Camshafts, idle quality, driveability and LSA-REAL WORLD EXP and OPINION

[yellow rose]

OK tough guy If you advance a cam the intake is open more than exh on overlap , straight up they are open equal, retarded exh is open more than int.If you do a quick check when a cam is advanced the int lifter is always open more than the exh. therefor there is less curtian area on int to try to control reversion .Any other stupid remarks you would like to make?In the meantime go back to your google answers.

First off all, that's not what you said at first. So you are teachable.

Second, reversion has less effect at overlap than intake closing. You can't be that hard headed can you? It's fairly simple to test.

If you know how far the valves are open at TDC, you will see that even with a very wild cam, overlap lift is very little. You can over scavenge out the exhaust. You can dilute the intake port with some exhaust. But reversion is mostly a product of intake valve closing.

Until that is pressed to the front of our minds, we will still make stupid camshaft decisions.

I'm thinking of starting a thread, but I'm going out of town for two days and won't be around.

When I get back, we can discuss things OTHER than LSA and see if we can learn from each other. I don't want it to be like the dog returning to his own vomit. Gotta tread new ground.


Plus, jpar gets all jiggy when I start a thread.

 

[yellow rose]

OP sorry for disrupting a good thread .Im really going to back out now.

See ya.

 

[roccodart440]

Here is the muthr thumpr and another cam.

Now what I will tell you about these cams in the same engine is the RPM range is very similar. Pulls to mid to high 5's. One comes on and falls off fast. The other make a ton of power all the way and falls off slow. One idles nicely, the other idles nasty, like ****. Both make similar power. One makes peak torque lower than the other. peak HP output happens at damn near the same RPM.

 

[yellow rose]

Can you post the rest of the numbers Rocco?

One has the timing at .050 and the other has it at seat timing.

I could do the math but it would be easier to compare if you posted them.


Also, the crank must turn backwards in the drawing. If the intake is on a 102 center line, the drawing is showing it as BTDC. It should be ATDC. Unless I'm reading it wrong.

 

[roccodart440]

This is all I can come up with for the thumpr

Intake Duration at 050 inch Lift: 235

Exhaust Duration at 050 inch Lift: 249

Duration at 050 inch Lift: 235 int./249 exh.

Advertised Intake Duration: 287

Advertised Exhaust Duration: 304

 

[4spdragtop]

I brought some too Tracy

 

[ir3333]

Cams mess me up...
having said that lets take a 350 hp 9:1 360 and add a cam with about .480 lift and 225 duration on a 112 lsa.
leave everything the same but change the cam lsa to 108.
now how will the performance change?

 

[Lustle]

Cams mess me up...
having said that lets take a 350 hp 9:1 360 and add a cam with about .480 lift and 225 duration on a 112 lsa.
leave everything the same but change the cam lsa to 108.
now how will the performance change?

Increased DCR. More torque, lower rpm. Shorter "power band".

 

[Ben Drinkin]

Increased DCR. More torque, lower rpm. Shorter "power band".

I'm all jacked up! I'd have guessed a tighter lsa (all else semi-equal) would have helped top end at the expense of low end. That's why i let people smarter than me figure that stuff out!

 

[Lustle]

I'm all jacked up! I'd have guessed a tighter lsa (all else semi-equal) would have helped top end at the expense of low end. That's why i let people smarter than me figure that stuff out!

You'd think considering how rough it can make a car sound. Make's it seem like a screamer. But it's the opposite. Tighter LSA closes the intake sooner. Creating higher cylinder pressure. That's where the more power comes in, along with the lower rpm. The valves opening and closing so soon to each other is what makes the narrower power band. As far as I understand it.

Basic rule of thumb - tight lsa = natural aspirated. Wide lsa = boosted application.

Wider LSA's are usually used in supercharged applications. Lets you force more air into the cylinder because the intake isn't open while the exhaust is, or for not as long anyways. On a supercharged setup, the sooner you can close that exhaust after the intake opens, the better for building more boost. Otherwise you just shove it out the exhaust.

