Calculate the flow of cam/head system
Posted: March 11th, 2012, 5:40 pm
Guy you will certainly comment this! At a first glance my reasoning is correct but further explanation is required...
I tried to link 2 important parameters concerning the filling of cylinder:
-The flow of the head function of the valve lift (Q=f (L))
-The lift of the valve function of the crank angle (L=f (CA)).
The idea is to get a curve of the flow function of the crank angle (Q=f (CA)).
If the result is in a table to the Excel format it is quite easy to calculate an integral and the mean of this integral so obtain the mean flow during a cycle of opening valve for a given head.
The goal is to compare for the same head the difference of flow between 2 camshafts and vice versa or mixing both modifications...
So I started from the GC figures found in the 1rst book for the flow of the head and the figures of the Ritmo 130TC camshaft I measured and the ones of the St3 rally camshaft found in the 2nd GC book.
Here below a drawing showing the idea in 3 steps (1) (2) (3)
The method to calculate integral is available on the web (or from your memory...). I used the trapeze method simple to implement in Excel (and giving good results compared to the real integral of the corresponding polynomial function).
The spreadsheet snapshots show the initial tables for Q=f (L) and L= f (CA) and the associated curves.
You can see also the resulting tables for Q=f (CA).
The mean flow is about 34 cfm for the OE cam profile and the mean flow is about the double 68 cfm for the St3 rally cam profile.
Obviously the torque and the power are not doubled too when you change the first camshaft to the second one.
But here I cannot say more because I don't know all the parameters entering in the obtaining of power.
Regards
Robert
PS: sorry I did not put the Excel worksheet as image but I did not find how to do...
I tried to link 2 important parameters concerning the filling of cylinder:
-The flow of the head function of the valve lift (Q=f (L))
-The lift of the valve function of the crank angle (L=f (CA)).
The idea is to get a curve of the flow function of the crank angle (Q=f (CA)).
If the result is in a table to the Excel format it is quite easy to calculate an integral and the mean of this integral so obtain the mean flow during a cycle of opening valve for a given head.
The goal is to compare for the same head the difference of flow between 2 camshafts and vice versa or mixing both modifications...
So I started from the GC figures found in the 1rst book for the flow of the head and the figures of the Ritmo 130TC camshaft I measured and the ones of the St3 rally camshaft found in the 2nd GC book.
Here below a drawing showing the idea in 3 steps (1) (2) (3)
The method to calculate integral is available on the web (or from your memory...). I used the trapeze method simple to implement in Excel (and giving good results compared to the real integral of the corresponding polynomial function).
The spreadsheet snapshots show the initial tables for Q=f (L) and L= f (CA) and the associated curves.
You can see also the resulting tables for Q=f (CA).
The mean flow is about 34 cfm for the OE cam profile and the mean flow is about the double 68 cfm for the St3 rally cam profile.
Obviously the torque and the power are not doubled too when you change the first camshaft to the second one.
But here I cannot say more because I don't know all the parameters entering in the obtaining of power.
Regards
Robert
PS: sorry I did not put the Excel worksheet as image but I did not find how to do...