[Craig Hendrickson]

Originally Posted by ry57pont

Craig, you are on the list of people i would like to sit down and have a beer with.

Thanks for the invite! If you are ever near Las Vegas, we can do that. In the meantime, how about a virtual clink of the beer mug?

[ry57pont]

Deal!

[Half-Inch Stud]

Originally Posted by OriginalHO

Which cylinder head flow values?

Any of the unported CYL head flowsets, whereas "you" dither the CFM at each lift and observe the NET CFM value. I found the 0.200" CFM dithering produced the most NET CFM change. Admittedly, I can be wrong but the casual observation after a few minutes brought that to light. Should be the "mid-lift value" (such as .250" lift for a .500" peak lift cam) that would mostly increase the AUC.

Again a "Gradient sensitivity" was my point. Fake example of a gradient sensitivity mapping:
lift Gradient Sensitivity to CFM @ LIFT
0.1" 0.2
0.2" 0.3
0.3" 0.2
0.4" 0.1
0.5" 0.1
0.6" 0.05

Such a mapping would promote putting the BEST valvejob on to promote 0.2" Flow numbers, and have USEFUL velocity at that lift time. Does it make you go HMMMM...?

[Craig Hendrickson]

Originally Posted by Half-Inch Stud

Any of the unported CYL head flowsets, whereas "you" dither the CFM at each lift and observe the NET CFM value. I found the 0.200" CFM dithering produced the most NET CFM change. Admittedly, I can be wrong but the casual observation after a few minutes brought that to light. Should be the "mid-lift value" (such as .250" lift for a .500" peak lift cam) that would mostly increase the AUC. (snip)

I do not get the same kind of "incremental improvement" in AUC that you claim. For example, using the flow numbers of the provided 6X-4 stock intake port:

lift-flow
100-79
200-139
300-187
400-202
500-211
AUC-143

Increase each 100 increment by 10% individually, leaving all the other flow values the same, results in these changes in AUC:

lift-AUC
100-144 (79-->87 only)
200-145 (139-->153 only)
300-146 (187-->206 only)
400-147 (202-->222 only)
500-145 (211-->232 only)

The largest value of AUC occurs at 0.400in lift, not 0.200. How did you do your analysis?

[Craig Hendrickson]

Here's the third in this series of calculators. This one is called "Head Flow with Cam Lobe Profile calculator". It essentially merges the capabilities of the first two calculators with further calculations.

http://www.originalho.com/HeadFlowCa...alculator.html

1. Pick or enter a cylinder head's flow data. Some stock and ported heads are provided in a pull down select list. Or you can enter your own data.

2. Pick or enter a camshaft's specs. Ditto on the select list.

3. Click on on the "Calculate" button. The calculated air flow between TDC & BDC on the intake stroke is displayed along with the AUC of that data.

You can try different combinations of head flow and camshaft noting the change in AUC. The same variation applies to rocker ratio and cam centerline. Please input "sane" values as I have not bulletproofed the JavaScript code against idiots.

If you are mathematically or programmer inclined, you may find it interesting to look at the code behind the scenes. Just right click on the display and pick "show source".

I don't think this program shows us too much valuable information yet because the flow values are all at a given pressure differential (28in water for the provided heads). Of course, this is not true in a running engine. Next, I'll add crank/rod/bore calculations with some attempt to figure the pressure differential at crank position and adjust flow accordingly.

[johnta1]

Looks great, Craig.

[Half-Inch Stud]

Craig, I used "attainable" flow improvement at each step, rather than a 10%. With that in mind, you're correct on the 10% dither/lift. Thought I was on to something. Sorry, HIS


Gonna have some fun with the Head-CFM-with-Cam-Profile-calc.

[Craig Hendrickson]

Here's the fourth calculator in the series. It takes crank stroke, rod length, compression ratio and rpm and computes piston travel down the bore, piston speed and volume ratio by crankshaft position between TDC and BDC.

This calculator is standalone and is not dissimilar from many of the same function on the web. I wrote my own in JavaScript because I need the routines for subsequent calculators. Also, this one is Pontiac-specific, at least in the pull down select choices. The direct link is:

http://www.originalho.com/CrankRodPistonCalculator.html

Also, I modified the OriginalHO.com front page to list only one link to a page with choices of all the calculators (4 so far). This way, you only need to bookmark one link, not one for every calculator. The link to the choice page is:

http://www.originalho.com/Calculators.html

[johnta1]

Nice, Craig.

Need to add the Crank Angle at the mean piston speed.



Crank Angle Calculator

[Craig Hendrickson]

Originally Posted by johnta1

Need to add the Crank Angle at the mean piston speed.

John,

Don't you mean the crank angle at which maximum piston speed occurs? A match of the dynamic piston speed with mean piston speed occurs four times, twice between TDC & BDC and twice between BDC & TDC, each time on both sides of maximum piston speed descending and ascending respectively.

In any case, also adding the "optimum" crank angle (ala TD-02 page 11) might be useful as it is not always the same as the above.

