 10000, 11000 = 8 x 3 = 24sec WOT (48sec for 500rpm steps)
tune - repeat -tune - repeat
tuning is slower, gotta consult bike's AF log, operator just making pulls,
I prefer the owner (me) making tuning adjustments
This is just my experience.
I heavily used those 2 dynos and had very successful results but I am NOT a dyno-smart guy.
Karl
-
.. Standing right next to a high hp, screaming bike engine is better than sex, WAY better! :-D....
Hope we don't have to give up one for the other :cry:,
Sum
-
15sec WOT pulls were a huge thrill for me. Standing right next to a high hp, screaming bike engine is better than sex, WAY better! :-D
As a long time engine guy, I know what you mean . . . .
But, perhaps, something is amiss on the other subject, and could use some "correction" . . . . . .
:roll:
Fordboy
-
15sec WOT pulls were a huge thrill for me. Standing right next to a high hp, screaming bike engine is better than sex, WAY better! :-D
As a long time engine guy, I know what you mean . . . .
But, perhaps, something is amiss on the other subject, and could use some "correction" . . . . . .
:roll:
Fordboy
Bahahahahahahahahaha
prolly not WAY better...
Bahahahahahahahahaha
:-D :-D :-D
-
It seems like these Factory Pro guys have a real bone to pick with DJ. I have some experience with DJ dynos both for cars and bikes but I have more experience with Mustang dynos and smaller roller style dynos (DynoCom, Dyno Dynamics, Mainline, etc, everybody makes one). Here are some thoughts from more of a car perspective.
The Dynojet brand dynamometers are inertia type as opposed to brake type.
Not all DJ's are inertia only. The new DJ's also aren't all loading types either. They sell both so the purchaser can choose between inertial only or loading. Inertial dynos are very simple devices and many years ago when DJ first starting selling "aftermarket" performance type dynos, the technology really didn't support having a loading dyno that could be remotely affordable. So all these performance shops bought up all these early DJ's and you started seeing more and more chassis dyno numbers showing up in magazine and what not. It's not that DJ had some evil plot to over inflate their numbers to sell more dynos (Factory Pro must be conspiracy theorists). It's just that they started out by selling low tech dynos that read a little optimistically.
There is a serious problem with the inertia type dynamometer in that they rely on how fast your motor can speed up the drivetrain and rollers. This is reliant on the rotational inertia of the system which changes...
Maybe this is more pronounced on bikes but this isn't really a serious problem on inertial car dynos because cars are all pretty big and heavy and you have to be way out on the fringe of the spectrum to see a significant reading error.
Brake type dynos directly measure torque and RPM then a straightforward calculation gives horsepower.
ALL chassis dynos have some inertial component regardless of the size of the roller they use. The final whp reading is a combination of acceleration/inertial torque and measured torque from the load cell.
The Dynojet operator can fudge the numbers up and down because of the lack of actually knowing the systems rotational inertia. This variable is not needed when using a brake dynomometer.
The operator of ANY dyno can fudge numbers up or down. Most dynos have a few different CFs to choose from - you can just pick the one that gives you the highest hp value. You can usually also dial in your own CF so to say that this is solely an evil DJ thing is kind of ludicrous.
For comparing one dyno pull to another Dynojet might be OK as long as things like gearing,tires and dyno settings are unchanged but I would never trust one for actual HP.
Comparing DJ to DJ and any other dyno to the same type of dyno is probably the only legitimate comparison. I know of one good magazine article where they took the same car to a few different dyno shops all in the LA area that all used different types of dynos and of course every single one read slightly different.
FWIW I prefer small roller style dynos because the big roller dynos have way too much inertia to do any kind of drivability tuning. The big rollers are great for doing sweeping power pulls plus you can usually run them a lot faster (200+mph) but for transient response tuning, small roller dynos are much much better at simulating real world "track" conditions where you accelerate, decelerate, upshift, downshift, etc.
-
:roll:
-
Ideally one would want to duplicate the rate of acceleration that the vehicle (or engine) under test would experience at Bonneville. Particularly in high gear. Such as at 100rpm/sec or whatever the number would be. However one would also have more confidence in the numbers if it was possible to prove calibration of the test gear. :-o
Inertia only dynamometers are not possible to calibrate easily in the field (on site) and thus rely on whatever the manufacturer says the inertia value happens to be....PITA! :-P
Now having railed on that stuff, what one really needs is very good repeatability so as to compare changes on the dyno whether engine or chassis type. :roll:
In my opinion, spending time on a dyno of any type is worthwhile before heading the path to Bonneville or any of the other high speed tracks. If nothing else, it will save some efforts and provides a chance to sort some of the variables out before a long tow. :wink:
As for the corrections schemes: There are many. And numbers only mean something if one knows where the numbers come from. Don't get caught up in the messy thinking that would have you (the consumer) suffer "You must pass the bill before you can find out what is in the bill..." Use test substituted for bill. :evil:
Now back to your previously selected program. :roll:
Regards to All,
HB2 :-)