Anyone Want to talk CAMSHAFTS

[jdb8297]

I'M new to the ATV world (not really i used to race a ATC250R in my younger years) but my son has got me back into atv's and I notice know one talks cams and what they are suppose to do! I design cams for a living for serval different race teams. So if you guys want to ask question about any cam I think it would be fun to answer them for you to the best of my knowledge!

I CAN'T DISCLOSE WHO I DESIGN CAMS FOR DUE TO CONFIDENTLY CONTRACTS SO PLEASE DON'T ASK THAT DIRECT QUESTION!

Understand I design v-8 Cams but all cams work the same way except for rocker and valve train geometry!

[Cody_300ex]

Where is the most power going to be in these two cams? 1.350 lift and 1.400 lift. Bottom, Mid, or Top?

[jdb8297]

When you say lift 1.350 or 1.400 do you mean .350 lift or .400 lift and to answer you question with info you provided me. With out knowing excatly what profile your talking about but just because one cam has more lift than the other does not mean that the cam with more lift will make more top end power. Alot of your bottom end power comes from how quick the camshaft comes off the base circle and starts to open the valve. For example if you took a camshaft that had .400 lift but opens the valve at 200 crank degrees at.006 LIFT compared to a cam that is .350 lift but opened the valve at 185 crank degrees at .006 lift the .400 lift would have more torque because of openning the valve quicker. I hope i answered your question with what info you gave me and if i knew more about the cam profile at what dur@.050 i could probly tell you more.
THANKS

[Cody_300ex]

I am pretty sure that it is measured in MM, put I know That they were measured with a dial indicator.

[jdb8297]

What exactly did you measure with a dial indicator and where did you measure?

[Cody_300ex]

I was Measureing the actually cam lobe from top to bottom. Another question, Is it possible to measure a cams duration?

[250R-Dee]

What duration, lift and center lobe separation would you suggest for a MX YFZ450 with a 13:5 piston, 41mm FCR, mild porting and yoshimura pipe? One of my Japanese friends owns this quad.

[jdb8297]

You can mearsure a cams duration by putting a degree wheel on the engine and dial indicator on top of the valve. I have not played with these atv engines enough to tell you how to get a degree wheel to hook up on the engine but i'm sure some one make a degree wheel! Now the answer to your question about lift and checking it would be put the cam in v-blocks and put a dial indicator in an magnetic base to hold it and start your indicator on the base circle to the top and you should be able to get your total lobe lift without valve lash. Or you could put a indicator on top of the valve retainer and measure that way of course it will have your lash in it, but this will also show what it is auctally doing at the valve and it may not be exactly what your cam card says because of the oil on it but it will be close. The true and most accurate way to check a cam is on a cam doctor.

[jdb8297]

TRX250RJAPAN
When you say center lobe sepration are you talking about intake center line or cam sepration they are two different things! Lobe sepration is fixed into the camshaft at the time it is made and is fixed and can't be changed. Intake centerline can be by grinding advance in the camshaft! For example a cam with a lobe sepration of 110 with four degrees advance in it would have a centerline of 106 with the exhaust centerline being 116! On v-8 I have actually made profiles with inboard and outboard cylinders with different intake centerlines ONE HELL OF A FUEL MILAGE CAM FOR NASCAR! As far as what lift and duration I would run I really can't answer that because I don't know enough about these engines and their cyl head design I think they have tit valves don't they? And if they do that makes a big difference in how aggresive you can make the cam design and just how good the head flows stock!
Thanks for you Question

[jdb8297]

lil 300ex after thinking about the lift numbers you gave me i went and measured a 250x cam thats all all have which has the lobes wore off it but i think you measured base circle and all and thats where you got those numbers a think those cams have .350 lift and .400

[jdb8297]

looking for questions

[FoxRacing81]

Maybe kinda dumb...and not even sure if you would know...but since you ask for questions...

Would it be normal for an aftermarket camshaft to tick a lot louder then normal?

