not another camshaft thread... more pointless dribble from a feeble mind

[Jim Ratto]

Don't know about you but when I can't sleep at night, I think about cams. All kinds of cams, stock, 1.1:1, 1.4:1, ramps, lobe centers, timing, lift rates... enough to drive a guy to drinking.

Here's a question for anybody out there that wants to chew on it...  with a 1.4/1.5 cam, should we be checking timing @ .050 at lifter or at valve? Seems to me you can't dial a ratio rocker cam realistically @ .050 lobe lift, though I always have (I'm just checking to see where full lift occurs in crank degrees so does .050 numbers even matter?...) I think this more comes into play if a guy wants to compare apple cam to orange cam, the apple being a 1.1 cam and orange being a 1.5 cam. Cam card may say the cam goes to .050" intake lobe lift @ 39BTDC, but in the real world, this isn't the case. Multiply by "real" rocker ratio, subtract lash... and you get .050" at valve happens at ___ BTDC. I kind of fooled around with this a few weeks ago with the 86C Web and my Scat 1.4. Didn't take good notes though, the cam is 1.5 deg advanced and there it is. I'm just wondering if in the real world, these high lift rocker cams, yes we mostly consider them on the "wild side" but in all fairness, if you take a pair of similar cams, but change rocker ratio between them, it's more than what it first appears, right? Take the FK10 vs 130 Engle, both have similar .050 durations, but if you crank the rocker ratio up as on FK10, things are happening sooner on opening and later on closing= more overlap. Something to think about when saying "this cam is same as that cam but runs 1.4's"

Another thought from 3:30am.... why are all the big guy cams up at .560"+? Some guys run (very well I might add) over .600" on the street. I've done it too, but cringed every time the tach saw the other side of 6500. I often think the point isn't the total lift our engines crave, it's the rapid rate of lift the valve experiences off the seat and how quickly that valve gets to "X" lift. in reality, you motor sees "full lift" (that .620 some guys run) for a hair of a degree. Ever degree a cam using lobe center method (not .050). You will see how quickly the valve gets to full lift and then falls back. It's nearly impossible to degree it without finding .005" on either side of max lift and dividing the difference.
OK my point here is, do we need to run the valve open to .600" plus to make the hp? What about a cam that has very very fast ramps, generous duration (like 325+ @ .020") but only .500 max lift? What would happen? If the cam gets the air pouring in at mid lifts nice and early, and fills the cylinder even beyond BDC, and we end up with 100% VE+ (more than 1atm @ rod starts swinging piston back up on comprende stroke), why worry about more spring pressure, more travel, more guide wear...etc.

Lastly, when cranking more and more duration into a motor, where we all know we need to crank up the compression to make the cam run well, what happens to valve cooling through closed time on seat? No mater how much duration you have or don't have you only have so much of a circle to work with, some of that "time" (in crank degrees) needs to be spent having the valve on the seat to cool off. The more duration you mix in, the less time on the seat. Where do you think that seat time begins to get too short and valve life suffers?

[Jason Foster]

   Where's Doug Berg when you need him?  huh Jim?

[Peter]

Jim,
dont worry,
these things are interesting, not pointless
The problem is: nobody knows these things;
If I had a question like that, I would ask you
Maybe Johannes from JPM or John Maher?
I would like to know as well, but its kind of a dark art

[John Maher]

Cam manufacturers have no control over the style of rocker assembly being used. In order to help you dial in the cam as they intended they must use a reference point that relates directly to the cam and not something that will give a multitude of different results dependent on type of rocker and how accurately (or not!) rocker geometry has been set up.

Yes, switching from a 1.4 to 1.5 ratio alters duration as well as lift at the valve (once it's off the seat).
Cam design is a very specialist subject - very few people understand it fully, myself included 

The cam designer will generally design the valve's lift profile first, effectively working backwards to arrive at the cam lobe design, once rocker ratio has been decided. But now the actual lobe design must be studied to ensure it's suitable for use with the diameter of lifter being used (more velocity requires a larger diameter lifter) and whether the rate of change in velocity (acceleration) is likely to be kept under control by the valve springs. Then you have a third derivative, jerk i.e. the rate of change of acceleration. Now take in to account the cam designer has no idea what type of valvetrain their cam will be used with eg, super lightweight titanium or heavy stainless valves with chromoly retainers etc etc. 

Yes, it's possible to come up with a design that accelerates the valve off the seat more quickly than most of the common cams and therefore has equivalent (or even more) area under the curve than a longer duration cam. Eg, take a look at Engle's FK4* series....

