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Calculator...

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Mgardiner1
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Re: Calculator...

Post by Mgardiner1 » September 10th, 2008, 3:49 am

Mgardiner1 wrote: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

You know, another thing i was thinking, now after looking at this timing gear (will upload pics in a second), seeing how far apart the degree'd numbers are spaced, it makes me wonder if cam timing per degree is equal to crank timing per degree (not doubled). See what you think.

spinning it 1/3 in either direction only yields 8 degrees adv/ret? Shouldn't the same measurement equal 120 degrees? or at least 60 camshaft degrees? I need to do some more reading...... :?: :?: :?:


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oletshot wrote:....and silvolites are only cast not hypericantspellits. :-)

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Re: Calculator...

Post by dwg86 » September 10th, 2008, 8:36 am

It is the relationship between the marked tooth and the key way for a specified avance or retard position... if that makes sense. They are using a different tooth and key way for each position.

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Re: Calculator...

Post by Mgardiner1 » September 10th, 2008, 9:10 am

So then when advancing to the next keyway, the cam sprocket will be set in a different position as well?
oletshot wrote:....and silvolites are only cast not hypericantspellits. :-)

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Re: Calculator...

Post by dwg86 » September 10th, 2008, 5:39 pm

Correct. Lets say you want to advance your cam 2 degrees, you use the tooth marked +2 and the keyway marked +2. The keyway that is cut +2 is a little different than the keyway for...lets say the 0 mark. Am I making sense?

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Re: Calculator...

Post by gradon » September 10th, 2008, 11:14 pm

Here's a good break-down:
http://www.carcraft.com/techarticles/11 ... index.html

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Re: Calculator...

Post by Muad'Dib » September 17th, 2008, 5:56 pm

So have we come to a conclusion?

Camshaft advance/retard spec given is always crankshaft degrees?
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 18th, 2008, 3:46 am

The few people i have talked to on the subject, say that camshaft adv/retard is ALWAYS given in camshaft degrees. These people are not professionals, just hobbiest, so i won't swear by them, but i do agree with them.
oletshot wrote:....and silvolites are only cast not hypericantspellits. :-)

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Re: Calculator...

Post by Muad'Dib » September 19th, 2008, 8:25 am

Mgardiner1 wrote:The few people i have talked to on the subject, say that camshaft adv/retard is ALWAYS given in camshaft degrees. These people are not professionals, just hobbiest, so i won't swear by them, but i do agree with them.
Always in camshaft degrees... ok well then until someone steps in with a different take on the subject, thats how it will be...
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 19th, 2008, 3:34 pm

I really feel like i'm being an a-hole....... But the 2 methods of finding DCR do not work together. A manufacturers spec for IVC includes the amount of timing already built into the cam. If you don't know the IVC and use the duration and LSA, it figures the DCR using 0 degrees advanced.

Going back to the mopar 30AB cam entering the following data: 260 duration, 108 LSA, and 0 adv/ret gives a DCR of 8.08 with the numbers i am using. If i use the same number, but check the box for IVC and enter in 54 (Supplied by dwg86 and reed cams) with a 0 adv/ret i get 8.28.

260/108/0 = 8.08
260/108/+4 = 8.28

So mopar's spec for IVC is 4 deg advanced that is built into the cam (meaning if you set your timing marks at 0, the cam is advanced 4 deg BY DESIGN). Of course, retarding it 4 degrees would make a 0 spec.

IVC i think is really the only true way to know what the DCR is. Duration and LSA are required to find IVC, but don't you also need Intake Center Line to find the IVC?
oletshot wrote:....and silvolites are only cast not hypericantspellits. :-)

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Re: Calculator...

Post by Muad'Dib » September 23rd, 2008, 1:39 pm

Mgardiner1 wrote:I really feel like i'm being an a-hole....... But the 2 methods of finding DCR do not work together. A manufacturers spec for IVC includes the amount of timing already built into the cam. If you don't know the IVC and use the duration and LSA, it figures the DCR using 0 degrees advanced.

Going back to the mopar 30AB cam entering the following data: 260 duration, 108 LSA, and 0 adv/ret gives a DCR of 8.08 with the numbers i am using. If i use the same number, but check the box for IVC and enter in 54 (Supplied by dwg86 and reed cams) with a 0 adv/ret i get 8.28.

260/108/0 = 8.08
260/108/+4 = 8.28

So mopar's spec for IVC is 4 deg advanced that is built into the cam (meaning if you set your timing marks at 0, the cam is advanced 4 deg BY DESIGN). Of course, retarding it 4 degrees would make a 0 spec.

IVC i think is really the only true way to know what the DCR is. Duration and LSA are required to find IVC, but don't you also need Intake Center Line to find the IVC?
So your saying it was a mistake for us to have the calculator use advance / retard when its only given a IVC angle? Or are you saying the math is wrong?

Here is what i get using your numbers..

