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Old 12-30-2016, 09:07 PM
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Default Choosing cams based on hyd intensity?

So lets say I'm comparing two HR street cams from different mfgs. How useful is Hydraulic Intensity parameter to compare between them? I'm assuming the adv duration numbers are both taken at .004".

Cam A is a 219 at .050 with a HI of 51, and Cam B is a 224 at .050 with a HI of 54 on the intake side.

Cam A is 227 at .050 with a HI of 51, and Cam B is a 230 at 050 with a HI of 59 on exhaust side.

Assume .520 Lift and 112 LSA are the same for both. Which is going to make more streetable power 2000-5500 in a 400?

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Old 12-30-2016, 09:15 PM
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Subscribing, i'll be interested to see what thoughts come out here. (Cam A , to me, looks like a Voodoo cam).

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Old 12-30-2016, 09:33 PM
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Quote:
Originally Posted by chiphead View Post
So lets say I'm comparing two HR street cams from different mfgs. How useful is Hydraulic Intensity parameter to compare between them? I'm assuming the adv duration numbers are both taken at .004".

Cam A is a 219 at .050 with a HI of 51, and Cam B is a 224 at .050 with a HI of 54 on the intake side.

Cam A is 227 at .050 with a HI of 51, and Cam B is a 230 at 050 with a HI of 59 on exhaust side.

Assume .520 Lift and 112 LSA are the same for both. Which is going to make more streetable power 2000-5500 in a 400?
First:
Most of Comp Cams hydraulics are rated @ 0.006" lifter raise.
I believe Crower hydraulics are rated @ 0.004" lifter raise.
I believe UltraDyne hydraulics are rated @ 0.0045" lifter raise.
Anyone know about any of the other cam companies?

I would also look at the 0.200" duration as well.

Stan

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Old 12-31-2016, 08:25 PM
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I dont have all that information off hand, only what is avail online. Is it fair to say that the higher the hydraulic intensity, the more aggressive the ramp is above .050" lift?

I'm just trying to avoid noisy ramps that look good on paper but don't actually perform as well. I got burned so bad by the Comp XE cam that I'm scared of any more of their fast-ramp hocum.

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Old 12-31-2016, 08:42 PM
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The Intensity metric is good.
I have not made that a top-metric because it has been tough enough to get dur/dur and LSA right for low compression.

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Old 01-01-2017, 10:42 PM
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What cylinder head?

Flow at .400, .500, .600

Rocker Ratio?

Duration at .200 for both cams?

Just a 5500 limit?

The Voodoo line are great.

For what you are looking at the Comp XFI hyd rollers should be great


Last edited by pastry_chef; 01-01-2017 at 10:54 PM.
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Old 01-01-2017, 11:14 PM
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Not all fast ramps are noisey. Harold Brookshire prided himself with his designs.(Ultradyne, Bullet and Lunati VooDoo series). That said there are others besides Comp that dont seem to have noise issues. (Though IMO I think some batches of Comp hyd lifters may be more at fault than their lobe designs for being noisey)

Solid lifters can run fairly quiet too and need not be "tight lash" designs. A well designed lash ramp takes the lash up gently. (one of a few reasons I personally wouldnt run solid rollers on a hydraulic roller cam).

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Old 01-02-2017, 08:50 AM
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Keep in mind that many lobe profiles are much slower on the closing side. Relates to this, a hint from the designer of UltraDyne cams & Voodoo lobes........

"I do all my cam designs as unsymmetrical cam designs. Although I design my hydraulics just like I do my roller profiles, The information I will give applies just to my hydraulic flat profiles.
Using Harvey Crane's Hydraulic Intensity formula, ALL my .842" tappet designs have an Hydraulic Intensity of 53.88 degrees. This is the duration at .050" subtracted from the duration at .004", where the SAE has decided that hydraulic durations begin and end.
This Hydraulic Intensity of 53.88 is considered to be very aggressive, yet the cams do not have that 'sewing-machine' sound to them.
The opening side of the cam has a 45.26 degree equivalent Hydraulic Intensity, and the closing side is 62.50 degrees Hydraulic Intensity. The SEATING velocity of the valve is only 37% as fast as the OPENING velocity. This seating velocity is only slightly faster than GM uses on all their engines. At UltraDyne, I have had many hydraulic, as well as solids, go over 100,000 miles on the street. I keep the edge of the tappet about .018" away from the point of contact between the cam and tappet.
That 'sewing-machine' sound is caused by the valves hitting the valve seats too fast. The original High Energy cams, which I designed, produced that sound. I was shutting the valve at .0007"/*, only .0002"/* faster than GM. After hearing about the noise, a little thought made me realise the .0002"/* was only 40% faster than GM.
You do not have to shut the valve faster to keep the charge from getting out.
You have to design the cam so the charge, or inertia ram, is still filling the cylinder when you shut the valve.
Every cam I design, hydraulic, hydraulic roller, solid, solid roller, is designed using the same theory I have used for the past 29 years, and they all make excellent bottom-end torque for their duration."
UDHarold


.

