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Formula jg · 11-25-2004, 11:53 AM

Also,
I have a solid flat tappet Crower #60310, does anyone know how much advance is manufactured into the cam?

Thx.

grandville455 · 11-20-2004, 04:00 PM

<BLOCKQUOTE class="ip-ubbcode-quote">quote:<HR>Originally posted by GoreMaster:
<BLOCKQUOTE class="ip-ubbcode-quote">quote:<HR>Originally posted by grandville455:
I am a bit confused tho for a comp of 9.3:1 I am only getting a dcr of 6.32...Seems awful low for what kind of numbers i am running.My car should be a pig shouldnt it not?.Of course it isnt

..any input here?
thanks <HR></BLOCKQUOTE>

Maybe you've found a bug in my formulas! It's always possible. It's hard to do extensive testing when you're correcting grammatical errors in the text all the time. What are the numbers you put in? <HR></BLOCKQUOTE>
As far as what numbers are you referring too?

MasterGore · 11-21-2004, 12:27 AM

<BLOCKQUOTE class="ip-ubbcode-quote">quote:<HR>Originally posted by DiamondJim:
Is there any way to add a field where you could just enter intake closing so it could be used with dual pattern cams? <HR></BLOCKQUOTE>

Consider it done! I've added the option to either have the calculator determine valve closing angle, or to type it in manually.

I'll try and tweak the calculator over the next few days to make it more user-friendly. Thanks greatly for the input!

MasterGore · 11-20-2004, 01:39 PM

<BLOCKQUOTE class="ip-ubbcode-quote">quote:<HR>Originally posted by BVR421:
nice calculator but javacrap is not welcome on a lot of computers <HR></BLOCKQUOTE>

I've heard this from other people before. Can you explain to me why it's so evil? Is it due to pop-up windows? Because those are easily disabled and aren't necessarily due to javascript. Or is there some myth about a risk of virus infection from javascript? I've personally never had any issues with javascript on the web whatsoever.

What else could I be using instead? Server-side is out of the question, way too slow, especially for dial-up users. VBscript is out of the question, that only runs on Windows and not Macs or Unixes. I'm no Java programmer, so that's out too. What exactly does that leave? Pen and paper? Kinda defeats the purpose...

Criticism is good, but only if it comes with explanations.

MasterGore · 12-14-2004, 07:14 PM

And don't forget that Pontiac advertised compression ratio numbers that were 0.5 higher than "real life". At 52.5 cc heads, you're just about at 10.25, which is 0.5 less than 10.75:1.

I'm still working on including a chart of head port volumes for those who aren't sure what numbers to include in that field. But at this point, I'm thinking there's a LOT of information on that one page that may serve to confuse more than help.

MasterGore · 11-20-2004, 03:02 AM

Yeah yeah yeah, I realize there's a million of these all over the web

But this one not only calculates static compression ratio and displacement, but also dynamic compression ratio! I initially coded it to help me figure out where I was going with my own engine building project, and then I thought other Pontiac enthusiasts might get some use out of it too. So here it is:

http://www.projectpontiac.com/ppsite...nt/view/11/43/

Feedback is always welcome, of course.

MasterGore · 11-20-2004, 04:13 PM

<BLOCKQUOTE class="ip-ubbcode-quote">quote:<HR>Originally posted by 242177P:
This one's from the Chevy guys, but it'll work just fine on our Pontiacs. Static and dynamic.
http://members.uia.net/pkelley2/DynamicCR.html
GoreMaster: If you're determined to get yours working right, I'm fairly certain that Pat could be a big help. <HR></BLOCKQUOTE>

Actually, that's the Visual Basic calculator that I was referring to above. Doesn't work on anything but Windows, so it's useless for me. However I did base many of my own formulas off the ones listed on that page, so it was already a great help.

MasterGore · 11-20-2004, 01:50 PM

<BLOCKQUOTE class="ip-ubbcode-quote">quote:<HR>Originally posted by grandville455:
I am a bit confused tho for a comp of 9.3:1 I am only getting a dcr of 6.32...Seems awful low for what kind of numbers i am running.My car should be a pig shouldnt it not?.Of course it isnt

..any input here?
thanks <HR></BLOCKQUOTE>

Maybe you've found a bug in my formulas! It's always possible. It's hard to do extensive testing when you're correcting grammatical errors in the text all the time. What are the numbers you put in?

BVR421 · 11-23-2004, 07:54 PM

projectpontiac.com seems to down or is it my dumb browser?

