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I must admit that I too did not really "buy" what it suggests on the thread from the PCA website. I had seen that before, and it does not make sense how the snorkle would actually cool air as it flows inward. Why would the restriction cool airflow?
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As someone who did their thesis on NACA duct research, I can tell you that you are somewhat correct so far as Ram Effect is concerned. In fact, a Ram Effect is not achieved within a NACA Duct until transonic speeds are reached (about 0.8 mach, or approx. 609 MPH). But, this isn't why NACA ducts came into widspread use in motorsports. It was because of a reduction in drag over previously used protruding intakes. This reduction in drag, not achieving a Ram effect, is what made them desireable... Happy Motoring!... Jim'99 |
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Feel free to call my facility, and we can set up a good time to baseline your powerplant. I love the porsche 6-cyl, and look forward to applying some concepts to extract power. I may even take you up on the exhaust testing. I also appreciate your kind words. Jim, I fail to understand why you feel this test is not factual. I duplicated both results, twice, as stated on page 1. As an engineer, who takes pride in being meticulous, I understand the value of repeating experiments to ensure validity. Such attention to detail has allowed me success in my present field of racing. In addition, I even invested in the most accurate and repeatable chassis dynamometer...no skimping there either. I am here to share my experience, not to blow hot smoke. Feel free to perform the same tests...I am confident that you will perceive similar results. In regard to the NACA ducts..at least we agree on that: http://i4.photobucket.com/albums/y14...tchCloseSm.jpg I use it to supply cool air to my induction throats! |
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Sorry, but we do not share the same confidence. In my years at the Naval Flight Test Center at Pax River MD, we spent about 5 times the effort on defining the methodology than we did in actual testing, to insure the results we got were valid, and even then, with virtually unlimited time and expenditures, we sometimes got it wrong. I was trained at MIT and Pax River to distrust all testing results until no other plausible explanation could be found to invalidate them. Your results, IMHO, lie within the degree of error of the testing methodology as you describe it (or even within the HP variation between individual cars and engines), which automatically makes them suspect, if not altogether invalid. You insinuate that this is the definitive test, but I remain skeptical for the reasons already stated. Did you even monitor Alternator Output? This variable alone could make your runs Doo-Doo. I'm glad you shared your experience, but I'm concerned that many less-knowledgeable people will take it as Gospel, which I don't believe is the case. Judging from some of the Pied Piper responses already, of people believing what they want to hear without question, this seems to be the case. A $61k Chassis Dyno, isn't any better than a $25k Inertial Dyno if the methodology is flawed. I'm not impressed by the cost of the gauges. An inertial Dyno can be just as good a tool, if used properly. I spoke personally with a Porsche Engineer (an invited Guest Speaker at a Tech Session) in 2005 and asked him specifically about the Snorkel. His response was that it was solely a Noise Abatement device, aimed specifically at the Swiss Market (but with an eye toward increasing Noise Abatement regulations in other countries as well). He said that several prototypes were rejected for various reasons, including a power reduction, and Porsche, rather than mute the exhaust note - a Marketing Decision, chose to meet the overall madated Noise Levels, by reducing the Intake noise instead, so long as it didn't interfere with creating power. He said that this gen of Snorkel showed no change to the power/torque curves at all, which is why it was approved for production. While I'm inclined to support his arguments, I am nonetheless prepared to change my mind in the face of definitive testing. I just don't think you have done any. You may in fact be on to something, but I don't believe you've proved it - yet. Improve your methodology, and you may just win me over. It isn't a matter of Snorkel vs De-snorkel to me, I removed my snorkel well over a year ago - but for the sound enhancement, not to try and eek another 1-2% from the motor. Good Luck... Happy Motoring!... Jim'99 |
Greetings Jim,
