Lotus350

[QUOTE=1999Porsche911]I would love to, except I am in CA and you are in Chicago.

Now, I don't want to start an argument OK. Keep in mind that modding a car can take form in all kinds of setup. So, we will have different ideas on how to do it "right". To me, doing it "right" will be very different when compared to what you think, or any other guys here. We have to accept what everyone may have difference ideas that we share on the board. That is why these boards are so valuable.

Well, since you aske me about the brakes again, I will share with you my thoughts...which will again be different than what you or others think. So, take it for what is worth.

The effect of a SC on brakes is that, with more HP, you get more speed (even in day to day driving). With more speed, you put more stress on the brakes to make the car stop. That is all I am trying to say. Yes, the stock brakes are capable in doing a great job even with a SC. But, your brakes are working harder from time to time to make the car stop.

If a SC car is babied..than I would agreed that there is no difference. However, if you take a SC car onto the track for example, and drive it like there is no tomorrow, those stock brakes would be stressed a lot more than a non SC car. If you keep it up long enough, I bet the stock brake pads will not last as long, or one might even experience brake fade earlier with a SC car. That is why when a car gets more HP, ususally that same car gets bigger brakes.

It's not a direct effect, but an indirect effect on the brakes.

Michael1

Can you explain to us what thermodymanic change the supercharger made to cause the supercharged engine heat rejection to be 5% less than the non-supercharged engine?

Michael

GT3BB

It car A is faster than car B, wouldn't car A need better brakes?

1999Porsche911

A supercharger does not make a car faster, but more powerfull. Stopping a car going 150 mph with a supercharger is no different than stopping one without one.

1999Porsche911

I never said that my cooler engine is a result of the supercharger.

Lotus350

Hmm...OK.

How about this logic?

If: Add SC = more powerful car.
Than: more powerful car = faster car.

Conclusion: Faster car = need better brakes.

Any thoughts?

Michael1

First we have this statement, "Stop by sometime and I'll show you that my SC'd 996 is running coolant temps that are more than 5% less than a stock 996 at all speeds and conditions."

Then we have this statement, "I never said that my cooler engine is a result of the supercharger."

The whole issue was that you need more cooling capacity for a supercharged engine. I give up.

Michael1

Why bring logic into this now?

Just read the supercharger manufacturers' marketing literature. It's obviously a bolt-on miracle device, with all upside and no downside.

Michael

1999Porsche911

Speed is limited by, amoung other things) the maximum rev limit. Therefore the car is no faster.

1999Porsche911

The whole point early on was a statement that a Supercharged engine creates more heat. I imagine if you don't know what your doing and don't install a complete system, that may be the case. However, the EVO system does not increase engine temperatures at all and further mods by me have enabled me to reduce the engine temps by another 5%.

Michael1

There is only one way that is true, and that is if the thermodynamic efficiency of the engine is improved by adding a supercharger. It isn't improved, regardless of what the EVO people have told you. In fact, thermal efficiency goes down, so an even a larger percentage of combustion energy ends up in the cooling system, and exhaust, at ALL engine speeds and loads. If you don't notice any change, it is because the operating conditions you are using are within the capabilities of the cooling system, and/or your measurement accuracy. Only a certain percentage of combustion energy goes to creating work. The rest ends up as heat in the cooling system and exhaust. Superchargers don't change the laws of thermodynamics.

Michael

1AS

If the mods included supplementation of the cooling system, then the above comment makes sense.
However, (and when I respond to this theme, there is always a however), many previous posters have noted the necessity for adding cooling capacity to the stock 996 for track use. This implies that cooling capacity is maximized for the standard engine at standard conditions.
Since the SC adds air, that allows the injection to add fuel, so there is more combustion leading to more power, which leads to more heat, which must be eliminated by the already-stressed cooling system. So the car can only run cool, as long as you don't use the capacity of the sc, which means don't keep the throttle down very long. So, if what you really want is a rarely used burst of power at the very top of the rev range, by all means install a supercharger. Your engine will run cool, as long as you aren't burning additional fuel.

