highest boost SR20?

[Gregariousgreg]

My mistake. I worded it wrong.

I was not trying to say that PSI has density, (I am aware those were my exact words and that was my error) just that density has to be present to create the pressure. Psi is just a measure of pressure against a surface at a given point of measurement. This pressure implies higher density because pressure is just a measurement of the amount and speed of molecules hitting a surface. I admit I left out one important part which is the speed at which the given pounds of pressure would enter the engine which you would use to calculate the actual density of the air being forced into the engine at any given moment.

I understand the PSI is a 2 dimentional measurement, where as volume and density have three dimentions. I was just trying to simplify the idea back down to two dementions so it might be more easily understood.

I WAS NOT TRYING TO SAY THAT YOUR EXPLANATION WAS WRONG AND I WAS TRYING TO CLARIFY MINE. You obviously know what you are talking about, but I know a little too and I was just trying to explain what I know to someone who might not know all the technical jargon or about physics. So please don't feel the need to threaten me by saying you're going to "slam [me] with the technical explanations". It is just a statement like that which makes me think you are being rude.

I would like to learn from you and I hope I can help you aswell. I'm sorry for any missunderstanding and I mean no dissrespect. However, I also would like a little respect in return.

[synik]

There are two differences in the turbos. One has a large a/f and the other is smaller (or you can look at it in terms of cfm). AT some point they make the same psi.but that same psi does not create the same power. The problem: WHY don’t they create the same power at the same psi?

First what is Power???In this example*, power is proportional to molecules of air. P(molecules) power is a function of molecules.

So power is defined. But what are molecules… how do we find out how many molecules get into this piston? Molecules inside a piston are obtained by forcing dense air into the piston. So molecules then are dependent on how fast the dense air can get into the piston.

So we know it depends on the molecules, but how are the molecules dependent on the psi or cfm??Since both turbos have the same psi we can ignore that aspect and then focus on the cfm of each**.

The cfm of the larger one will be greater than the cfm of the smaller.So now we have gotten to a point where we can find out which turbo gets more particles into the piston.

One has a larger cfm than the other. So therefore, one can move more air (of the same psi) into the piston.

Since the larger cfm turbo can move more air into the piston... it moves more molecules. Power is dependent on the molecules... so the larger turbo will put more molecules into the piston and therefore create more power.

*This simplification I think is justified because this is the main deciding factor. All other factors are the same… except for this factor. That is why I think it is valid to use this simplification.

**Because the psi is constant for both you can ignore it as a factor in this argument.

[synik]

I would just like to make a comment here about what I stated...

I spoke about psi and cfm and said that they are independent. But I am not sure if it is really possible for this to be true...

One could argue that it is impossible for cfm and psi to be linked... because otherwise the power would have to be the same. But at the same time one could argue that they have to be linked together because the pressure (psi) is increased by the movement of the air (cfm).

[synik]

I explained a lot of this vaguely... but if you like I suppose it could be elaborated. (It's my experience that things that are too long tend to just be ignored... hence the shortness).

[Gregariousgreg]

You seem to have run into the same problem that I did. When you shorten things for simplicity, you lose a lot of details that some people might find more important than others. That is a good explanation though.

P.S. That explanation reminds me of my philosophy class I took this year

[Drakon]

I read the words, but they go soaring over my head......look at them go!!

[SRdave240]

Synik - should I really be reading an automotive explanation from someone who doesn't know the difference between a cylinder and a piston?

[60dash1]

You haven't been taught very much by any of these explanations. Do not equate PSI to flow as PSI seen is a function of many things. What creates the pressure you see? For a given compressor speed, any resistance to flow will create an increase in pressure. A good example is to place a pressure gauge on your air compressor line and start it blowing. If you place your finger over the nozzle the pressure in the line will increase, but you have actually decreased the flow coming out of the nozzle. Now to answer your question of how 2 different turbo's with the same running pressure and intake temps can make different power on the same motor. When you look at the compressor maps they are rated in lbs/hr which relates to the density of the charge. What does a compressor wheel do? It compresses the air making it more dense. Sorry, I like to ramble. So, for a bigger turbo it will pack more air molecules into a fixed volume as compared to a smaller turbo. Even though you have the same pressure you have more efficiently compressed the air molecules, making the charge more dense. The more air molecules you can pack into the motor the more power you will make. Just to give a real world example, if you are running a whimpy T25 @ 15psi you may make 300hp, but swap to 60-1 @ 15psi and you may make 350hp. No more boost, but more air molecules are put into the motor. Turbine efficiency and other factors do affect you ability to make more power, but I am just trying to convey how this stuff works in a simple way. I hope this helps.

You are completely right, PSI is no indication of air density, just pressure.It all has to do with efficiency,wheel size,blade pitch and compressor housing size.The larger turbo doesn't have to work as hard(it's more efficient) to produce the same boost.lets say your outlet temp on a t25 at 14 psi was 150 deg, and on a t3/to4e 57 trim it was 120 deg,these numbers are just for arguments sake. you will make more power with the t3/t04e because the cooler the temp the more dense the charge air.We all know that cooler temps are more dense so that tells us that the cooler charge will be able to pack more air molecules in the same given area (motor) as the latter.As 240z twin turbo stated, this is a small piece of a big puzzle, but I hope it helps.

[240Z TwinTurbo]

If it makes anyone feel better, my new TT setup should be running tomorrow. BTW, I will be in Gainseville in 2 weeks(Sunday only) to make a few passes at the World import Nationals. I hope to see some 135mph traps.