 

[Ben Drinkin]

You'd think considering how rough it can make a car sound. Make's it seem like a screamer. But it's the opposite. Tighter LSA closes the intake sooner. Creating higher cylinder pressure. That's where the more power comes in, along with the lower rpm. The valves opening and closing so soon to each other is what makes the narrower power band. As far as I understand it.

Basic rule of thumb - tight lsa = natural aspirated. Wide lsa = boosted application.

Wider LSA's are usually used in supercharged applications. Lets you force more air into the cylinder because the intake isn't open while the exhaust is, or for not as long anyways. On a supercharged setup, the sooner you can close that exhaust after the intake opens, the better for building more boost. Otherwise you just shove it out the exhaust.

So a 'tight' lsa while keeping duration in check doesn't kill DCR? I assumed that in general, the tighter the lsa, the more overlap (both valves open) and the lower your DCR.. i got lots to learn! Been following these crazy threads trying to get educated. Seems the more i learn, the less I know!

 

[Lustle]

So a 'tight' lsa while keeping duration in check doesn't kill DCR? I assumed that in general, the tighter the lsa, the more overlap (both valves open) and the lower your DCR.. i got lots to learn! Been following these crazy threads trying to get educated. Seems the more i learn, the less I know!

Tighter lsa = more DCR. This is because compression doesn't start to build until the intake is closed. Tighter LSA closes the intake sooner = more dcr. There is more overlap. Which is good for scavenging (exhaust pulling out burn carbon, and helping flow fresh air in). But with the tighter lsa the intake closes sooner into the compression stroke (because it's close to the exhaust stroke). Building higher cylinder pressure.

If any of that makes sense. I can have a hard time describing things sometimes.

 

[Ben Drinkin]

Ok. So i think i finally got the visual in thick skull (put the bourbon down for a moment).. I've been focusing on exhaust closing/intake opening (overlap if I'm not mistaken). Reading your description, intake closing point seems more important. . Close the intake earlier, make more compression. How does one determine the optimum point for intake closing? If that's not a moronic question...

And you're doing a hell of a good job 'splaining stuff!

 

[Lustle]

Ok. So i think i finally got the visual in thick skull (put the bourbon down for a moment).. I've been focusing on exhaust closing/intake opening (overlap if I'm not mistaken). Reading your description, intake closing point seems more important. . Close the intake earlier, make more compression. How does one determine the optimum point for intake closing? If that's not a moronic question...

And you're doing a hell of a good job 'splaining stuff!

Optimum intake closing really depends on what you want/your application. Ideally you want scavenging (in a naturally aspirated motor). That is overlap that allows for exhaust to draw out all the burnt carbon as it brings in fresh fuel/air. A perfectly designed motor would sense the very last atom of burn carbon on it's way out and close the valve at that exact moment before any fresh air/fuel got into the exhaust. Obviously this isn't possible, so you want to get as close as possible.

Then, you want it to close early enough to build pressure, but not so early as to make so much pressure it causes detonation. You also don't want it to close so early you don't get enough air in there.

What I do to figure out optimum intake closing, is use it to determine DCR. Your dynamic compression ratio. Wallace Racing: Dynamic Compression Ratio Calculator

8.5 max DCR on iron heads with 91 octane. 9.5 on aluminum heads. As a rule of thumb.

I pick a cam based on it's entirety. You want to pick a cam that will fit all your needs on that engine. Whether it be high revving horsepower, low end grunt, or something in between. Intake valve closing will play a part in that. And from that you can determine your DCR.

Pick a cam for it's entirety, not just one part. And remember, a good engine is built around all the parts. And how they work together.

 

[RAMM]

Pick a cam for it's entirety, not just one part. And remember, a good engine is built around all the parts. And how they work together.

