[Bulti]

Not to mention you can't compress a fluid (ok -barely-: water requires a pressure of 217 atm to compress it by 1%) so air and water react very differently when being forced through or in somewhere.

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[flash]

yeah - i didn't want to get into that one.  fluid dynamics is confusing enough when talking about air.  i really didn't want to come off like a jerk.  i only put stuff up to say that the emissions would definitely change as the result of a supercharger, unless you did what i did, and added fuel and retuned everything.  living in california, i am keenly aware of the complications of such a thing, and as a result of my project, probably know more than anybody about what a supercharger does to a 968 engine.  i just didn't want anybody thinking they could just grab one bolt it on, and run with it.  it just doesn't work that way.

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[wildcat]

Hey I got it!  I'll disconnect the water lines into the throttle body and drill out the little holes to make them larger,  then I'll epoxy in some tire valve stems into the pipes where the water went, get a couple of 12v tire air compressors with 60 psi pressure put in a switch and I'm good to go.  No, I'll have to remap the computer, but the up side is no pulleys and belts to add!  (Don't mind me, just having a little fun.)  I can see Bernoulli isn't real popular around here. Here's what I'm saying.

 

You have two pipes,  both are three inches in diameter, but one has a funnel in the middle of it where the same end is connected to a two inch pipe. The funnel is the compression. Run water  through the two pipes with the same water pressure,  the velocity of the water coming out of the two inch pipe will be greater than the three inch pipe.  But the volume of water will be the same or slightly less coming out of the two inch pipe. The shape and length of the funnel having a minor impact due to resistance.

 

When the pressure of air from the compressor into the combustion chamber is greater than the pressure associated with the downward stroke of the piston drawing in air,  you'll get more air, and hence need to remap the computer, otherwise you're reducing the effort the engine is expending drawing in more air but the amount of air is the same.

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[flash]

a supercharger requires effort ALL THE TIME, just to spin it, hence the mixture is never the same as without one, at the same places on the maps.  it is also compressing the air ALL THE TIME.  how much is dependent on the resistance of the engine and the rpm of the engine.

 

there is never a situation of the maps being the same with and without the supercharger.  even the idle maps change, though obviously to a lesser degree.  the bottom line is that if you don't change the maps, the emissions readings change. period.  you will fail emissions tests if you don't add fuel to compensate for the increased air.  been there done that.

 

lol - i'd be happy to sell you a supercharger kit and let you find out for yourself.

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[wildcat]

I was a Jet Engine mechanic and the engine was a TF-30-P3 Pratt+Whitney engine for the F-111e.  A dual spool axial flow turbo-fan with 8 combustion cans and and afterburner.  Bernoullis principles apply. The pressure would decrease but you have a commensurate increase in compressor speed as a result of the increase in engine rpm which is what is driving the supercharger. But this topic is played out IMO.

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[flash]

funny - i designed some of the electronic gear for that plane.

 

again, while they both have a compressor, that is where the similarity stops.  a supercharger is NOT like a jet engine.

 

i would be happy to sell you a supercharger kit, and you can try to get it smogged without the maps and fuel changes.  you will find you fail on more than one area of the test, due entirely to the increase in air VOLUME being introduced into the engine.

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[wildcat]

I didn't want to get into the supercharger/turbocharger debate but I have a working knowledge of both.  Fluid dynamics include gas and Bernoulli pretty much wrote the book.  And while jet engines and superchargers are vastly different in complexity the principles are the same.  Know what a 968 and a turbofan jet engine have in common?  They both have long drive shafts supported by bearings.  The fan's shaft runs through the compressor's shaft,  both run through the hot section and have separate turbine rotors attached. 

 

With regard to volume, I previously implied that the fact you had to change the maps convinced me that your system was indeed increasing the air volume, maybe I was unclear on that point.

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[flash]

yeah - they taught us that stuff in college (mechanical engineering).  it seems like a lifetime ago (30 years).

 

no worries.  i don't want to get into a protracted debate either.  this stuff is pretty basic, and readily available in most text books.  we're already fairly off topic, and need to return.

 

my only point was to say that the emissions readings will definitely change the second you add the supercharger, regardless of how much boost you run, and that it is amazing at how easy it is to upset those readings.  it took me a while, but when i was done, i ended up actually running cleaner than stock.

 

the single largest factor in why our cars run so clean, is the precious metal cat.  porsche spent a ton developing that, and even used it in the advertising campaign.  it's all over the sales literature.

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[Bulti]

Just one more thing about Bernoulli (not trying to be a wiseguy here, but just to be complete):


Like Wildcat says the law involves gases too, but not if the volume and pressure change both at the same time, which is very much the case here.


Taken from Wikipedia:


"Bernoulli's equation is sometimes valid for the flow of gases: provided that there is no transfer of kinetic or potential energy from the gas flow to the compression or expansion of the gas. If both the gas pressure and volume change simultaneously, then work will be done on or by the gas. In this case, Bernoulli's equation – in its incompressible flow form – cannot be assumed to be valid."

