Tony D Posted March 7, 2011 Share Posted March 7, 2011 (edited) Yep. My standard answer is that vacuum is the absence of pressure---not the relative dearth of it. How do you make an absence of pressure? Where does the pressure go, how does the piston 'consume' the pressure? Proponents of the 'vacuum' theory have never answered that one for me yet. The only 'vacuum' that exists in reality is in space. Here on the earth, pressure is produced by virtue of the weight of air to the atmosphere's limit, pressing down. The ONLY thing you can do with that is control where that pressure goes. In space there is a vacuum not for 'making' of it, but by anything lacking a frame of reference to produce pressure. Dealing on earth, we have pressure from the atmosphere, and that is the source of all filling. An ICE doesn't work in space because if the piston created vacuum, it could 'draw in' something out of the vacuum of space. But the closer you get to space, the worse an N/A engine works. Why? Less atmospheric pressure----the motive force that makes the engine breathing apparatus go! We all look for things that make us go! As for the EFI/Carb difference, it's having to do with the way the flow ratings are derived. You don't need differential for atmoization of the fuel in an EFI T/B, you will always need some in a Carb, and therein lies pumping loss. Generally the tests done for HP are limited to the same RPM from what I've seen. And again, from what I've seen EFI runs the exact same engine to a higher peak rpm to make the power. A carb makes 217HP at 7500, the exact same engine with comparable EFI (45TWM ITB's on a Cannon Manifold -vs- 45DCOE Webers with 36mm Venturis) makes 257 at 8250. The Weber engine ran to 8250, but it's power was WAAAAY down compared to the EFI. I think the limiting factor may be something mechanical in the engine which is limiting terminal flow in and out, which is aside from the induction system. Just my thought on it. It's a 'they say' kind of thing that I've not replicated in my testing and it confounds me. Lord knows I would have loved to stick with carbs! But when you look at 55 Webers in comparison to 45ITB's the pricing is attractive, and you can then use your ITB's on your 2 Liter, whereas having 55 Webers kinda sticks you in a pidgeon-hole! (And there is another hint00the 55 Webers have venturis near the size of the TWM ITB's, 45 to 48MM---flow dominated by pressure drop across an orifice!) Edited March 8, 2011 by Tony D Quote Link to comment Share on other sites More sharing options...
zredbaron Posted March 8, 2011 Share Posted March 8, 2011 (edited) HAHA! Love the pic of the star trek idiots! (What was that race again?) How do you make an absence of pressure? Where does the pressure go, how does the piston 'consume' the pressure? Proponents of the 'vacuum' theory have never answered that one for me yet. Where does love go? A soul? Can I touch them or put them in a bottle? HAHA. Pressure is the combined forces of all the particles slamming into the surface that is resisting it (ie the air is "pressing" on the surface, a balloon presses outward on the rubber barrier as you blow air into it). This is true of fluids and gases. In air, this includes water vapor and inert gases other than Oxygen. Psi is of course lbs per square inch (pounds are actually a force, not a mass -- grams are mass -- lbs assume we're on earth with a G-force of 1 [gravity]). Metric is better! As temperature of the air goes up, kinetic energy (a relationship of mass and velocity) of the air particles goes up, and pressure goes up. (tempurature is defined as the average random kinetic energy of a system) So, the faster particles move (tempurature), the more pressure. Also, the more air particles there are (either in a container, or in a column of air) the more pressure. In a pure vacuum, there are zero air particles, and it only exists in theory. Space is very close, but there are still gases present, just not enough to be anything more than negligible, trace amounts. In a relative vacuum, the pressure doesn't go anywhere, it's still there. Take a piston in a cylinder, since this is what we're really talking about. Let's "pause" time / flow and make it a closed system so it's easier to explain/visualize, ie, seal off the intake and NOT let air come in. "Vacuum theorists" claim as the piston moves down, a relative vacuum is the result, right? Obviously there was *some* amount of air in the combustion chamber before the piston draws down, right? Let's just say there are 1000 air particles in this tiny space, let's call it 10ccs, are at some pressure, let's call it 1 atmosphere and assume there was no compression and the valves just closed, too. Nevermind the actual volumetric expansion math. As the piston draws down, let's say the 10ccs became 1000ccs by the time it reached bottom dead center. This larger area still contains the same number of air particles, but now instead of 1000 