Heres a good topic.

I have a camshaft with a peak lift of .500". The head has been warmed over, but runs like a dog until the engine comes "on the cam" then it really screams, but i stil feel it could be better. My flow numbers down in the .100-.350 range werent so hot, but around .500 where my cam peaks, im flowing darn near 300cfm!

Why should I care about the low lift figures?

Heres a picture of a cute dog, the image icon next to the thread title probably drew you in.

 

How long does your cam stay at .500? how long @ .100-.350?

 

...I was suckered in here by the picture icon

cute puppy

 

DonF's knowledge-base makes him overqualified. Dont listen to him!

 

You want to maximise flow in all areas, specifically those areas where the cam is the most. For reference, the graph below is raw data from a Honda CBR F3 intake cam (only raw data I have on this computer). I divided the areas into three regions. Low lift (blue), medium lift (red), peak (green). Your peak lift, in this case above .300", is only 'on' for ~25 degrees. Whereas the mid-lift is on for over 50degrees and low lift for 120degrees!

We know that peak lift is where you have the greatest potential for maximum flow, so the benefits of improving peak lift flow is obvious. However, most people don't really look at the lower lift numbers. In terms of throttle response and air charge, I've found that improving low lift flow dramatically affects throttle response. Just by enlarging the valve area near the edge of the combustion chamber can have a noticeable affect on how the engine reacts to changes in throttle, of course you are limited to how much area you can work with by your bore size.

I don't know much about headwork or flow or the workings of valve angles and throat dia...etc, so wait to hear from someone with more experience before taking my word

 

how far open is the valve at peak flow demand??

 

Is this an "area under the curve" thing.How about "it's only at .500 once but it's at .350 twice".

 

Alot of good answers! Most seem to be alluding to the time in cranksghaft degrees that the valve is open in reference to the peak lift of the cam., ie. your cam spends more time going from .100-.350 than it does at .500, this is absolutely correct!

But there is one more, much less obvious answer that will really get you thinking about "the big picture"...

 

maybe its the itbs

 

Maybe we haven't realized that the less obvious answer is the less obvious answer because we are looking at the most obvious answer. So if we are looking at the most obvious answer, then obviously we know the less obvious answer.

 

Well the obvious reason is that the more flow you recieve everywhere, increases the potential for more air. More air + the correct proportion of fuel = more power.

Are we talking more or less obvious than that

 

some people make more power without itbs.
their heads flow better all round with a manifold. increasing velocity in the low lift areas will help with the problem
why not mention it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Combustion Contraption &raquo;</TD></TR><TR><TD CLASS="quote"> the image icon next to the thread title probably drew you in.</TD></TR></TABLE> Damb it.

 

Why do I feel like threads like these are like a pissing match? Sure it's informative, but whats with all these "pop quizes" that are being made? Is it to showcase your knowledge, or that you have more experience than the next guy?? Do we need to start recieving report cards in the mail so I can show my dad and make him proud of me?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by clean rice &raquo;</TD></TR><TR><TD CLASS="quote">Why do I feel like threads like these are like a pissing match? Sure it's informative, but whats with all these "pop quizes" that are being made? Is it to showcase your knowledge, or that you have more experience than the next guy?? Do we need to start recieving report cards in the mail so I can show my dad and make him proud of me? </TD></TR></TABLE>They sometimes tend to be pissing matches. But i dont care which A member thinks they know more then B member. Aslong as i can give the noggin a good work out im happy. Just take in the info you feel is relevant and useful and leave

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Combustion Contraption &raquo;</TD></TR><TR><TD CLASS="quote">Heres a good topic.

I have a camshaft with a peak lift of .500". The head has been warmed over, but runs like a dog until the engine comes "on the cam" then it really screams, but i stil feel it could be better. My flow numbers down in the .100-.350 range werent so hot, but around .500 where my cam peaks, im flowing darn near 300cfm!

Why should I care about the low lift figures?

Heres a picture of a cute dog, the image icon next to the thread title probably drew you in.

</TD></TR></TABLE>

How much does that dog flow?

A couple of things on cams and cylinder head airflow:

You need to have the valve open to where the air flow starts peaking before the piston reaches maximum velocity. This occurs when the rod is 90 degrees to the crank and is usually between 65 and 80 degrees ATDC. Where it velocity peaks depends on your rod/stroke ratio. This is when the pressure differential between the cylinder and the intake port is the highest. You want a higher rod/stroke ratio because it delays this point of maximum piston velocity and allows you to get the valve open more.

