BlkOps

Hey guys,

Anyone have any advice or experience on the separation angle for the cam.
I am thinking a 112 is probably okay for a daily. Any thoughts?

Also, my understanding is that LSA will effect how the car sounds at idle. Is that true?

Thanks in advance,

HCI2000SS

iTrader: (2)

It just depends on what you're looking for, your goals, the rest of the specs, etc...What are we talking here?

00pooterSS

iTrader: (40)

there's 100 other questions to go with that

For example. A tiny cam with low duration say 190/190 with 112 lsa may not chop at all, but a 240/240 with 112 will big time

Overlap is where that chop comes from, overlap is a much better representation of how it will act at idle, LSA is not necessarily.

You absolutely can do a 112 in a daily. Or a 110. Or a 117. All the other numbers outside of the LSA are more important to answer your question.

00pooterSS

iTrader: (40)

This will help you a ton man. Read through this.

https://ls1tech.com/forums/generatio...-t-matter.html

G Atsma

^^^^ That is SUCH a good sticky! Lots of good info to help sort out how it all works together.

kingtal0n

iTrader: (1)

Some people like the engine chop and enjoy the added difficult of driving the car like that. They like to claim "only I can drive my car" and "my car is too hard to drive for normal people" and "I like to start my car and watch peoples reactions"

its all for show. Because in a daily/street application, You dont need alot of chop to go fast, or even a loud exhaust, since you are limited by the tire anyways. For example a stock cam/quiet turbo can still have double the output of the same engine with all it's chop and noise. As an added bonus, the turbo car can also have chop. But now we are talking significant power levels beyond what a typical street tire will do without a ton of vehicle weight, since the very act of changing a cam means you are anticipating moving somewhere between 10lb/min and 50lb/min to the right of a typical street car's compressor map.

98znasty

To somewhat answer your question I have a 228/232 @112 cam and I think it would be fine for a daily could even be a little more aggressive and get away with it but really it depends on you and your build

kinglt-1

iTrader: (26)

Your thread title should be "overlap for a daily" because that is what really matters when it comes to how a cam is going to act. Keep the overlap under 5 degrees and it should be pretty civil. Keep overlap under 0 and it will drive like stock.

kingtal0n

iTrader: (1)

careful quoting overlap numbers. Factory camshaft probably has many degrees of overlap from seat to seat.

G Atsma

It doesn't matter as long as everyone's on the same page, as in using duration at .050" lift, which is the norm when quoting overlap numbers. What you say could be true, but hardly anyone quotes seat to seat numbers except for old "advertised duration" numbers.

kinglt-1

iTrader: (26)

exactly...

kingtal0n

iTrader: (1)

Sometimes in kinetics, especially with angular rotation/momentum type questions, I don't write the units because it can muddy everything up.


The answer makes sense to me, so why should it matter? The instructor also doesn't seem to mind. However, any 3rd party person inspecting the work or stumbling upon it without significant background wouldn't be able to use the resulting math/equations, even if everything is correct, because the units are missing. Unless they themselves are already very familiar with the type of question or have experience dealing in kinetics/dynamics, motion of objects.

Units are very important, even when obvious to "you", because not everybody else looking in knows what "you" know.

G Atsma

If you are referring to my post above, I'm sure you know that around here cam duration is most often quoted at .050" lift, and LSA calculations follow from that. So when you talk about events from "dead closed", it shifts the parameters a bit, as far as the common "cam language" as used around here. You appear to live in an educational environment where the terminology is a bit more precise and quantitative-analysis based. So I see where you are coming from.

kingtal0n

iTrader: (1)

having a number and unit is quite different than saying something is big or small.

"The Tiny dog is in the humongous purse of a very short lady".

Every persons mind will assign their own size to each object.


We can be "more precise" but too much precision can muddy things up, the 34.158329586435" by 56.00000000144" might be necessary if it was a space shuttle landing, but we could leave off many of those decimals in other practical applications.

For a public forum, the discussion rarely concentrates on ramp rate. Ramp rate from 0.00001" of lift to 0.501" of lift will be faster on solid-roller setups, and it will change the height of the valve at .050". There are also flat-tappet style camshafts which have even slower rates than hyd. roller. So many types of camshaft, ramp rate designs exist, some of the info is historical i.e. this is for learning objectives. Some profiles are so fast they trash valvetrain components within 24 hours, performance in the head at the expense of wear and tear, to win a race.

