Sorry to say this but actually the dimples on a golf ball provide LIFT not reduced drag.

Edit to add: here is a little reading for you to learn from like I do.

http://www.leaderboard.com/WHYDIMPS.htm

Not trying to be a jerk, but the assumption are wrong. yes atomization is somewhat still important in a FI vehicle but since the fuel is injected directly at the intake valve (or pretty close) and on SEFI setups injected while the intake valve is open the intake plays ZERO part in that (no part of a modern multi port injection intake runner actually has fuel mixture in it, the fuel is injected into the airstream as it levels the runner)

OH and any turbulance reduces airflow as it causes a physical restriction in airflow. The reason slightly rough intakes make more power on a dyno is because in a CARBERATED engine the fuel is better atomized and thus burns more efficiently. If your assumptions were correct then all the race teams in the world would be using rough paint jobs on their race cars. Sorry but a rough surface does NOT flow better then a smooth surface.

 

Rob,

Good recall! I remember another college buddy who had the 4.3L with a 4 bbl. Still, I think the bore was the same but the stroke was different. It's been 25 years, so the memory aint what it used to be.

Kevin

 

I'm not being a jerk either. I know what I'm talking about. And you are not reading this article accurately. It is the spin that produces the lift, not the dimples. A ball with less pronounced or no dimples will produce a lot of lift, but will also produce a lot of drag, and its spin will slow down quickly. So the ***** total resistance is reduced. A ball with a better dimple design will go farther because its drag is reduced, decreasing both the drag that slows the ***** flight down, and the drag that slows the spin down. So the ball spins long and travels farther.

Mythbusters tested this proof of concept, that the dimples reduce drag by dimpling a car, and proving its wind resistance was greatly reduced (far more than they expected). So what does this prove? It proves that smoother objects are not necessarily more aerodynamic than rough objects, and that friction between a gas or liquid against a solid object is different than friction between two solid objects. The dimples break up the boundary layer and create little mini vortexes that allows the other air to flow around the object more efficiently.

The article you selected misrepresents the dimples. If they wanted to grab the air, they would have used grooves instead of dimples or would have inverted the dimples into bumps. The object of the dimples is strictly to reduce friction. The article you presented was not written by a scientist or a physicist, or and expert on aerodynamics. It was in all likelihood written by a golfer, a golfer with no background in the physics of moving air. If he were to compare his findings with reality, he would find that they might clash.

So where does this stack with a slightly rough finish in the intake versus a mirror finish? Well, why would the physics behave any differently? It is a false conclusion that air flows better over a smooth surface than a slightly rough one. You need those mini vortexes to make the air flow more efficiently, versus a smooth surface that will simply slow the air down.

The whole idea behind porting is to remove the rough castings and sharp edges that create turbulence in the airstream. Air doesn't like flowing over a sharp edge, it makes it swirl and tumble in proportion to the size of the offending surface. When you port an intake, you remove all those sharp edges, and leave a sanded surface. This surface under magnification would have some pits and tiny ridges, that allow the boundary layer to tumble and swirl in a way that allows the rest of the air to flow over the boundary layer with greater ease, much the same way a golf ***** dimples allow it soar through the air with ease.

 

The mythbusters episode like most of them isn't exactly scientific, the took a car and proved that keeping it clean and polished actually increased the fuel economy. (first off this test is not repeatable like most times they do this. a minute change in temp, wind, barometric pressure etc doing it in an uncontrolled situation means it's um uncontrolled) Then they put clay on the car CHANGING ITS SHAPE. The went back and put dimples in it to "prove" it helped. You physically change the shape of the vehicle you change the affects something like dirt and dimples would make on it. ti's a cute show but rarely proves much.

You just can't make blanket statments like polishing is evil.

 

Gents,

Great input!! This is what makes me appreciate forums like this. The discussion around whether or not to polish is important in that if it's decided that polishing is not optimal, then the home mechanic saves time and money. If it is decided that polishing is important, the investment of time and effort has a positive return. Also not to be lost, is the level of improvement: is the investment of time and effort that result in improvement warranted.

A discussion lke this invites the reader to dig deeper to make a more informed decision. Chanticlear thought the sun came up every day because he would crow to the sky, but then one day, woke up late to find the sun had rose anyway. Theory can be disproved by a single event contrary to the hypothesis. Bottomline is this: I appreciate the exchange on theory. It drives us all to a better solution.

Regards,

Kevin

 

Ok I am not explaining this very well but let me try this again.

first off I shouldn't have let you drag me down the rabbit hole with the golf ball but I did. These are NOT the same thing. Your discussing External aerodynamics to prove internal aerodynamics and they are not the same thing. We shall get back to this in a bit tho.

Ok back to the mythbusters even though it doesn't relate to this discussion at all, but since I let you drag me down this road I now have to show why. Ok first off lets for the sake of argument say that their findings are honest on the MPG. Your contention that a rough surface flows better is disproved by their little test. Had that concept held true then the dirty car should have gotten better fuel economy then the clean car but alas it didn't. So now you use the contention that the dimples drastically increased the aerodynamics of the vehicle, assuming that there isn't OTHER factors like the fact the air was getting much cooler by the time they did the final test in the episode and cooler air is denser making the engine have better power etc. Then yes they increased the aerodynamics of the car. Does this prove that the rough surface decreased the drag of the air across the surface of the car? No it proves that the airflow changed allowing the car to produce less drag. Without a wind tunnel you don't know why. Little fact, the car has a dead air spot behind it, this is the phenomena that allows for drafting. it also creates a huge amount of the drag on a vehicle. by changing the way the air flows over the car, it changed the way the air exits past the vehicle so even though it may increase drag on the actual surface it can and will REDUCE the drag at the rear of the vehicle where it doesn't touch anything. Doesn't prove that the dimples make the air flow over the vehicle better.

