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Discussion Starter #1
With all the dyno'ing going on and mixed bag of claimed Horse Power Torque readings I figure lets attempt to gather some understandable info ....
Enjoy !!!!!!!




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First, we want to make sure everyone is aware that chassis dynamometers are NOT the be-all and end-all to engine tuning. The dyno is only as effective as the operator, just like any other tool. Our operators have years of experience with rolling roads and have Dyno Dynamics dealer training.


How is engine power measured?
The fact is there is no way of directly measuring power - all types of dynamometer measure torque and then power is calculated from the formula BHP = Torque (ft/lbs) x rpm/5252. This basic equation is the foundation of all engine design, development, and tuning. Two main methods of measuring power are used in the automotive industry - (1) measurement at the crankshaft of the engine or (2) measurement at the driving wheels.

Chassis dynamometers, these are used to measure power at the driving wheels. This avoids the inconvenience of having to remove the engine to test it if a tuning modification has been made. However, it means that the power figures obtained will be lower than the flywheel power because of the frictional losses in the drivetrain and tires. This leads to one of the biggest sources of confusion, error and plain misinformation in the tuning industry. You see, as discussed above, all major manufacturers quote flywheel power so it is understandable that people want to know if the hard earned cash they have spent on performance upgrades has increased the power of their engine and by how much. To know this for certain means knowing how much the transmission losses are.

There is enormous pressure on rolling road operators to be able to quote flywheel bhp rather than wheel bhp and most operators now run proprietary software systems which supposedly print out "flywheel" power figures. These software systems are useful for estimating factory performance figures. However, in our experience, as engine performance is increased their "flywheel" power figures generally become unreliable. We know the majority of other rolling road tuners in this country quote "flywheel" figures and here's us saying it is irrelevant. So we'd better explain how a rolling road dynamometer works. The car is driven onto a rig so that the driving tires are resting between two steel rollers. The torque is measured at different speeds in exactly the same way as an engine dyno works except that it is torque at the rollers rather than torque at the flywheel. The braking load is applied to one of the rollers by either a hydraulic (water brake) or electrical system again in just the same way as the engine dyno would apply a torque to the crankshaft of the engine. The same universal equation, BHP = Torque (ft/lbs) x rpm/5252, can then be used to calculate bhp at the rollers by knowing the torque and the rpm of the rollers (NOT the rpm of the engine at this stage) - but if the engine rpm is measured simultaneously then we know roller bhp at a particular engine rpm.

How does an inertia type rolling road work?
The majority of rolling roads used to determine power figures in the US are inertia dynamometers. Inertia dynos do not directly measure the force on the dyno rollers to determine power figures. Instead, these systems calculate the force on the rollers using the formula:
F = ma
Where F is force; m is mass; a is acceleration

The mass and system inertia of the dyno rollers is known. In order to calculate the force applied, inertia dynos measure acceleration of the rollers by measuring the increase in current and voltage production when the dyno's eddy-current retarders are used as a power generator instead of a power absorber (as used to hold the dyno load when mapping engines).

Force on the rollers is therefore the roller mass multiplied by the acceleration
 

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You forgot to include this bit at the bottom of that web page Mac. I have visited there often.
http://www.pumaracing.co.uk/power3.htm


"This article is the intellectual property and copyright of David Baker and Puma Race Engines. Reproduction in whole or in part without written permission is strictly prohibited. "


There was also an interesting article in June in TURBO Magazine that was pretty insightful.


JessEdited by: jesshd
 

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Another thing that effects dyno readings is wheter or not
your "pane" bottle is filled and plumbed properly!

Tom
 

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Discussion Starter #4
jesshd said:
You forgot to include this bit at the bottom of that web page Mac. I have visited there often.


http://www.pumaracing.co.uk/power3.htm


This article is the intellectual property and copyright of David Baker and Puma Race Engines. Reproduction in whole or in part without written permission is strictly prohibited.


Jess
HUH ??

Site was not Puma my info was gathered from .... But KDR Performance ....

Yes Puma Race Engines you are linking to has the dissclaimer ....

Wazzzzz Up !!!!

