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

[pecivil]

Bisimoto!!

Welcome to the board! You are definitely the kind of Boxster guy we need on here.

I would love to drop by your place and test my engine. There are some great roads through the hills in Hacienda hts. I have transplanted a 3.4l 996 carrera engine in my car. I have revo software, the K&N intake and a somewhat screwed up set of headers, 200 cell cats and muffler from a shop in Maryland that was supposed to be designed for the swap. Alas, the exhaust system sounds really great, but there are fitment issues with suspension. I would love to see what you come up with for the 3.2 engine exhaust wise. The 3.4 and 3.2 are (almost) the same engine.

If you need/want a guinea pig for exhaust system work, I would be happy to volunteer!!

BTW nice work on the desnorkleing. I did this a long time ago, and decided it was worth it just for the sound. Glad to see it does add a bit of torque.

Monte

[Bisimoto]

Originally Posted by pecivil

Bisimoto!!

Welcome to the board! You are definitely the kind of Boxster guy we need on here.

I would love to drop by your place and test my engine. There are some great roads through the hills in Hacienda hts. I have transplanted a 3.4l 996 carrera engine in my car. I have revo software, the K&N intake and a somewhat screwed up set of headers, 200 cell cats and muffler from a shop in Maryland that was supposed to be designed for the swap. Alas, the exhaust system sounds really great, but there are fitment issues with suspension. I would love to see what you come up with for the 3.2 engine exhaust wise. The 3.4 and 3.2 are (almost) the same engine.

If you need/want a guinea pig for exhaust system work, I would be happy to volunteer!!

BTW nice work on the desnorkleing. I did this a long time ago, and decided it was worth it just for the sound. Glad to see it does add a bit of torque.

Monte

Greetings Monte,
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:



I use it to supply cool air to my induction throats!

[MNBoxster]

Originally Posted by Bisimoto

...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...

Hi,

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

[Bisimoto]

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.

[MNBoxster]

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

[porsche986spyder]

MN Boxster, give it up already. :ah: Don't beat this poor dead horse already. We here what your saying. :dance:

[z12358]

Originally Posted by porsche986spyder

MN Boxster, give it up already. :ah: Don't beat this poor dead horse already. We here what your saying. :dance:

IMO, nothing wrong with a good debate, and this one's especially educational.

Z.

[JackG]

Originally Posted by MNBoxster

Hi,

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.

Happy Motoring!... Jim'99

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.

[maxster]

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.

[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