air particles occupying 10ccs, 1000 air particles are occupying 1000ccs, which is 100x the volume. There's more to it than this mathematically, but the relationships are the same: as volume goes up, pressure goes down. The 1000 air particles, instead of bouncing off the *surface area* of the 10cc container, 1000 air particles are now bouncing off the *surface area* of the 1000cc container. So, *per square inch* (for the psi pressure unit), there are very few air particles bouncing off the container *relative* to the 10cc container. The pressure is still there, it's just been spread thin to the point of being somewhat negligible compared to when it occupied the tiny container. This relative vacuum is very trying on the container, so much so, that outside air will try very hard to force it's way in (just like water tries to force it's way into a boat's hull -- exact same principle, only with water the density is for all intents and purposes constant). Open the valve, and air rushes in from outside the head, just like opening some fresh-sealed foods hiss and let IN, also similarly, opening a can of beer let's air OUT. Ambient (outside air) pressure is again the result of the cumulative weight of a column of air from the surface up to infinity. At 4000', you have 4000' less in this column AND the bottom parts of the column are also the most DENSE due to the weight of the column above it quite literally compressing it closer to the earth's surface (due to gravity). We didn't even talk about density of the outside fluid (air), composition of the air (inert gases, humidity, dust / pollutants), all of which significantly affect flow performance. You can't ever stop going deeper in the weeds, really. An NA internal combustion engine (ICE) in space doesn't fail because of a vacuum... it fails because there is no oxygen for combustion. Yes, we're both saying the same thing, but well, if an NA motor were at altitude (4000' lets say) but in *pure oxygen* instead of "air," it would significantly outperform an NA engine at sea level running on "air" (assuming the engine were tuned for the change). It would be more along the lines of running on pure nitrous full-time. Also a totally different ball of wax, but the performance comparison is similar. As for the ITB/venturi discussion, 36mm venturis aren't remotely comparable to 45mm ITBs in my opinion. Nevermind the jets and venturis vs. injectors, air being shoved through a 36mm orifice can't possibly be compared to air being shoved through a 45mm orifice. Not a fair comparison; one is moving very fast and one is not. We agree carbs need a venturi, so we would literally have to flow test whatever venturi could keep up with a 45mm ITB. This would have to be flow-tested, because as already pointed out, the venturi incurs significant head loss and the ITB just doesn't restrict the flow as much. Sure, it tapers, but tapering is NOT a venturi. A venturi narrows and expands again by definition. Literally, a flow restrictor in and of itself. It's for this reason that I glossed over intake for JDM vs domestic L6s. If you *properly* supply the head with the airflow it is capable of (by proper ITB / venturi size), it then is simply a matter of achieving an optimal AFR for every throttle position / load / RPM combination. If you accomplish this, well, you're intake is no longer restrictive. The only way to accomplish this as far as I know is through experimentation on a dyno. You can get "close enough" if you are a carb guru, but with modern engine control (ie the computer for injector and ignition control) you can literally map out data points (for AFR and spark advance) for every permutation of throttle position / load (vacuum) / RPM (and even MPH in the case of Electromotive, and this matters because with cold air intake a measurable ram effect is experienced), and even further refine your starting points based on a temperature sensor in the [cold] air intake plenum and utilize the required feedback of an O2 sensor in the exhaust. There's just no way a mechanical device can compete with that, which is what makes a well-tuned motor powered by carbs so appealing. It's just that much more elite. There are of course intake design factors like how much to taper (ie 50mm air horn down to 45mm throttle body tapered down to your intake port diameter) across whatever distance (how steep is the taper angle?), how far the injector is from the port, injector size, etc. and well, I know of these concepts but I have no *practical* knowledge and have not studied how one affects driveability (torque) vs. hp or WOT flow, all with respect to RPMs. I might be able to talk to it based on what "makes sense to me," but it would be theoretical ONLY, not checked by any personal experience in the industry. We totally jacked this thread btw. I'll admit it. Sorry guys! Edited March 8, 2011 by zredbaron Quote Link to comment Share on other sites More sharing options...