[johnta1]

Yep, meant max.


Saw the mean at the bottom of your table and it stuck in my head.



Optimum crank angle would work, also.

Like to see what the max cam flow to occur at max piston speed, is.
Try and get the most suck when the cam can give the most flow.

[Craig Hendrickson]

Originally Posted by johnta1

(snip) Like to see what the max cam flow to occur at max piston speed, is. Try and get the most suck when the cam can give the most flow.

Yes, wouldn't we all! LOL.

[Craig Hendrickson]

Per John Wallace's suggestion, I added to:

http://www.originalho.com/CrankRodPistonCalculator.html

Optimum crank angle (where rod & crank pin are at right angles)
Maximum piston speed (self explanatory)
MPS crank angle (where above speed occurs)

Note that the two angles are not exactly the same, but pretty close.

For sake of vertical compactness, I added these output fields under the "Calculate" button rather than trying to rearrange the whole output display. It should be self explanatory.

[johnta1]

Alright!

That's better.

[Craig Hendrickson]

This is the time for a recap before proceeding with the next calculator or two.

1. AUC4HF calculator: This computes the Area Under (the) Curve for (4) the Air Flow of a cylinder head port at 0.100 valve lift increments. Essentially, the average air flow of a cylinder head port. This is some measure of the performance of a head. There are several on the web, so this is nothing unique other than it runs standalone on a browser using JavaScript language.

2. Cam curve calculator: This program computes a simulation of the camshaft lobe profile given some minimal data points (lift@adv,.050,.200 & max). It then computes the duration at increments of 0.100 tappet lift. As far as I've been able to find, this program is unique, especially using the "spliced Gaussian curve" technique that I employed.

3. Head Flow with Cam Lobe Profile calculator: This program merges the capabilities of 1. & 2. It essentially says: if you have a head, valve train and cam bolted to an engine, what will be the resultant air flow down the cylinder if you can suck on it at the bottom at the pressure differential specified (28inH20 usually) as you turn the camshaft, noting the crankshaft position. Again, I could not find a program like it on the web.

4. Crank/Rod/Piston calculator: There are many like this program on the web. However, this one is Pontiac specific, at least in the pull down choices and output details. The purpose of this program is to build the program subroutines which will hopefully allow me to take the capabilities of all these programs and produce a fifth or maybe sixth program which will give some reliable measure of the expected engine output as the input parameters are varied. In effect, an engine simulation program without all the hassle and expense!

The following is an interesting graph I found on the web and modified slightly for our purposes. This graph relates to integrating all of the above into a fifth program which will hopefully be simple to use, standalone and relatively accurate in predicting the performance result of changing any or all of the inputs to the previous programs. I will use this as a basis for discussing the capabilities of the next calculator. Input is welcome!

[johnta1]

Needs a CSA input?
Something to figure out intake ramming effect?

[Craig Hendrickson]

Originally Posted by johnta1

Needs a CSA input?
Something to figure out intake ramming effect?

That would probably be version 2.0, if we get there. :-) But, I like the way you think!

[Craig Hendrickson]

Getting back to the previously posted pressure diagram...

The IVO & IVC points on the X-axis are for a 270 adv duration camshaft. IVO is 25deg BTDC and IVC is 65deg ABDC.

Interestingly, the curve marked "Actual cylinder pressure" crosses the 1-bar (atmospheric pressure) Y-xaxis at about TDC & BDC between the IVO & IVC points. This makes sense because that is when the piston is starting down at TDC and has finished travelling down at BDC. The piston speed values (curve) computed by calculator #4 is in proportion to the "Actual cylinder pressure" curve between TDC & BDC. This is no surprise due to Bernoulli's law which states that one can trade pressure for velocity in an incompressible gas.

We have the air flow at any crankshaft position from calculator #3. We can adjust the input (@28inH2O) air flow at a crank position for the "theoretical" air flow corresponding to the calculated pressure differential from the piston velocity curve above. We use the relation that the ratio of the squares of the air flow ratios are equal to the pressure ratios, which is the well-known flow bench pressure difference correction factor.

The result of the above should be a kind of "volumetric efficiency" curve that varies by rod/stroke/bore, head air flow, camshaft intake lobe lift and rpm. From this, an indicated or scaled horsepower and torque at rpm can be calculated. This is what I had in mind from the beginning.

I will code this up into calculator #5 and we'll see what results.

[Craig Hendrickson]

To add to my previous discussion...

The result of what I described would essentially be the "cylinder fill amount" (AUC). This would then drive the "power stroke" part of the Otto-cycle given some assumptions about heat added during combustion, etc. I intend to address the power stroke part in calculator #6.

For calculator #5 (the one I'm working on right now), data values like cylinder inflow due to piston speed (Bernoulli's Law), FMEP (friction loss due to bore/stroke & RPM), PMEP (pumping loss of pressure at RPM, primarily due to inlet tract components upstream of the inlet port) can and will be calculated and displayed, with lots of assumptions to simplify things to a manageable degree.

Are we having fun yet?

[johnta1]

I am!