Porting heads for more power

[JBrady]

you'll get more gain working on the "short turn" shape on the inlet than anywhere when it comes to porting. make it as straight as possible and watch the power and torque figures climb.

Actually, there is MUCH more to it than that. You do not want to "shear" the flow if at all possible. Shortening and straightening the short turn radius will likely increase shear and change the approach angle to the valve. The port must be engineered as a whole. Most should NOT alter the basic shape. It takes a great deal of experience, know-how time and testing to develop a better than stock shape. I am not saying that stock cannot be improved apon but rather most can actually end up worse off after a lot of hard work.

 

[rarson]

Another thread resurrection.

As many have said before, I agree that mirror-finish polishing is detrimental for fuel/air mixing. The better the mixing, the better the burn, so I think we are taking a step backward with just a mirror polish.

In analyzing the effects of the polish, we must consider the length of travel. The fuel injector is fairly close to the valve, so will such a short distance matter in the long run?

But do we want to take that chance of degrading mixing? The mixing is already less than adequate, based on the proximity of the injectors. The farther away from the port they are, the better the fuel and air can mix. So I don't think we want to sacrifice any mixing.

What we need to do is combine the polish with a turbulence-creating modification, how about the golf ball? Larry at ENDYN does this on his high-performance Honda heads (though he only uses about 9 dimples, which I don't think is enough), and while his reputation is shakey at best, I believe some of his ideas are relatively good, this one being a fine example. The benefit of using dimples is that the design is very easy to replicate. It would be much easier for the backyard porter to add dimples than to add a spiral cut.

With regards to the longer polished surfaces creating more friction, I can understand how that would be, but it seems pretty typical for people to extrude hone intake manifolds and such, I would think it wouldn't be so popular because of this. However, this is still usually a pretty short length, so perhaps it's not much of an effect at that length.

At any rate, I'm interested in experimenting with the golf ball dimples on a naturally-aspirated engine. I'll be using ITB's so the intake path will be very short. I don't plan on increasing port size much, if at all. I think most amatuer port jobs take too much out, when the focus should be on the bowl area. I will likely just port-match everything, polish, and dimple, with extensive work around the valves. I am concerned mostly about velocity since it's N/A, but at the same time, it need to rev to 9k, so I also need a lot of flow area. Obviously these two must be a compromise.

Check out www.theoldone.com to look at Larry's dimples. I haven't been to the site in a while, but I specifically remember seeing pictures of his ported heads with the dimples.

Thanks for letting me ramble on guys, that's why I like this forum so much. Everyone is so respectful of each other. Keep it up!

 

[rarson]

Ah, I found a picture. I didn't quite remember it correctly, but this is it:

http://www.theoldone.com/articles/badtothebone/clicking_clearance.jpg

I really think that more dimples over the whole surface area would promote better mixing without impacting flow much at all. It seems like we would almost get the best of both worlds.

 

[SCV8]

I have some pictures of a Porsche GT3 head/ports, but I'm afraid they wouldn't scan well.
I got them from a co-worker.
The pictures show the machine tool marks and are very revealing as to the shapes, appears the improvements were subtle, just opening things up a bit, and blending it all down to the seat areas. The divider-vanes are quite thin, 3mm and less towards the port opening versus the usual 6mm. This would indicate that around 1-2mm had been removed from around the openings. These dividers also extend out towards the opening about 13mm more than on our engines, this was likely done to help with draw with the cams that offer less vacuum at lower revs.
When I measured around on our castings, they would only allow around 1-1.5mm to be removed, as the castings were only 3mm thick in certain spots.
The ITBs will be more tolerant of larger ports/cams than the plenum-type intake manifolds the rest of us have.

 

[rarson]

I think that having a longer divider wall might help direct the flow into the combustion chamber, based on the fact that it has more time to stabilize before reaching the valve. That's purely a guess.

I wish you could scan those pictures because I'd LOVE to see them. I agree that the best porting method involves minimizing material removal while maximizing the flow. Take too much out of the ports, and you'll lose velocity. Though as I plan to increase displacement on the engine I use, I think I will be opening the ports up a bit. Well, maybe, maybe not. I'll cross that bridge when I come to it.