260DET Posted March 9, 2011 Share Posted March 9, 2011 (edited) Looking at that Sunbelt head that was shown about a million words back and noting the differences between plug in and plug out flow raises a relevant question I'm thinking. Which is, why such a big flow difference? If the air is moving out from under the valve radially and fairly evenly then its difficult to understand how something small like plug electrodes could cause such flow obstruction. But if the air was rotating then such items could cause considerable disruption, acting like say a post in the middle of a water stream as shown by the wake. This is just my theory as a possible explanation for the plug in plug out difference. Which leads me to thinking that an ordinary flow bench is totally inadequate for any serious port flow development process, it would be a big advantage if using a realistic setup replicating the real process flow could be observed by using smoke and other aids. Edited March 9, 2011 by 260DET Quote Link to comment Share on other sites More sharing options...
zredbaron Posted March 9, 2011 Share Posted March 9, 2011 (edited) More like 5 million words ago! Turbulence has a HUGE affect on fluid flow, more than I ever would have thought before I was taught to respect turbulence. Turbulence literally has vortices (eddies), which means some of the fluid travels in reverse before its path returns to the direction you want it to go. Laminar flow is more compact and goes one direction only for the most part, therefore you get more bang for the buck. This is why mandrel bends in intake and exhaust are so crucial. If we *really* wanted to be accurate for what's *really* going on, we would flow-test mass flow rate in addition to volumetric flow rate. What flows well with one density (proportional to pressure) will not flow well at another. Also, what flows well at one speed (venturis / tapers) will not flow well at another. Everything has a bell curve. Your idea of smoke and what not like they do in aero tunnels is a great idea, but is likely so cost-prohibitive that it's only practical for the budget of a manufacturer and used in an R&D fashion rather than tuning a personal race motor. As for the spinning fluid part, great idea to explain the disparity, and it's plausible, but what would impart the rotation to begin with? Our intakes, carbs/ITBs, and ports are not rifled in any way. I can't think of a way that it would begin spinning outside of "nature wants to spin" because of earth's rotation and reference bathtubs draining and hurricanes. That level of theory is beyond me. Additionally, throttle plates at WOT are literally a horizontal plane, which would resist any fluid rotation and attempt to straighten it back out. As for why it makes so much of a difference, I have a guess (exactly that). The only comparison to radial flow (outward from a center vice spinning) I can offer is from helicopter aerodynamics, but again, there is obviously some spinning going on with helo aerodynamics and it doesn't quite compare. Back to the flow bench, I believe it's wholly adequate for how it's used. Ok, so it doesn't perfectly simulate what's really happening (hell, pistons go up and down on a four stroke cycle, so it's pulsing like the pump it is, not a constant flow like a flow bench provides). To the point, it's a relative test. It allows you to take a baseline, port the head, and note that you made a 33% improvement or what not. If you figure out that putting a triangle in works well, or going HUGE and shiny like JDM works well, again, it's relative to what you started with. You incorporate a change, and if it was a bad one, your flow will go down or plateau, and with a good change the flow will go up. I imagine that a port job is much better on the torque band if the builder stops porting just as it plateaus. If you keep porting and don't increase flow, by removing more material, you have a larger radius, larger radius means slower speed going in. Not ideal in my understanding, but again, I'd still like an engine builder to comment on the practicality of our discussion. More flow is easily accomplished by bigger ports or valves, but even after reaching the limit of port size, they can continue to increase the flow by shaping the ports / turns more efficiently (more laminar). It's for these reasons that I stress the need for a practical perspective. The practical perspective is actually more relevant than the theoretical. There are no doubt hundreds of theoretical great ideas for F1 cars that are tossed out every year because when they took it to the dyno or the track, it didn't produce a benefit, despite the fact that all the engineers thought it would. At the end of the day, it's the lap time that matters, not theories. (In my mind I don't type to hear myself talk, but rather in response to the questions / discussion at hand. Anyone feel differently about said dissertation(s)? I'd hate to be "that guy." Hah. ) Edited March 9, 2011 by zredbaron Quote Link to comment Share on other sites More sharing options...
Leon Posted March 9, 2011 Share Posted March 9, 2011 Laminar flow has been thrown about a bit in this discussion. If you calculate out the Reynolds Number from the flow in the intake tract, I doubt you could ever get laminar flow, unless the tract is very smooth and large in diameter. Therein lies your contradiction, you want to have laminar flow yet you want velocity relatively high. These are conflicting goals. By the way, a large port is not detrimental either as long as you match the intake geometry accordingly. Turbulent flow is not necessarily bad and laminar flow is not necessarily good, at least in the case of internal combustion engines. The turbulent flow in the intake is beneficial to mixture homogeneity which is in turn important in maintaining consistent and more complete combustion. Mandrel bends in the exhaust have nothing to do with laminar flow and everything to do with minimizing pumping losses by having a bend of consistent radius and diameter. A crush bent radius will have a smaller effective diameter than the rest of the straight piping which would increase frictional losses in that bend. My 2 cents... Quote Link to comment Share on other sites More sharing options...
