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Calculator...

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Flash
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Re: Calculator...

Post by Flash » August 26th, 2008, 9:44 pm

About the IVC thing flash, im not really sure how to do what your asking with the forumula's i have...
thats OK, will figure it out some day!!!!!!!

As far as the crane cam(901) we should change it to a (905) It is the same cam spec as the 901..............but was replace with the 905 that has a slight, more taper on the cam lobe to keep the lifter spinning(or so i have read......a....some wares ;)) .....

Flash
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Re: Calculator...

Post by Muad'Dib » August 27th, 2008, 8:23 am

Flash wrote:
About the IVC thing flash, im not really sure how to do what your asking with the forumula's i have...
thats OK, will figure it out some day!!!!!!!

As far as the crane cam(901) we should change it to a (905) It is the same cam spec as the 901..............but was replace with the 905 that has a slight, more taper on the cam lobe to keep the lifter spinning(or so i have read......a....some wares ;)) .....

Flash
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If it feels right, then STROKE it!
You're lucky that hundred shot of CAPS LOCK didn't blow the welds on the forum!!

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Re: Calculator...

Post by Mgardiner1 » September 8th, 2008, 2:36 pm

I was just running some numbers on the CR calculator and i realized something.... I'm pretty sure the cam adv/retard feature is backwards.

Using these #'s
3.935 bore
3.895 stroke
60cc head
0 clearance
.043 gasket
20cc piston
5.875 con rod


When i put in an IVC of 54, and 0 adv, i get a DCR of 8.42
When i put in an IVC of 54, and -4 adv (4 deg retarded), (which effectively changes the IVC to 58), the DCR 8.61

How can the DCR go up if the Intake valve is closing with the piston farther up in the bore? Less stroke goes into compressing the cylinder, therefor the DCR should GO DOWN. I used a different DCR calculator, and when i used a value for IVC 58 (54IVC cam retarded 4 deg) i get a DCR of 8.21


Just thought i should say something. NOW I MAY BE 100% WRONG!!!!!!! And if i am, please please PLEASE correct me (and tell me what i'm doing wrong so i don't make the same mistake again!)
oletshot wrote:....and silvolites are only cast not hypericantspellits. :-)

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Muad'Dib
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Re: Calculator...

Post by Muad'Dib » September 8th, 2008, 5:09 pm

Isnt it IVCA + advance/retard NOT IVCA - advance/retard?

If so using your numbers it would be 54+(-4) = 50

??

On another note, dont forget that when you enter the advance/retard degrees the calculator wants CRANKSHAFT degrees not Camshaft degrees... Thanks for making me think about that also.. i need to change an equation (for calculating DCR when advance/retard is given AND IVCA is given)!!!
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Re: Calculator...

Post by Mgardiner1 » September 8th, 2008, 6:19 pm

Reason i brought it up, when using my desktop dyno, with IVC at 54, and then adding -6 cam timing, it changes the computed IVC value to 60. Maybe the software is wrong? I think your equation is wrong..... 54 degrees at 0 timing. If the cam is 4 degrees late (read as crank is 4 degrees EARLY, or AHEAD of camshaft), then the crank will have traveled further before the IVC reaches the closed point. Or am i just making this stuff up?

LOL seems logical to me anyway.....
oletshot wrote:....and silvolites are only cast not hypericantspellits. :-)

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Muad'Dib
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Re: Calculator...

Post by Muad'Dib » September 9th, 2008, 9:15 am

It seems that you may have caught something!
Retarding the cam delays intake closing and decreases the DCR. Advancing the cam causes the intake valve to close earlier (while the pistons is lower in the cylinder, increasing the sweep volume) which increases the DCR.
I changed the equation .. please try it now! It should be fixed.
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Re: Calculator...

Post by Mgardiner1 » September 9th, 2008, 12:02 pm

Not to beat a dead horse, but i think it got confusing because you were using CRANKSHAFT degrees. +2 crank degrees would be the same as saying -2 camshaft degrees
oletshot wrote:....and silvolites are only cast not hypericantspellits. :-)

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Re: Calculator...

Post by Muad'Dib » September 9th, 2008, 12:35 pm

Mgardiner1 wrote:Not to beat a dead horse, but i think it got confusing because you were using CRANKSHAFT degrees. +2 crank degrees would be the same as saying -2 camshaft degrees

+2 camshaft degrees would be the same as +4 crankshaft degrees.

-2 camshaft degrees would be the same as -4 crankshaft degrees.

It got confusing because when i added advance / retard into the equation i (because i had bad information) had it add instead of subtract.
If it feels right, then STROKE it!
You're lucky that hundred shot of CAPS LOCK didn't blow the welds on the forum!!

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Re: Calculator...

Post by Mgardiner1 » September 9th, 2008, 2:33 pm

TDC crank with a TDC cam (0 timing)
TDC crank with cam +2 degrees (2 deg advanced cam)
crank -4 degrees with a TDC cam (2 deg advanced cam)

Holding the the cam at TDC and turning the crank back -4 (retarding the crank), then when spinning them together in normal engine rotation, when the crank reaches TDC, the cam will have spun 2, making it a 2 degree ADVANCED cam when the piston is back at TDC. Follow?

I really think mentioning crank degrees is throwing everything off. all measurements should always be done with crank and #1 at TDC.

BTW, i did want to mention as well, I LOVE the CR calculator and find it extremely useful and helpful. I think by going back and fourth about this, i'm more or less thinking outloud and learning as we go.
oletshot wrote:....and silvolites are only cast not hypericantspellits. :-)

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Muad'Dib
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Re: Calculator...

