114 have a broader torque curve where a 112 has a peakier torge curve,they may make the same horsepower just depends where and when according to your application ,gears,trans and rear end gear or power band you want it to live.The same two cams with same specs except one is 112 and the other 114 would make about the same numbers only at different rpms..

 

I hear this generalization all the time. I'm wondering if it isn't false, or at the very least, misleading more often than not. I guess it also depends upon what part of the torque curve you're looking at...if looking all the way down to the idle-2000 RPM range, the wider LSA might do better making the torque curve look "flatter" or "broader."

But when you look at the curve in the RPM range the car will be using while racing, it's often a different story. Those interested in a "fast car" should be more concerned with that part of the curve than the idle/drivability/emmissions part.

 

Good comment Jon. That's exactly how it works...

A higher LSA will cut down on overlap which can improve low RPM TQ due to less exhaust gassing being mixed with the intake air/fuel charge. It's going to get killed after that thru the midrange by lower LSA cams.

On top of this the LSA is also going to move the valve events too so that's going to change how the cam acts as well.

Generalizations on LSA have been around because people never take into account all the ways that they change the valve events and how each one of those changes effects the TQ curve.

Bret

 

Taking that statement at face value, trusting I am not taking it out of context, I can now, without reservation, state I agree with you. I"ll dramatize a little, by stating two cams, with the same LCA, can be worlds apart, in regards to their character. Toooo many, (including some that should know better, when they proclaim cam characteristics based on LCA, and not realize the weight their word of mouth carries), 'blanket' the character of a cam based solely on LCA (or LSA) without ANY regard to duration, or more to the point, where the valves open/close. To me LCA means very little, as I've stated before. Characterize a cam by the open/close specs, and it's overlap, with the resulting LCA falling where it falls. AFAIC, because LCA by itself, does not take into account the truely important features/points of the cam, it is a very inaccurate way of characterizing a cam.

 

Don't know about blanketing but lots of people like to talk cams and then when they get to knowing a little more about them they'll throw stuff out like.... "What matters is the cam events!".

Well duh.... but how many people really understand how they impact engine performance? If you want to claim that you can look at IVO, IVC, EVO, EVC events and postulate an outcome then you are either bull****ting yourself or you're a hell of a lot smarter than 99.9% of the people out there.

What does it take to make REAL sense of all these variables?? A lot of unsteady gas dynamics modeling. How many here know much about doing that with a pen and piece of paper?

Yeah, you need software..... software that uses a bit more than quasi-steady flow models and you need pressure-volume diagrams. Oh yeah, you need to know how to interpret the data. Not only that but you need to input meaningful/accurate data to get accurate results.... GIGO.

Now, if you are one of those people who don't want to go through all this and/or don't have the appropriate software.... well, you are better off just learning the basics of IVO, IVC, EVO, EVC, how they effect performance, then come to some understanding of what LSA does to these events.

David Vizard's article is real good lay person stuff. Pay special attention to the graph half-way down the page. Imagine the graphs if the static comp was corrected to the same dynamic comp for each cam swap. Interesting.... May open some eyes and at least get people thinking a little more.

http://www.babcox.com/editorial/ar/eb90252.htm

-Mindgame

 

Trusting this was aimed in my direction, I'll respond accordingly.

Cam events.... That IS what matters, to me anyway. There is no important overlap figure without them. Without them, there is no 'all important' (see below) intake closing event, and oh yea, the 'gee whiz' LCA figure. Give me the timing points, and a lobe CL, and keep the LCA and duration. I got all that I need. Now I can make meaningful comparos, if necessary

Don't care to bullsh*t anyone, but speaking of bullsh*t, when someone has this secret cam, and doesn't want to let out the specs, he'll disclose the duration and LCA. Who's bullsh*ttin' whom here? Basically, a whole lot of nothin'. All the person needs to state, is his preference to keep timing specs to himself.

You sound like a software salesman. And those software generated cams don't get tweaked or altered to perform as originally planned/expected? Sure, they have their place. Not intending to insult engineers here, but I consider it a great starting point.

I consider Vizard as a good source of info. First I've seen of that particular article though. After reading it, I frankly do not see any conflict between that article, and my post above. I particularly like his opening comment under LCA. Also speaking in regards to that article; and I'm not sure of your intented audience or reaction, by relating the importance of a cam software program as noted above, when virtually a small handful here, really understand cam degreeing, or are convinced of it's importance/benefit. What good is the 'perfect' software generated cam, when install is treated haphazardly?

Seeing I've already posted questionable and/or controversial statements, and speaking of software programs, I question the programs that put such great importance on the intake closing point. I consider the attention a little misplaced, because I believe it to be of a narrow focus, in the results obtained. An important factor, without question, but is the quarterback deserving of all the hype, at the expense of the other 10? Without the (important) support of the other 3 events, the intake closing has lost it's luster, AFAIC. Disagree? It's expected.

