ORIGINAL: aangelet
I don't know about dyno results or intake shapes, but after reading the above posts, I took the venturi (is that what it's called?) out of the carb, then tuned it for the larger intake hole. The speed and power are insane. After doing this, I could nail the throttle from a dead and the car would do a 360. The top end was noticeably faster.
I think I'm going to take the smallest insert and chuck it up in my lathe and turn the inside out at an angle. Perhaps, starting out at the widest possible opening at the top and then tapering to the size of the intake at the bottom will result in an air "acceleration" effect. Who knows, I don't have a degree in engineering, but I may stumble onto something. As far as the 9mm minimum requirement, do they go by the largest diameter of the opening or the smallest?
The smallest is what tech goes by but noticeable modifications may not pass tech inspection.
Thank you for trying out what I was preaching. The power increase is unreal in both bottom and top end.
As far as modding an insert: The problem I ran into with trying to get maximum flow and a smooth air flow with the insert was getting it big enough to make a huge difference over stock difference. After about 11mm enlargement you become dangerously close to cutting into the ribs that are cut into the outside of the insert for the O-rings. If you’re off center, you’ll cut into one of these ribs or grooves before you get to the inside diameter you desire. But hey, give it a shot, see what you come up with, experiment a little.
Rock on!