Ya Eric, you tell me! And check your emails. Or are you just ignoring me?lol

Scatter, that dont sound good. I hope all is well.

 

Not to start too much crap, but......... Eric left all the clues necessary in his post for anyone with an internet connection and some thoughtful analysis to figure it out.

He is trying to get us to think about it so we understand it well enough to explain why it works and have the ability to filter out misinformation on the subject. If he just gave us the answers we would always say, "well this is what MisterHP said about porting but my race shop said something else so I don't know who to believe."

Ron

 

Ok, I'll give it a shot, Bigger Valves? yes if the cam design takes advantage of the valves.

Giant ports lose bottom end because the velocity is not there yet.

Big ports, big cams? not necesarilly so, the duration of the cam plays a big role.

Yes it is possible to gain bottom and topend, it goes back to the cam design.

I think the engine gains power from porting due to the fact that now you have the opportunity to increase valve lift and duration to take advantage of the increased capacity of the engine to flow air in and out.

This is my opinion, subject to change if the "experts" make a sound case for me to do so.

 

I have been thinking about this a bit but haven't had time to research it so, like Ben362, I reserve the right to change my mind.[img]i/expressions/face-icon-small-wink.gif[/img]

Regarding the valve size question...... It isn't just a bigger valve to get around, the opening that the valve closes is also bigger which will allow more volume of air and fuel to enter the cylinder. By the time the air and fuel reach the valves, there is no purpose in reducing their size to increase air velocity. If you maximize air velocity earlier in your porting, you will need to increase the valve size proportionately to make sure you don't have a line waiting outside the door. You can increase the valve flow capacity with any number of combinations of lift, duration and valve size. If you upgrade your valves to 40/34 valves but don't increasethe lift or duration of your stock cams, you could probably have gained as much valve flow capacity by leaving stock valves and going nuts with lift and duration.

I would think all three of those components of valve flow capacity would have their own benefits under different circumstances. Duration will be limited mostly by the window of time where good compression is necessary. Lift has physical limitations due to valve length, high compression piston at minimum clearance, the height at which the cams are mounted, etc.

If porting technology increases to the point where you need a way for all that fast moving air to cram into the cylinder without slowing down and you are at the limitations of what lift and duration can do for you already, the obvious next step is to install bigger valves.

Enough for now.

Ron

BTW, If this is true then you should be able to get a pretty good idea how much air velocity and volume a builder is capable of with his porting by what cams and valve size he pushes............Assuming he has mapped everything out and has done the R&D for maximum performance as opposed to merely selling porting and parts because that is what someone asks for.

 

I am most intrigued by the question about how power is made by porting. Porting and air flow are way out of my realm of understanding but here goes a guess.

Think of a hose that is turned on wide open. The water shoots out in great volume but only goes 2 or 3 feet before falling to the ground. If you install a nozzle, the water shoots 20 feet before falling to the ground but the hose pressurizes which obviously means the nozzle is restricting volume. Regarding bottom end power and top end power determined by port size, the trick seems like it would be to have smaller ports for bottom end biased machines. It would increase air speed into the cylinder at lower rpms making more power earlier, the dark side of that seems like it would be the restriction of air volume once you reached a certain rpm threshold. This would cause torque to drop off earlier thus determining an earlier and lower peak horsepower.

Bigger ports will do the opposite. I think they will cost on bottom end because at low rpm, the air is moving much more slowely into the cylinder but at a certain rpm threshold, there will be enough volume coming through the ports that they will start acting like a nozzle again which will hold onto the torque curve longer allowing peak horsepower to come later and ultimately be higher.

The only way I can think of to have both is like this. You can't get it perfect but you can get it close. The air comes in through the filter, down the snorkle, through the carb, then the intake manifold, through the intake ports past the valves and into the cylinder. On a normally aspirated motor the air does not blow through this process, it is sucked in by piston displacement. The filter is big the snorkle tapers smaller, then through the carb. The air then is pulled through the intake manifold which separates into two channels which I would guess that the overall area of the two channels at the port entrance combined is less than the area of the front of the intake manifold at the back of the carb. So from the carb through the intake manifold we are seeing tapering that is intended to increase air velocity. Somewhere in the porting the nozzle is completed and it is reversed opening up to your big valves for high volume. A straight big port will allow lots of volume but lower speed which compromises at low rpm, a straight small port will create great air speed but will eventually restrict volume at higher rpms. If you put in a slight bottle neck, which I will call the nozzle, that opens right back up, it can be as small as the small port but it will function to increase air velocity dramatically without markedly restricing volume within the usable rpm range of a motor.

I would venture to say that the nozzle functions best in the porting because it is close to the source that is drawing the air in. This means from the filter all the way to the nozzle you have a greater volume of air already committed to travel through that nozzle in a given period of time this creating more volume and velocity. I would also guess that you could with experience tweak almost any power curve any way you wanted by moving the nozzle closer or further from the valves or changing the duration of the nozzle...........

I hope I am on track because this was a lot of typing to be mistaken. [img]i/expressions/face-icon-small-wink.gif[/img]

I am curious to see what the real answer is......

Ron

 

once again...Your wrong!!!!!! lol,nah im just joking, i just wanted this thread to get bumped up so we can get the answer.

 

Big show,

LMAO![img]i/expressions/face-icon-small-happy.gif[/img] I honestly believe we have helped the ratings around here! I know some of the old timers are uncomfortable with the banter but this is how I interact with people. I've been this way all my life.

That being said......... Ah, nevermind. I am tired. I'll get ya next time![img]i/expressions/face-icon-small-wink.gif[/img][img]i/expressions/face-icon-small-happy.gif[/img]

Ron

 

The Bigshow, I dont think we will get many answers. The builders I have talked to dont want no screaming matches, and dont want to give out there opinions or ideas.

But I see you have the HPR head, hows it run?

 

I think Big show is running Gary's head.

 

dsnut, had to fight the earge didnt ya...lol...

650viper, right now im running TVI's Race head, it has all the same componants as a HPR'S with acception of the port job..i really cant complain, it puts up great numbers on the dyno and with the help of my lectron 48" it hasnt lost any bottem end, actually i think i picked up some bottem to mid, not much, but it is noticeable......i would really like to see a TVI/HRP shootout with the port job, just change the heads out and re-dyno, i think it would be interesting....but somehow i dont think that will be happening any time soon..[img]i/expressions/face-icon-small-wink.gif[/img]