 

Mindgame,

I've read that before in a Engine Builder magazine, that article is a great article to reprint in about anything.

"So what is the price paid for a LCA that is artificially spread from optimum? Answer: a loss of ft.lbs. throughout the rpm range."


This is a great paragraph....

"The best way to cover this is to start from an optimum and see what we lose by first going too tight (a smaller number) then too wide (a larger number). If we have an optimally spec’d LCA for a race engine then we find that as the LCA is widened torque over the entire rpm band used drops off quite rapidly. For example, in a 350 SB Chevy, two degrees too wide can mean a loss of 20 or more ft.lbs. throughout the rpm range. On the other hand 2° too tight will have almost no effect on the output over the rpm range used while racing. If the LCA is too tight the motor needs to turn higher rpms before it comes on-the-cam and the idle is rougher. For a race engine then it is best to err on the tight side rather than the wide side. Because the idle quality goes as overlap is increased it is better to err slightly on the wide side if we are talking street usage. Here I am talking 2° off optimum, not the 4° to 6° and even 8° that is often seen. If you are installing such cams in commonly modified engines then you might want to consider upgrading your source of cam advice."

I think that all is completely true too.

I think you and I both fall into this category too.....

"Lastly there is the "do it right by whatever means it takes" method. This, in its most convenient form, can involve adjustable timing gears; less conveniently, offset dowel pins; and the worst-case and most time-consuming scenario, shims and files. "

That's why I can't get paid enough hourly on a engine assembly, this is just one of the many things that takes WAY too much time.

Things like this are great for guys to read, it brings the importance of cam installation into view.

Bret

 

I understand part of that for sure.... To me even with durations and LSA you don't know enough for it to matter. There is still lobe selection and where the events happen. I always give the example: If you are looking at a 230 @ .050 duration lobe from Comp, you have 33 different options easy on getting the right lobe for the job just from them in the Hyd Roller section.

To me it's not about magic but math. I just like to keep the specs under wraps due to the fact that it's not just the lobes and where they are but the parts that work with them to get the results.

Bret

 

In case you were unsure, that comment certainly, was not aimed at you specically, but an overall accessment in general. Another 'blanket' statement, if you will. Based on the majority of the questions asked on this forum, regarding complementary components, and the experiences, with those 'complementaries' selected by owners, I have no problem, with your reasoning above.

 

arnie,

You need to go back and read my 1st response if you really want to gage where I'm going with my comments.

No one is arguing the importance in a general understanding of cam events. No one is arguing the fact that LSA/LCA/LDA are "dependent variables".

What I will argue with anyone on this forum is this.... A small amount of textbook knowledge in regards to cam events... the effects earlier/later opening and closing points have on engine performance etc.. is not enough education to optimize cam events for a particular engine build. Unless your name is Ed Iskenderian or someone like him, you aren't going to look at IVO, IVC, EVO, EVC... consider the induction, weight of car, length of exhaust and other variables that make your combination of components unique, then make an optimal or close-to-optimal cam choice.

Now, if you understood the importance of a PV diagram (engine simulation as described before), then you will understand that THAT is the way to place the events because in doing so you can see their effects on the pumping loop. Some software packages will also show intake and exhaust port pressures any point in the cycle.

Selling software? No, but I have designed plenty of it. Everything from FEA to cryptographic algorithms.

And arnie, it is ok to use sentences. No need in imbedding a dozen or so different thoughts in one sentence. It makes your stuff, as tactful as it may be, and probably IMO only, possibly to others on the board, very difficult to follow.

And back to my point before I call it quits.... simulation is the key IMO. You don't need to go out and invest in it. You just need to employ the services of those who already have if you're after near optimal results.

-Mindgame

 

After three pages finally a solid answer to the original question.

 

OK, could have saved some typing time. BTW, definite value in reading (or rereading) your initial post, MG.

A person could consider it one of my defects. I'll attempt to work on that. May have some impact, on an occasional misinterpretation of some of my posts.

I can understand the value of GOOD software programs, in saving time, and net $$$ for race teams/vehicles in particular.

 

The question has been answered a few times now.

Some people want to be spoon fed... problem is, none of us want to hold the spoon. If you follow what's being said then you'll come out with a lot more than just an answer.... like the how's and why's. Imagine that.

And that quote was from the article by David Vizard... you should check out the rest of the article. It's good too.

-Mindgame

 

Good post Mindgame.....

Holding the spoon can get very old. That's why the "biggest cam I can put in my stock bottom end" threads don't get many looks by me. You can only say something so many times before u are banging you head against the wall.

Bret

 

Most of the posts in this thread had nothing to do with answering his question, they just chastised people who ask such questions. If you don't want to hold the spoon, fine, stay out of the thread. Imagine that.