Because my 400ex gets a very loud ticking noise when it get's warm. I am starting to think that this is normal because my mechanic said he figured it was just a loose valve and nothing was really out of ordinary when he checked it, and it still ticks. The timing chain is brand new and everything so I know its not that. I'm starting to think it's normal.


Thanks alot if you can answer this question.

-Mx

[jdb8297]

ABOUSTLEY!!!!!!!!
THE RAMPS ON TH CAMSHAFT ARE ALOT FASTER AND WITH IT BEING A OVERHEAD VALVE IT'S GOING TO MAKE SOME NOISE! HOW MUCH IS HARD TO SAY DEPENDS ON CAMSHAFT DESIGN.

DID YOU HAVE A VAVE JOB DONE WHEN YOU PUT THE CAM IN?

IF YOU DID THE MACHINE SHOP COULD HAVE GRINDED THE SEAT DOWN WHICH WOULD HAVE MADE THE VALVE SET TALLER, AND AFTER IT HEATS UP IT EXPANDS CAUSING IT! THE EXPANDING OF THE VALVE DEPENDS ON THE MATERIAL IT'S MADE OF! DIFFERENT MATERIALS DO DIFFERENT THINGS I KNOW THEIR ARE SOME VALVES FOR V-8S FLOATING AROUND THAT ARE MADE OUT OF SOME TRASHY METAL (TAWIAN) ALSO REMBER THES VALVES ARE SETTING IN A ALUMINUM HEAD HOPE I GAVE YOU SOME INSIGHT ON YOUR QUESTION.

THANKS FOR ASKING

[jdb8297]

bump bump rump rump need some questions!

[wilkin250r]

I know the basics, but I would like to delve a little deeper. I know the theory behind overlap and scavenging, but that's about as far as my knowledge goes. Can you get in depth?

You talk about ramp times, how does that affect power?

What are the disadvantages (besides piston/valve clearance) to higher lift?

What are the effects of advancing or retarding your cam timing?

[jdb8297]

I'm going to try to give you this in the simplest terms as I know how with out going in to munch depth. The first thing we will start out with is terms and what they mean.
1: Slope of Curve The slope of the lift curve is Velocity, Velocity always goes back to 0 at max lift speed.

2: Acceleration is the steepest slope of the velocity curve

3: Lift is in inches and is lobe lift Max lift is at the rocker and valve

4: Velocity is speed in inches per degree And always the first difference of the lift curve.

5: Acceleration is inches per degree square

6: Jerk is the rate of change of accelration

7: Jounce / Snap is the rate of change of jerk

8: Crackle rate of change of snap

9: Pop is the rate of change of crakle
And none of what I just told you makes any sense to you right now and it will not because all of thes are measured in linear thenths.
But what i'm going to tell you about now will!

First lets establish different camshaft and we will start with mechanical lifter here how it works. (EXAMPLE)
Major Intensity - EXAMPLE 260@50 298@20 If you subtract 260 from 298 it will = 38 Take 50 and subtract from 20 gives you major intensity. The smaller the number at .020 the flatter the torque curve will be by the lower number at .020. Tight lash is designed with lower number at .020 The shorter the seat timming (OVERLAP MEANS CROSSOVER AREA) shorter the valve event at .020 the more torque the engine will produce Overlap can also be produced by advance the camshaft for example a camshaft which has lobe sepration of 110 (LOBE SEORATION CAN NOT BE CHANGED IT IS FIXED IN THE CAMSHAFT AT THE TIME OF PRODUCTION) if you advance this 4 degress your intake center line will be 106 you just put more overlap in the camshaft. Lobe sep will also change overlap. I'm out of room for this post would you like to go on?

[jdb8297]

Let me explain hydraulic lifters a little!
Leak down rate of a hydrulic lifter stock is thirty seconds Rhodes is less than a second and hard to measure. Cranes hi intensity is is 3 to 5 seconds and all hydraulic were designed for SAE 30 weight oil.