zredbaron Posted March 9, 2011 Share Posted March 9, 2011 (edited) Damn good two cents! I hadn't thought of laminar not doing any mixing and turbulence helping the mixing / atomization. Excellent point! Surely there is a happy medium between the two, because too much turbulence would get in the way of the fuel/air behind it in my mind. I would think deliberate turbulence would be more important for carburetors than for ITBs / EFI, since jets produce crude droplets of fuel relative to the finer spray produced by injectors (assuming the injectors aren't too big) due to the higher fuel pressures. Perhaps the expansion after the venturi is enough relative turbulence (anything flow following a restriction is "unhappy" until it steadies out again) for this mixing? What about direct injection? You mean to say that the intake manifold would be deliberately turbulent on the way in so that when the injector sprays fuel it's turbulent / primed for mixing, or are the injectors just that good? I would think that ideally you could cram more air/fuel through the port by designing an injector that sprays so finely it doesn't require the turbulence for atomization (which of course means high fuel flow for high RPM power would take the hit). I thought that with ITBs for example, the long runners with injectors not being too close to the intake ports allowed the distance the mixture has to travel do the work to atomize the fuel along the way, and in this case, heat is good to help atomize, so long as the heat is post-injector. Right? Wrong? I've seen ITB setups that have two stages of injectors for this reason -- one for the fine sprays, one for the high volume sprays. This really only makes sense to me if you want a high hp motor that's also a daily driver and fuel economy matters. Or is there a reason a race motor would want the fine spray, too? (if memory serves, I think the finer spray was the furthest from the port, which is opposite of what I would guess, but again, if memory serves) (I'd like to get a better grasp on this for when I start making design choices for my switch over to ITBs in a year or two.) With exhaust, we agree that a bad bend would incur a pumping loss (head loss) and is therefore restrictive, but I still think that turbulence in this case is always bad. Why would it have nothing to do with laminar flow? That statement seems contradictory to me, so I'm not quite sure I'm reading it right. Or are you saying that after the scavenging portion of the exhaust it simply is irrelevant whether it is laminar or turbulent so long as head loss is minimized? Edited March 9, 2011 by zredbaron Quote Link to comment Share on other sites More sharing options...
zredbaron Posted March 9, 2011 Share Posted March 9, 2011 (edited) EDIT - duplicate post - is HybridZ slow lately or is it me? Edited March 9, 2011 by zredbaron Quote Link to comment Share on other sites More sharing options...
zredbaron Posted March 9, 2011 Share Posted March 9, 2011 (edited) When in doubt, just keep clicking! FAIL. Edited March 9, 2011 by zredbaron Quote Link to comment Share on other sites More sharing options...
Leon Posted March 9, 2011 Share Posted March 9, 2011 I'll try to break this down, it's getting late. Damn good two cents! I hadn't thought of laminar not doing any mixing and turbulence helping the mixing / atomization. Excellent point! Surely there is a happy medium between the two, because too much turbulence would get in the way of the fuel/air behind it in my mind. There's always a happy medium or compromise, and in this situation it's fuel mixture homogeneity vs. pumping losses. At some point, one overwhelms the other and you get diminishing returns in mixture uniformity while further increasing head losses. I would think deliberate turbulence would be more important for carburetors than for ITBs / EFI, since jets produce crude droplets of fuel relative to the finer spray produced by injectors (assuming the injectors aren't too big) due to the higher fuel pressures. Perhaps the expansion after the venturi is enough relative turbulence (anything flow following a restriction is "unhappy" until it steadies out again) for this mixing? The injectors do atomize fuel better initially due to a much greater deltaP than carbs, but the location of the injectors matters as well. If they're far away from the valve then you still need to rely on the intake to mix the air and fuel properly. I would tend to agree that in general, carbs need more help in getting the mixture uniform when compared to EFI. What about direct injection? You mean to say that the intake manifold would be deliberately turbulent on the way in so that when the injector sprays fuel it's turbulent / primed for mixing, or are the injectors just that good? I would think that ideally you could cram more air/fuel through the port by designing an injector that sprays so finely it doesn't require the turbulence for atomization (which of course means high fuel flow for high RPM power