PRI Show
PRI Show
(OP)
I am new to this site and find it very informative.
I also recently attended the PRI Trade Show in Orlando and saw some interesting products while there. One company had a boring head that was programmable & expanded as it machined below the minor diameter. It appeared to be a high quality piece and is targeted to cylinder head technicians.
Another company had an inertia type engine dyno with a series of large diameter, heavy flywheels. It also had a Stuska absorber connected to the main centerline. I do not fully understand the concept and was hoping that someone here could explain it to me.
Thanks.
I also recently attended the PRI Trade Show in Orlando and saw some interesting products while there. One company had a boring head that was programmable & expanded as it machined below the minor diameter. It appeared to be a high quality piece and is targeted to cylinder head technicians.
Another company had an inertia type engine dyno with a series of large diameter, heavy flywheels. It also had a Stuska absorber connected to the main centerline. I do not fully understand the concept and was hoping that someone here could explain it to me.
Thanks.





RE: PRI Show
Shane
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Your thoughts lead me to another question: How do the typical dyno companies compensate for engines with different inertia-effects (rotating/reciprocating weight)? Are there formulas involved?
BTW: I do not remember the name of the inertia-dyno company, however the rep claimed much closer repeatability figures than the normal +/- 0.5%. It seems like he spoke of around 0.25% or so. Why would this dyno be more repeatable than a traditional brake dyno?
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I am guessing that this company is trying to give you some transient testing ability without the complexity and cost of an AC or DC dyno system.
The inertia effects for each engine are typically ignored for steady state systems (typical eddy current and water brake dynos). For transient testing with an AC or DC dyno, these effects can be measured by motoring the engine with the dyno (without combustion).
Shane
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I should've given more information about my question concerning "inertia-effect" of each engine. I was speaking of the formula/procedure for calculating this effect during acceleration testing on the brake-style dyno's. This could lead to erroneous readings if not calculated corectly and I am trying to find out how each company figures this number.
Our company is looking for a dyno that will be used primarily for development testing. The repeatability claim of the inertia dyno has us giving it more consideration. The AC & DC dyno's are too expensive for us to think about and I am not sure they would be any better than the inertia dyno for our needs. (Perhaps not as good!)
Also; I found out that an engine builder named Ron Hutter has used on of these inertia dyno's for a few years now and likes it. Does anyone know Ron?
Thanks.
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I had a couple of observations and would greatly appreciate input from members on here.
1) They use a "Lenco" case to engage and disengage the inertia mass and it seems to work fine. I know nothing about the Lenco box and would like some input from anyone who is familiar with them.
2) Concerning the software: The dyno repeats so well that it's almost a little hard to believe. I know that a fairly large amount of mathematical filtering is necessary for traditional dyno's to produce smooth & repeating power curves and asked the engineer about their filtering set-up. He claims that they do not filter elapsed time but do apply a light filter to engine rpm. (Due to engine torque spikes). Can anyone offer input on this? How much filtering is too much? (I would not want to "filter-away" good data in the interest of a pretty power curve!
Overall we left pretty impressed. Unless somwething is revealed that we are unaware of, we are probably going to purchase one of these machines.
Thanks.
RE: PRI Show
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: PRI Show
Ideally there would be no filtering, however I have yet to see any raw data from a dyno test that was legible enough to decipher. There are even a few companies that do not provide the ability to view the raw data. The reasons for filtering are complex and also at times seem a bit controversial. At any rate - I realize the need for filtering and know that the best situation involves the least amount of filtering to produce a legible curve.
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True throughout testing. Just give me the raw data and calibrations and I'll choose my own assumptions when processing. Raw data is really cool stuff.
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Michael
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where in NC is this dyno located? Just curious.
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SomptingGuy: That's an interesting reply. When viewing all of the raw dyno data from various companies - I've never been able to draw reasonable conclusions without some "smoothing" effect. Do you have your own program and use ascii data?
stout1: Sorry, but I am not familiar with a centrifical dyno. The inertia dyno I saw uses a series of large flywheels to simulate the vehicle's inertia. It also uses a gear-reduction unit. They tell me that Ron Hutter tests 1700+ HP Pro Stock engines on one of the same machines. I saw them test a NASCAR Busch engine on it and they told me that it can simulate the straightaway of any NASCAR track.
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Also you can never simulate what an engine will do on the track, at best what it does on the dyno is an estimate. I have seen engines with identical power and torque curves act very differently on the track. On the other hand the more ontrack testing of dynoed engines that is done the smaller that your error will be, but it will still be there.