You can get a feel for how quickly these cams accelerate the cam off the seat by comparing their 'running duration' figures against 'duration @ .050".
Running duration is normally taken at .020" lift by most of the VW cam makers. Subtract 'running dur' from 'duration @ .050"....
the lower the figure, the faster the acceleration is between those two values.
On paper the faster accelerating cam looks good. It should deliver a better spread of torque through the entire rpm range. But in the real world, as many people on here know from first hand experience, cam grinds of this type have a tendency to wear cam follower bores and maybe trash other valvetrain parts. Short of putting your cam on a computerised cam measurement device, the cam card alone reveals very little about the camshaft's design. Instead we rely on recommendations and/or experience.

It stands to reason there is room for improvement in VW cam design. Most of the grinds available have been around for at least 20 years plus, many of them based on old Chrysler V8 grinds for no other reason than Chrysler used a tappet diameter closer to the stock VW tappet than either Ford or Chevy (both smaller than Chrysler). With the advent of advanced camshaft design software and CNC production techniques, there's scope for someone to come up with more advanced designs. Currently, Johannes Persson (JPM) is the only person I know of who has looked seriously in depth at aircooled VW camshaft design, specifically from the point of view of optimising duration, velocity, acceleration and jerk and not only as a theoretical exercise. He has taken into account the whole dynamic running situation. In the real world his cams allow higher rpm before hitting valve float compared to the camshafts we've all been using for years and this is achieved with less spring pressure than conventional stock diameter dual valve springs, let alone K800s!

With regard to whether it's necessary to run lifts of .600" or more...
Another complicated subject but I'll attempt a brief(ish) explanation. The amount of lift required can be roughly based on valve diameter i.e. the larger the valve, the more lift you need. In very basic terms, the valve must be lifted by approx 0.25 x its diameter just to make enough curtain area to equal the inside diameter of the seat (curtain area = valve diam x 3.14159 x lift). Continuing lift above this point sees flow continue to increase . You can often hit a lift figure equivalent to greater than a third of the valve's diameter before further lift sees little or no improvement in flow (depends on quality of head work). The actual calculations are a little more complicated but this gives the general idea.

Take a head fitted with 48mm intake valve. You need to see an absolute minimum of 0.472" lift (48 x 0.25) for the head to start flowing reasonably. If the seat, port and chamber have been  well modified, flow should be excellent to around 33% lift (0.623") or more. If this is a max effort engine, running anything less is leaving potential power on the table.

OK, so if that head's flow maxed out at 0.623" lift, is there any point using even more (assuming there are no mechanical limitations to doing so)?
YES, because using more lift increases the amount of time available for flow to enter the chamber i.e. you get a better fill (increase VE) and therefore make more power. Maxing lift at 0.623" limits the time available for flow at that increment to a fraction of a second. Going further can increase time by a huge percentage.

Like everything else in the engine, you cannot look at one component in isolation and expect to make huge gains. It's all about how everything works with everything else but the cam and heads should come pretty high up the list if you're looking for good results.

[RFbuilt]

interesting discussion!  (grabs popcorn)

specially John Maher's touch on valve Lift / diameter ratio ,

also mr john m. wouldnt this be a similar reason why : 
web 110   .435" lift  284* dur. and 256* dur. @0.050
engle w120 .435" lift 294* dur. and 253* dur @0.050 

the web performs usually better.. due to its faster "ramp" ?

[John Maher]

interesting discussion!  (grabs popcorn)

also mr john m. wouldnt this be a similar reason why : 
web 110   .435" lift  284* dur. and 256* dur. @0.050
engle w120 .435" lift 294* dur. and 253* dur @0.050 

the web performs usually better.. due to its faster "ramp" ?

I've not used a web 110 so don't have any personal experience but yes, based on the figures you've quoted, the web 110 accelerates the valve off the seat more quickly than the Engle 120 between .020" and .050" cam lift. It starts later than the E120 but has caught up and passed it by .050".
In theory that should deliver better throttle response, plus improved low and mid range performance due to less overlap.

It seems any cam with around a 30° difference between lift @ .050" and running duration (.020") can be regarded as high velocity. The likes of Engle 110, 120, FK8, FK10 etc have a difference closer to 40°. This observation is based on cam card data only - like I said before, the cam card doesn't reveal the full picture. There's a lot of things that can be altered on the opening and closing side below that advertised (.020") figure to control how the valve is lifted off and then returned to the seat. That info will never appear on a cam card 

PS maybe this thread should be moved to the 'Pure Racing' section?