I do not want to turn this into a debate, but honestly, feel free to perform the results yourself. Voltage will not skew results even within 8to 14.4volts since modern day EMS/ECU units have compensation values integrated into their programs. The $25K, or more, intertia dynos CANNOT replicate the sensitivity or repeatability of the hub chassis dyno simply because of the varibles introduced by the tyre, and the tyre interface...both of these in addition to how those dynos measure power. Even very slight changes in room temperation can affect the tyre growth and skew results. Straps introduce even more questionable readings the aformentioned units. Bottom line, everyone is entitled to their opinion, but opinions can further become validated with data. Have a pleasant balance of the week. |
Hi,
As you say, "everyone is entitled to their opinion, but opinions can further become validated with data". But, I think you're not fully understanding why I think your results are in jeopardy due to the Alternator Output. I'm not referring to the Voltage variation and it's possible effect on the DME. I realize that it (DME) has compensatory circuitry designed to make it perform through the range of possible voltages it can see. I am referring to the mechanical power draw of the Alternator itself to produce that voltage. An Alternator's parasitic draw from the crankshaft is variable. It can range to almost nothing (maybe as low as 0.05HP) to as high as 30HP depending upon how much electrical demand it's being asked to supply. Alternator's are not very efficient so far as power generation in a car is concerned. First, they produce Alternating Current (AC) for a machine designed to use only Direct Current (DC). In order to convert this AC to DC, the current is passed through a series of Diodes and Rectifiers which results in tremendous losses (mainly as Heat) due to inefficiencies. So much so, that Modern High-Amperage Alternators are now starting to become water-cooled, transferring their Heat to the Car's Cooling system to be carried away. GM has several of these in use today, and they will become standard in just a few years. But, it's advantage (aside from the fact that it can produce larger amounts of current in roughly the same size pkg. than a Generator can) lay in the fact that, unlike a Generator, which has a constant parasitic loss of CHP (Crank Horse Power) regardless of the amount of demand placed upon it, the Alternator is variable - almost Freewheeling when not in demand, but can consume pretty high amounts of CHP when demand is high. Similar to the power consumption of the AC Compressor - Low when AC is OFF, but rather high when the AC is ON. This is where it can skew the results of your testing. If the Alternator is really pulling on one run, but not the next, this will have a definite effect on the amount of WHP (Wheel Horse Power) you see on the graph, and well within the gains shown in your results. Unless you're monitoring the Alternator Output (and extrapolating it's CHP draw from that data), you simply cannot be sure you've duplicated the Test Conditions from one run to the next. This is what I mean when I refer to your methodology, you simply haven't accounted for everything. If the reported gains were in the 50HP range, then the Alternator draw would have no bearing on whether or not there was a definite increase (only the value of that increase). But, when you report gains of only 5.78 (CHP) and 5(WHP), you are smack in the range where the Alternator draw can mask your results leading one to draw a possible incorrect conclusion. You could in fact actually have a decrease in WHP and not know it. The graph would lead you to assume otherwise, though incorrectly so. This is why I say that your results are within the degree of possible error which is at least the 0.05-30 CHP the Alternator can draw off before the Chassis Dyno can extract it's data. Put simply, you're reporting a positive variation of 5 WHP within a test which has a ± variance (or degree of error) of at least 0.041 - 24.6 WHP (accounting for drivetrain losses of the Alternator draw). I say at least, because I believe there are other variables which could affect this as well, such as the fact the Sanden AC Compressor used in the Boxster is also variable, and never OFF (according to Porsche). It too draws a varying amount of CHP. Also, while I agree with you that an Inertial Dyno introduces the variables of the Tire dynamics into the results. Except for finding absolute values easily, it too can be sufficient to determine whether or not a change in output is observed... Happy Motoring!... Jim'99 |
MN Boxster, give it up already. :ah: Don't beat this poor dead horse already. We here what your saying. :dance:
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Z. |
I gotta go with Jim on this one. We have a verified increase in intake noise and a possible measurable increase in horsepower. Four dyno runs don't make it gospel. Too many variables and margin for error to give us a confirmed scientific study. It does look promising though. I will be interested in how all this pans out.
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Alright, professional statistician with a degree in engineering weighing in here...