Michael
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The concept makes sense to me. Is there anything I am missing here guys?
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Most of the cup guys that I know are using A/C dynos for track simulation these days. I'm not sure how much they worry about trying to simulate drag, etc. but I'm sure they will be looking into ways to increase the correlation between the dyno and the track as NASCAR continues to restrict their on track test days.
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I guess my question then becomes: If a test "window" is taken from on-track Pi-data and the dyno is physically configured to match those figures, how far off would you be?
Ex: Let's use hypothetical information from say - Richmond Raceway.
The engine is at WOT for 6.5 seconds.
Beginning rpm (at throttle open) is 6500.
Ending rpm (at throttle closed) is 9500.
So we've established that the engine accelerates "the mass" (as this is data straight from the car's data acq - aero and all other friction-loads would be included in this E.T.) from 6500 to 9500 rpm in 6.5 seconds. [Call this "the run".]
Now, you set-up the gear ratio and inertia wheel arrangement of the dyno to exactly mimic the run data. (Engine accelerates the inertia mass from 6500-9500 in 6.5 seconds at WOT.) At this point, the dyno run is pretty close in simulation to the on-track run. [I agree that the aero and other load curves would be slightly different between the 2 runs, but not as much as one might think.] I then go to work on the engine and try to reduce the E.T. of the dyno run. If I am able to reduce the E.T. - wouldn't this always result in better on-track performance? The performance gain may not be linear from dyno to track, but it seems that it would be very close.
Again - please offer your thoghts.
Thanks.
RE: PRI Show
RE: PRI Show
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: PRI Show
There is no gear change made during the acceleration run. It is more like the final drive ratio on a vehicle.
RE: PRI Show
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: PRI Show
Our interest is only for engine-acceleration testing. Not for durability testing and/or endurance testing. We have no need to exactly simulate deceleration, gear changes, etc. (although we will be doing some part-throttle and off-throttle testing in addition to WOT testing). Sorry for the confusion.
RE: PRI Show
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: PRI Show
As for the filtering question, our ac dyno has four outputs for speed and torque
1. Raw data
2. a 1hz filtered and averaged signal used for feedback control
3. a 1hz 4th order Chebychev filter
3. a 10hz filter for displaying stable readings to the user
I log the raw data and filter it in Excel, etc depending on the desired final product. The level of filtering depends on your sample rate. Our software can record at 4167 Hz, so it takes a good bit of filtering to make a nice power curve. If I am doing a power curve on an engine that is already calibrated I reduce the sample rate to about 20 Hz to clean up the data.
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I took the message of the engineer at this dyno company to be that the inertia dyno could replicate the acceleration characteristics of an engine on the race track more closely than a brake style dyno.
I did a poor job in conveying his message!
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NCShane(or anyone for that matter): Check out this info the the DEPAC "special statistical process". Let me know what you think--thanks.
ht
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bsfc9: I am pretty familiar with the DEPAC system and it is very good. However the "smart-averaging", like filtering is utilized to smooth the data enough to practically analyze it. (I use the term 'filtering' as a blanket description for any manipulation of the raw and/or real data, which would include any "averaging".) Each dyno software company utilizes a filtering process. They use different methods, but all do it. There is too much "noise" involved in testing a race engine and the filtering is necessary to smooth the data. ("Noise" from rf, power pulses, ignition scatter, etc.)
The problem comes in when a dyno software utilizes excessive amounts of filtering in order to manipulate the data to an extreme. (I've witnessed dyno [acceleration] tests that sound like a stepped test - yet when the graphed data shows on the screen, it is very smooth, rounded, etc. and looks nothing like the run it came from. In my estimation - this is too much filtering! That particular dyno-company does not allow the customer access to the raw data!
This is one feature that is attractive about the inertia dyno. Since the engine is accelerating a fixed mass (just like a car) the acceleration run is very smooth and the data does not need the excess filtering to smooth it.
RE: PRI Show
Yes, we will get the dyno with the water brake attached.
.75 Hz is the amount of filtering they were using on the rpm channel of the inertia dyno, no filtering on the elapsed time. I did not check any other channels, but all are user defined as to the filtering %.
The software uses a 3000 Hz board and up to 1000 Hz per channel.
What brand of AC dyno do you own?
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fishracer: We have a Schenck Pegasus AC unit.
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