The more the valve will flow before this the better since the pressure differential is smaller. However, you can only open the valve so fast before the rocker goes flinging off the cam. The maximum acceleration of the cam is limited by the width of the contact patch on the rocker. If you have a head where the intake port flow tapers off at, say, .450" then why would you need to open it further? It seems like a lot of people want a huge cam with, say, .750" lift but what is this going to gain them? Nothing. Of course, you always end up opening the valve slightly higher than where the flow starts tapering off so you can keep it past this max flow lift longer. Cams with more lift than necessary spend much less time at this peak flow point than a cam that is only lifted as much as is needed. There is a saying, "Dwell is equivenlent to lift", meaning that having a rounded nose of the cam rather than a pointy one, will flow as much as a high lift cam because it has opened the valve as much as needed and then stays there. This is because in order to get it open that far you have to slam it open really fast and then slam it closed just as fast. This requires really stiff springs and limits the RPM at which the engine can run. I'm not sure if that made sense so feel free to criticize, but basically it means when the cam is correctly designed there is more 'area under the curve' as far as airflow is concerned.

I'm not even sure if that started to answer the question but it's just a few facts on cam design. I'm tired, somebody please tell me if that made sense.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Professor15 &raquo;</TD></TR><TR><TD CLASS="quote">They sometimes tend to be pissing matches. But i dont care which A member thinks they know more then B member. Aslong as i can give the noggin a good work out im happy. Just take in the info you feel is relevant and useful and leave </TD></TR></TABLE>

I feel the same way. There seems to be so many ego's in here and everyone looks at the next guy as "competition" or something. I know when to shut up and listen, and I know where to make my personal opinion, but it seems as though others have something to prove to everyone else and thats what I think is ridiculous. Whatever, I'm over it now

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by clean rice &raquo;</TD></TR><TR><TD CLASS="quote">Why do I feel like threads like these are like a pissing match? Sure it's informative, but whats with all these "pop quizes" that are being made? Is it to showcase your knowledge, or that you have more experience than the next guy?? Do we need to start recieving report cards in the mail so I can show my dad and make him proud of me? </TD></TR></TABLE>

Sorry we're not talking about teh lat3st K-series hotness in SoC4l y0 nor mugen wheels.

This forum is used for learning purposes, either take advantage of them and participate or shut teh hell up. Not everything is a battle for "e-street-cred" and if you devoted your life to the study of internal combustion you would be anxious to comment here like they are

If you want a good report card learn how to spell

r-e-c-e-i-v-i-n-g

 

Has Rocket hijacked your account Steve?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mgags7 &raquo;</TD></TR><TR><TD CLASS="quote">

Sorry we're not talking about teh lat3st K-series hotness in SoC4l y0 nor mugen wheels.

</TD></TR></TABLE>

I have no idea what that just meant.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mgags7 &raquo;</TD></TR><TR><TD CLASS="quote">
if you devoted your life to the study of internal combustion you would be anxious to comment here like they are
</TD></TR></TABLE>

Actually I think I would keep my secrets to myself, not toot my own whistle and let my results speak for themselves. I guess some people are humble and some are not....obviously you aren't.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by clean rice &raquo;</TD></TR><TR><TD CLASS="quote">

I have no idea what that just meant.
</TD></TR></TABLE>

Let me rephrase myself: There is no new smsp header owner for you to congratulate, a dyno sheet for you to give "props" to, or any other waste of space post here.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by clean rice &raquo;</TD></TR><TR><TD CLASS="quote">
Actually I think I would keep my secrets to myself, not toot my own whistle and let my results speak for themselves. I guess some people are humble and some are not....obviously you aren't.</TD></TR></TABLE>

How is keeping knowledge to yourself humble? You learned because someone decided to share knowledge with you, sharing it with others should be congratulated. There are some on here that solely post their info to better the rest of our understanding.

You must have some misconception that there is no reason to do anything unless it personally benefits you.

 

there really is no "secret" in this thread. this is the downfall of the sport compact scene. uneducated people that dont really wish to learn.
everyone gets hyped about kseries this, or 300cfm that, or so-and-so's cam, but they have no idea why it is good or works. or if it does work.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by lohatch &raquo;</TD></TR><TR><TD CLASS="quote">there really is no "secret" in this thread. this is the downfall of the sport compact scene. uneducated people that dont really wish to learn.
everyone gets hyped about kseries this, or 300cfm that, or so-and-so's cam, but they have no idea why it is good or works. or if it does work.
</TD></TR></TABLE>

It's true.

Most of the problem is the fact that (unfortunately) my generation is built on the basis that everything is handed to us, and information is spoon-fed.

What happened to reading a book?

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Combustion Contraption &raquo;</TD></TR><TR><TD CLASS="quote">Heres a picture of a cute dog, the image icon next to the thread title probably drew you in.

</TD></TR></TABLE>

No it didn't!...

- Derek

 

[QUOTE=Combustion Contraption]

Why should I care about the low lift figures?
QUOTE]


the motor runs on lower lift numbers during cam duration alot longer than peak lift. the motor is at .500in only for a short duration of the cam!

 

This wasnt meant to be a pissing match at all, im sorry if people took it that way.

No, Rocket didnt hijack my account, if he did, im sure he'd be doing far more creative things with it. I like Rockets style of threads, but he isnt the only one who creates threads like that. Maybe on HT, but i migrate out of the HT forums once and a while.