I totally agree. When I started this thread it was because I kept reading that LSA doesn't effect idle quality when I KNOW it does. LSA has a larger effect on idle quality than duration does. I also wanted to dispell the notion that cubes "eat" duration--totally false as well. When I decide on cam timing events I take into consideration so many aspects of the build from the hard parts to the totally subjective aspects it would take a long time to put pen to paper. I do have a bit of a "system" but its more based on experience and it wouldn't translate to paper well at all. J.Rob

 

[rigger3006]

and here i thought you started this thread to watch the feathers fly,lol! i have a tough time ingesting the ''math'' of it all, my mind shuts down just like it did in high school, i failed math! i have a handle on lift and duration at 050, after that my brain pushes back, ive read this and many other threads(arguments) on cam timing and i decided awhile ago i will just follow the old direct connection formulas for performance, just my take on it!

 

[roccodart440]

Cams mess me up...
having said that lets take a 350 hp 9:1 360 and add a cam with about .480 lift and 225 duration on a 112 lsa.
leave everything the same but change the cam lsa to 108.
now how will the performance change?

Increased DCR. More torque, lower rpm. Shorter "power band".

There is another thread that was posted and I've linked to it that shows this exact comparison in a members 340. I linked to it in the original thread where the initial disputes of LSA took place.

Keep in mind on what lustle said that the torque itself may not happen at a lower RPM, just the peak HP.

 

[318willrun]

Increased DCR. More torque, lower rpm. Shorter "power band".

Did I read his question right and your answer right??
You are saying you'll have more low end torque with a 108* LSA and less with a 112* LSA?

His question

Cams mess me up...
having said that lets take a 350 hp 9:1 360 and add a cam with about .480 lift and 225 duration on a 112 lsa.
leave everything the same but change the cam lsa to 108.
now how will the performance change?

 

[roccodart440]

Did I read his question right and your answer right??
You are saying you'll have more low end torque with a 108* LSA and less with a 112* LSA?

His question

The more torque part is debatable. It definitely won't always happen at a lower RPM.

 

[318willrun]

The more torque part is debatable. It definitely won't always happen at a lower RPM.

I know how it works, but the question and answer is written somewhat confusing and unclear. So, to let them clarify what the question actually was (or at least how I read it) and the answer, I re-asked it to be clear.

 

[IQ52]

Some actual dyno tests changing LSA only...........

http://www.cranecams.com.au/pdfs/MAY14-Lobe_separation_article.pdf

Lobe Separation Angle Explained and How it Affects Horsepower

 

[roccodart440]

The narrow LSA cam
immediately delivered the authoritative and extremely choppy idle we expected from it.


“The 104 LSA cam is going to exhibit some drivability
problems,” said Crane Cams Valve Train product manager,Chase Knight. “ Torque between 500-1200 rpm is going to suffer.”

The high amount of overlap in the 104 cam allows exhaust reversion at very low engine rpms. This dilutes the intake charge and contributes to poor slow speed torque and part throttle manners.

The anemic idle
vacuum also rules out the use of power brakes. “This would be a good cam for a manual transmission car or an automatic with a very high stall,” said Knight.

If you can stomach the extremely aggressive idle,lack of power brakes and have the proper driveline to take advantage of a tight LSA cam, it would make for a very peppy ride.


Also, spoiler alert. The 110 made the most HP. Not the 104 nor the 114.

 

[roccodart440]

the 110 LSA cam perform, it is easy to
see why this grind has become such a favorite of aftermarket. (Remember the whole bit about common LSA range?) cam grinders. The balance of midrange torque, idle quality and top-end horsepower seems to lend this cam to the majority of street/strip engines.

This LSA is a great middle-of-the-road cam that offers a taste of both worlds.

It also made peak HP.

 

[roccodart440]

The 114 LSA cam would seem to be the underdog of
our test, but it is just as relevant in the right application.

The smooth idle and strong, vacuum signal are excellent
for a daily driven vehicle and will allow an EFI system to function easily.

In forced induction applications, the inherently low overlap of a wider LSA cam can help prevent boost from escaping out the exhaust valve.

Also the early exhaust opening helps to reduce residual pressure in the cylinder before the intake valve opens. detonation resistance/pump gas friendly

This cam (242/[email protected]) in a little 350 ci engine pulled 11 inches of vacuum with the 114LSA).

 

[roccodart440]

The 2nd article yielded similar results but the power really went the other way when they went to max LSA. They used 120