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Old 01-02-2017, 09:23 AM
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Side note that might relate to the material I posted by Harold Brookshire. With this statement in mind....

"ASYMMETRICAL refers to a camshaft lobe profile where the opening and closing ramps are not exactly the same. The reason some camshafts are this way is to try to achieve an opening ramp profile that has a high velocity and a closing ramp profile that has a slower velocity. In this way the valve can be set down more "gently" than the rate at which it was first opened."

Now note what Harold stated:

"The opening side of the cam has a 45.26 degree equivalent Hydraulic Intensity, and the closing side is 62.50 degrees Hydraulic Intensity. The SEATING velocity of the valve is only 37% as fast as the OPENING velocity."

I have questioned if maybe he stated it backwards. Or I'm I way off base and interpreted it wrong. Comments from the cam experts ?


.

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Old 01-02-2017, 09:31 AM
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And also related, David Vizard's comments here regarding “hydraulic intensity” might be of interest....

http://www.enginebuildermag.com/2006...ifter-failure/


.

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Old 01-02-2017, 01:29 PM
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Assuming 1.65 rocker.
A factory d-port around 240 CFM.

For 5500 RPM

Comp XFI hyd roller
Intake 13080
278 adv dur
228 @ .050
152 @ .200
.360 lobe lift

Intake centerline at 109

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Old 01-02-2017, 08:49 PM
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Quote:
Originally Posted by Steve C. View Post
And also related, David Vizard's comments here regarding “hydraulic intensity” might be of interest....

http://www.enginebuildermag.com/2006...ifter-failure/


.
Thanks, Steve. The notes from Harold Brookshire and the Vizard article provide much food for thought on this subject. Speaking from ignorance, I don't know that the OP will find hydraulic intensity outside of the 50*-55* (53.88* per Harold) range to be as useful to him. Cam A sounds like it has the best HI for power , but Cam B would have more gentle ramps if I understand all this correctly. Like you, what do the cam experts say?

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Old 01-03-2017, 12:24 PM
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If interested additional info here regarding Opening and Closing Rate:

http://www.tildentechnologies.com/Ca...rformance.html

"In practical terms if two cams with similar lobe designs have the same duration at 0.050 lift, maximum torque and horsepower will be almost identical. However, the cam with the quicker opening will have a smoother idle, better off-idle response, superior low speed drivability and a broader power curve."

Many will not accept that conclusion and suggest it does not apply to a "Pontiac". Especially in the street section where some seem to demand slow lazy cams with a lot of seat timing, and the "041" is king of the hill

Now all this all said, note Mike Jones comments in this entire thread and the suggestion it's a marketing tool. However keep in mind the discussion here is regarding a solid cam and the effect of valve lash. Apples-to-oranges regarding a hydraulic cam.

http://www.yellowbullet.com/forum/sh...d.php?t=455257

There are some big players on both Yellowbullet and Speedtalk forums that get involved with the subject. Seek it out if interested.


.

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Old 01-03-2017, 01:17 PM
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Again I ask about 0.200" lifter raise duration.

If you look in the Comp Cams Lobe Catalog at High energy hydraulic cams. There are 3 cams rated 260 degrees @ 0.006" lifter raise and all are 212 degrees at 0.050" lifter raise.

Next step. Yes, they all have different lobe lifts and different duration @ 0.200" lifter raise

Stan

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Old 01-03-2017, 02:24 PM
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Stan, your example. Two similar lobes:
260 at .006 / 212 at .050 / 117 at .200 / .2790 lobe lift
260 at .006 / 212 at .050 / 122 at .200 / .2960 lobe lift

First reaction, the second lobe has more area under the curve ?

Then you can Goggle up related tid bits...

Under The Curve
http://www.superchevy.com/how-to/148...mshaft-basics/

What Wrong with Area Under Lift Curve?

http://www.tildentechnologies.com/Cams/Take_Area.html

"Well graph out a valve motion chart and you will be surprised at the amount of time the valve spends a different lifts... last time I checked the valve spent the least time at mid lifts, most around peak (upper 10-15%).... there is usually a good amount of cylinder filling done at this time. The funny thing is the low lifts sub .200 have some interesting things going on, overlap, high port pressures etc.... so sometimes more flow down here is not always the best thing."

http://speedtalk.com/forum/viewtopic.php?t=1148


.