would take the hit). Yes, take diesel engines as an example, they're all direct injection. Even though air is all that flows through the intake, it is still beneficial and actually more important to impart spinning/twisting forces pre-combustion chamber in order for the mixture in the cylinder to be better distributed. You don't want the incoming air charge to be shot straight into the cylinder with some air getting a bunch of fuel and the rest getting too little. You want it spinning and swirling turbulently as the fuel injector does its work. Port design is much more at play here, with intake design taking a back seat here. However, in order to change the angular momentum of the incoming air you do sacrifice volumetric efficiency through pumping losses. This is more evident at high rpm where higher flows mean higher head losses. Also with the air charge coming in at a higher momentum at high rpm there is less of a need for swirl and tumble to get the job done. For more info, you can look up the terms swirl and tumble as they pertain to IC engines. I thought that with ITBs for example, the long runners with injectors not being too close to the intake ports allowed the distance the mixture has to travel do the work to atomize the fuel along the way, and in this case, heat is good to help atomize, so long as the heat is post-injector. Right? Wrong? More time for the air and fuel to mix is good, but heating your intake charge is a double-edged sword; it benefits fuel atomization while being detrimental to volumetric efficiency (air temp goes up, density goes down). As rpm increases heat transfer effects decrease, so ITBs with injectors far from the valve will have better atomization and mixture distribution at high rpm with the sacrifice of low rpm efficiency. The magnitude of the sacrifice would have to be empirically quantified on a dyno, where the same engine would be tested with different injector locations. Injector placement is an oft-overlooked but important piece of the puzzle, finding the "sweet spot" takes testing. I've seen ITB setups that have two stages of injectors for this reason -- one for the fine sprays, one for the high volume sprays. This really only makes sense to me if you want a high hp motor that's also a daily driver and fuel economy matters. Or is there a reason a race motor would want the fine spray, too? (if memory serves, I think the finer spray was the furthest from the port, which is opposite of what I would guess, but again, if memory serves) (I'd like to get a better grasp on this for when I start making design choices for my switch over to ITBs in a year or two.) The main reason for having staged injectors is when using larger injectors that cannot adequately and precisely control the smaller pulse-widths required at idle. I suppose there are some secondary mixing effects from this, but I would consider it negligible for all but the most detailed builds. One injector per cylinder placed correctly should be able to deliver a good, well-distributed mixture given that the demanded pulse-width doesn't go outside the injector's realm of predictable operation throughout the engine's speed range. Hope that made some sense. With exhaust, we agree that a bad bend would incur a pumping loss (head loss) and is therefore restrictive, but I still think that turbulence in this case is always bad. Why would it have nothing to do with laminar flow? That statement seems contradictory to me, so I'm not quite sure I'm reading it right. Or are you saying that after the scavenging portion of the exhaust it simply is irrelevant whether it is laminar or turbulent so long as head loss is minimized? You're getting caught up in describing flow as laminar or turbulent when it doesn't really matter as you won't get laminar flow from an engine anyway. You get high speed pulses tossed in the exhaust which would never come close to being laminar flow. Your last sentence sums it up pretty well, but laminar or turbulent is the least of your worries even in the scavenging portion. There are greater effects to take advantage of than trying to hit an unattainable and unnecessary goal of achieving laminar flow in your exhaust, or intake for that matter. 1 Quote Link to comment Share on other sites More sharing options...
260DET Posted March 9, 2011 Share Posted March 9, 2011 To continue with my thoughts on the Sunbelt head, when you look at the inlet valve placement in relation to the combustion chamber wall the inlet charge must surely swirl in a circular motion in order to get the flow volume it does. Compare that combustion chamber with say those of the VG two and four valve heads, the inlet valves on those heads are much more openly located, no vertical chamber walls nearby. I don't have figures but I bet that the Sunbelt flow figures are not much inferior to those of the stock VG's at all. Someone has done some very tricky work with that Sunbelt head. Quote Link to comment Share on other sites More sharing options...
