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Step in the throat

General engine tech -- Drag Racing to Circle Track

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GT50
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Step in the throat

Post by GT50 »

There mixed points of view on this matter, if you have a difference in diameter below the bottom seat and the throat two millimeters there would be a step and the benefits are to pulverize the fuel better specially the liquid fuel and that is in a carbureted engine or monopoint injection system it probably would work on multi injection.
mag2555
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Re: Step in the throat

Post by mag2555 »

It would work yes to one degree or another, but there can be times when the fuel is already too finely atomized in the port runner and this vapor is now taking up room that would otherwise be both air and fuel with the end result being less power.

The steps placement in the valve bowl would need to be found on a wet flow bench, but if you look into the valve bowl on a LS7 head you can see how those engineers chose to go about it.
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Re: Step in the throat

Post by steve316 »

Leave the angles on intake seat; radius exhaust seats.
GT50
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Re: Step in the throat

Post by GT50 »

Do you mean making the step offset opposite side of the ssr? In the monopoint injection system you will have wet fuel. In my point of view the manifold is poorly designed also the fuel is pulverized to the throttle blade and right down to the plenum and air dislikes to turn but fuel will turn and that is why there is wet fuel.
GT50
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Re: Step in the throat

Post by GT50 »

I wanted to say fuel will not turn at all.
Steve 316, do you mean not to leave the step in the bowl just the three angles 30,45 and 60 degrees on the intake port ?
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Re: Step in the throat

Post by steve316 »

Yes leave the angles off the seat in the bowl. Helps the flow turn. I have seen radius intake angle cost as much as 16 cfm.
GT50
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Re: Step in the throat

Post by GT50 »

steve316 wrote: Fri Feb 07, 2020 8:52 am Yes leave the angles off the seat in the bowl. Helps the flow turn. I have seen radius intake angle cost as much as 16 cfm.
You are right about that radius seats in the intake seats are bad because they also don't help to pulverize the fuel at all. I have seen in Diesel engines that below the seat angle it is radius to help the air stay atache ( Coanda affect).
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