Mac
 

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Plaugerism abounds! The Puma site has LOTS of good information on what it really takes to make HP. Another good one is


http://www.sdsefi.com/tech.html Not a ton of diesel information, but nice basics. I am still waiting for someone to come up with an ECU "cracker" so we can really see what is going on with the tuning boxes and what they are really doing with the injector timing and injector pulse width. This is something that we have had visibility into in gas performance cars, especially forced induction cars, for a really long time. As soon as we have more than code compilers and Tech II's to work with, it will be a lot easier to understand what is happening. I am sure that most of the programs that the tuning boxes use is not a ton different than the PCMs used in the gas cars and will be easy to relate to. Just need someone to get busy and build an understandable interface to the diesel engines.


JessEdited by: jesshd
 

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Discussion Starter #6
jesshd said:
Plaugerism abounds!





Perhaps but theirs only so many ways to "say it" .... Where T is torque; F is force; r is radius of application
Power is determined by using the formula:
BHP = Torque (ft/lbs) x RPM/ 5252

I'm carefull and read the fine print .... Now that all the legal sh*t is under our belts ,lets rumble ....

Mac
 

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Interesting stuff, so one can use steriods and cheat the machines by playing around with the parameters. Only one way to settle this like men, the old fashioned way, take to the track and get it on!!!!!


LOL
 

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The drag strip is the test. And the HP calculators that are out there do work. Jus thought I would let you know the source of the information so that you could make an informed decision and set the tone for the dieselplace as far as integrity goes. There are too many variables to call the dyno the yard stick. There are differences at sea level vs altitude, DynoJet vs the others, temp and parameter setting on the software, tire pressure, wheel weight, traction efficiency, direct bolt on vs rollers, dynamic intertia readings vs constant load, environmental settings such as barametric pressure and temp and humidity, etc, etc etc....


The only valid comparison is what you have done already. Take the truck back to the same dyno and measure it after changes to the truck. Or and then measure different trucks on the same dyno at the same time. In my experience, I have seen as much as 40-50 hp difference and 20-75 lb/ft on the same car at different dynos at different days at different altitudes. Perhaps the power forum would be the better place for this information?


Could just post a link to this information instead of cut and paste?


JessEdited by: jesshd
 

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Dyno correction factor "fudges" are legendary in the racing engine building business.


As the article states, air temp, barometer, and humidity all play a part in the "corrected numbers". The correction factor/t-b-h will change throughout the day. Corrected numbers are necessary to be able to compare test results throughout the day or week or months of testing. Dynos that sample the test conditions "automatically" just before the test should offer more repeatable results. Making sure the exhaust is routed far away from the intake of the engine is critical. It is amazing how little exhaust ingested by the engine, will lower it's performance output.


Of course there is always the "STD" vs "SAE" corrected data debate, but you guys already touched on that in another thread.
 

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Mackin touches on some interesting information but some does not correctly apply to the DynoJet 248.


This dyno uses acceleration of the fixed mass (drums) to calculate HP. Each DynoJets software is calibrated to it's set of drums as no two sets are exactly the same.


My Dyno Jet calculates it's own correction based on the readings of the "weather station". I cannot change the settings to "create" the reading I want.


Other dyno's I have seen have places for input of the operator that do change the output. I can see this being a BIG source of inconsistant. This is not the case with DynoJet WINPEP software. I cannot fabricate numbers.
 

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so yours is a dyno jet, that answers my next question. The online calculators based on weight and speed in my opinion dont take into effect the torque a turbo diesel puts out and inflate the horsepower number.......king of the dyno and king of the track (as one buddie explaned to me earlier)might not bet the same due to different weights for duallies as for 3/4 ton trucks and a number of other factors.....both dynos in CT had weather stations and those factors are printed and stored with in the run information........I personally prefer the tech 2 method with a optical sensor if any thing it does give you a check from vehicle rpm to dyno rpm. Is always been my understanding(whether correct or not) that dyno runs were to be made at a 1 to 1 ratio. I think torque convertor slippage could cause a flair or spike and this might explain the got juice phenonmin(nick wheres our spell check)and with the tranny locked out of fifth and convertor locked its just one more potential skewing varible erased. I realize you have dynoed hundreds and I understand that it takes more time to use the optical setup and time is money.....I for one think its worth it.Edited by: sdaver
 