[Zach Gomulka]

You lost me at "camshaft thread"

 

[Jim Ratto]

Hi John, thanks for your very informative reply. You're correct, this topic of cam design, polydyne correction, lifter diam vs lift per degree per degree... all specialized (very). I can remember back when I was 18, building my first stroker in 1989 and just scanning Engle list and my thought process was "most guys I know run the 120, so I will go one better and go for 125" not knowing the first thing of what I was doing. Luckily, it was a good "guess", later I would do much the same and not be at all so "lucky." But in last 20 years, I studied what I could get my hands on, and looked outside the VW world to try and gain a grasp of what works and what doesn't. Of course, being a garage hobbyist, and not an expert with a flow bench and dyno and computer cam analyzer limits my understanding. I'd say the last 10 years worth of motors I've done for myself and friends turned out successfully, and probably a little out of the norm, but I and the owners of the others have been happy with the characteristics and longevity of the outcomes.
I think something that might be advantageous to the scene/industry/hobby would be for manufacturers to offer "systems" (and better catalogs!). You are right, Engle Web, etc... have no control over what a guy does once UPS delivers that the guy is going to spring it, which rockers, etc. But if they sold a kit or system, rockers, springs, followers, retainers,  gave the guy his installed height, full open LB, and instructed the guy to keep rpm under _______, things could be optimized in a better and more systematic approach. I think the Berg catalog did a pretty good job, for the most part, pointing a guy in the right direction as far as what to use and what to expect. I would say every other cam catalog for VW I have read lacks big time. No reference to cyl cc vs rpm or headwork/carburetion needed. Just "drag race competition use only." or "off road cars". Leaves a lot to be determined.
It's fun to study some of the old Porsche 4 and 6 cylinder cam profiles. Old Ernst Fuhrmann and H. Mezger had an obviously good grasp and how to make things "work", and yes I know we are comparing some OHC to OHV, and acceleration rates can be cranked up with less weight, but duration vs. cyl cc can be compared. Where cams are timed in comparison to crank degree can be compared. Valve and port diam vs cyl cc too. Interesting that Porsche used monster diameter valves in so many of their motors, relative to cyl cc, and yet only lifted maybe 12.5mm at most (much less on later 6 cylinders, this was 587 904 4 cam motor). I've read the 33% figure like you posted, I think in AG Bell's book which also goes (very) in depth on this topic. It was required reading for a cam/engine class I took in 2000.

[Jim Ratto]

yeah if moderators would like to move to Pure Racing, it's probably more appropriate.

[dannyboy]

You lost me at "camshaft thread"

 

in the words of oddball from kellys heros
hey man i just drive them i dont know how they work

[Jim Ratto]

You lost me at "camshaft thread"

 

in the words of oddball from kellys heros
hey man i just drive them i dont know how they work

awesome movie... hahahah haven't heard that in years... 

[Zach Gomulka]

You lost me at "camshaft thread"

 

in the words of oddball from kellys heros
hey man i just drive them i dont know how they work

Fuck me I just watched that a few months ago! Great!!!

[Jim Ratto]

I've not used a web 110 so don't have any personal experience but yes, based on the figures you've quoted, the web 110 accelerates the valve off the seat more quickly than the Engle 120 between .020" and .050" cam lift. It starts later than the E120 but has caught up and passed it by .050".
In theory that should deliver better throttle response, plus improved low and mid range performance due to less overlap.

It seems any cam with around a 30° difference between lift @ .050" and running duration (.020") can be regarded as high velocity. The likes of Engle 110, 120, FK8, FK10 etc have a difference closer to 40°. This observation is based on cam card data only - like I said before, the cam card doesn't reveal the full picture. There's a lot of things that can be altered on the opening and closing side below that advertised (.020") figure to control how the valve is lifted off and then returned to the seat. That info will never appear on a cam card 

PS maybe this thread should be moved to the 'Pure Racing' section?
[/quote]

good point on spread of "catalog duration" (.020?) vs .050 lobe duration.... look @ VZ cams for example, or yes the FK4_ series. Thing is, again, we only have so much of a "circle" to deal with, how much of it can be used as ramps and flanks to get cam open quickly keep it open and shut it quickly without shocking valvetrain? or not giving enough rest time to valve on seat?

[nicolas]

I think something that might be advantageous to the scene/industry/hobby would be for manufacturers to offer "systems" (and better catalogs!). You are right, Engle Web, etc... have no control over what a guy does once UPS delivers that the guy is going to spring it, which rockers, etc. But if they sold a kit or system, rockers, springs, followers, retainers,  gave the guy his installed height, full open LB, and instructed the guy to keep rpm under _______, things could be optimized in a better and more systematic approach.

