Engine build on the brain
You are on the right tack with this, OP. So that is good. Just needs some adjustment....My hat's off to you for trying to figure this all out.
can't tell
.020 is meaningless for input so is .050
what's your lash?
any idea what .006 at the valve is (taking the lash out of the investigation)
or even .004 or .006 past the lash point
any way to plot your cam
what rocker ratio
Wyrm is asking the right questions.
- These calculators spit out their best results when the lifter lift is around .005-.006", or valve lift around .009-.010" for these engine's rocker ratios. (wyrm, check me on that matter...) Hydraulics are easy as that is where most cam mfr's measure the advertised duration. Soilds have to account for the lash to determine the angles.
- So if your valve lash is .020", the lifter has moved up approximately .013" to close that lash up and start moving the valve. So now you need to know how many more degrees it takes to move the lifter up another .005-.006", which depends on the rate of the lobe at that point.
- As you are probably not past the sloow lash ramps (where the lift is changing something like .0005" per crank degree) to the fast part of the ramps (where movement exceeds .002" per degree), then I'd make a guess at .001" lifter lift per degree of crank rotation in this area of the cam ramp.
- So, to figure the extra crank degrees to get the lifter to move up another .005-.006", then just reduce the .020" duration by 5 or 6 degrees on both the opening and closing ends, or 10-12 degrees total duration reduction.
- That would make the ICA for use in these calculators something like 71-5=66 degrees.
- If you change lash, then you re-figure it.
- This is all much easier and more accurate if you have the cam and can actually measure the angle for .005.-006 lift on the lifter. And since you have the cam card, I'd guess you have the cam..???
- Is your brain hurting yet? LOL
This effects your DCR and so it looks rather critical for your setup on pump gas. So I'd personally make the cam measurements to be sure. I've asked for this data from Howards and Jones and got stiff -armed both times, so we're on our own for this.
And I see you are entering the altitude for your locale, which is a very real effect. Guys at Denver need to run a lot more SCR to get a decent
effective DCR, which is what really effects your cylinder pressures and moves you towards or away from detonation issues.
FWIW.... Just my experience....
as it applies to engine operation below 3000 RPM (below the main torque band) or so and seat-of-pants feel.....
- You will feel .25 point change in DCR
- The engine will feel very differently with a 0.5 point change in DCR
- The engine will be a completely different engine with a 1 point change in DCR.
Having said that, the high RPM performance will be much less effected. And the point about some margin for operational changes is well made. 91 octane does not seem as forgiving as 93 octane. Dry, cool air in the fall is your biggest enemy.
