Throttle Bodies too big???

[MarioVelotta]

My thought was throttle response and top end with a carb can be greatly improved by changing venturi size. The butterfly stays the same in this case.

Even though the fuel is not metered in TB wouldn't we still get the same effect? You would gain velocity past the blade.

[Paul H]

My thought was throttle response and top end with a carb can be greatly improved by changing venturi size. The butterfly stays the same in this case.

Even though the fuel is not metered in TB wouldn't we still get the same effect? You would gain velocity past the blade.

That's the reason why carbs are poor compared to TB's because the butterfly has to be larger than the required venturi so gives bad throttle resolution.

[trbugman]

My thought was throttle response and top end with a carb can be greatly improved by changing venturi size. The butterfly stays the same in this case.

Even though the fuel is not metered in TB wouldn't we still get the same effect? You would gain velocity past the blade.

This effect in carbs is from getting the correct vacuum signature so it can meter the fuel correctly, and this is a compromise between drivability and max HP.

With a large dia. throttle off, idle response can be hard to control because a small amount of throttle angle exposes more area for air to enter quickly. This is why I made my restrictors block half of the throttle opening.

With any luck I'll make the last 2 pieces I need and get to installing fuel injection this month.

[Paul H]

That's similar to how OEM's design their throttles to gain low speed throttle resolution and they oversize the throttle overcome negate the turbulence of the odd shaped throttle bore. I suspect you will have turbulence issues at mid/full throttle. Personally I'd just spend a little more time tuning the low speed and rework the throttle pedal/cable/linkage to give super smooth action.
Sometimes you will find a little more power at 95% throttle than at 100% and this is due to the angle of the butterfly in relation to the shape of the manifold-this is turbulence, and on other setups you can release the throttle and not loose any power until below 65% throttle