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sdaver said:
so yours is a dyno jet, that answers my next question. The online calculators based on weight and speed in my opinion dont take into effect the torque a turbo diesel puts out and inflate the horsepower number.......king of the dyno and king of the track (as one buddie explaned to me earlier)might not bet the same due to different weights for duallies as for 3/4 ton trucks and a number of other factors.....both dynos in CT had weather stations and those factors are printed and stored with in the run information........I personally prefer the tech 2 method with a optical sensor if any thing it does give you a check from vehicle rpm to dyno rpm. Is always been my understanding(whether correct or not) that dyno runs were to be made at a 1 to 1 ratio. I think torque convertor slippage could cause a flair or spike and this might explain the got juice phenonmin(nick wheres our spell check)and with the tranny locked out of fifth and convertor locked its just one more potential skewing varible erased. I realize you have dynoed hundreds and I understand that it takes more time to use the optical setup and time is money.....I for one think its worth it.

I agree the online calculators are close, but not dead-on. They don't expect this torque, nor do they account for the difference in drag coefficient of these bricks we call trucks. There is a site I use that is the best one I have found called SmokeMup.com.


As far as the optical sensor, I agree, I much prefer to use it and it was not a time issue. I didn't use it this weekend because I am working with dynojet to prove one way or another, is this causing my hardware stack to fail like what happened in Michigan. I have blown four of these this year, one my fault (can we say dropped it) and the other three while running diesels. I have spoke with three other shops that have had failures too while running diesels and the only difference between running gas and diesel is this sensor. I will use it as soon as I complete my research into the failure. But remember, on a dynojet, there is no dyno rpm, only engine rpm as picked up from the optical or inductive pickup. This does not change the HP reading.


1 to 1 is used for gas engines. I was told to use OD when running a turbo diesel by DynoJet. Reason was to allow the turbo to get full spool. But running in a higher gear should give you a lower number, not a higher number and this IS the case with a normally aspirated gas engine. So far my testing has showed very little difference with a diesel between 4th and 5th.


Ain't this stuff fun...
 

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Hey David. Wow you are everywhere. Well I bought a new truck. A crew Cab Duramax with the Allison. Will it fit on your dyno?
 

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we saw big differences in a 6 speed in 6th as compared to 4th.......what would account for this? much lower numbers in 4thEdited by: sdaver
 

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Ok, I gotta ask:


"Who's bright idea was it to run the 6 speed truck at a 1.31 ratio???"
 

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not sure it was 4th but the 1 to 1 to which is 5th.........but should it really matter
probably
 

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Discussion Starter #17
Kennedy said:
Ok, I gotta ask:


"Who's bright idea was it to run the 6 speed truck at a 1.31 ratio???"
You'll have to ask Jesse .....

Regardless his numbers were subdued with the TST Comp ....

Mac
 

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Hired Gun said:
Hey David. Wow you are everywhere. Well I bought a new truck. A crew Cab Duramax with the Allison. Will it fit on your dyno?

Now this I don't believe!!!
Did you sell that bad a$$ Dodge? The one that looked so good, especially the Avatar on the dyno? Jared??



Congratulations Jared. When did this happen? I'm sure you are listening to these guys, they will steer you right. I've been telling folks for a year or so that the Dmax is the best bang for the buck on the market IMO. Very Nice truck indeed. If I had the cash, I'd have one too.!!


Yes your truck will fit on the dyno. Did you ever get on a dyno with your Hot VP44? Man I had no idea you were even considering selling it but you did as I probably will, move on to a true crew when the time comes and it will most likely be GM. Put in a Suncoast, get yourself a Quad stealth and atittude and in the words of Dennis Perry - Bye Now. Get that GN hitch installed and lets try pulling the dyno with it so I can see how it does.



Congrats Jared
 

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Kennedy said:
Ok, I gotta ask:


"Who's bright idea was it to run the 6 speed truck at a 1.31 ratio???"

Sounds like something I'd try... oh wait, didn't I dyno mikes truck in 3rd Saturday? Yep and it made it a girl too.
 

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I think someone got their gear position quote crossed up... I hope.





My $.02 on this: Same dyno, same day, same conditions, and NOW you have a comparison...





Additionally, FWIW, I've had days where the 230VA was the single box HP Champeen, and on others, the TST Comp....
 
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