OK, so bergs catalog did say that, and i really want to have one, but i think that about 1% of the people in our hobby 'care' about these things and want to have a headache about it. so what they want to see is 'great dragrace cam, that runs supersmooth in a daily streetdriver, pulls from 1500 to 10000+ and works great in every engine combo you can come up with'.

they need to put something behind the cam just people can chose. more and more i am thinking i know very very little about the subject and when i read the post from JMR i think i have my reasons to think this, and more and more i am thinking that Bruce was right when he said that a headporter needs to recommand a cam for his heads and the combo they were made for. more often then not it looks like the cam is the last thing to buy and the only real 'debate' is wheter i should use 1.4' or stick with the 1/1's

sorry to be so negative, but in a way i like it when these topics DO come up. it has some very valuable info in it. and no it should not be moved to the 'pure racing' section, they more often know what to do and have in general a better understanding of what goes on in an engine and what works and what not (or at least they should,... or they were lucky their engine didn't brake that often yet...)

[Jim Ratto]

Hi nicolas, thanks for your comments. I agree, probaly most guys that are buying cams don't want to know "more than they know", which is too bad. Not that everybody needs to become cam grinders and designers, but there's little wrong with having a little better understanding of how the end result comes to be, and how to optimize it.  To be led to believe the W130 cam is 'drag race competition only', without knowing rest of the story, is wrong. One could install that grind in a 1700 and yes, that description would probably be pretty accurate, though I suspect some guys could live with it in a driver. However, drop the 130 in a full tilt 2276 or bigger, with all the stuff to make it run sedately as a street cam, and you'd have just that. A nice street cam. It isn't simple but some of the factors involved are pretty easy to spell out.
I think guys need to think more of their engines as "systems" and less as a bunch of numbers they can brag about. Everything needs to marry everything else. Maybe we just have too many choices of displacements, rocker ratios, cams, heads, etc? It would be awesome for someone like Johannes or Mr. Maher to engineer systems, maybe it would even involve really thinking outside of the 40 year old box this hobby has been in and coming up with off the wall cam grinds or rocker ratio.
Though I've had a few berg catalogs since 1989, I still take time and go back and re-read what I thought I knew. Sometimes I walk away with a new understanding or outlook on something. Same with the old Bill Fisher book.
If I were to write a cam catalog, I can promise you, it would go way beyond "drag race competition use only" 
The 911 guys seem to get it better. But that's a can of worms we can leave closed now.

[JS]

It would be awesome for someone like Johannes or Mr. Maher to engineer systems, maybe it would even involve really thinking outside of the 40 year old box this hobby has been in and coming up with off the wall cam grinds or rocker ratio.

Actually Johannes kinda does that already. I bought the cam, lifters and springs from him and he designed a custom cam profile to give maximum hp @7000rpm, knowing the flow numbers on my heads, engine size, compression, rocker ratio etc. 

[tikimadness]

It would be awesome for someone like Johannes or Mr. Maher to engineer systems, maybe it would even involve really thinking outside of the 40 year old box this hobby has been in and coming up with off the wall cam grinds or rocker ratio.

Actually Johannes kinda does that already. I bought the cam, lifters and springs from him and he designed a custom cam profile to give maximum hp @7000rpm, knowing the flow numbers on my heads, engine size, compression, rocker ratio etc. 

Cool I was wondering if he could/would do that. I bought a set of his springs and he was very interested and helpfull with information on installation pressure and max pressure on full lift.

Think I might give him a call next winter.

Michael

[ALB]

Great discussion, guys; very informative!! A couple of questions- are the Webcam cams (say that 3 times fast!) with the 30 degree difference between advertised and @0.050" durations (eg- the 110 or 109) harder on lifter bores like the Engle VZ and FK40 series cams? And how much does the dur @0.050" change when using 1.25 or even 1.4 rockers with a cam designed for 1.1/1 rockers?

[John Maher]

And how much does the dur @0.050" change when using 1.25 or even 1.4 rockers with a cam designed for 1.1/1 rockers?

Forget using 1.4 rockers on E125!!

Duration @ .050" valve lift increases by about 5° when swapping from 1.1 to 1.25 rockers
and around 12° @ .200"

The graph below shows lift and duration differences at the valve based on 1.1 and 1.25 rockers (Engle 125)

[ Attachment: You are not allowed to view attachments ]

As you can see, there's a healthy increase in area under the curve. Even if the port's flow were to max out at say .400", adding the 1.25 rockerextends the period of time available for flow to enter the combustion chamber.

