**turbo math pg 4**
(Now lets talk about what can effect your overall outcome of power. After punchin numbers I found that DR and PR have the largest effect of overall out put. So these are the numbers you really want to design a system around. So Ideally, if you want a number, you design around that number to get what you want. Also the air fuel ratio and burn rate of fuel will change your numbers. The less fuel burn per hour and the leaner the mixture will net you more power. But then you run into the possibility of detonation and burning up pistons. That’s is my own theory and opinion. I could be wrong. We can see how the tuning of the ECU has a LARGE impact of the output)

Compressors

This next section is about compressors and how to find out their efficiencies. Remember the number I used earlier? This is how I get that number. In this section, we will start combining numbers and looking at compressor maps to see how this all comes together. When looking at a map of a compressor, you basically want to stay in the “zone” of a particular turbo when matching to the engine specs. Lets first look at how to get the efficiency of a compressor..

EFFcomp = [(Tin+460)(PR^.283)-(Tin+460)] / (Tout - Tin)

= [(85+460)(1.68^.283 ) - (85+460)] / (200 - 85)

= [(545)(1.16) - 545] / 115

= (632.2 - 545) / 115

= .758 or 75.8%

That percentage is BEFORE it enters the intercooler. Taking this number we are close to start looking at maps to see what we can find. These maps are produced and graphed from the engineers at the factory using math that I do not under stand. Basically those guys did all the hard work for us. This is the link to all the maps of the garrett turbos from this website:

http://www.atpturbo.com/root/index.htm
Here is an example of a map for this turbo application. Just look at the airflow, then go up to the desired PR and you can see at what efficiency the turbo is best at. Now you can read these maps and make sense of it.

But before we start looking at maps, we have to size a compressor to out application. This is where we start combining past equations to see what we want. Our engine operates at 85 percent VE, a PR of 1.68 of the compressor, a PR of 1.61 of the SYSTEM (that is running through a intercooler). We have a temp out of 200 degrees F. (Remember the past calculation of EQ2).

Now we look at how an intercooler effects the system. We will use 70% intercooler efficiency (EFFic)

Tic out = Tcomp out - (EFFic)(Tcomp out - Tamb)

= 200 - (.70 x (200 - 85))

= 200 - (.70 x 115)

= 200 - 80.5

=119.5 degrees F

Now we calculate the DR using the equation from before but we already did that using 120 degrees as the base.

DR = 1.61 x [(85 + 460)/(120 + 460)]

= 1.51

Now we bring in the VFR and plug into the MFR equation using this adjusted DR. VFR was 366.72 CFM at 5300 RPM. But if you did this earlier then all numbers should be the same. So you can play with numbers and see if your DR changes your output changes. It is all in design. Now you can design your system to work in your area. Example is why run numbers at sea level at an average of 85 degrees when most of your time may be spent above 6000 feet elevation with an average temp of 70 degrees. So you can see how just your location in the world will have a severe impact of the design and output of the system. So NOW is the time to get some MFR rates at different RPMS and we can start to plot on compressor maps to find the best one for out application.

So lets work with the following numbers and start plotting

MFR of 11.43 at 1500 RPM

MFR of 22.85 at 3000 RPM

MFR of 40.38 at 5300 RPM