Porting pi heads

[Wichers123]

Lol in all honesty though the roughness you get from porting and even cnc porting is even better is enough texture to allow the fuel from sticking. After a port job you can always take them to have them bead blasted to roug up the surface in the port. I was always told never polish the intake only the exhaust. The more mirror finish helps keep the heat in the flow and out of the head material. The same goes for the Pistons and combustion chamber.

 

[Wichers123]

Here is a cnc job and look at the texture. And then every cylinder is 100% matched too.

 

[96blak54]

Rottlers programing is top dog!

Not real sure $1000 port job is worth it to pi heads....at least not to me. Maybe the heaviest pi hitters! This touches TFS territory.

 

[Wichers123]

I would buy tf heads first before I spent big money on porting.

 

[96blak54]

Exactly! So help me here and keep this focused more geared on the cheap.

 

[chris91]

Wish I had pics of the port work on my Fox Lake Stage 2 PI Heads. I will say the car is a completely different animal with the addition of them and the Hitech Stage 2 Cams though for sure. I'm sure there's more untapped potential in the setup though.

 

[OLD H2S]

This is the reason I like to port cast iron heads, the random dimpled surface is easy to produce from the cutter chattering, but the iron is so hard that each port takes along time to cut. And as a teaser I figured out a way to match port volume form hole to hole, cheap. That will be a new thread later. Carry on.

 

[96blak54]

Fox lake is the only company ive seen that gets what a cylinder head is designed for. Them other companies fall victim to the CFM race.

 

[96blak54]

If anyone has the opportunity to stick their finger down into a pi port valve seat side and give it some lovin...hehe....youll notice the valve seat has an overhang. The over hang may seem like core shift, but I assure you its not. A stream of air passing through an orfice creats a phenomenon called vena contracta. As the air is drawn through the port, vertices are created directly behind the sharp edged back of the seat, much like a rear wing on a car. This vertice is unbelievably fast and benifits the vena contracta to arch around the seat in the direction of swirl and to the exhaust valve.(like a rear wing on the car back creating vertice to bend the air down behind the car. Using air flow properties to bend the air). Smoothing the the back edge out will actually help max lift flow, but offers the fuel to tract on the valve seat by eliminating the proper vertice needed and low lift gets comprised. Think of the vertice there as a roller for the incoming air,...to help roll the air in the direction needed.

 

[Ineedav8]

Very interesting read ! Love to read anymore tech you post up !!

 

[96blak54]

Ive got more, just been watching the count. I figured more comments would popup....

 

[Wichers123]

If anyone has the opportunity to stick their finger down into a pi port valve seat side and give it some lovin...hehe....youll notice the valve seat has an overhang. The over hang may seem like core shift, but I assure you its not. A stream of air passing through an orfice creats a phenomenon called vena contracta. As the air is drawn through the port, vertices are created directly behind the sharp edged back of the seat, much like a rear wing on a car. This vertice is unbelievably fast and benifits the vena contracta to arch around the seat in the direction of swirl and to the exhaust valve.(like a rear wing on the car back creating vertice to bend the air down behind the car. Using air flow properties to bend the air). Smoothing the the back edge out will actually help max lift flow, but offers the fuel to tract on the valve seat by eliminating the proper vertice needed and low lift gets comprised. Think of the vertice there as a roller for the incoming air,...to help roll the air in the direction needed.

there is only one problem. You need to promote swirl if not it's just gonna stall at the seat. So the question is does the port flow like a drain?

