Dan From Sault Ste Marie Ontario

Dynomation can compare up to 4 graphs at one time, so I did all but the Summit 8707 camshaft. The
Summit 8707 is actually in Sim01 with the stock heads. Which Sims would you like to compare it with
when I use the AFR heads? You can pick up to three other Sims.

The graph gets very congested with four engines being compared. At the bottom of this post is a full size
version for you to use.

Sim07_Sim08_Sim09_Sim10_Compare.jpg
 

Attachments

  • Sim07_Sim08_Sim09_Sim10_Compare(Full-Size).jpg
    Sim07_Sim08_Sim09_Sim10_Compare(Full-Size).jpg
    67.5 KB · Views: 2
Those are all pretty close to each other, and pretty much where I want the combo to be. I recall that in the earlier we didn't see a big change in power with increasing the compression ratio. I think lower compression ratio would suit the truck better as it will be used in town a whole lot and probably driven more often then not. Could we compare the Sum 8708, 8707 camshaft and the CamMotion camshaft for the engine parameters listed in the attached table?
 

Attachments

  • Low Compression Comparison.pdf
    412.2 KB · Views: 2
  • Low Compression Camshaft Comparison.pdf
    226 KB · Views: 2
Before I post more Simulation Graphs, I would like to verify some numbers that don't seem to
jive for me. I've been looking at them for couple of hours and I cannot see a consistent application
of the numbers in your table below. If you like I can apply the numbers and then show
you what Dynomation is reporting at 5° additional / 8° total advance.

- How did you apply the 8° advance, is that additional or total ? The Summit cam cards already shows 3° advance.
- All the table numbers should be per the cam card or I can go direct to the cam card and ignore the table numbers ?
- We should agree on a set of numbers, then I can run the simulations.

LowCR_CamSpecs_Sum8707_Sum8708_CamMotion.jpg
Summit8707_CamSpecs.jpg Summit8708_CamSpecs.jpg

LowCR_CamSpecs_Sum8707_Sum8708_CamMotion_Commented.jpg
.
 
Hi Rick,
I have attached the corrected table.

Let me clarify how I got to my valve timing numbers.
  • When I spoke to cammotion and summit they told me that the valve timing events were listed on the cam card already considering the ground in advance. So with a zero degree advance the Summit 8707 would close to 0.050" at 43 deg ABDC (cam installed straight up).
  • By advancing the camshaft 8 degrees this would make the intake valve close at 35 deg ABDC. This is shown in the corrected table.
  • There should be a consistent 8 degree additional advance on all the valve timing events. (The corrected table shows this)
  • The calculated intake valve closing is:
upload_2020-6-24_19-10-16.png
For the above equation the advance was 8 degrees.

Indycars said:
How did you apply the 8° advance, is that additional or total ?
Click to expand...
Additional 8 deg

Indycars said:
Are the timing numbers at the seat and 0.050" per the cam card or the 8° advance?
Click to expand...
In the corrected table the timing events are per the 8 deg advance

Indycars said:
We should agree on a set of numbers
Click to expand...
I absolutely agree. Am I using the calculated intake valve closing correctly?
 

Attachments

  • CORRECTED - Low Compression Camshaft Comparison.pdf
    408.1 KB · Views: 2
Daniel Westerbaan said:
So with a zero degree advance the Summit 8707 would close to 0.050" at 43 deg ABDC (cam installed straight up).
Click to expand...
Straight up (StrUp) and dot-to-dot (dtd) are two different things.

StrUp and Split Overlap (SpOv) are the same number. Which is Exactly zero advance, no matter what the cam card says.
Dtd is lining up the dots on the cam gear & crank gear. This is the same as the advance ground into the cam.
SpOv is when the intake centerline = exhaust centerline. OR overlap / 2.

So I can work best with cam card "+ - the changes you want to see in advance / retard from the cam card numbers.

These problems are typical. It is in my mind is up to the user to determine just how precise I need to be. I like splitting hairs so it's not a problem for me, but it's what I like to do. What is your pleasure ?

It's late for me, so I will address each of your questions tomorrow if I have not already done so.

BTW, numbers that end in 0.5 are because things like duration that are an odd numbers, devided by two always do.
Example.
3 / 2 = 1.5
So some graphics I post from Dynomatiom may appear to be off by 0.5 or 1.0 with round off.
 
Daniel Westerbaan said:
Am I using the calculated intake valve closing correctly?
Click to expand...

Your numbers don't seem to agree with your equation below, for example Summit 8708.

(280°/2) +113° - 180° - 3° - 8° = 62° ..... (Your table says 65°)

index.php


For me when viewing the info below, you are saying 5° additional degrees advance or 8° total
advance. There is already 3° advance and you want 5° more.

upload_2020-6-25_10-25-0.png

Your calculations are also showing an additional 5° advance.

(280°/2) +113° - 180° - 3° - 5° = 65° ..... (Your table says 65°)

So it really seems like we are saying the same thing now, but just have a different name for it. Thus
causing the confusion !

BTW, 8° advance is alot !
@Grumpy what do you think about 8° advance ??? Have you used that much advance ???
.
 
if you need more than 6 degrees advance or retard from the strait up cam index location
:rolleyes:
YOU OBVIOUSLY HAVE THE WRONG CAM FOR THE INTENDED APPLICATION
 
Grumpy said:
if you need more than 6 degrees advance or retard from the strait up cam index location
:rolleyes:
YOU OBVIOUSLY HAVE THE WRONG CAM FOR THE INTENDED APPLICATION
Click to expand...

To confirm then, we are within the 6° that you state above, since we added 5° to the cam's DtD or StrUp ???

Using 8° advance (3 + 5) in the simulations below

Sim11_Sim12_Sim13_Comparison.jpg

For your reference I have included what Dynomation is using in Sim11. Sim12 and Sim13 are going to follow the same pattern except with your numbers. Also shows the new lower CR of 9.81 .

Sim11_CamTimingNumbers.jpg

What do you think Daniel ? What do you want to see now ?

BTW, if you have noticed many cam companies publish a Lobe List. You could pick 2 lobes
from that list for your intake and exhaust, specify the LSA you want and not incur a especially
high up charge I believe.

https://cammotion.com/lobe-list/

CamMotionLobeList.jpg
.
 
Hmmm, it seems that I have more to learn regarding the definitions of advance, ground in advance and how they apply.
At least I am learning before I built the engine.
 
Thanks for the links Grumpy. I will work away at them

I just gout out of the hospital. I was actually there all week for emergency surgery.
Gonna need to get well before I get back to this
 
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