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Old information here:
http://www.hotrod.com/articles/0712p...tiac-trans-am/

Sponsor of the world's fastest Pontiac powered Ford Fairmont (engine)
5.14 at 140 mph (1/8 mile) , true 10.5 tire, stock type suspension
https://www.youtube.com/watch?v=qDoJnIP3HgE
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Old 01-03-2017, 02:47 PM
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Quote:
Originally Posted by Steve C. View Post
Stan, your example. Two similar lobes:
260 at .006 / 212 at .050 / 117 at .200 / .2790 lobe lift
260 at .006 / 212 at .050 / 122 at .200 / .2960 lobe lift

First reaction, the second lobe has more area under the curve ?

Then you can Goggle up related tid bits...

Under The Curve
http://www.superchevy.com/how-to/148...mshaft-basics/

What Wrong with Area Under Lift Curve?

http://www.tildentechnologies.com/Cams/Take_Area.html

"Well graph out a valve motion chart and you will be surprised at the amount of time the valve spends a different lifts... last time I checked the valve spent the least time at mid lifts, most around peak (upper 10-15%).... there is usually a good amount of cylinder filling done at this time. The funny thing is the low lifts sub .200 have some interesting things going on, overlap, high port pressures etc.... so sometimes more flow down here is not always the best thing."

http://speedtalk.com/forum/viewtopic.php?t=1148


.
Since I do not have the actual lift profile for these cams, this is just an approximation of what their lift profiles might look like.

Stan
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Old 01-03-2017, 09:26 PM
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Multi-dimensional and ever moving...the graphic art required to get a visual of all things occuring thru a complete 4 cycles.... even if broke down in 10 degree increments of rotation...would be quite an art feat.
You actually need to graph a running engine with the cam you've chose and be able to record the pressure traces of rising/falling pressures(intake exhaust and cylinder) thru events across 720 degrees combined with a graph of the actual valve lift curves.

I dont think any of us are equipped to do this at home

For me one of the better visuals is putting a head on the drivers side bank and no piston in #1 hole... no head on passenger bank but a piston and rod in # 6(connected to crank of course). Put cam, timing chain, solid lifters etc in so you can actuate the valves, put a degree wheel on and start turning the crank.
Remember that #6 piston motion is same as #1's. Keep in mind what should be occurring if it were actually running and try to visualize increasing and diminishing pressures. As you stop along the way look under and see valves in #1 hole and look at # 6 to see whereabouts the piston would also be in #1.

Alot of work for some insight(but its good). You still need to know when one function is handing off to the next function and be able to consider what would enhace and what would detract at any given point.

Ultimately it all boils down to a set of best compromises for any given application.

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Old 01-03-2017, 10:44 PM
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Area under the curve...
Something like the lowly "N" cam(066) could be the start of a fairly high performance cam! BOTH could share the same valve seat time and lobe separation angle and intake centerline. The difference would be in .050" duration and durations beyond the lift of an N cam!

"N" cam is 273/282 duration(at the valve) with .050 cam lift duration 197/206 and valve lift .420/.426 111.5 LSA/107 ICL
Change the lobe and you could get same seat time but .050" cam durations could be upped to 243/252 degrees(or more) with valve lift over .550" . They will NOT idle same or share the same power band. Torque/hp peaks would probably rise 1000 rpm or more depending on rest of combo.

Hmmm a race cam could have 273/282 duration at .050and over .700 lift at the valve same LSA/ICL...thats a bunch of area under the curve, over the curve, and a whole different planet then the cam that came in grandmas Pontiac.

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Old 01-04-2017, 11:35 AM
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Bruce, just putting a second dial indicator on the exhaust would like shock most people. Especially guys running hi rpm solid rollers.

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Old 01-04-2017, 01:23 PM
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A follow up. This regarding the question I posed within post number 9 if maybe Harold Brookshire stated it backwards on the percentage of the opening and closing sides of his lobes. And if I interpreted it wrong.

I got a private message from a friend with his opinion on that......

"No I don't think Harold stated it backwards. What I think he meant/said: in the opening side takes about 45* of rotation to go from the adv duration lift point [ say, 0.006" ] to the 050 lift point; on the closing side, it takes longer, more rotation of the cam, 62*, because of the slower closing."


.

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Old information here:
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Sponsor of the world's fastest Pontiac powered Ford Fairmont (engine)
5.14 at 140 mph (1/8 mile) , true 10.5 tire, stock type suspension
https://www.youtube.com/watch?v=qDoJnIP3HgE
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