Finally: Dyno charts of de-snorked 986S!!!

[MNBoxster]

Originally Posted by JackG

A couple of points...

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.

Hi,

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

[ohioboxster]

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.

[rdancd816]

To Ohioboxster - couldn't have said it better myself! To steal from another thread...Huh?

[porsche986spyder]

Originally Posted by rdancd816

To Ohioboxster - couldn't have said it better myself! To steal from another thread...Huh?

Now that's funy! :dance: :ah:

[blue2000s]

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.

[MNBoxster]

Originally Posted by blue2000s

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.

Hi,

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

[blue2000s]

Originally Posted by MNBoxster

Hi,

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

That's totally incorrect. It's always a restriction and there will always be some pressure drop, no matter how much or little the engine is pulling in as long as some air is moving. A flow bench would show a pressure drop as soon as any air started flowing through the snorkel.

[xclusivecar]

@ 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!

[MNBoxster]

Originally Posted by blue2000s

That's totally incorrect. It's always a restriction and there will always be some pressure drop, no matter how much or little the engine is pulling in as long as some air is moving. A flow bench would show a pressure drop as soon as any air started flowing through the snorkel.

Hi,

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

[wanna986]

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.