First of all here is how you calculate IVC from LSA and Duration:
First our Givens:

Code: Select all

duration1=duration/2
IVCA1=lsa-advance
Now to the actual math:

Code: Select all

IVCA=duration1-(180-IVCA1)
Now if i use your numbers:

duration1=130
IVCA1=108

Now:

IVCA=130-(180-108)
or
IVCA=58

So your right there is 4 degrees of crankshaft advance built into their IVC spec... So that tells me that when using LSA and duration, you need to punch in 4 for advance....
You can see by the math above that the numbers are punching correctly... so it seems to me that the figures that you were given do not include the 4 degrees of advance when the IVC spec you were given does.

Does that make since?

So basically is seems when using IVCA, the advance / retard feature of the calculator should not include the actual cam advance.... only the amount of manual advance or retard they plan to use right?
Lets look at the specs below:
Duration=260
LSA=108
Advance=4
IVCA=54

When using Duration and LSA, we would punch in 4 degrees advance.
When using IVCA we would leave the advance field blank. (Because apparently IVCA includes the amount of advance).

Now when cam manufactures give IVCA, does that spec ALWAYS include advance / retard? If so then what i stated above is true. If not, then we have an entirely new problem that could never be resolved.

Am i following so far, or am i way off base?

Also, please dont feel like your being an asshole... the more feedback we get on the calculator, the more accurate it will be.
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 23rd, 2008, 4:57 pm

This is a really tough call...

Manufacturers usually do not list built in adv/ret, so calculating DCR by duration and LSA will never be accurate because there is always a variable that may or may not be known (You know the length and the distance, but not the starting point).

IVC is the only true way to figure out DCR, and from your math, TRUE IVC can only be calculated by DUR, LSA, and ADV/RET

Most companies list IVC specs for their cams, but i can't say i recall seeing the degree of timing listed often.

I would say if the DUR and LSA fields are being used, then it ADV/RET should be a required field as well.

If IVC is being used, ADV/RET should be optional (if advance == NULL then advance = 0). I think it would be easier to read (and less mistakes) for people to punch in the IVC and desired ADV/RET on top. Some people might get confused that 54 IVC = 56 IVC + 2deg ADV.

I know its a little more technical then it needs to be, but if someone is trying to figure out the difference between 87 and 93 gas usage, then these are things they need to know


BTW, i dropped off my block, head, crank, rods, pistons etc at the machinist today :-) Hopefully things will start coming together next weekend
oletshot wrote:....and silvolites are only cast not hypericantspellits. :-)

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Re: Calculator...

Post by Muad'Dib » September 24th, 2008, 9:04 am

Mgardiner1 wrote:This is a really tough call...

Manufacturers usually do not list built in adv/ret, so calculating DCR by duration and LSA will never be accurate because there is always a variable that may or may not be known (You know the length and the distance, but not the starting point).

IVC is the only true way to figure out DCR, and from your math, TRUE IVC can only be calculated by DUR, LSA, and ADV/RET

Most companies list IVC specs for their cams, but i can't say i recall seeing the degree of timing listed often.

I would say if the DUR and LSA fields are being used, then it ADV/RET should be a required field as well.

If IVC is being used, ADV/RET should be optional (if advance == NULL then advance = 0). I think it would be easier to read (and less mistakes) for people to punch in the IVC and desired ADV/RET on top. Some people might get confused that 54 IVC = 56 IVC + 2deg ADV.

I know its a little more technical then it needs to be, but if someone is trying to figure out the difference between 87 and 93 gas usage, then these are things they need to know


BTW, i dropped off my block, head, crank, rods, pistons etc at the machinist today :-) Hopefully things will start coming together next weekend
I understand what your saying...

The way it stands right now, the advance / retard feature of the calculator is optional. If you enter nothing, or leave the value at zero, then it basically ignores that field.

Maybe i should make a note next to the Advance field that says something like if using IVC, then dont enter the amount of cam advance unless you plan on manually advancing or retarting the cam. Since its already figured with IVC spec.
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 24th, 2008, 12:05 pm

Either that or make IVC the only option. Again, if someone is inputing DUR and LSA, but is unaware of what the IVC or manufacturers timing is, then the DCR will be miss leading because it will always assume 0 for the start angle, and DCR will always be off by a few points (obviously depending on the severity of the manufacter's IVC)
oletshot wrote:....and silvolites are only cast not hypericantspellits. :-)

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Re: Calculator...

Post by Muad'Dib » November 4th, 2008, 4:05 pm

Alpha 5 is here!

I have changed alot of the coding for the calculator. I changed some functions so hopefully they will be better and smoother.


Please anyone and everyone test it and test it some more. We want to make sure its great!!

If everyone seems satisfied with this this release, than i will consider it a full release close this thread and make another in the Forum News!
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 » November 4th, 2008, 6:06 pm

any light as to what has been changed? my numbers prove to be the same as before. What gives?
oletshot wrote:....and silvolites are only cast not hypericantspellits. :-)

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