I know I'm always talking about DSMs, but that's because that's what I know the best. Anyway, the 90-94 4g63 head has big ports, a third bigger than the 95-99 ports (or rather, the later ports were about 2/3 the size of the older ones). Keep in mind these are turbocharged engines. When cams were swapped into 4g63's, owners of the later engine were noticing a lot more gains from them than those with the older engine. Also, after quite a while, the consensus was that the bowl area was the weakest point of the head design, which required the most attention when porting. It was agreed between many people that the most effective porting, even on the smaller ports, was just cleaning up the bowl area and removing casting flash. That, along with cams, almost entirely made up for the difference in port size.

I will also say on my own car, with a '97 engine, I still have a lot of nice low-end after installing big cams. I believe this is due to the higher velocity of the smaller ports.

 

[vvega]

its called creating a boundry layer effect (google it if you want more info
the dimples create a layer of air that effective supports the fuel suspention
this layer effectively creates a swirling effect much like standing on ball bearingss this prevents the fast moving flow from touching or been affected by the surface of the port
smaller ports make this effect more out pronounced as higher velocity makes the effect stronger

what i was taught
i come from a motrocycle backround and lernt my porting from 2 strokes while most will think this is erelevan some will understand the 2 strokes are more relyant or port effects that a 4 stroke ever will be

now from my experiance you want a 180 finish on any intake surfaces past the point of fuel suspention and a polished exhaust surface
why you ask

the exhaust is of a hot high pressure nature thus eliminating the effect know as laminar flow"plasma flow dynamics"
also the mirroe finish helps stop carbon forimg somthing that absorbs that presous exhaust energy that you then want to use to create a tuning effect
i.e headers or pluse tuning

now for intrest
someone here said that dividers are better not sharp
sory mate untrue
plane wings ane seup the way they are to creat lift i process of useing forward movement and energy to lift the aircraft
this uses resistace to creat a vacum above the wing thus creating lift
in laymans turms

a port divider on the other hand is a atempt to split the air without creating resistance(energy loss or heat or a reduction of velocity)
a plane wing uses resistance to create a effect with this energy

so tell me
why would you want to make any of that stored energy(portflow) into lift(resistance) ??

sorry i have not read the entire threed im sure some of you are on the right track but

all in all the only thing he has done wrong is polish the intake ports at the injection point the rest of his wok is quite spectacular and something to behold in both effort and patiance

so kudos to you now get out ya flapper whell and die grinder and roughen up those head inlet ports

v

crednials
motorcyle mechanic and race engine builder
fitter tuner welder /hydrolics
aircraft manufacture and part development (PAC NZ)

sorry for the shocking spelling its just my crappy typing and to be honest free advice is very rare nowdays !!!

v

 

[vvega]

I have some pictures of a Porsche GT3 head/ports, but I'm afraid they wouldn't scan well.
I got them from a co-worker.
The pictures show the machine tool marks and are very revealing as to the shapes, appears the improvements were subtle, just opening things up a bit, and blending it all down to the seat areas. The divider-vanes are quite thin, 3mm and less towards the port opening versus the usual 6mm. This would indicate that around 1-2mm had been removed from around the openings. These dividers also extend out towards the opening about 13mm more than on our engines, this was likely done to help with draw with the cams that offer less vacuum at lower revs.
When I measured around on our castings, they would only allow around 1-1.5mm to be removed, as the castings were only 3mm thick in certain spots.
The ITBs will be more tolerant of larger ports/cams than the plenum-type intake manifolds the rest of us have.

some great thoughts there
you got the reson why the ports dividers are longer
he best porting you will ever see normally look quite subtle
its called maximizing effect with minimal labour
basically useing your experance to get the most effect with as little labour as you can
just for refeance sometimes making ports smaller increases power

porting is not just making ports larger its restructuring them to inprove h/p or to gain midrange or basically do what is a advantage to your style of use on the racetrack
if making them smaller to because velosity is low then thats what needs to be done
if you hve massive cams to use hemmoltz to to most effect you muct have at least one reversion pulse to be isolated to create a stronger effect
the stronger the effect the more it will do

kk thats me
bf2 time

v

 