99/911's comments indiacte his sc isn't doing much for power, since his engine actually runs cooler.
And since it's cooler, it's not going any faster which means it's not challenging its brakes, so they are adequate too. Becaues if it was going faster, it would be challenging the brakes. So altogether, it sounds like a great use of about $12,000.
Clearly, Porsche engineers never learned of the supercharger when they were trying to wring more power out of the 996. So they had to go to simple things like vario cam to eke out a few more horsepower. Because if the 996 block could take an sc, then imagine how much power they could wring from the tt case. But, for some odd reason, they didn't make that choice. Wonder why. AS

PTEC

The car is faster in the sense that it accelerates quicker.

If you track your car at all, you will need better brakes. Areas where you used to hit 60 you will hit 75 now with the increased hp. I would definately call that a little extra stress on the brakes.

My sentiments exactly.

Lotus350

Wow...it's very clear to me now that I don't think you really understand the dynamics of how a SC works!!

SC 101 here: Law of phsics here! When air enters the SC compressor, it is compressed and fed into the engine. By the mere fact that air is compressed (as in boost in SC or turbo cars), the byproduct is HEAT! Therefore, anytime you put a SC to an engine with boost to it, HEAT is created.

When you increase the inlet temp of the air going in, you get more air to the engine. When you get more air into the engine, you need more fuel to be dumped into the engine to maintain a proper A/F ratio. When you get more fuel, you get a BIGGER explosion inside the piston...which leads to more HEAT. So many parts of the engine gets heated up more, plus all the exhaust system now that has do deal with the hotter exhaust coming out of the engine.

So, the notion that a SC system does not increase engine temp. is a total BS!!! I don't this anyone that understand how SC works would make such a fales claim.

You also stated that "an engine cannot withstand either constant boost or redline for long."

Did you know that SC systems puts positive boost to the engine the entire time the engine is running (although amount of boost varies by the RPM)? Now...that is constant boost my friend!! That's putting stress on the engine the second you turn your key to fire her up. (Only turbo cars create boost only on demand. SC pumps compressed air into the engine ALL THE TIME.)

By the way, can you please tell us what items you installed to reduce your temp by 5%? Also, how did you measure such decrease? Since I answered your "brake" question, I hope you will answer your 5% reduction question.

1999Porsche911

Ok, now you have confirmed that I am dealing with nothing more than a moron who if only interested in an arguement rather than learning something. I will take each of you points individually and I'll type real slow so you might understand.


SC 101 here: Law of phsics here! When air enters the SC compressor, it is compressed and fed into the engine. By the mere fact that air is compressed (as in boost in SC or turbo cars), the byproduct is HEAT! Therefore, anytime you put a SC to an engine with boost to it, HEAT is created.

Ever hear of an aftercooler? Know what it does to the heated compressed air before it enters the intake?

When you increase the inlet temp of the air going in, you get more air to the engine. When you get more air into the engine, you need more fuel to be dumped into the engine to maintain a proper A/F ratio. When you get more fuel, you get a BIGGER explosion inside the piston...which leads to more HEAT. So many parts of the engine gets heated up more, plus all the exhaust system now that has do deal with the hotter exhaust coming out of the engine.

What happens to the heat created by the explosion? 1/3 goes for power, 1/3 out the exhaust and 1/3 is absorbed by the cooling system. As long as the exhaust and cooling system are the right size and design, engine temps will remain the same.

Did you know that SC systems puts positive boost to the engine the entire time the engine is running? Now...that is constant boost my friend!! (Only turbo cars create boost only on demand. SC pumps compressed air into the engine ALL THE TIME.)

Wrong! Rather than explain the details of the operation of a supercharged system, since you have already proven you have no interest in learning the facts, I'll just state that the bypass of boosted air in the car is the same as a turbo. There is no compressed air entering the system 99% of the time the engine is running. Boosted air into the engine at all times if funny, though!

These forums are about learning and solving problems. People like you, who obviously have no knowledge or experience in a subject matter does a disservice to those who are trying to learn the real facts. I suggest that you change your screen name and come back and listen for a while before speaking out of the wrong end.

There are many good sites on the web that can explain how a supercharged engine operates if you take the time to do some reseach.