Author Topic: Motorcycle (and car) dynamometer results data  (Read 9040 times)

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Offline entropy

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Re: Motorcycle (and car) dynamometer results data
« Reply #15 on: February 02, 2015, 05:54:05 AM »
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
« Last Edit: February 02, 2015, 06:04:36 AM by entropy »

Offline Sumner

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Re: Motorcycle (and car) dynamometer results data
« Reply #16 on: February 02, 2015, 09:23:47 AM »
.. 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

Offline fordboy628

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Re: Motorcycle (and car) dynamometer results data
« Reply #17 on: February 02, 2015, 10:55:46 AM »

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:
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Offline entropy

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Re: Motorcycle (and car) dynamometer results data
« Reply #18 on: February 03, 2015, 03:27:04 AM »
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

Offline NathanStewart

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Re: Motorcycle (and car) dynamometer results data
« Reply #19 on: February 04, 2015, 11:30:31 AM »
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.

Quote
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.   

Quote
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.   

Quote
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. 

Quote
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. 

Quote
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.
El Mirage 200 MPH Club Member

Offline DaveB

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Re: Motorcycle (and car) dynamometer results data
« Reply #20 on: February 04, 2015, 05:45:15 PM »
 :roll:
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Offline Harold Bettes

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Re: Motorcycle (and car) dynamometer results data
« Reply #21 on: February 04, 2015, 07:17:21 PM »
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 :-)
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