Possible insight into the TDB "cam wars"

[Joe R.]

Re: Possible insight into the TDB "cam wars"

Your summary of EA's effective overlap area seems to mostly jibe with what I have, but remember that it also takes into account valve size, so the Duntov cam has less effective overlap with the 1.72/1.50" valves used on most 283s, than the 1.94/1.5" used on 327s with the Duntov cam.
Duke

Hi Duke:

Yes, I thought valve size would be a factor in the calculation, with larger valves contributing to larger overlap area.

The comparison I posted was done with the same set of OEM 462 heads with 1.94/1.5" valves (as modeled in the EA library), so the only variable was the cam timing as represented in the EA library models for those cams.

That's an interesting point that the original Duntov cam had less overlap area when used with the smaller valves of the era.

[Joe R.]

Re: Possible insight into the TDB "cam wars"

Joe,

Very well written commentary!

Remember that the cam lift areas (units: "inch-degrees") that you specified above were derived using the guesstimates that are plugged into EA3.0's algorithm as "mild", "moderate" and "aggressive" "flat tappet" or "roller" lobes. Those lift areas, figured using more accurate ramp acceleration rates (based on actual rated durations @ specified lobe lifts) as is done with EA Pro will be different. Comparing lift areas that are within a 2 inch-degree variation based on those "guesstimates" is like adding .51 + .52 and then giving the answer as 1.030.

Hi Joe:

I am using EA Pro version 3.2 that I bought a few years ago. This version does not appear to have the more detailed ramp model that version 3.5 has. I would be happy to upgrade to version 3.5 if it provides useful improvements.

Does version 3.5 have the more detailed ramp models built into its library models, or does it simply allow you to enter that data if you have it?

[Duke W.]

Re: Possible insight into the TDB "cam wars"

Hi Duke:

Yes, I thought valve size would be a factor in the calculation, with larger valves contributing to larger overlap area.

The comparison I posted was done with the same set of OEM 462 heads with 1.94/1.5" valves (as modeled in the EA library), so the only variable was the cam timing as represented in the EA library models for those cams.

That's an interesting point that the original Duntov cam had less overlap area when used with the smaller valves of the era.

I developed my own models for the OE cams using data taken directly off the GM drawings, my measured 1.44:1 max rocker ratio, and lash on mechanical lifter cams specified at 1.44 times clearance height ramp that I derived from the engineering drawings.

Looking at the accleration and jerk data that I computed from the detailed lobe height data - height in inches to five figures every cam degree - the tops of the constant velocity clearance ramps are very clear.

Duke

[Joe C.]

Re: Possible insight into the TDB "cam wars"

Hi Joe:

I am using EA Pro version 3.2 that I bought a few years ago. This version does not appear to have the more detailed ramp model that version 3.5 has. I would be happy to upgrade to version 3.5 if it provides useful improvements.

Does version 3.5 have the more detailed ramp models built into its library models, or does it simply allow you to enter that data if you have it?

Joe,

Performance Trends has updated its software three times over the course of the last 7 years. The basic program has changed from v3.0 to v3.2 to v3.4. The full featured program known as EA Pro has gone from v3.5 to v3.9.

I have never used EA's library models. I always go directly to the manufacturers website and get the cam card, or use my GM files and specs for factory cams, and input the specs directly from these. I prefer seeing exactly what I'm entering rather than trusting their pre-packaged models to do it for me. I have EA Pro installed on a dedicated computer. If you are serious about paying $469.00 for the download or $494.00 for the CD, then I'll dig out the details for you.

It appears that you fell for Dupe's smokescreen gambit; there was no need for you to explain yourself. He has now muddied the waters re: cam overlap and "effective" overlap. And, yes, valve size, engine displacement and a myriad of other things will certainly affect "effective" overlap. Absolutes are always best when making direct comparisons.