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Old 09-04-2009, 03:14 PM Thread Starter
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Different turbos each have different properties which make them correct for different applications. These flow properties are shown in a graph called a compressor map.
Garrett explains the different parts of a compressor map very well:
Quote:
Originally Posted by As found on Garrett.com’s Turbo Tech103 Article
1 Parts of the Compressor Map:
The compressor map is a graph that describes a particular compressor’s performance characteristics, including efficiency, mass flow range, boost pressure capability, and turbo speed. Shown below is a figure that identifies aspects of a typical compressor map:

Pressure Ratio
Pressure Ratio ( ) is defined as the Absolute outlet pressure divided by the Absolute inlet pressure.



Where:
o= Pressure Ratio
oP2c = Compressor
oDischarge Pressure
oP1c = Compressor Inlet Pressure
It is important to use units of Absolute Pressure for both P1c and P2c. Remember that Absolute Pressure at sea level is 14.7 psia (in units of psia, the a refers to “absolute”). This is referred to as standard atmospheric pressure at standard conditions.
Gauge Pressure (in units of psig, the g refers to “gauge”) measures the pressure above atmospheric, so a gauge pressure reading at atmospheric conditions will read zero. Boost gauges measure the manifold pressure relative to atmospheric pressure, and thus are measuring Gauge Pressure. This is important when determining P2c. For example, a reading of 12 psig on a boost gauge means that the air pressure in the manifold is 12 psi above atmospheric pressure. For a day at standard atmospheric conditions,
12 psig + 14.7 psia = 26.7 psi absolute pressure in the manifold
The pressure ratio at this condition can now be calculated:
26.7 psia / 14.7 psia = 1.82
However, this assumes there is no adverse impact of the air filter assembly at the compressor inlet.
In determining pressure ratio, the absolute pressure at the compressor inlet (P2c) is often LESS than the ambient pressure, especially at high load. Why is this? Any restriction (caused by the air filter or restrictive ducting) will result in a “depression,” or pressure loss, upstream of the compressor that needs to be accounted for when determining pressure ratio. This depression can be 1 psig or more on some intake systems. In this case P1c on a standard day is:
14.7psia – 1 psig = 13.7 psia at compressor inlet

Taking into account the 1 psig intake depression, the pressure ratio is now:
(12 psig + 14.7 psia) / 13.7 psia = 1.95.

That’s great, but what if you’re not at sea level? In this case, simply substitute the actual atmospheric pressure in place of the 14.7 psi in the equations above to give a more accurate calculation. At higher elevations, this can have a significant effect on pressure ratio.
For example, at Denver’s 5000 feet elevation, the atmospheric pressure is typically around 12.4 psia. In this case, the pressure ratio calculation, taking into account the intake depression, is:
(12 psig + 12.4 psia) / (12.4 psia – 1 psig) = 2.14
Compared to the 1.82 pressure ratio calculated originally, this is a big difference.
As you can see in the above examples, pressure ratio depends on a lot more than just boost.
◊ Mass Flow Rate
Mass Flow Rate is the mass of air flowing through a compressor (and engine!) over a given period of time and is commonly expressed as lb/min (pounds per minute). Mass flow can be physically measured, but in many cases it is sufficient to estimate the mass flow for choosing the proper turbo.
Many people use Volumetric Flow Rate (expressed in cubic feet per minute, CFM or ft3/min) instead of mass flow rate. Volumetric flow rate can be converted to mass flow by multiplying by the air density. Air density at sea level is 0.076lb/ft3
What is my mass flow rate? As a very general rule, turbocharged gasoline engines will generate 9.5-10.5 horsepower (as measured at the flywheel) for each lb/min of airflow. So, an engine with a target peak horsepower of 400 Hp will require 36-44 lb/min of airflow to achieve that target. This is just a rough first approximation to help narrow the turbo selection options.
◊ Surge Line
Surge is the left hand boundary of the compressor map. Operation to the left of this line represents a region of flow instability. This region is characterized by mild flutter to wildly fluctuating boost and “barking” from the compressor. Continued operation within this region can lead to premature turbo failure due to heavy thrust loading.
Surge is most commonly experienced when one of two situations exist. The first and most damaging is surge under load. It can be an indication that your compressor is too large. Surge is also commonly experienced when the throttle is quickly closed after boosting. This occurs because mass flow is drastically reduced as the throttle is closed, but the turbo is still spinning and generating boost. This immediately drives the operating point to the far left of the compressor map, right into surge.