As an engineer, I agree completely w/ Jim's points regarding the factors that could influence these results, and that when you're talking about a 1-2% gain on 4 runs, anything--even the temperature of the room from previous runs, time since you opened the garage door, or wind could come into play here! However, as a statistician, I'd say that just because you can't model these other factors into your test doesn't mean you can't get reliable and significant results. In all probability, there is SOME correlation between output and presence of the snorkel. It's silly to say that a thousand other factors to which output is sensitive could be screwing with your test, but that the snorkel has no impact. Which is it? Is HP so sensitive that any chance can result in a different reading (in which case the snorkel qualifies as a change!), or do items like the snorkel have no impact, in which case we can discount the snorkel AND a thousand other variables. I think it's the former. But back to my point -- the fact that you can't account for all the external variables is fine, as long as you can randomize them across your trials. If you want a decent but simple test, run this 10 times (in my line of work we'd have a couple million data points, but obviously we have to comprimise here). Each time, flip a coin, heads=snorkel; tails=no snorkel. Then model your runs using a regression w/ 2 independent variables predicting HP -- iteration # (1-10), and an indicator for the snorkel being present. Try to minimize changes, but if you think of something halfway through that you have to change (your wife calls you in for dinner and you take a 1 hour break between iterations 3 and 4), just add indicators for these events in your model. Assume everything else is random -- alternator draw, etc., because once you account for time, you've accounted for most of your unknowns implicitly. Jim -- would the results of something like this satisfy you? Not that the increase is exactly 5.xxxx HP, but that there is an increase in the order of magnitude of 2%? |
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I beleive you're overplaying the role the alternator would have on the test performed. The car's battery has one primary function... to start the car. Once started, the alternator has two jobs... to top off the battery's charge, and to power the car's electrical system. Topping the battery back up after starting would be a small load, and is essentially repeatable. The large HP drains you're quoting would only be present if you were running many peripherals such as headlights, brake lights, ventilation fans, rear window defogger, etc. As long as the test were done with the same loads on the alternator each time, the difference should be insignificant. In fact, as the car is shut down and restarted for subsequent pulls, the battery would lose some of it's charge each time, and the load on the alternator would be larger on each pull. If that's the case, he should have seen the HP go down on the later pulls as the alternator works harder to charge the battery back up. Since the HP went UP, that seems to bolster the case for the snorkle slightly restricting the airflow, and its removal making a small, but measurable difference. The fact that diodes (which are the same things as rectifiers) generate heat as they pass current has absolutely nothing to do with whether or not snorkle removal makes more power. Non sequitur. |
alternator load
I think the alternator theory may be somewhat suspect; a typical alternator is rated for 70amps. This would equate to (70amps)(12volts)=840wats/746wats/HP=1.13 HP, a typical alternator is between 50% & 62% efficient, this means the mechanical HP required would be between 1.13HP/.5% = 2.26HP and 1.13HP/.62% = 1.8HP. If the car has a good battery and the lights are off the draw is most likely 50% output or less. Remember this 70amp alternator is sized to charge the battery and run with all electrical equipment on. Add the loss due to the drive belt and it normally would draw 2HP. Under the test conditions as described I don’t see how the alternator could cause more than a tenth of a HP change in load.
The test should be performed in the reverse order; snorkel off then on, to verify the results are the same. |
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In theory, you, Maxter, and YellowJacket have some excellent points. But, perhaps less so in practice. First @ Jack - Your theory about Alternator draw increasing as subesequent testing continues is fine, but only if you assume one thing, well several actually, but one in particular, and that is the state of the Battery prior to the initial run. An assumption, about an inknown. The tester mentions that he just acquired the car. He does not mention replacing the Battery, so we can reasonably assume it is a used battery, to whatever degree. Such degrees can range from a relatively new Battery (which may or may not have sat on a Dealer lot for some time - and we know how Boxster Batteries respond to non-use) to a very old battery which may have broken or shorted internal plates and be incapable of holding a full charge, or if so, not for very long. So, it is quite feasible that the Alternator draw was maximized on the 1st run. But, as I keep saying repeatedly, the issue here is the unknowns. I never said the Lister's findings actually were faulty, only that there is a good possibility they may be. BTW, I know that Diodes and Rectifiers are the same thing, or rather that Diodes are Rectifiers. But, in Automotive Speak, I have always heard the Output Diodes referred to as Rectifiers and the Field Diodes referred to as simply Diodes, so I use this terminology (although technically, perhaps incorrectly). I also realize the non-sequitur of bringing up the heat produced by the Alternator as affecting the snorkel vs non-snorkel debate. I brought it up to point out the inefficiencies of the Alternator and why it requires so much CHP to produce power. @ Maxster, I realize what you are saying, but I don't believe you've allowed sufficiently for the mechanical inefficiencies involved. All the data I have read indicates that Alternators do draw the amounts of crank horsepower I've stated (though these amounts are not for the Bosch Alternator specifically, but accepted norms). Additionally, the Boxster uses a 120Amp alternator, not the 70Amp one described in your example, so any effect is nearly doubled (at least assuming linearity). @YellowJacket, I appreciate your input, you make several good points. But, we're not modeling here and while statistics do accurately support trends, they may not always apply to a specific example, especially when the gains reported are so small. I honestly believe that without further data points (such as those already described), with so small a % reported gain, we're operating within a degree of error which makes any results inconclusive. I'm not saying the Lister is wrong, not at all, he may very well be right. But, I cannot unconditionally support this view when so many variables which could swing the resultant conclusion remain unanswered. The convincing factor to me would be to show that alternator output (and consequently it's mechanical draw) was the same for each of these runs. I'm not merely being stubborn, I doubt that Industry or the Military would support such conclusions given the methodology used. They would require that all possible variables which could be controlled, are controlled, before comitting to the result. Peace!... Happy Motoring!... Jim'99 |
Newton's theory of gravitation was soon accepted without question, and it remained unquestioned until the beginning of this century. Then Albert Einstein shook the foundations of physics with the introduction of his Special Theory of Relativity in 1905, and his General Theory of Relativity in 1915 (Here is an example of a thought experiment in special relativity). The first showed that Newton's Three Laws of Motion were only approximately correct, breaking down when velocities approached that of light. The second showed that Newton's Law of Gravitation was also only approximately correct, breaking down in the presence of very strong gravitational fields.