Tony D Posted March 9, 2011 Share Posted March 9, 2011 "As for the ITB/venturi discussion, 36mm venturis aren't remotely comparable to 45mm ITBs in my opinion. ... Not a fair comparison; one is moving very fast and one is not. We agree carbs need a venturi, so we would literally have to flow test whatever venturi could keep up with a 45mm ITB. " That's why I said 'exact same engine'---that was an example of our engine and what happened when WE went from Carbs to EFI. We needed to be able to run the engine below 6K rpms, and the way a 55MM DCOE works.... We could have gotten that HP from the 55's, but look at what size carb you have to use to get it.... is that 'fair'? And therein lies the point behind my 'they all stop at some arbitrary rpm'.... I don't see someone taking a similar sized carb and ITB... And by that I mean Physical Size. Sure carbs can make HP on my L Engine, but do I want the 55's? Do I want the custom intake manifold---that doesn't seem to be cricket to me either! What we did was pull the webers off, put the TWM's on, and then run it. The only thing changed was the metering device. We could have gotten 40mm TWM's... they still would have made more HP than the 45DCOES as they STILL had a 2mm per barrel bigger orifice. What people never clarify is '750CFM Holley -vs- 750CFM ITB' --- does anybody know where that comparison exists? While terminal HP may be similar (? May ?) the power under the curve, etc will wash out some advantage. I was just stating the for all the people who say Carbs and EFI make the same HP when in 'ultimate' application, by my experience there needs to be some serious consideration on exactly WHAT efi they were using, and what carbs. 55 DCOES and 45ITB's may be 'the same' but it's not a direct swap fitment for existing 45DCOE's! 45 ITB's are, though. Quote Link to comment Share on other sites More sharing options...
josh817 Posted March 9, 2011 Author Share Posted March 9, 2011 (edited) Not that I have much to contribute here but what Tony and Baron said is what I'm hoping for with my intake project. I can see a good mix of not too turbulent but enough to keep the fuel mixed, as far as my application goes... Only because I'm doing what Baron mentioned, staged injection.... but without the first stage... From everything that I have read elsewhere, there could be problems with fuel falling out of suspension (proper term?) at lower RPM's, depending on how much you're dumping into the runner. I could imagine that a little turbulence would help it stay mixed but once you get into the higher RPM's the intake velocity should take over unless you're REALLY saturating the charge with fuel. At my fathers shop, when he tells me to port manifolds and gasket match ports he says to not make them smooth and shiny as per Kas Kastner's performance book. I wouldn't call the finished producted rough since they're cast iron heads but it wasn't mirror finish either. I haven't read the book but I'm curious what his explaination is. I wouldn't be surprised if it was "there is no point on doing the labor to smooth the port when it's going to be gunked up anyway". British car people are a different breed, not to my liking. Edited March 9, 2011 by josh817 Quote Link to comment Share on other sites More sharing options...
zredbaron Posted March 9, 2011 Share Posted March 9, 2011 (edited) Fantastic input, Leon. Thank you for helping lift some of the fog for us as these concepts all tie together in a *practical* use with ICEs. You're getting caught up in describing flow as laminar or turbulent when it doesn't really matter as you won't get laminar flow from an engine anyway. You get high speed pulses tossed in the exhaust which would never come close to being laminar flow. Your last sentence sums it up pretty well, but laminar or turbulent is the least of your worries even in the scavenging portion. There are greater effects to take advantage of than trying to hit an unattainable and unnecessary goal of achieving laminar flow in your exhaust, or intake for that matter. When you're right, you're right. I myself even acknowledged the pulsing nature of the 4-cycle pump, but I failed to apply my own recognition to the way I was conceptualizing everything. Glad to take a step back and recalibrate my perspective. I still would argue that laminar flow does occur, just exclusively within small pulse widths, ie as the wave is passing by, there is a (very small) period of time that is laminar, which is of course preceded and followed by turbulence. Splitting hairs, I admit, but I'm stubborn and I still think designing flow paths to promote laminar flow is a relevant performance goal, despite the fact that I agree that the pulsing action generally speaking is not laminar by definition. 260DET, I just poked my flashlight around my intake ports (head is completely off at the moment) and you might be onto something with Sunbelt's triangles imparting an angular momentum. Maybe. However, looking at the head in person, I initially was going to object to your theory until I noted that every single cylinder has an *ever-so-slight* offset of the triangle to the valve guide. This curious consistency is why I think that your theory is plausible. *If* a measurable angular momentum is imparted, it is *very slight.* I will caveat all of these observations that I may simply be seeing what I went looking for, and had I not been looking for it, I may not see it this way at all (a bad scientific approach to observations). Bottom line, you're theory is not disproved in any way, and if correct, this effect is *very slight.