B303 Cam Question

[tjm73]

Using the 0.05" durations they both have zero overlap.

I know that's not correct. The B303 has overlap. I once had a program that graphed valve events (I lost it when my pc got a virus that wiped out everything) and the B303 has overlap.

EDIT - I've been looking at thesse numbers for 10 minutes tryign to make sense of this and still can't decide if there is or is not any overlap.... I wish I had that ol' program.

 

[90Notch]

"I know that's not correct. The B303 has overlap."

I use Desktop dyno using cam events from when I degreed the cam in to figure out overlap. I assumed this program was correct and never verified so if it is wrong then I apologize. Now you have my curious what Engine Analyzer shows.

 

[90Notch]

DP

 

[tjm73]

"I know that's not correct. The B303 has overlap."

I use Desktop dyno using cam events from when I degreed the cam in to figure out overlap. I assumed this program was correct and never verified so if it is wrong then I apologize. Now you have me curious what Engine Analyzer shows.

Engine Analyzer!! That's the program I used to have. If you have it, please run both the cams and screen shot the two graphs and then post them. That will end the confusion for sure.

 

[90Notch]

No need to just look at the timing events. Overlap occurs when intake valve opens and exhaust valve is closing so if you look at the timing events for the B303 at 0.05" how can there be any overlap? Intake valve opens at 5 BTDC and exhaust valve closes at 5 BTDC (or -5 ATDC)..the same time. Impossible to have overlap. Sorry Tom something is wrong in spreadsheet check your absolute values.

 

[tmoss]

tjm73 - look at my post above - verifies your numbers........

 

[tmoss]

No need to just look at the timing events. Overlap occurs when intake valve opens and exhaust valve is closing so if you look at the timing events for the B303 at 0.05" how can there be any overlap? Intake valve opens at 5 BTDC and exhaust valve closes at 5 BTDC (or -5 ATDC)..the same time. Impossible to have overlap. Sorry Tom something is wrong in spreadsheet check your absolute values.

I don't think you looked at the sheet - it verifies no overlap. Isn't that your position?

 

[90Notch]

"I don't think you looked at the sheet - it verifies no overlap. Isn't that your position?"

No I did I got overlap cell and exh cell above mixed up, it's right on..sorry about that.

 

[Michael Yount]

At .050" both the B and the E cam have zero overlap. The reason the B can have more duration than the E, and they both have zero overlap at .050" is because the B has a wider LSA than the E - 112 to 110.

As for aggressiveness of the ramp, there's another important variable that's been left out of the discussion - and that's the shape of the lobe at the top or peak. Without that info, it's really impossible to determine which ramp is more aggressive, not withstanding my previous comments about advertised duration vs. .050" duration. If lifts are close (and .480 to .498 is pretty close), comparing advertised duration to .050" duration is still the best way to determine relative ramp rate. Another example - CompCam Xtreme Energy line (known for their fast ramp rates) XE270 has 270 degrees .006" and gets 218 degrees at .050" out of that. Compare to the E which needs 282 duration at .006" to get 220 at .050". Said another way - it stays open for nearly as long at .050", but it waits 6 degrees longer before it gets to .006", and it drops from .050" to .006" on closing 6 degrees sooner -- that means the ramp rate has to be quicker.