Another example of this is the front air dam on aero packages of many vehicles including the COT cars used by nascar. This is a vertical surface, that cuts air out from under the vehicle where it would react with the rough surfaces of the suspension and cause drag. The actual shape is very in-aerodynamic yet the end result is increased aerodynamics overall.
So using that analogy, lets show why you can't take external aerodynamics and apply it to internal. Take that same shape of the airdam on the front of a vehicle and make a small version of it and put into a port. Whats going to happen? it's the same thing as saying the dimples helped the car, yet you know already that putting an air dam in a port will reduce the flow.

Ok now that we have that little part out of the way lets get into internal. if you create a rough surface to cause a boundary so the air flows over the part better then you claim it would increase flow. Correct? (and in some situation this can be true such as a pickup bed, the tailgate up creates a bubble in the bed causing it to theoretically be more aerodynamic but once again external vs internal) But what you forget in internal situation is you don't have unrestricted area to work with like you do with external. If you create a 1/16" boundary on the walls of the port you effectively reduce the size of the port by 1/8". to keep it simple lets do a simple round port of say 1.5" physical size. now the port is actually 1.375 size as far as the air is concerned. Or 8% smaller. Even if the layer is only 1/64th or .0156 of an inch thick it still reduces the actual port size by 2%.

Now there is a LOT more to what shows up on the dyno then pure flow. and in a carb vehicle it shows up way more due to the velocity of the mixture determining if the fuel stays atomized (it's why putting a restriction or filling a port on a 351c 4v head and intake can increase power on the dyno) But in pure airflow situations like a FI vehicles using the 1.5" port at a velocity of 200ft/sec (arbitrary but constant numbers to show the reduction in amount of flow) you end up with a flow rate of 147.26cfm. same velocity put in the 1.4844 port using the 1/64th in boundary you end up with 144.22. over 3cfm drop in flow. now do it with the bigger layer and see where you end up.

The problem is in external aerodynamics you only have to worry about how the air gets out of the way and goes around the object. In internal aerodynamics or fluid dynamics you have to concern yourself with the dead air spots that reduce the area the air can flow thru. Dead air spots are bad, it's why short turns on intakes are bad, they create a dead air spot similar to the dead air spot right directly behind a car. BUT that dead air spot on a car pushes the air away, in a port it can only push it so far until it hits the other wall.

hope that's a little clearer.

 

Kevin, irregardless of the discussion of whether polished vs unpolished matters as I said earlier in a ranger it's probably irrelevant and a waste of time for a home mechanic to do it. The amount of flow differential we are talking about would only make a difference on top end and max flow rates. This is theoretical in nature and really rarely if ever would make a difference on a street driven vehicle.

So basically I am saying on a typical street vehicle it's not worth the effort. But it won't hurt anything either.

 

Thanks Rob. I imagine that over the past couple of decades, automakers have made improvements to optimize engine outputs. Yet, having worked in manufacturing for my entire career, I can attest that leadership sometimes opts out of making the finest refinements in products that would further optimize the user/owner experience because the product margins would be negatively impacted. Understandable on the business level, but on the grander scale of social responsibility, lacking in many, many ways. Simply, things by manufacturers can be further optimized. The question is to what degree given the availble resources, skills and technology.

What I've been tracking here and elsewhere is where or how a Ranger can be optimized. Lots of theory out there (as we see here) and tons of experiences. For me, it's a bit of a hobby or current interest, but it drives towards a higher benefit if broadly shared. I realize that the Ruggles experience was 25 years ago when rougher castings were more likely the rule than the exception and a real possibility that performance gains of a greater magnitude as a result. It's good to get your input that on more modern vehicles, the gains would probably be far less. So I'll give up the thread to the group with this question - What is possible (without the obvious turbo charging option)?

Kevin

 

That would depend on how far you want to get into it. combustion chambers can be made more efficient then as cast for example. Cam profiles could be optimized for performance rather then all around and to meet stringent EPA modes. Fuel maps in the programing can be optimized for either more power or better economy or in some instances both.

I know for instance the fuel rails on my 99 4.0 are dead head, changing over to a regulated return system would net cooler fuel in the rails and thus might improve efficiency (gained my some on my 7.3 when I switched from dead head to regulated return for example)

revamping an intake system so it pulls nothing but cool air helps, insulating it so it stays cool also helps.

 

Yeah i agree, the gold ball is something that being thrown through the air vs internal air being sucked in. and i finished my intake i made it into a cold air intake. But whats this i hear about switching fuel rails for colder fuel

 

lol lot more to it then just switching rails.

on the 7.3 I had to revamp the entire system from my filter on. At least on the psd it was returned at the filter to the tanks and dead headed in the heads. I took the plugs out of the heads and bulit return lines to a regulater then bypassed and plugged the factory regulator and used that return line back to the tank.

Not saying you couldn't do it but would take some fabrication on both the engine AND the fuel tank.

 

ooh alright,, yeah thats why i thought id ask . And yeah with CAs smog **** id really have to do it right for it to pass

 

Using Mythbusters and science in the same sentence is an insult to the educated world.

Just wanted to throw that out there.

Continue

 

haha yeah,, Ok i gota through this out there. Theres this guy that seriously will to pay 6000 for my truck... haha he asked me how much i wanted for my truck and i said it wasnt for sale, and i just said jokingly 6k and he said ok. And now hes wondering if i still want to sell it for 6k .. and like i loooovveeee my truck and workd so ****n hard for it but hey 6 grand man is alot. My truck is worth 3500 in a good econ.

 

6k can get you a truck with the stuff you want on it so you don't have to do any major work...

If it were me, I'd jump on it - that is, if the buyer is truly serious...

Your mileage may vary...