Hydraulic Ramps Magic Formula: Closing ramp always makes hyd cams noisey.
@.0004 cam ramp velocity should never exceed .0008 11/0 degrees on closing side only better practice would be .0006 11/0
smaller is better! Stock is 0004 11/0 to 0002 11/0
Camshaft will make more power if you exeed .008 11/0 but will be more noisey. THER IS NO SUCH THING AS A ANTI PUMP LIFTER.
And solid lifters cams and hydrulic lifter are both FLAT TAPPET CAMSHAFTS! The difference is the bleed down rate of the Hydrulic lifter and what i just explained above.

ONE THING THAT IS THE MOST IMPORTANT THING YOU CAN DO WHEN YOU INSTALL ANY CAM AND I MEAN ANY CAM IS TO CHECK THE STRAIGHTENES FROM ONE END TO THE OTHER IF YOU HAVE A CAM THAT IS BENT ONLY ONE THOUSANDS OF A INCH BY THE TIME YOU TURN THAT CAM 6500 RPMS THAT ONE THOUNSAND GREW TO ABOUT EIGHT THOUSAND SO YOU JUST LOST YOUR CAM PROFILE.

[jdb8297]

Guy's I have to leave now will be back soon when i come back we can talk cup cams or rollers Keep your questions comming i'll try to answer them if i can!!!!!!!!!!!!!!

[wilkin250r]

It sounds like something that cannot easily be explained in a few words.

As a mathematician, I certainly understand the different rates of change. Position would be the baseline scale, Velocity would be the first derivative, Acceleration the second, Jerk would be the third, and so forth. This is interesting, because I never really saw any need or application for the third derivative (jerk), yet you are saying you are working with the SEVENTH derivative (pop)?


Originally posted by jdb8297
The smaller the number at .020 the flatter the torque curve will be by the lower number at .020.

So, tell me if I have this right. 260@50 298@20 means from 0.050 inches open to 0.050 from being closed is 260 degrees of duration, and 298 degrees at 0.020 open and closed. So a smaller number, say 280@20 would mean you open the valves faster. Theoretically, 260@20 would mean the valves open instantaneously from 0.020 to 0.050, and close just as fast.

[jdb8297]

Wilkin it may take two page of post for me to expalin OK
My techique of cam design is I design the entire postive acceleration area totally seprate from the negative accelration are. This technique allows me to estblish the maximim postive accelration peaks and the maximum velocity. Maximum jerk values are set and the maxmum rate of change of jerk is carefully controlled.
What is the rate of change of jerk called? I call it snap and of course the rate of change of snap must be crakle. This leads to what is the rate of change of crakle? It must be pop!
Let's talk about snap first of a simple constant velocity ramp. The rise of accelration from the end of basecircle thru the ramp accelration pulse and then back down to zero accelration results in constant velocity. This rise in acceleration is the most common location for serious cam profile manufactering problems. And the best way to test for this is: If the jerk difference at this transition point exceeds .00001000 inches per degree cubed (in one half of one degree of cam rotation) then this area must be redesigned if the manfacture wants a accurate profile.

[wilkin250r]

I'm very familiar with the delicate balance between performance and manufacturability.

[jdb8297]

If ZERO ACCELERATION is used to dwell the MAXIMUM VELOCITY, this same test should be met.
I use an entirely different program to design Negative accelration area. I can spend more time in optimizing the Radius of Curvature ACROSS the nose of the design. If you used the same POLYNOMIAL exponents program to shape both postive and negative areas of the cam then the postive accelration is ALWAYS compromised in order to fix the nose radius problems.
In the case of roller cams this is especially true as the design should not have a large reverse curvature in the flank area, if the cam must be made with a normal FULL SIZE DIAMETER grinding wheel.

As for flat face, or nomimal 35 to 70 inches of spherical radius tappet design. it is my concern with too much velocity for a givin tappet wear surface diameter. So i fix the maximum velocity with an seprate postive accelration program before designing the negative acceleration portion of the cam profile.