[Toysrme]

I like a 100% mirror polish
1) Netiher way is going to make a big difference. I know... I've done both.
2) It's a lot neater if contaiminates are introduced (Carbon / Oil)
3) Velocity is power

If you've got an FI'ed engine, polish, polish, polish, polish until you're sick of it. Too bad people rarely polish anything.:shrug:
I nothing else, polish until the fuel injector. Even better... Polish until the fuel injector, smoothe after & introduce a fine crosspattern if you are the type to believe in the texture.

The "fuel will stick" which is why it won't make power is a lame explaination. If fuel hits a port wall, guess what... It's going to miss the intake event one way or another. Polished, it will slow down, textured will stay in a pit.

The real deal is Velocity VS Turbulence & Cost. I take Velocity. You can't add it to an engine, while adding inconcequenctial amounts of fuel is easy.


When paying for your porting, it takes a hell of a lot longer to polish than it does run a sandingwheel through a port.






My favorite pics (from this board no less!)

 

[rarson]

Wow, that is quite a polish.

 

[vvega]

The "fuel will stick" which is why it won't make power is a lame explaination. If fuel hits a port wall, guess what... It's going to miss the intake event one way or another. Polished, it will slow down, textured will stay in a pit.

as i said read up on boundry layers they will explain to you why the fuel will not stay or even hit the wall in a properly textured finish
where as on a polished finish it can have a tendance to pool creating a uncontrolled fueling situation and all the velocity in the world wont help if you cannot control the fueling properly........and when your dealing with decent hp i.e 700+ it dont take much of a misfueling to eathier make ya engine go pop or bog and borewash
bear in mind im only taking the area from the atomisation stage and lower
also look up tumble and swirl you definatly have the right idea and the comitment to do a good job just sounds like you need a little more guidence as to why people have done all this before and moved on and found inprovements on this these small steps have been proven on both on the dyno and the racetrack worldwide and are not things often shared


k out again
please dont take wht im saying as a insult
your workmanship is above question if that finish is anything to go by
i waz lucky enough to be taught buy a man who had a lot of cutting edge experiance
thanks for your time and consideration

v

 

[SCV8]

That's the first time I've received a positive response from my divider sharpening, seems most would rather do nothing, yet still wonder how power is produced.
My personal thoughts on the boundary layer manipulation would be to get the swirls as close to the port walls as possible such as to preserve the dimension of the port.
I'm pretty happy with the ports, they match the valves, and without much testing, may not function any better with the stock cams and would now like to try some runner volume mods, just to see what would come of it.

 

[rarson]

I'm not sure the port finish would affect turbulence. Let me explain before I draw fire from a few people. This is based off my limited understanding of fluid dynamics.

Obviously, a smooth port wall will create more of a "laminar" flow versus a rough wall. The rough wall will be more turbulent. However, say we take a rough-wall turbulent flow at x velocity and smooth the port out. Obviously we've lost turbulence. But, if we increase velocity, turbulence will also be increased. So therefore, we can make up for the lost turbulence with increased velocity.

Now, the thing is, if polishing the port walls in itself results in higher velocity, then it well may be that the problem is self-solving. Or, maybe it's possible that the velocity is already high enough that the reduction in turbulence will be negligible.

I can definitely see the benefit of a rough surface in something such as a cooling system. Not only will the lower flow be more turbulent, but should also absorb more heat from the walls of the coolant channels, due to more surface area. But intake ports are an area where we don't want the fluid (air) absorbing the heat, so this could possibly be another benefit of polished port walls.

What do you guys think? Like I said, this is based off my limited understanding of fluid dynamics. However, it does seem to me that, considering the mass of air a turbocharged engine would be consuming, polished ports shouldn't be a problem with regards to turbulence period (on a turbocharged engine), especially if the port size is kept close to stock.