[Simpsonshoe]

Great discussion, guys; very informative!! A couple of questions- are the Webcam cams (say that 3 times fast!) with the 30 degree difference between advertised and @0.050" durations (eg- the 110 or 109) harder on lifter bores like the Engle VZ and FK40 series cams? And how much does the dur @0.050" change when using 1.25 or even 1.4 rockers with a cam designed for 1.1/1 rockers?

To a degree.A degree or two.

[Cheesepanzer]

Take a head fitted with 48mm intake valve. You need to see an absolute minimum of 0.472" lift (48 x 0.25) for the head to start flowing reasonably. If the seat, port and chamber have been  well modified, flow should be excellent to around 33% lift (0.623") or more. If this is a max effort engine, running anything less is leaving potential power on the table.

Some great comments on this thread.  This particular comment was one of thos "light bulb" moments for me.   

Good stuff guys!

[Torben Alstrup]

Great discussion, guys; very informative!! A couple of questions- are the Webcam cams (say that 3 times fast!) with the 30 degree difference between advertised and @0.050" durations (eg- the 110 or 109) harder on lifter bores like the Engle VZ and FK40 series cams? And how much does the dur @0.050" change when using 1.25 or even 1.4 rockers with a cam designed for 1.1/1 rockers?

As said, forget using 1,4´s on W  or VZ cams.
Wrt the opening ramps and the difference between seat duration and dur @ 0,050", there is more to it than that. JMR´s explanation is good, but in an explanation like this he can only generalize. If we took 2 cams out and began to disect them individually, we could really see where the differences are.

Another aspect in selection of cams (when we talk street cams) is temperature. You can have 2 cams grinds that looks about identical and performs almost the same, but the one cam runs maybe 10 - 15 degrees less cylinderhead temps.

Part of that is because most of the grinds we use come from Chevy, Ford and some motorcycle cams. Very few have actually been developed for acvw´s. That is also why I for one, have never been married to one cam grinder. I use cams from 4 - 5 different brands (Again when we talk street engines)

Now, if we go back and take the beforementhioned Web #110 and compare it with the Engle W120, we will see that the duration @ 0,50 is almost the same, 3 degrees apart. The seat duration is 10 degrees apart. Then the average Joe would assume that the Web #110 was much more agressive on the ramps than the W120. But if you take same 2 cams and put them in a cam dialer, you will see that it is not so. And THAT`S where the interesting part comes. It would take me the rest of the day to try and explain that, and even then I´m not sure I can do it so most people understand. it´s a complicated subject that I am not entirely comfortable with either. So I´ll leave that to the real pro´s
T

[Johannes Persson]

Hello,
During the last two years I have designed and developed a new series of cnc grinded cams for acVW's.
Their designs are based on TA(time area) calculations for different displacements and performance goals.
Acc, velocity , jerk and ramps is adjusted to best suit the type1/4 valvetrain, practical tests has been made in my single cyl engine and my own streetcar.
The grinds has about the same dur at 0.05" as the most popular grinds on the market but all of them has different ramps that suits the big valve lash a hot VW engine has, they also have increased valvelift area without going bigger on valve lift, this is possible thanks to different acc.
They also operate with less spring pressure than what we are used to.

One example is Peter Shattocks 91x69 engine, which I guess some of you knows about, at his last race he achieved 116mph top speed which equals 8970rpm.
The spring pressure is 110-120lbs closed and about 250lbs at full lift(15.5mm 0,610"), even with a light valvetrain this is very low pressure.
An other example is my own street car it has 48x38 ti valves only the outer of my OTEVA75 springs, about 75lbs closed and 180lbs at full lift(15.4mm 0,606") and good for 7500rpm+.
With this kind of spring pressure I recommended to use a good quality alu push rod and you get rid of the big valve lash and noise from the valve covers.

The cams are only sold as a kit with matched lifters and brake in oil with extra zinc.

/Johannes Persson

[Zach Gomulka]

Can this graph/program be found on the 'net? I'd like to play around with different cam/rocker combinations.

[Jim Ratto]

Hi Johannes, where can a customer find more out about your grinds?
I'm very interested.

Thanks for the information

Jim R.

[fish]

Jim, that's like asking a magician to show us his sleeves.....

[Jon]

Jim, that's like asking a magician to show us his sleeves.....

Yes, but with a big difference... he is selling his "magic tricks" over the counter!!

Today you can buy a real cool running 230 hp everyday aircooled engine over the counter... history is being made today!
Engines are no longer "built", they are designed!
Why the magazines don't pick up on this is beyond me...  but luckily we have the Lounge....

You heard it here first
- The Lounge

 

[Torben Alstrup]

"You heard it here first"

There is a difference 

T

[Jon]

Fixed, thanks!