Newton vs. Einstein: Albert's Turn to Kick Butt We shall consider Relativity in more detail later. Here, we only summarize the differences between Newton's theory of gravitation and the theory of gravitation implied by the General Theory of Relativity. They make essentially identical predictions as long as the strength of the gravitational field is weak, which is our usual experience. However, there are three crucial predictions where the two theories diverge, and thus can be tested with careful experiments. 1. The orientation of Mercury's orbit is found to precess in space over time, as indicated in the adjacent figure (the magnitude of the effect is greatly exaggerated in this figure). This is commonly called the "precession of the perihelion", because it causes the position of the perihelion to move. Only part of this can be accounted for by perturbations in Newton's theory. There is an extra 43 seconds of arc per century in this precession that is predicted by the Theory of General Relativity and observed to occur (a second of arc is 1/3600 of an angular degree). This effect is extremely small, but the measurements are very precise and can detect such small effects very well. 2. Einstein's theory predicts that the direction of light propagation should be changed in a gravitational field, contrary to the Newtonian predictions. Precise observations indicate that Einstein is right, both about the effect and its magnitude. A striking consequence is gravitational lensing. 3. The General Theory of Relativity predicts that light coming from a strong gravitational field should have its wavelength shifted to larger values (what astronomers call a "red shift"), again contary to Newton's theory. Once again, detailed observations indicate such a red shift, and that its magnitude is correctly given by Einstein's theory. 4. The electromagnetic field can have waves in it that carry energy and that we call light. Likewise, the gravitational field can have waves that carry energy and are called gravitational waves. These may be thought of as ripples in the curvature of spacetime that travel at the speed of light. Just as accelerating charges can emit electromagnetic waves, accelerating masses can emit gravitational waves. However gravitational waves are difficult to detect because they are very weak and no conclusive evidence has yet been reported for their direct observation. They have been observed indirectly in the binary pulsar. Because the arrival time of pulses from the pulsar can be measured very precisely, it can be determined that the period of the binary system is gradually decreasing. It is found that the rate of period change (about 75 millionths of a second each year) is what would be expected for energy being lost to gravitational radiation, as predicted by the Theory of General Relativity. In closing I feel desnorked car will preform better. |
To Ohioboxster - couldn't have said it better myself! To steal from another thread...Huh?
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I'm having trouble understanding how anyone who proclaims to be knowledgable in fluid dynamics can look at the snorkel and look at the intake without the shorkel and decide there isn't a flow benefit to removing it.
The intake is just as smooth and radiused into the intake without the snorkle as it is with so the vena contracta won't be an issue without the snorkel. The inlet area of the snorkel is smaller than that of the outlet, causing a pressure loss and the cup at the end of the snorkel will further restrict inlet flow. I wouldn't guess what power difference removing the snorkel would make, but I can look at it from an engineer's perspective and know it's a restriction without a doubt. |
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It's only a restriction if the engine can gulp more CFM than the Snorkel can provide. If the Snorkel meets this demand (which I suspect is the case), then it's merely a smaller hole, but with no consequence. You'd need a Flow Bench to say for certain. Excellent observation though... Happy Motoring!... Jim'99 |
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@ Everyone-- Lets just all de-snorkel and be happy for the great sounds we have just unleashed and the possibility of 1-2% more HP ±2% of that HP. ;)
@ All the engineers-- These debates make the common man (myself) just smile. I have no idea what is being debated, yet love the fact that it is! Keep it up everyone! :cheers: |
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Of course you are correct. I just meant to express that I just think this differential in pressure has little to no effect on overall Volumetric Efficiency which of course is a major determinant in how much power the engine can produce. I'm not convinced that the Snorkel makes a significant difference, but that aside, I don't think the lister has proven otherwise. Mrs. MNBoxster is away doing the Accenture Match Play Tourney in Tucson, and I'm having some guys over tonight for a little Boozer. But, I have a neat little engine where I can model AVF, TAF rates and VE, for given engine volumes and parameters. I'll plug in the Boxster data to see what we're looking at. With that, and some measurements of the Snorkel (which I have on a shelf in my garage), we should be able to have something more concrete. But, It will be a day or two. I'll come back to this in a separate thread. Hope to have your input there... Happy Motoring!... Jim'99 |
self-levelling annoyance
Jim, while we're on the topic of factoring in variables, do remember to take into account the "self-levelling annoyance" caused by the vodka you mentioned in a previous thread. :cheers:
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Wow..this is so sad...so much happened on the board while I spent more time beating my poor S on the dyno today. I have repeated the results on 17...yes 17 passes with and without the "snork". The data remains the same. For what it is worth, this mod produces 4.6~5.5whp at high rpms. Whew!
