awesomerott

thank's for the #s.
what do you think of this DD,just curios.

awesomerott

were can i learn how to read these #'s and what it mean.

rmbuilder

Isky rates adv dur for Hyd roller @.007 so trying to DD this with adv #,s will be invalid as valve events will not be comparable. Thats what leads to false output with these programs. Your only apples to apples would be the .050" numbers.
Isky 228*/238* 112*LSA 112*ICL
IVO 2* BTDC
IVC 46* ABDC
EVO 51* BBDC
EVC 7* ATDC
Crane 731 226*/236* 112*LSA 107* ICL
IVO 6* BTDC
IVC 40* ABDC
EVO 55* BBDC
EVC 1* ATDC
Keep in mind the Isky is straight up while the Crane is 5* adv. Changing your center lines will alter the valve events so use these as a baseline
Bob

rmbuilder

If you advance the Isky numbers 5* they are nearly identical with the Crane
IVO 7* BTDC
IVC 41* ABDC
EVO 56* BBDC
EVC 2* ATDC
As you can see this is where the output on the computer sims gets very skewed, very quickly, many times without the user even knowing. Its been said that they are useful in predicting "trends" like peak TQ/HP placement, VE, etc but, in my opinion, I would never seriously consider component selection, especially camshaft profiles, based on the output.
Bob

awesomerott

bob i think i enderstand wath you mean about DD.
is there a simple way to explain how this motor would perform with these two cam ?

rmbuilder

To clarify my last statement re; cam selection. Because there is not a set uniform standard for rating seat duration (a very important number), lobe area, accurate duration ratings @ .020/.100/.150/.200 etc your sims is really just giving a guesstimate at the actual lobe profile. Your very (expensive) advanced computer modeling programs utilize sophisticated cam measurement specifications in units of measurement in/deg at multiple points of lifter rise.

Crazyhorse

DD is a nice program to use when comparing parts from a baseline model. I like to use it and see how close the actual dyno results are.
rmbuilder, thanks for the cam specs. I appreciate it.

rmbuilder

By examining 10 different intake lobes with the same duration in detail (example 280* seat duration intake lobe) with a CamDoctor program at multiple lifter rise points, it illustrates that single point references can be very generic, and that the 10 examined lobes can be very different from each other.
Bob

awesomerott

So unless you have extensive knowledge(like you and other) or expensive hardware,software it's very tuff to say wich one would work best when two cam profile are close.

rmbuilder

Experience and knowledge base are important. In the case of the 2 very similar(duration) appearing lobe profiles you have inquired about the next step is to compare the lift figures(and requirements) which vary by about 10%, lobe intensity (rate of lifter rise), duration at .200", and lobe placement. Establish your valve events around your mechanical parameters, find the lobe that best fits within those events and you are much closer to an accurate choice.
Hope this helps
Bob