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Author Topic: Team Go Dog, Go! Modified Partial Streamliners  (Read 519249 times)
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wobblywalrus
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« Reply #2490 on: August 01, 2016, 11:43:34 PM »

This is the piston demand curve bases on PipeMax.   


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« Reply #2491 on: August 02, 2016, 05:11:34 AM »

Is there an on-line calculator or way for PipeMax to display or list piston demand at 28 inches vs crank angle for pistons with offset pins?

Not that I know of.    PipeMax is a very basic tool.     There might be an offset pin option in EA Pro from Performance Trends or Engine Pro from QuarterJr.    But if your pin offset is "reasonable", the difference is going to be very small.    It will matter for the best cam timing, but a vernier cam drive and dyno testing at various cam timings, will resolve that issue.

Nice looking adaptors by the way.   On an "orphan" build like yours, expect to have to make the "special" tools and adaptors you will need to do the job properly.    Just the way it is.   Also, if you can buy or adapt something to work in this regard, do it.    Do NOT re-invent the wheel.     Save your efforts for things that are truly "custom" and one-off.

 cheers
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« Last Edit: August 02, 2016, 05:18:19 AM by fordboy628 » Logged

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« Reply #2492 on: August 02, 2016, 05:33:07 AM »

This is the piston demand curve bases on PipeMax.  

OK.   Now overlay cam motion + head flow to see how well the "demand" is satisfied.   The easiest way is with CamFlowRPM from Schmidt Motor Werks, another useful, but basic program.    I hope you have it already.    I'm thinking it is no longer available.

Don't forget that there is a fulfillment lag dependent on rpm.    Model in the center of your proposed rpm range for best results, or across the complete rpm range if you want more data.

 cheers
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« Reply #2493 on: August 02, 2016, 05:47:11 AM »

Bo,

You (and others) might want to read through this thread on SpeedTalk:

http://speedtalk.com/forum/viewtopic.php?f=15&t=29407&p=488263&hilit=camflow#p488263

It is a couple of years old, but gives a better overview of the "demand" & "flow" concepts.    And yes, "It's Complicated".

 cheers
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« Reply #2494 on: August 02, 2016, 07:50:56 AM »

Interested in the "Gone Fishing". Care to elaborate?. grin
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wobblywalrus
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« Reply #2495 on: August 02, 2016, 11:19:02 PM »

Hi Mike, I could not find any references to "gone fishing"in the build diary.  I can try to explain something if I know more about what it is.

The cams are proprietary so I will be vague about their specs.  So as to stay out of trouble, the first intake cam is Moe.  Moe is a big bruiser.  The head flow steadies out at around 231 cfm at .400 lift.  This cam has .061 inches more lift than this and this is .021 inches more than recommended by EnginePro.  The other specs in comparison to EnginePro recommendations are the cam's LSA is 6.5 degrees more than recommended, the intake centerline is 9 degrees farther from TDC than suggested, and the exhaust duration is 10 degrees more than desired.

It will cost a lot of money to modify the cylinder head to accommodate this rascal and the delayed inlet valve closing drops the dynamic compression ratio considerably.  This looks to be more cam than the engine can use.  Does this seem reasonable?
 


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« Reply #2496 on: August 03, 2016, 07:52:07 AM »

Wobbly, a few puzzlements on all this cam work--

Since “piston demand” is purely a geometrically and engine speed derived quantity, why do you keep citing it as being  at 28” ?   What does 28 inches have to do with it?  Also, the rpm at which this demand is calculated has not been given.

That being the case, on Moe’s graph, why does it show a demand after BDC? 

If this demand curve came out of EnginePro or someplace else, they apparently have made or used assumptions on the entire inlet tract--which gets into gas dynamics and is an area that EnginePro’s expertise may be doubtful.  In that case it is not so much “piston demand” but “ideal inlet tract demand discounting the existence of valves and other impedimentia as well as transient wave effects”.

You seem to put a lot of credence in EnginePro’s recommendations, but what is their basis for making those recommendations?  Is it for a good street engine or a full-on racer, or what?