[jdb8297]

Wilkin: those numbers a gave you are to mesure major intesity and cam companys use them as a numbers game to sell you a camshaft. When design a true camshaft to what some one wants first you have to know how big base circle and cam journal size and how big the lifter? Rember the bigger the lifter the more true accelration and velocity you can put in the camshaft. Most all cam companies design camshaft using a small block chevy lifter (.812) let say you put a VW lifter on that cam what did you just do? You speed it up you more contact there to follow it!!!!! Not only that when you put that chevy design on a VW base circle (2.100 I think been awhile since i've measured one) compared to 1.080 what did you just do!!! Same with Rocker Arms you change all camshaft timming when you up rocker Ratio. I design cams today that are 2:1 ratio so i slow down the ramps because the rocker is going to change everything. I hope I answered your question Thanks for asking!

[jdb8297]

Wilkin
One thing I failed to metioned those nubers I gave you of 260 and 298 is crank degrees also!!!!!!

[jdb8297]

Wilkin
The other thing I failed to metioned is if you change that number from .020 to .006 the .006 number is bigger because rember we are saying at .006 lobe lift the crank is at (312 just a example) and thats how cam companies play the numbers game the call it advertised duration when they tell you that ask them where they measured to get that number because that is measured at thousands per lift. Real simple just put a degree wheel on a motor and you will see!!!! Play with a couple different cams and measure each cam at .006 .020 .050 .100 and you will see that the duration numbers at .50 can be the same but the other number tell just how fast your opening the valve. Rember the faster the opening of the valve more torque you build!!!!!!!!!!

[jdb8297]

I hope I didn't confuse anyone this is a lot more simple to understand when you have a degree wheel on a motor or a cam doctor sheet to show and point out different things. Kepp the questions comming I will answer them a little more in simple terms I can get way out their talking about three different things and not even relizing it some times because I probley desiging your favorit drivers camshaft on my other computer and what i'm talking about is WHAT I'M TRYING TO FIX!!!!!!!!!!!!!!!

[jdb8297]

bump

[jdb8297]

Wilkin
i NEVER GOT A RESPONSE TO SEE IF I ANSWERED YOU QUESTION?

[wilkin250r]

I certainly understand that measuring the duration at numbers OTHER than 0.050 lift will tell you how fast you're opening your valves.

I'm not quite as interested in the mechanics and actual numbers, but more so in the theory behind them. Correct me if I'm wrong, but more overlap (intake and exhaust valves are BOTH open) will give you more top-end power due to scavenging, but up to a certain point. However, overlap will also give poor low-rpm performance, specifically idle.

How does opening the valves faster give you more torque? Is it as simple as allowing the engine to breath better in a shorter period of time, thus allowing more total air in the cylinder at low RPMs.

[jdb8297]

Wilkin
Actually more overlap increase bottom end power and gives you a less upper RPM power. Overlap is the cross over area when the intake is opening and the exhaust is closing. When you advance camshaft timming you put more overlap (Crossover Time) BETWEEN THE VALVES. Overlap is the actual rump rump you hear when the engine is idling. Overlap also increases cylinder pressure(not compression) thats the reason when you run Nitrous you want to run a wide lobe sepration with not much overlap because cylinder pressure and Nitrous mix like oil and water>

Opening the valves faster creates a shorter seat timming, shorter seat timining does allow the engine to get a little more air but it actually builds more cylinder pressure at TOP RPM the easiest way to achevie short seat timming numbers in a v-8 is with the rocker not the cam you actually make the cam very mild but when you put the rocker on it it changes everthing!

Thats the reason I'm trying to figure out opening and closing numbers on quad cams because they don't use a radius bucket style rocker but a flat pad that makes one heck of a difference in camshaft profile. Keep asking I'll try to keep answering!

[jdb8297]

Wilkin
I didn't answer all your question Openning the valve faster is more area under the curve of comming off the camshaft in relationship of were the piston is in the motor as it is openning.
Therfore it actually scavenge the cylinder better for the exhaust so thefore it builds more torque.

[tex440]

..I know tihs is old,but isnt LOBE SEORATION adj. on an DOCH motor? What would be ideal for a motor turning 10,000rpms?