So yes, in the context of measuring a camshaft profile and determining the quality of lobe, I think it is important to be aware of the difference in seat-to-seat, ramp rate, and .0501" to .0500" that our camshafts can provide. I say our because there are engines out there with multiple camshafts, which allows for rotation of one set of valve events (say you only wanted to advance the intake valve events, but not the exhaust valve events). Some engines can even change overlap by advancing or retarding each camshaft independently from the computer. It allows for a perfectly flat torque curve, since now you can optimize valve events at every RPM instead of having one specific ground in split between them which peaks at only one specific point. By reviewing history, and other engine's technology differences from ours, learning how they are doing things, and seeing new ways of thinking about how a valvetrain is controlled, what we go through to get extra lift (trying to get more flow) the next engine manufacturer can get the same or better by just moving one camshaft relative to another from the computer. Because the naturally aspirated engine is capped around 100%VE, even if it can get 105 or 108% with a tunnel-ram, it isn't much past "100" we simply can't do better than that, and if I can get 100% using an incredibly low lift just by timing my valve events correctly for that exact RPM I can avoid all the unnecessary wear and tear.



Next, and perhaps more importantly, there are calculations for fuel injector spray timing in most ECU. Even my 20 year old Gen3 ECU has a couple, "small" (couple of 1-row ) injector when-to-spray and end-spraying tables. Knowing exactly when, not sort of when but exactly when the exhaust valve is absolutely shut beyond all reasonable doubt is not essential because we can always fudge factor a couple degrees after that spot. So precision isn't super important. Even so, we should know or be aware of the full advertised duration of the camshaft to get this number without going overboard.


In conclusion, the overlap feature that is ground into Chevy V8 camshaft has ties to various aspects of performance and tuning. It can be used to model the behavior of a variety of aspects of an engine's performance, even the behavior of fuel.

00pooterSS

iTrader: (40)

godzilla facepalm

99 Black Bird T/A

iTrader: (4)

kingtal0n

iTrader: (1)

I must say this forum is the most regressed I have seen. Even the young kids of zilvia and hondatech seem more interested in education and learning. Everyone here seems like they want to avoid reading and learning at all costs.


Lets talk about human behavior for a minute. If I can put my injector spray right where I want it and have the best looking plugs, the most efficient engine and best economy, and I am actually late to the party since people have been doing this stuff already for years before I even knew about it.

Then to find a forum on the infinite plane of internet space, where, not only does nobody even know overlap-based injector phasing maths exists, they actually reject learning what so many others have discovered so long ago. Its like finding a sub population of humans that still think the Earth is flat, and refuse to change from that belief.

I found the epic thread where this is discussed by those who came before us, and did all the hard work for us:
https://www.hptuners.com/forum/showt...light=ecu+warm

Calling it bullshit is like saying the first person to notice planets have simple harmonic motion was a witch and should be burnt. Call them witches if you want; their cars are faster because of it.

Darth_V8r

iTrader: (4)

So.... if she weighs... the same as a duck.... then she is.... made of wood?

G Atsma

King, what you don't see is that so much of the stuff you put out here IS knowledge, BUT adds NOTHING that does any good towards improving performance besides what is known already. Many of the guys here might not know the terminology you do, but they damn sure know what they are talking about. You make it sound like you just discovered the Earth is round, and the rest of us ******** must still think it's flat because none of us has said it is round, even though it is common knowledge. You learning something does NOT suddenly make it true. Many know it IS true, but you JUST learned it as truth. Plus, your attitude as above doesn't make things better.
We don't need to know every little detail of theory about something to make it work. Only enough to make it work and have a good working knowledge about it.
Read JakeFusion's post below- A good example of good working knowledge from someone who knows how to apply it without adding non-relevant factoids and stats

JakeFusion

iTrader: (7)

Well, EOIT is something that's pretty common knowledge for tuners... because it's a PCM-related function and not a function of the engine or cam spec. And, it's done much more extensively on the Gen IV PCMs allowing you to vary based on things like RPM! On the Gen III... it's a one-size fits all approach based on operating temperature. So it's not as much of a panacea or whatever the hell you think overlap-based injector phasing is (which isn't what EOIT is - these are not VVT engines).

So the problem is, you're conflating EOIT with overlap. And that's not how this works.

Overlap is determined by the valve events in degrees. EOIT is determined in some GM-specific 720 degree cycle that is shown in Normal and Boundary terms in a Gen III PCM. The idea with EOIT is to set when the injector fires, so the fuel hits a hot exhaust valve.

But guess what, LSA and EOIT are not the same thing. You don't even consider EOIT when you're spec'ing a cam. What if it goes in a Carb motor? There is no EOIT at play. Or what if it's a Gen IV PCM where the EOIT changes based on RPM?

No, overlap derives from the actual, physical specs of the camshaft. And you can only tune around it so much. Physics dictates what the cam does. And valve timing can be whatever the hell you want it to be. Doesn't mean the engine will like it and perform correctly. But EOIT is just telling the PCM how much to delay firing the injectors. And you can alter EOIT based on whatever cam you put in there. But most folks don't change anything and their cars run fine. I played with EOIT to get the fuel smell reduced and to improve low-speed power. And I've altered EOIT on every cam swap I've ever done because it's a good practice to do.

But it means absolutely zero when spec'ing a cam.

Just like LSA doesn't mean anything.

I have a cam with 115 LSA... and it chops harder than most people's cams on a 111 or 110. Because it has a healthy amount of overlap.