* If this very slight angular momentum is by design as you suggest, then you're right, this is some very tricky work indeed! Regardless, it's a very interesting theory! I would suggest, however, that these triangles are nothing new in the world of race-quality port jobs. I personally don't think that by looking at pictures, or even a shop studying the head in person, would be enough info to truly understand the how and whys gained from proprietary R&D, and therefore attempting to duplicate may not work out well at all simply because it all depended on a certain detail that well, was proprietary. Just my opinion. What people never clarify is '750CFM Holley -vs- 750CFM ITB' --- does anybody know where that comparison exists? While terminal HP may be similar (? May ?) the power under the curve, etc will wash out some advantage. I totally agree, and I think ultimate HP would also go to ITBs for the aforementioned reasons (the head loss incurred by the venturi). There is zero doubt that power under the curve goes to ITBs. What I also want to know is, since my flow bench test gives cfm numbers for steady flow (not pulsing like a real engine), is the cfm rating for carbs or ITBs also rated using steady flow, or is it talking about a "for real" cfm flow of an actual four-stroke cycle's pulsing flow patterns? At my fathers shop, when he tells me to port manifolds and gasket match ports he says to not make them smooth and shiny as per Kas Kastner's performance book. I wouldn't call the finished producted rough since they're cast iron heads but it wasn't mirror finish either. I haven't read the book but I'm curious what his explaination is. I wouldn't be surprised if it was "there is no point on doing the labor to smooth the port when it's going to be gunked up anyway". British car people are a different breed, not to my liking. A good point, it will get gunked up anyway, and this gunk will no doubt have an orange peel texture at the very least. From a strictly theoretical standpoint, a rough surface will cause a boundary layer of localized turbulence across the rough surface. If laminar flow is near this turbulent boundary layer, it encounters less drag than a slick surface would (golf ball effect). Less drag (head loss), more flow, regardless of the flow being textbook laminar or the pulsing pressure waves of an ICE or what not. Less head loss is less head loss. They obviously went out of their way to polish the surface. I wonder why? Edited March 10, 2011 by zredbaron Quote Link to comment Share on other sites More sharing options...
josh817 Posted March 9, 2011 Author Share Posted March 9, 2011 (edited) Going to have to wait until tonight when I get home to see my other pictures... Everytime I stumble over a ported head I mark down its application and save the pictures. Maybe we can find a pattern. This is my head though. It did have a ridge in mine but not as prominent as yours. I always thought that ridge was there to simply direct the charge around the guide... I don't know much about this but it doesn't seem proper to impart a spin on the charge through the middle of a radius. Edited March 9, 2011 by josh817 Quote Link to comment Share on other sites More sharing options...
zredbaron Posted March 10, 2011 Share Posted March 10, 2011 (edited) I think in Josh's head the triangular shapes are also appear consistently slightly offset. Anyone else think so, or is this another case of seeing what I want to see? This is either a result of parallax error or perhaps minor inconsistencies (all are done by hand, after all, perhaps the result of a dominant hand and dominant eye combination?). I suggest this as a possibility in my own head, too; if it were a deliberate swirling, one would think it would be more pronounced. I would think, anyway... Those Watanabe heads are probably some of the finest examples of hand-made detail I've ever seen. Hard to believe anyone could be so good with a dremel, regardless of design / performance considerations. Those ports and combustion chambers are incredible! Edited March 10, 2011 by zredbaron Quote Link to comment Share on other sites More sharing options...
Tony D Posted March 10, 2011 Share Posted March 10, 2011 I totally agree, and I think ultimate HP would also go to ITBs for the aforementioned reasons (the head loss incurred by the venturi). There is zero doubt that power under the curve goes to ITBs. What I also want to know is, since my flow bench test gives cfm numbers for steady flow (not pulsing like a real engine), is the cfm rating for carbs or ITBs also rated using steady flow, or is it talking about a "for real" cfm flow of an actual four-stroke cycle's pulsing flow patterns? Yeah, that is all I was saying--the pumping losses are less, and it confounds sometimes the contentions being made when they are clearly apples and oranges. A stock 280Z T/B flows something like 500CFM... Look at that package size compared to most Carbs of the same flow. Almost all flow benches use a standard vacuum aparatus to measure flow, the dampening required for a pulsation check would add immeasurably to the cost. An inclined manometer and vacuum motor (vacuum cleaner) with a given orifice somewhere to read flow is all that is needed, and 'methodology' really isn't that critical, other than it must be repeatable and used identically head to head, port to port. Mondello is now using 'wet flow' for more precise measurements and it seems to have some merit. It's a slightly different methodology, but the same basic engine for vacuum source. Quote Link to comment Share on other sites More sharing options...