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What's that all about? You're just being NASTY! No call for that - shame, shame... That's very Clintonesque - attack the detractors - congratulations! Anyway you cut it, thats a cheap shot - Thanks for your valuable contribution to this thread. Feel Good now?... |
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Well you're certainly getting consistent results. I may be starting to come around. This is for the 3.2L, I doubt the 2.5L w/o egas, Motronic ME 7.2 and variable intake will achieve anywhere near the same result. I called a friend who owns a shop w/ 2 inertial dynos, and just for ********************s and giggles, I'm gonna run over there this spring and see what it tells me, even with the tire dynamisicm, I should also get consistent positive results based on your findings. A good engineer is also intuitive and still I have this nagging sense that something's amiss. But, at least for now - You Da Man! Congrats! Happy Motoring!... Jim'99 |
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Jim, I may be wrong, but judging by the "tone" and context of his post, I am sure he was only joking. :) |
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I think Jim knows I'm joking :confused: |
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Could've fooled me :p But maybe that was the point :eek: |
good reading on this post. The "snorkle" is from what I can feel and hear on my 2000 S is definitely a mod one needs to do for what ever reason. Now some data on added hp. There seem to be the question on how to do this. well here's the link.
http://www.ppbb.com/boards/ppbbphp/showthreaded.php?Cat=&Board=ARCHIVES&Number=820409 &page=&view=&sb=&o= One might have a calibrated body to feel the gain but you sure can hear the change from doing the mod. Ben |
Is there really that much of a difference in sound? I've driven a few of my friends' Boxsters with the snork removed, and didn't really notice much difference from mine, hence never removing my snork.
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Cool
Thanks for the great info. For most of us, it's not worth the cost of the dyno run. But it's good to know.
Did you alternate snork, no snork, snork, no snork, etc.? The reason I ask is that the DME does some weird ignition advancement/retardation compensation when it senses a change in air flow. I know that if I unplug my MAF, I get a noticeable increase in power. Would you be willing to try the same thing with the stock air filter versus K&N? |
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That's interesting. I was wondering about that. Will remove mine tomorrow, btw :D |
Congratultions on your new Boxster project car!
Thank you for posting your dyno info. I will look forward to your continued HARD work on your Boxster.
I have put up a suggestion that Deluboz send you a set of headers to dyno. We all have been searching for reliable test data on ALL matter of engine modifications --- as you can see by the reponses to your post :cheers: You have sparked great interest with your Dyno results -- I will continue to watch for all your future hard work results and appreciate your efforts to document the work (especially the photos). Take care, Ed |
When you unplug the MAF you will get a CEL. You can easily reset it by disconnecting the battery for a short time (first make sure you have your radio code if your car is pre-2003) or by using a OBD-II reader.
When you unplug the MAF the car freaks out briefly. Then it uses an approximation (based on throttle body temperature readings, I believe) to decide how much air is coming in. The car has a tendency to stall when warmed up and idling. But in my base 1999 Boxster, I could keep up with 2000-2002 BoxsterS cars in flat out acceleration up to very high speeds. |
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Ed, I am willing and able to test the exhaust systems. I have also ordered a Porsche System Tester 2 to assist with my diagnosis during testing. Thanks for the kind words, and I will keep all informed of my data aquisition. |
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Forgive me for not being clear: I ordered a PST from Durametric for $630. I wish I had DEEP pockets..lol.
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For what it is worth, here is info on the 987/Cayman.
http://www.pca.org/tech/tech_qa_question.asp?id={24041683-6376-4DD9-80EC-3A5F748391BF} If the link does not work I think you have to copy and paste. |
OK, now I am REALLY doing this today!
If my friend ever stops sleeping, damn it :\ |
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