DiamondJim · 11-22-2004, 05:42 PM

OK, I'm blind, didn't see the print button-

DOH! -Jim

DiamondJim · 12-01-2004, 05:53 AM

The advance/retard feature does not seem to be working. It has no effect on DCR but it should. -Jim

nosliw · 12-04-2004, 12:15 AM

wait wait wait...

i've got a 326 in my tempest and my chiltons book is giving me a 10.75 CR while this doo-dad is giving me a little over 7:1

DiamondJim · 11-21-2004, 09:32 AM

Goremaster, You Da Man!!

-Jim

MasterGore · 11-27-2004, 08:07 PM

<BLOCKQUOTE class="ip-ubbcode-quote">quote:<HR>Originally posted by Pastry_Chef:
Awesome work Frank.
It needs one small correction to match up with a camcard.
<HR></BLOCKQUOTE>

Thanks! Those changes have been implemented. I was actually asking for advance in camshaft degrees, mostly because I wasn't sure wheter crankshaft or camshaft was the accepted standard. I've adjusted the formula and changed the text on the page to reflect a change to crankshaft degrees instead.

DiamondJim · 11-21-2004, 11:08 AM

Is there an easy way to move it so it prints out better? Not complaining, I hope you don't mind my suggestions. -Jim

DiamondJim · 11-20-2004, 08:02 AM

Wow, that is really neat. Works great for single pattern cams. Is there any way to add a field where you could just enter intake closing so it could be used with dual pattern cams? Not complaining, I appreciate all your hard work!! -Jim

grandville455 · 11-20-2004, 08:23 PM

Here's the #'s
4.19
4.21
98 c.c
.005
.039
6.6
.1
.0028
6.625
290
112
+6

MasterGore · 11-30-2004, 03:32 PM

<BLOCKQUOTE class="ip-ubbcode-quote">quote:<HR>Originally posted by Geoff:
Also, using the 'advertised duration' will give varying figures. If you use a Comp Cams hyd, they usually quote their hyd cam figures at 0.006"; Crane often use 0.004" . Could get a different DCR for essentially the same lobe profile because of a difference in the quoted 'advertised duration' figures.
<HR></BLOCKQUOTE>

The difference that 0.002" makes in valve closing angle is extremely minimal. The actual calculated difference turns out to be negligeable. The only truly accurate way to determine intake valve closing angle is to measure it yourself using a degree wheel and a gauge that measures piston height. All other means (most of them involve basing calculations on the cam duration) are a "best guess" which can be plenty accurate for baseline figures. This is why I added a means to manually enter the closing angle, some people have gone through the process of measuring it themselves.

<BLOCKQUOTE class="ip-ubbcode-quote">quote:<HR>Originally posted by Geoff:
The very fact that it is called 'dynamic' means that it is changing. And that is exactly what it is doing, constantly: changing. I feel there are too many variables involved to get DCR from a formula or equation. <HR></BLOCKQUOTE>

Actually no, the dynamic compression ratio does not change throughout the RPM range, it is fixed. Just because it's called "dynamic" does not mean it changes. I agree that it's a misleading term to use, but it wouldn't be the first technical event that's poorly named

In this case "dynamic" refers to the fact that the compression ratio can be varied independantly from the static compression ratio (ie. with cam timing).

There's a few excellent explanations for dynamic compression available on the web. Jim Hand wrote one, and there's another article that's been pointed out numerous times in this very thread.

Anyways, cylinder pressure isn't measured as a ratio. That wouldn't make any sense. Cylinder pressure is measured in psi.

pastry_chef · 12-01-2004, 08:40 AM

Jim, the advance/retard input is not factored when the box is checked and you enter manual intake closing.

If you know the degree at which the intake closes.
To advance "X" amount of degrees... subtract (-x) from the original number.
To retard "X" amount of degrees... add (+x).

MasterGore · 11-20-2004, 12:48 PM

<BLOCKQUOTE class="ip-ubbcode-quote">quote:<HR>Originally posted by DiamondJim:
Wow, that is really neat. Works great for single pattern cams. Is there any way to add a field where you could just enter intake closing so it could be used with dual pattern cams? Not complaining, I appreciate all your hard work!! -Jim <HR></BLOCKQUOTE>

That was going to be the next thing I tackle. I initially set it up with cam duration and LSA because I'm too lazy to manually figure out closing angle for each cam I'm considering, but then I noticed that my formula for determining closing angle wasn't coming up with the right number for dual pattern cams. I figured I'd stick with duration and LSA for now anyways since a lot of people don't even know how to figure out closing angle in the first place.

Giving users the option of using either duration/LSA or directly inputing closing angle themselves can get a bit more tricky, but I'll see if I can find an elegant way of doing it in the next few days.

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