zredbaron Posted March 10, 2011 Share Posted March 10, 2011 (edited) Mondello is now using 'wet flow' for more precise measurements and it seems to have some merit. It's a slightly different methodology, but the same basic engine for vacuum source. Cool! I went to their site hoping to read more about it and found no mention of it. TERRIBLE website btw. Luckily google helps out: http://www.mondello....atalog_pg09.htm Unfortunately, the article is a sales pitch to other engine builders and doesn't really say anything particularly useful. From what I gather the idea is to see where the liquid tends to gather, and try to experiment with the port shape to maximize even dispersal...? It does throw around "turbulence" a lot, contrary to our discussion about pulsing, but as you said, Tony, it's a flow bench after all. I *assume* that by "wet" they mean mostly air with an amount of moisture added that's fairly comparable to an ICE's A/F ratio? It doesn't come out and say it directly. An interesting approach, regardless. I suppose if it's worth any salt it will catch on. Good share, Tony. Edited March 10, 2011 by zredbaron Quote Link to comment Share on other sites More sharing options...
josh817 Posted March 10, 2011 Author Share Posted March 10, 2011 (edited) I can't help but think the whole swirl thing really only aids in low-end performance. From reading some of Braaps posts and stuff, without being too general/making it sound simple, some of the finer details are only for low RPM where the velocity isn't up. First thing that comes to my head is 5 angle valve jobs, I think he said. I could be making this all up as its been a long day and my roomie decided to spew her brains out in the bathroom sink which consequently got clogged. She took a day off and instead of unclogging the sink or scooping the stagnant puke out with a bowl, or even spraying some smell good in the air, I guess she thought watching Hulu was better. Therefore, I get home and clean the **** up and speak my mind to her, and now she's pissed. So, I'm not mentally stable right now. The reason why I am getting a that hunch is because of ZBarons suggestions that the picture of heads and exhausts is to reap the benefits of WOT. When I flipped through my pictures, all the heavy duty porting I see, they totally get rid of that guide boss rather than shape it. First thought that comes to my mind is "cram as much charge through the port that will possibly fit". I have some pictures of a Don Potter "hot street" port and then another of a turbo ported head that someone was selling on here. Neither had a shaped boss. Also just a quick note. My head did have shortened guides. About the same length as the ones I posted a picture of except the exhaust didn't have a taper to them and they didn't have "hats" on them but rather the regular clip typically used. Edited March 10, 2011 by josh817 Quote Link to comment Share on other sites More sharing options...
260DET Posted March 10, 2011 Share Posted March 10, 2011 All I'm trying to do is to find a reason why L6 heads can be made to flow so well, given the shape of the combustion chamber and the proximity of the valve to the sides of the chamber for a lot of its circumference. The difference between 'plug in plug out' flows got me looking for reasons as to why that was. I don't think shaping the valve guides could do enough to significantly influence a flow pattern but I'm done guessing. We need the owner of that Sunbelt head to push some smoke though a port and report back Quote Link to comment Share on other sites More sharing options...
Tony D Posted March 10, 2011 Share Posted March 10, 2011 When you get into it, especially in EFI, you realize the fuel wets the wall. It does, period. The key to proper homogenous mixture is to keep this layer (referred to in some texts as 'the tau layer') as consistent as possible. When you snap the throttle open, this tau lessens---making the mixture rich off calibration, when you drop throttle it may get large. If it concentrates in one spot, then it can make for really big swings. On off on application of the throttle can really screw up the tau layer and make tuning the engine a beyotch royale! Minimize places where it may pool, make the air work to move the 'puddle' to a more homogenous layer over a bigger area and tuning becomes easier. This is the root of the Mondello discovery---EFI R&D people have worked to keep the effect of Tau constant because of emissions calibration during transitions. What Carbs benefit from is that (as you surmise) the whole tract is evenly coated, then you minimize the effect of the layer during transitions. The transitions are where you sue accel pump, deaccel enrichment, etc... And that can eat a LOT of fuel. Before the development people concentrated on only airflow and maybe turbulence for swirl in the chamber. Now, with the importance of Tau being recognized, you port based on making that layer equal as it makes tuning under all conditions easier. It's late, best I can do right now... Quote Link to comment Share on other sites More sharing options...
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