 

[Toysrme]

It's cool, I'm not taking it the wrong way.
I'm saying off both first hand experience & testing The texture put in a head doesn't do anything for it. It's not just that you can't really tell a measurable difference, it's easily demonstrated.
Take an intake manifold, or a head. Leave one runner with stock casting marks, smooth one, polish another.
Take a vacuum cleaner, or leaf blower & attach it to the runners one at a time with as good a seal as you can.
Shoot a very small amount of fluid through an injector / small cold-start injector / spray bottle with a good atomizer on it.
Guess what? There is the same fuel hitting the wall on everything. If it's just smoothed, polished, or textured. Any fuel that hits the wall is going to either glance back into the air stream, or roll along the wall until it get's back into the air stream.
Some people try to make the case that "well the particle that hits the texture will be thrown back into the air stream". That's not how it works overall - when you look, the textures simply start to fill up with fuel.
When you stop the test & look at the ports, they all will all have the same wet spots. The difference is a smoothed/polished port will "eventually" move the fluid down the head faster.
It's really that simple.
Even better. Carbon loves to build up in the texture, along with any oil. A polished surface will be much less prone to carbon buildup. The only places where it can build up is a place where oil has baked on the wall where it can stick instead of the entire port.









Anyone can easily try this buy taking a dremel & buying two of the flap wheel sanding parts. Run it through the engine & it will smooth the texture out quickly.
Vacuum the small shavings & crap out with a shop vac. Try to get most of it out, but don't worry about any tiny bits that you can't vacuum. Just let it warm up & cruise around before you jump on the throttle. The tiny bits of Aluminum dust will burn up pretty quickly.

#502 = 80 grit

#503 = 120 grit

FYI the flow is laminar for the 98% of the mixture that doesn't hit a port wall.

 

[Toysrme]

If you don't want to test it, shove a cold start injector into the rubber air hose going to the TB. Run the engine at WOT for a few seconds so it sucks some down & take the intke manifold<s> off.


They're wet with fuel on them.

 

[JBrady]

Whoa there Toys.

Everyone please note: DO NOT run your engine with leftover sanding debri in the ports. Sandpaper is ABRASIVE. This abrasive makes up some of the remaining debri. You do not want this sort of thing stuck to piston rings or aluminum "dust" burnt on to valve seats. If engines easily tolerated this sort of abuse we would not need air filters.

I stand by my earlier statements on port polishing. Waste of time. Loss of performance. Looks pretty. Nobody will see them except in pictures.

 

[vvega]

the point of the ruffing is to create a boudry layer
this keeps the fuel from atually touching the walls and increases atamisation

........edited from a half asleep dribble

sorry there brady

 

[JBrady]

please qualify this with other than a opinion
there are pleanty or resorces and race teams that completely opose your point of view
personally i cant see why anyone would blatently deny millions of dollars of race development and procedure
maybe you sould call a top race engine builder and get a job there because you must know something none else does

secondly the point of the ruffing is to create a boudry layer
this keeps the fuel from atually touching the walls and increases atamisation

Excuse me but what are you talking about? :wtf:
From your ealier posts you would appear to support my position that being that a rough surface is superior to a polished surface for intake port wall finishing. You either have not read my ealier posts or have me confused with someone else.

 

[vvega]

i concure :S
sorry nout that

v

 

[rarson]

the point of the ruffing is to create a boudry layer
this keeps the fuel from atually touching the walls and increases atamisation

........edited from a half asleep dribble

sorry there brady

Roughing the walls will increase turbulence. By design, this means the fuel will have a greater chance of touching the port walls. There is much more mixing of a fluid against the wall when the wall's surface is not smooth.

But personally I think the fuel is going to hit the wall anyway, and I don't see a reason why we should be concerned about that.

 

[Trvln Nalzmn]

It increases turbulence at the SMALL layer of air close to the wall. This wall actually lubricates the laminar air above it and puts up resistance to fuel hitting the wall. That would be my guess anyway.