 

[OLD H2S]

What about cutting sharp vertical notches into the back edge of the seat, it would help the CFM and induce more turbulence and shear, could even cut them at an angle to increase swirling. One of the key points is why do we need tumble port and swirl port design in the first place? Poor design. The manufacturers designs have to try to get a homogenous mix for best combustion= power=MPG= cleanest emissions, for cheap.The pretty pictures of fuel injectors spraying a fine pattern do not translate when shooting down an intake port and it does not matter how big the port is it is still too small and causes the fuel to condense on the wall falling out of suspension as seen as by the "clean" spots where the fuel is hitting the port wall. Velocity is the helper to keep the suspended gas in the best mix for all of the above, and the sharp edge of the back of the seat is an easy way to help poor head designs which are caused by trying to make the part cost low. One of my old bosses was a retired VP at Ford and we would talk about best theory VS cost, I was young and dumb and not even into Fords at the time but the business truths are the same for all big car makers he would show me. Back when I was building big block Mopars the ports and head flow was huge, air speed was not with big carbs, big cams and a great way to reatomize the mix was to use intake gaskets that had fine mesh screens molded into them, cut down the CFM alittle but the liquid gas went back into suspension and lit off better=more power, which is counter intuitive. Which brings me back to building a high compression, close clearance set up for a NPI?

 

[96blak54]

there is only one problem. You need to promote swirl if not it's just gonna stall at the seat. So the question is does the port flow like a drain?

I like your question, but I gotta narrow down what youre thinking. You state swirl and stall at the seat....are you referring to swirl happening within the port just before the valve seat? Does the port flow like a drain....this question leads me in that direction.

The pi port is a straight shot port. However their are a few raised sections creating coanda to get the rush moving into the direction needed.

Does the incoming rush move in the port before the seat like water gravity draining in a sink? No. Imagine a solid steel bar shoved into the port(bar representing the air rush) and the end towards the valve gets fanned out because the valve changes the shape as the rush enters the chamber.(even though the valve back is equally angled to the port angle) Now the cylinder wall shrouding will create the turn needed for the infamous 2v swirl. As this turn takes place, the piston is pulling this turning rush down the cylinder(the piston moves so fast, the incoming air could be veiwed as a steel bar and doesnt want to change shape easily) That swirl dam thingy....well it keeps the rush from re-entering itself while the valve is open and aiding in the "tornado" vortex towards the piston crown. All happening in the cylinder as the piston keeps pulling it down. If the rush reunites itself, the mixing stops becoming uniform, causing liquid to develop,....hello advanced timing. Now this explained, the pi head starves the cylinder with a uniform speed mixture. When the piston slows and reaches the bottom, the begining point of that rush isnt moving like it was when entering at the top. The swirl slows at the bottom while the top is still fast. Not a bad thing because 2v heads will always swirl axial to the bore and be far more vicious than it needs. 4v heads kinda goes against the grain so to speak and is much much worse when piston reaches the bottom. The 4v tumble axials perpendicular to the bore axis. Then we can go into why the 03/04 cobra heads are so awesome over say the navigators....but this is about pi heads. Although alot of this info carries over to C-heads......

2v heads will alway out do port injected 4v heads with in cylinder motion, hence the need for direct injection.

 

[96blak54]

The pi heads design is beautiful in terms of technology. Its a straight shot port with proper corners, bumps, and edges to promote mixture. I got a few more pictures to post that make you say hhmmm.

 

[OLD H2S]

The Bosch web site has Good design information on GDI. Gasoline Direct Injection is pretty simple, just need a donor car car for the salvage parts and some machine work. I can see the hard part being the computer interface but "necessity" will win out and GDI will be the hotrodding wave of the future. A Lot of headaches and standard information will become moot. Damn kids got it easy.

 

[Wichers123]

Direct injection comes with new problems and faults. Injectors and pump work 10x harder. Valves collect more carbon because there is no fuel to wash valve. Then on top of all that its expensive.

 

[evilcw311]

I have a love/hate relationship wth my direct injected Genesis. As it is with all direct injected cars when your sitting close to aw wall at the bank or drive thru you always think your valvetrain is ticking cause of the injector pump.

They need to be serviced for carbon build up every 15-20k.

Cold start up is more noticeable


This message courtesy of crapatalk!

 

[96blak54]

The performance aspect of GDI out weigh the negatives. If gaining a solid 50rwhp just because of GDI, your not going to mind flogging the intake maintenance at certain intervals. These coyote guys are eating it up! I know one personally thats pulling off 10.3sec quarters in the coyote class. He loves it! ....im jealous!