Post by Muad'Dib » September 9th, 2008, 3:24 pm

Im confused again... Lets start over talking about advance /retard and how it effects the crank and / or my calc... since the other problem seems to be solved.

This is what my calc says:
Remember to use crankshaft degrees, and not camshaft degrees. If you have a value in camshaft degrees, double it to get the right crankshaft degrees (eg. 4 becomes 8, or -3 becomes -6).
I would assume that most numbers given would be crankshaft degrees... since really when you think of a measurement that is camshaft degrees the only one should be the LSA (Lobe Seperation Angle). So the above statement serves really as a reminder if you for some reason have camshaft degrees. IS the reminder causing the confustion?

Now think of a cam and a crank and how they turn together.

Here is an illustration i just made in photoshop:

Image

The small circle is the crank and the larger is the cam. The arrow shows turning direction.

We know that for every one turn / revolution the cam makes, the crank makes 2. In other words, the cam rotates at half of the engine speed.

Now imagine the cam reversing 10 degrees in one direction.

If the cam reverses direction by 10 degrees, then the crank would also reverse direction, but by 20 degrees.

Do you see the math now?

If for every 1 (cam) you get 2(crank) then x*2

Using the 10 degrees above that we reversed the cam (-10) we now have -10*2 which equals -20.

This of course applies to how you get crankshaft degrees from camshaft degrees NOT how you actually advance the cam... that could be where the confusion enlies.

My question is now this... when say for example the crane cam for our I6's give the spec for retard at -2 degrees, is this spec at the cam or at the crank? Thats the real question! I would assume the spec is at the cam since its usually relative to the intake lobe at TDC right? THAT is why the reminder is there! You have to take those cam degrees and double them so we can get crank degrees.

So are you now saying that the advance / retard figure that is entered by the person using the calc should be in cam degrees instead of crank degrees?? If so, we cant do that because having the cams retard / advance in crank degrees play an integral role in how DCR is calculated. .. well i guess i could change the math to do the multipication for the user ... are you thinking i should do that???
If it feels right, then STROKE it!
You're lucky that hundred shot of CAPS LOCK didn't blow the welds on the forum!!

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Re: Calculator...

Post by kris » September 9th, 2008, 3:56 pm

And to confuse things further...

Im confused about the dynamic compression numbers Im getting.
Im building with the 30ab cam, not that it should matter but thats the numbers Im using...

For my build, if I input an intake closing time of 54* or 56* (depending on where you look), I get a DCR of 8.02:1/7.93:1 respectivly.

If I input 260* duration with the 108*LSA, I get 7.83:1.
256* (Gradon posted in dwg's post) gets back to the 7.93:1DCR


Which is correct ?

k.

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Muad'Dib
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Re: Calculator...

Post by Muad'Dib » September 9th, 2008, 4:14 pm

Flash wrote:
About the IVC thing flash, im not really sure how to do what your asking with the forumula's i have...
thats OK, will figure it out some day!!!!!!!

As far as the crane cam(901) we should change it to a (905) It is the same cam spec as the 901..............but was replace with the 905 that has a slight, more taper on the cam lobe to keep the lifter spinning(or so i have read......a....some wares ;)) .....

Flash
Flash, after discussing the calculator indepth more with Mgardiner1, i think i know how to do what your asking.

Did you want this to be a result at the bottom along with SCR and DCR?
If it feels right, then STROKE it!
You're lucky that hundred shot of CAPS LOCK didn't blow the welds on the forum!!

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Mgardiner1
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Re: Calculator...

Post by Mgardiner1 » September 9th, 2008, 5:03 pm

Muad'Dib wrote:This of course applies to how you get crankshaft degrees from camshaft degrees NOT how you actually advance the cam... that could be where the confusion enlies.

LMAO i'm glad you put that into words, because i don't think i could have. You are absolutely right, my explanation is defining the relationship between the crank and cam @ 2 different positions. The only message your trying to get across is the 2x crank rotation per cam rotation, and for figuring out the quantity of degrees, you are 100% correct. :cheers:

I'll shut up now LOL :lol: :doh:
oletshot wrote:....and silvolites are only cast not hypericantspellits. :-)

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Muad'Dib
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Re: Calculator...

Post by Muad'Dib » September 9th, 2008, 5:34 pm

Mgardiner1 wrote:
Muad'Dib wrote:This of course applies to how you get crankshaft degrees from camshaft degrees NOT how you actually advance the cam... that could be where the confusion enlies.

LMAO i'm glad you put that into words, because i don't think i could have. You are absolutely right, my explanation is defining the relationship between the crank and cam @ 2 different positions. The only message your trying to get across is the 2x crank rotation per cam rotation, and for figuring out the quantity of degrees, you are 100% correct. :cheers:

I'll shut up now LOL :lol: :doh:
Please dont.. i greatly appreciate any and all feedback. Thats how we become better and stand out from the rest.

Did you by chance read or have any responses to my questions at the end of my last long post?

Thanks for all your help.
If it feels right, then STROKE it!
You're lucky that hundred shot of CAPS LOCK didn't blow the welds on the forum!!

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Mgardiner1
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Re: Calculator...

Post by Mgardiner1 » September 9th, 2008, 7:01 pm

Let me take a look at the adjustable timing gear set that i have in the basement, and see if i can figure if 2 degrees is for the cam or the crank.

common sense says "figure on camshaft degrees" but is that the standard? or is crankshaft degrees the REAL standard??!! LOL i'll see what i come up with
oletshot wrote:....and silvolites are only cast not hypericantspellits. :-)

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