ArKay99
August 11th, 2006, 03:39 AM
I have been looking at this a bit recently since I now have a good tune in the car, I naturally have to find ways to tweak it, because I can. :D
I recently read a thread started by Redline Motorsports Redline MotorSports thread (http://forum.efilive.com/showthread.php?t=2684)and one of the contributors, DrX, had very good insight and helped with some calcs to narrow this down. I took a look at my stock settings for my operating system (12221588 - 2002 Z06) and what I ended up with. I also looked at a stock 99 C5 values and they were the same. They both were .0255. I looked at the units as per DrX's illustration and they didn't match. When I found the root of the calculation of .0255 I came up with ~70.65mm for the throttle area. I had a stock -ported 78mm throttle body in the basement and got the caliper out and started measureing. I found that the overall outside measurement was ~101mm. The inside overall at the lip was 94.5mm. The opening at the back of the throttlebody was 78mm and the operating area of the throttle blade was 75.1mm. The throttle blade itself is 75mm. These measurements are subject to the accuracy of my caliper and my ability to get it at the correct spot. The inside of the throttlebody right in front of the blade, where the rise is is ~73mm. So where is the last 2.35mm? I looked at the blade sitting at rest and it is open ~10% giving an elliptical cross-section to the incoming air. If I eyeball measure this cross section with my caliper I get slightly larger than 70mm.
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The difference in cross sections from closed to open is ~6%. When my car is idleing nicely my throttle position reads close to 6%. I don't know if this correlates but maybe worth noteing.
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I haven't done anything with my 90mm throttle body, because I have to take it off to make these measurements. I'm thinking of trying some value between 6% and 0% for this throttle body and figureing the ETC parameter from there. When I get a chance later, I will report what I've found.
I recently read a thread started by Redline Motorsports Redline MotorSports thread (http://forum.efilive.com/showthread.php?t=2684)and one of the contributors, DrX, had very good insight and helped with some calcs to narrow this down. I took a look at my stock settings for my operating system (12221588 - 2002 Z06) and what I ended up with. I also looked at a stock 99 C5 values and they were the same. They both were .0255. I looked at the units as per DrX's illustration and they didn't match. When I found the root of the calculation of .0255 I came up with ~70.65mm for the throttle area. I had a stock -ported 78mm throttle body in the basement and got the caliper out and started measureing. I found that the overall outside measurement was ~101mm. The inside overall at the lip was 94.5mm. The opening at the back of the throttlebody was 78mm and the operating area of the throttle blade was 75.1mm. The throttle blade itself is 75mm. These measurements are subject to the accuracy of my caliper and my ability to get it at the correct spot. The inside of the throttlebody right in front of the blade, where the rise is is ~73mm. So where is the last 2.35mm? I looked at the blade sitting at rest and it is open ~10% giving an elliptical cross-section to the incoming air. If I eyeball measure this cross section with my caliper I get slightly larger than 70mm.
---
The difference in cross sections from closed to open is ~6%. When my car is idleing nicely my throttle position reads close to 6%. I don't know if this correlates but maybe worth noteing.
---
I haven't done anything with my 90mm throttle body, because I have to take it off to make these measurements. I'm thinking of trying some value between 6% and 0% for this throttle body and figureing the ETC parameter from there. When I get a chance later, I will report what I've found.