MelloYellow

I don't totall understand overlap. I know that generally a 114LSA with low to mid duration is concerend to be a good cam without too much overlap.

How much overlap would a 216/224 114LSA 110CL have? Generally speaking?

What is the general line for the typical 7-10# Superchargers? I also notice more people mentioning a 112CL lately.

Thx!

qqwqeqwrqwqtq

216/224 114LSA 110CL

in valve open- 2 deg atdc
in centerline- 110 atdc
in valve close- 38 deg abdc


ex valve open- 50 deg bbdc
ex centerline- 118 btdc
ex valve close-6.8 btdc

overlap- NEGATIVE 8.8 degrees

Meaning, the exhaust valve closes 8.8 crankshaft degrees before the intake valve starts to open.

NeeleymanZ28

INTMD8, could you please post the formula that you used to derive those calculations? Thanks

ChrisB

I doub't INTMD8 used a formula and did it all manually (if he did I am impressed!) What I would do is just plug those numbers (duration @ 0.050, etc.) into something like desktop dyno and it will give you an approximate overlap value.

The problem is this is a value that assumes a certain opening profile from closed to the duration @ 0.050 numbers - if you want to get the actual overlap specs you need to contact the cam manufacturer or put it on a cam doctor.

Just as a point when you talk about "CL" (centerline) you probably want to specify if you mean the intake or the exhaust (centerline). Normally people refer to the intake (ICL). Your intake centerline is going to be the LSA - Advance (negative if retard), and exhaust centerline is going to be LSA + Advance.

If you are trying to cut down on overlap with a blower setup in mind probably your best bet is going to be to move the intake valve opening a bit later - this way you don't cripple the exhaust side by closing it sooner. You can do this by either widening the LSA or retarding the entire camshaft (as well as selecting different lobe profiles). Don't be afraid of narrower LSA's on a blower car as long as your duration is small - the "114lsa" by itself isn't any sort of magic number, etc. When your duration values get much bigger then you simply need wider LSA's just to keep the intake opening/overlap reasonable - but the LSA is a byproduct of the larger durations, not any sort of panacea in and of itself.


Chris

qqwqeqwrqwqtq

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by NeeleymanZ28:
<strong> INTMD8, could you please post the formula that you used to derive those calculations? Thanks </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I just scratched it out on a piece of paper. (took a little while though <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> )


ChrisB, if you type the cam specs into desktop dyno will it give you all of the valve events or just an overlap value? It would definitely save me some time if it did all of the above.

A DEE O

iTrader: (2)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by ChrisB:
<strong> I doub't INTMD8 used a formula and did it all manually (if he did I am impressed!) What I would do is just plug those numbers (duration @ 0.050, etc.) into something like desktop dyno and it will give you an approximate overlap value.

The problem is this is a value that assumes a certain opening profile from closed to the duration @ 0.050 numbers - if you want to get the actual overlap specs you need to contact the cam manufacturer or put it on a cam doctor.

Just as a point when you talk about "CL" (centerline) you probably want to specify if you mean the intake or the exhaust (centerline). Normally people refer to the intake (ICL). Your intake centerline is going to be the LSA - Advance (negative if retard), and exhaust centerline is going to be LSA + Advance.

If you are trying to cut down on overlap with a blower setup in mind probably your best bet is going to be to move the intake valve opening a bit later - this way you don't cripple the exhaust side by closing it sooner. You can do this by either widening the LSA or retarding the entire camshaft (as well as selecting different lobe profiles). Don't be afraid of narrower LSA's on a blower car as long as your duration is small - the "114lsa" by itself isn't any sort of magic number, etc. When your duration values get much bigger then you simply need wider LSA's just to keep the intake opening/overlap reasonable - but the LSA is a byproduct of the larger durations, not any sort of panacea in and of itself.


Chris </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Chris, could you please go through this same explanation for a turbo applicaton. I have a 224/224/561/561/112LSA. I have the cam doctor and it says :ICL 107.7ATDC--ECL 115.7BTDC. It has +4deg built into it. My car is getting the CAS TT kit as we speak. This is the cam that is in the car now.. I will be setup for 6#'s of boost. Thank's in advance.....Angelo

MelloYellow

INTMD8:
Wow! Thanks for taking the time.
That's nice to have those specs.
<img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

So, is Negative 8.8* of Overlap considered good, bad, ok? Anything Negative is ok? What should we consider the rule?

P.S. ICL is 110.

qqwqeqwrqwqtq

No problem <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />


IMO that is a good blower cam.

MelloYellow

Cool. If you have time I think the most common Cam floating around out there is the 224/224 114LSA 110ICL.

Would it's overlap be much different?
Anything negative is good, eh?