Flow bench development on 16v Cosworth head
Posted: November 19th, 2006, 8:06 pm
Hi Guy and everybody,
I have currently purchased a flowbench from Superflow - the SF120E along with Flow Comp with motor control, flow bench swirl meter, 4 valve universal opener with dial gauge, exhaust velocity pitot tube, inlet velocity pitot tube, head adaptor for cylinder simulation!
In the past I have been porting cylinder heads (still do), for racing engines based on the information From Guy's Fiat Lancia Twin Cam book, (The Bible as I refer to it!), and I had very good results, but as Guy would agree there is a point that you need the right equipment for the development of such a serious and high standard job!
Its the first time that I have been using a flow bench and I must admit that Guy's tips were a great help to get going!!
My 1st project Job is a Cosworth head (currently standard) and after sand blasting and cleaning thoroughly, I was ready to do some flow testing with the bare head at 10" Test depression.
To my surprise the max bare head flow from a standard Cosworth head is only 117.5 for the inlet ports and 89.6 cfm for the exhaust - 76% compared to the inlet flow. Has anybody any flow tests for the bare standard head for comparison ?
I have also measured on all tests the velocity in the inlet port at half way into the port about an inch before the valve guide and I will try and see the difference during the porting steps! The velocity test was performed with a pitot tube at nine different points on the cross sectional area on the port one inch before the guide. I will try and attach the files with the 4 different tests.
First was a bare standard head test. Then the first step (Test Bare head 1) was porting (with 50 grit) the inlet ports 1 mm oversize up to the valve guide. After this modification the results were 119.4cfm. The second step was another 1mm of porting up to the valve guide and the results were again surprising ¢‚¬Å“ only 119.6 (test 2) and indicating that there was a restriction on the other half of the port towards the valve seat and short radius.
Conclusion from the 1st two test is that Cosworth had done the math correctly...the first half of the inlet port flow is well balanced compared to the other half of the port towards the short radius and valve seats. Opening up just the first part of the ports will have no effect on the flow since there will be a restriction on the other half.
Third step was 1mm porting on the other half of the port with a minor ‹Å“sorting out¢ž¢ on the short radius - the result was a big increase - 136.5cfm !!
My next step will be the splitter vane and then with the valves in, so I can see what is happening. I will try and measure the velocity on the short and long radius and compare.
I know there is still a lot to get from this head but I would rather do it step by step slowly so I can learn from it than just get carried away and rush things just to get the big numbers.
Guy, I would like to ask what do you use for the initial quick opening of the port diameter....I used the Ata bands 50 grid but it takes time !! Any recommendations?
I find difficulty to attach the test files ....they are converted to ASCII files from the original Port Flow analyzer Pro software.
Best regards,
Mike
JMC Power Automotive, Cyprus
I have currently purchased a flowbench from Superflow - the SF120E along with Flow Comp with motor control, flow bench swirl meter, 4 valve universal opener with dial gauge, exhaust velocity pitot tube, inlet velocity pitot tube, head adaptor for cylinder simulation!
In the past I have been porting cylinder heads (still do), for racing engines based on the information From Guy's Fiat Lancia Twin Cam book, (The Bible as I refer to it!), and I had very good results, but as Guy would agree there is a point that you need the right equipment for the development of such a serious and high standard job!
Its the first time that I have been using a flow bench and I must admit that Guy's tips were a great help to get going!!
My 1st project Job is a Cosworth head (currently standard) and after sand blasting and cleaning thoroughly, I was ready to do some flow testing with the bare head at 10" Test depression.
To my surprise the max bare head flow from a standard Cosworth head is only 117.5 for the inlet ports and 89.6 cfm for the exhaust - 76% compared to the inlet flow. Has anybody any flow tests for the bare standard head for comparison ?
I have also measured on all tests the velocity in the inlet port at half way into the port about an inch before the valve guide and I will try and see the difference during the porting steps! The velocity test was performed with a pitot tube at nine different points on the cross sectional area on the port one inch before the guide. I will try and attach the files with the 4 different tests.
First was a bare standard head test. Then the first step (Test Bare head 1) was porting (with 50 grit) the inlet ports 1 mm oversize up to the valve guide. After this modification the results were 119.4cfm. The second step was another 1mm of porting up to the valve guide and the results were again surprising ¢‚¬Å“ only 119.6 (test 2) and indicating that there was a restriction on the other half of the port towards the valve seat and short radius.
Conclusion from the 1st two test is that Cosworth had done the math correctly...the first half of the inlet port flow is well balanced compared to the other half of the port towards the short radius and valve seats. Opening up just the first part of the ports will have no effect on the flow since there will be a restriction on the other half.
Third step was 1mm porting on the other half of the port with a minor ‹Å“sorting out¢ž¢ on the short radius - the result was a big increase - 136.5cfm !!
My next step will be the splitter vane and then with the valves in, so I can see what is happening. I will try and measure the velocity on the short and long radius and compare.
I know there is still a lot to get from this head but I would rather do it step by step slowly so I can learn from it than just get carried away and rush things just to get the big numbers.
Guy, I would like to ask what do you use for the initial quick opening of the port diameter....I used the Ata bands 50 grid but it takes time !! Any recommendations?
I find difficulty to attach the test files ....they are converted to ASCII files from the original Port Flow analyzer Pro software.
Best regards,
Mike
JMC Power Automotive, Cyprus