The point is, making tuning evaluations on the basis of unclear representations may not produce the desired or indicated result.
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wobblywalrus
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« Reply #2497 on: August 04, 2016, 08:52:59 AM »

An error is corrected and the demand curve is moved over to where it should be as shown on the attached.  This is demand at 8300 rpm which was peak HP rpm when we did the dyno work using the lower lift cams.  Peak demand does change with rpm.  It does not make sense to use peak HP rpm.  This is on the decay side of the torque curve and inherintly flow into the combustion chamber does not equal piston demand.

What is the best rpm for these flow vs demand comparisons?

Engine pro is a program based on regression analysis statistics where they determine the characteristics of engines that give good performance in their sample population.  It gives a good idea of what seems to work.  It is good for telling the designer if they are out of the norm with some characteristic such as duration, etc.  It is not a design program.

The Schmidt program is not available.  What is a good program for analyzing this stuff including lag? 


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« Reply #2498 on: August 04, 2016, 08:56:35 AM »

Bo, I get the basics but you lost me at Triumph!!!!!. grin
That's some serious delving there. cheers cheers cheers
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« Reply #2499 on: August 04, 2016, 04:24:15 PM »

Bo...........Your chart says that maximum flow is occurring at TDC shocked

Despite the annomoly, when piston demand exceeds flow capability................get out the Dremel..............or...........install a ram-air system............or both..............or............turbo/supercharge the motor.   
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« Reply #2500 on: August 04, 2016, 08:41:05 PM »

Hi, Mike.  The first step in fixing any valve train durability problem is to verify the cams are correct for the motor.  The disadvantage of cam on bucket systems is the lack of lift multiplication from a rocker arm.  The cam needs to do it all.

The Moe intake cam has a very successful history.  It was developed for an engine with much different airflow than the one I have.  It has plenty of lift and the lobes have a sort of fish head shape that gives plenty of lift for longer durations than a typical cam.  Unfortunately, it drops the valves onto their seats a bit fast.  Valve train longevity might be an issue.  This is something I need to figure out.  Is the massive amount of lift and duration it gives worth the added valve train wear?

The piston reaches bottom dead center and its motion no longer sucks in the mixture.  There is some momentum in the mixture traveling through the open intake valve and this forces the fuel/gas blend into the cylinder when the piston starts its upward travel.  This stops when the intake valve closes.  After this, the piston is traveling upwards and it compresses the mixture prior to combustion.  The intake valve closing is a critical event and I need to make sure it happens at the right time.  That is what I am trying to figure out now, and it is the optimum degrees for IVC.

Dennis, the head was reworked by one of the best guys in the country.  He found a lot of air flow in ports that had previously been ground on by others.  All I can do is to screw it up if I get out the Dremel.  What I am going to do is to lower the rpm I tune to so it matches what the head can flow.  I do not have much expertise in this and that is why I am posting it. 
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wobblywalrus
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« Reply #2501 on: August 04, 2016, 11:04:14 PM »

Interested Observer, thanks for mentioning rpm and demand.  I was not aware of that.  The lower curve is at 7,800 rpm.  The maximum piston demand and the flow the head can supply match at 231 cfm at 28 inches.  It makes more sense to tune pipe lengths, pipe diameters, cams, etc to this flow rather than a larger one the head cannot supply.

Tonight I will start to measure the lift vs degrees of Larry.  This is the rephased exhaust cam I used as an intake cam.


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wobblywalrus
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« Reply #2502 on: August 05, 2016, 11:46:14 PM »

All of this cam stuff has me confused and I need to get it figured out.  last night I was looking around on the I-net and I found this www.audietech.com/dynomation-wrapper.html.
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« Reply #2503 on: August 06, 2016, 07:35:42 AM »

Wobbly,
The Dynomation program you found appears to be a dressed-up, more elaborate, and more user-friendly version of  the engine analysis program developed by Dr. Gordon Blair some while back.  His primary achievement was automated calculation of the gas transient dynamics involved in the inlet and exhaust tracts.  As such, the program would be a good tool for engine analysis/design, however, and I haven’t checked, you probably want to be sitting down when you look at the pricing.
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« Reply #2504 on: August 06, 2016, 08:47:32 AM »

WW, you can buy direct: http://www.motionsoftware.com/purchasejac.htm

Some Dynomation data I can share from a [V-8] project just to show it's complicated! Units are mixed to get everything on one graph.

You can download the Dynomation manuals and it is a good education for free! Good overall explanations of a complicated, interactive subject.

You will still need a calibrated hacksaw to get the tuned lengths correct!  shocked grin



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