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[wildcat]

Not to be a wise guy either, and I really intended to drop this subject but the citation you quoted really went contrary to what I'd been taught in jet engine school.  I'm not going to address that aspect as it isn't relevant, but... the Wiki citation is highly suspect because without noting or expressing the relationship between volume and density the assertion becomes meaningless. Consider the effect of barometric pressure on the density of air. I have read the classic definition of a super charger which states "a greater volume of air than is possible at ambient pressure".  Sure, but it leads to an erroneous conclusion. Compression leads to higher density, which when allowed to expand produces greater initial volume but not necessarily more air, if you get the distinction. The air expands more rapidly than it would at ambient pressure.  Some superchargers, turbos, blowers do push more air (greater density as well as volume) into the cylinder. Depends on the boost value.  In the case of the supercharger in question, I think the fuel / air ratio was too heavy with regard to fuel, and that remapping leaned it out.  Considering the ratio in that context implied that the density of air was less which is why it was failing emissions.  But this supercharger is atomizing the fuel better, due to increased velocity IMO, and as a result, combustion is better (ie. more power) and the emissions are lower with better fuel consumption because the mapping is leaning out the fuel. Got the best of both worlds and that's my perception.

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[flash]

all superchargers produce more air.  how much depends on a number of factors.  keep in mind that the cylinder is either closed or under pressure as well, so expansion is really not possible at any point of the cycle.  this can be shown with a boost gauge.  it does not go up and down at all, but rather remains constant and rock solid.

 

in the case of my kit, i had to add 30% more fuel, as a result of the additional 30% more air (5lbs boost).  it's no coincidence that the numbers matched.  had i not have done that, it would have been too lean, and the emissions readings would have been out of range, and the car would have failed the test.  too lean is just as bad as too rich.

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[Bulti]

More air molecules get trapped into the cilinder, so more gas molecules have to be added to get a stoich mixture. Correct me if I'm wrong :-)

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[flash]

that's correct.  that's why when the air volume increased 30% (5lbs of boost compared to 14.7 lbs of air naturally aspirated) i had to increase the fuel 30%

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[wildcat]

O.K.  B)

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[ds968]

Had the DD smog-tested today ( clean as a whistle, just as expected ) and while I was waiting and talking to one of the two technicians I was informed that the Sate of Ca is considering abandoning the requirement to smog-test any vehicle older than 20 years. Currently only cars older than 1975 are exempt.

Apparently there are too few cars on the road of that age for the Sate to make enough money on certificates to cover the cost of managing the system . The threshold is said to be 5% cars in use, when it drops below that the State supposedly will waive the smog requirement . Nomidea what stats one can find out there but according to the info this guy gets from the state the number of cars older than 1995 is already below that 5 % mark . That surprises me, I thought we ( as in Californians ) hang on to our old cars a lot longer ..

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[968Syncro]

If I read this report correctly, it applies to vehicles over 30 years old:

• owners must still to get a vehicle that's from 1976 or newer smog checked, and if the model fails, they must make the necessary <a class="" href="http://www.autoblog.com/auto-repair/">repairs</a>. After a second unsuccessful test,
  
• then fork over the $200 to keep the car on the road. The cash would go to the [peoples Kommarden Air Quality Improvement Fund,]
  
• Owners must conduct a biennial check if the vehicle is from 1976 or newer.
  

Just search on "AB 550", for this proposal (not passed by a long shot) for the Cali legislative agenda.  It will reveal the draft, and many car mags with analysis.  Ok, fine, what Cali legislator in his right mind would back this bill?  None, because they only want money and power, they never do the right thing.

 

WOW!  Congrats to all of our elected representatives and all government employees.  Amazing and fantastic!   Apparently it got moved up from 1974 to 1976.   Wow, this is great, thank you for your service!  

 

I am simply amazed in wonder of the decision making of our government.  They are fantastic, much better than the common man --- probably the individual would not be able to survive without the GUBMINT and therefore should be thankful and bow and pray to the GUBMINT.   And the money our government has, and the government employees, and the unions, and the buildings and the power  - and how legislators and employees and unions and contractors and politicians -- and how they represent the common people like they promised, and how they claim to be statesmen who keep their word.  They are unbelievably fantastic -- we should love and honor them all!!!     Especially the chicken-s**T bureaucrats.  And -------- who have destroyed this once wonderful country and enjoy only 2 things:  1. the power to tells us what to do, and 2. looking forward to sitting on their butts at 55.

 

If there is a lesson for the rest of us, given by our government leaders and government union employees -- we should all improve our abilities to lie, cheat, steal, and use anybody.  Guys, does anybody in this state understand that government unions can give money to candidates for election?   So sad, they get to bribe their bosses -- and then they probably blame other countries for being corrupt.

 

Whoa, gotta stop writing, so tired of the government oppression in this county, ....   not sure who is reading, but are there any other 60's guys around who didn't sell out?

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[wildcat]

Ever since over 50% of the population works for the govmint in one form or another it has taken on its preservation of self. And the elected officials are members of self and Donald thinks he's going to change self. Selling out? Hmmm its a dysfunctional co-dependent society, some realized the fact and the joined others, some continue to fight within the system which is really the only way, and others just sit on the sidelines and harken to Shakespeare... "all the worlds a stage, and we are but merely players". 

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[ds968]

https://www.yahoo.com/autos/volkswagen-a...41557.html


Wow. Brilliant on one hand, deviously audacious on the other .

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[Bulti]

Yesterday I was watching this on the news with my wife. I said to her: "want to bet that VW is definitely not the only one?". Sure enough, seconds later, other manufacturers came into the spotlight (Daimler, Opel, PSA, Renault,...). They are manipulating things over here too. The closet which is filled with skeletons is about to open...

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[williamoss]

Has anyone tried to run the car without the catalytic converter? Back in 1979 when I had a 924, a lot of owners took out the catalytic converter put a pipe in the line, increased the gas pipe restrictor to allow the larger size filler tube and we would mix both leaded and unleaded gas, to improve the octane rating. Of course now there is now sense in doing all of these modifications as leaded gas is no longer available in most markets.

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