But what has this got to do with a venturi in the exhaust system????
Temps
- Thread starter mike97760
- Start date
Venturi draws air into pipe so it is there instead of exhaust gases to help fill cylinder. You were thinking of venturi restricting exhaust flow.
Tap for egt can be used similarly to get air into pipe. Distance from port tuned for rpm desired.
That restriction could be considered a venturi, but it is not the venturi effect that improved the cylinder scavenging. Back pressure in the exhaust is as incorrectly referred to as the term Billet. In reality you are looking for a lack of pressure at the valve, you want the lowest pressure you can cause. Placing restrictions or designing pipes so that atmospheric pressure never has the opportunity to reach the back of the valve between exhaust strokes. After each exhaust pulse is a negative pressure area, make certain that negative area does not leave the system before the valve opens again. 95shaw are you suggesting flowing fresh air into the cylinder through the exhaust valve????
Are you familiar with emission controls, for years they have injected air into exhaust manifolds, it does not make it's way into the cylinder. It is one of the first systems next to EGR that you would get rid of if you are trying to make power. Your straw example does not add much to this reasoning.
More than one way to skin a cat.
Is not a bolt and go part. Whole system needs to work together for benefit.
Allowing oxygen to enter the exhaust stream causes unburned fuel to burn in the port, which would cause excessively high temperatures, this would be the cause of the need to reseat valves regularly. Several automotive manufacturers struggled with this through the seventies, the lack of lead in the fuel and extreme temperatures in the exhaust caused early valve failure. I do remember regularly repairing burned valves, and that was in the day of it being a job that could be done in an afternoon.
Are you suggesting flowing fresh air into the cylinder from the exhaust pipe during the overlap phase?
We have a winner!!!
If that occurs you have the worst operating engine on the planet, in approximately 15* of crankshaft rotation you have reversed direction of the flow in the exhaust port, at the temperature, pressure and velocity of the gasses do you understand what would be required to do that.
If the upside overcomes the downside, more power is the result. Your mileage may vary.
One last thing. Reversal is already happening. Just taking advantage of what is already occurring.
flattop1
Dawg 89
I assume you understand the reason that valve float worked in the flathead.
My thought is, it was do to the valve being lofted further than the actual lift, supplied by the cam.
with the overhead valve, you have the push rod and rocker to contend with, which seems to make it not feasible in that situation.
Absolutely. The point was it worked in spite of thought was valve float was bad.
So bringing up the slapper cam is just to show an example of the rules being changed?
Not at all. Just interesting fact. Since we got off track of original post, once more shouldn't hurt. Original poster feels he got his answer.