Surge will decay once the turbo speed finally slows enough to reduce the boost and move the operating point back into the stable region. This situation is commonly addressed by using a Blow-Off Valves (BOV) or bypass valve. A BOV functions to vent intake pressure to atmosphere so that the mass flow ramps down smoothly, keeping the compressor out of surge. In the case of a recirculating bypass valve, the airflow is recirculated back to the compressor inlet.
◊ The Choke Line is the right hand boundary of the compressor map. For Garrett maps, the choke line is typically defined by the point where the efficiency drops below 58%. In addition to the rapid drop of compressor efficiency past this point, the turbo speed will also be approaching or exceeding the allowable limit. If your actual or predicted operation is beyond this limit, a larger compressor is necessary.
◊ Turbo Speed Lines are lines of constant turbo speed. Turbo speed for points between these lines can be estimated by interpolation. As turbo speed increases, the pressure ratio increases and/or mass flow increases. As indicated above in the choke line description, the turbo speed lines are very close together at the far right edge of the map. once a compressor is operating past the choke limit, turbo speed increases very quickly and a turbo over-speed condition is very likely.
◊ Efficiency Islands are concentric regions on the maps that represent the compressor efficiency at any point on the map. The smallest island near the center of the map is the highest or peak efficiency island. As the rings move out from there, the efficiency drops by the indicated amount until the surge and choke limits are reached.


Now that you know how to read compressor maps, it’s time to move onto the next step of the process, learning to use them to find out which turbo is right for you:

Quote: As found on Garrett.com’s Turbo Tech103 Article 2. Plotting Your Data on the Compressor Map
In this section, methods to calculate mass flow rate and boost pressure required to meet a horsepower target are presented. This data will then be used to choose the appropriate compressor and turbocharger. Having a horsepower target in mind is a vital part of the process. In addition to being necessary for calculating mass flow and boost pressure, a horsepower target is required for choosing the right fuel injectors, fuel pump and regulator, and other engine components.
◊ Estimating Required Air Mass Flow and Boost Pressures to reach a Horsepower target.
• Things you need to know:
• Horsepower Target
• Engine displacement
• Maximum RPM
• Ambient conditions (temperature and barometric pressure. Barometric pressure is usually given as inches of mercury and can be converted to psi by dividing by 2)
• Things you need to estimate:
• Engine Volumetric Efficiency. Typical numbers for peak Volumetric Efficiency (VE) range in the 95%-99% for modern 4-valve heads, to 88% - 95% for 2-valve designs. If you have a torque curve for your engine, you can use this to estimate VE at various engine speeds. on a well-tuned engine, the VE will peak at the torque peak, and this number can be used to scale the VE at other engine speeds. A 4-valve engine will typically have higher VE over more of its rev range than a two-valve engine.

• Intake Manifold Temperature. Compressors with higher efficiency give lower manifold temperatures. Manifold temperatures of intercooled setups are typically 100 - 130 degrees F, while non-intercooled values can reach from 175-300 degrees F.

• Brake Specific Fuel Consumption (BSFC). BSFC describes the fuel flow rate required to generate each horsepower. General values of BSFC for turbocharged gasoline engines range from 0.50 to 0.60 and higher. The units of BSFC are lb/(Hp*hr) Lower BSFC means that the engine requires less fuel to generate a given horsepower. Race fuels and aggressive tuning are required to reach the low end of the BSFC range described above.
For the equations below, we will divide BSFC by 60 to convert from hours to minutes.
To plot the compressor operating point, first calculate airflow:
Wa = HP * A/F * BSFC/60
Where:
• Wa = Airflowactual (lb/min)
• HP = Horsepower Target (flywheel)
• A/F= Air/Fuel Ratio
• BSFC/60= Brake Specific Fuel Consumption ÷ 60 (to convert from hours to minutes)




Now it is time to put that information to use:
Quote: From Garrett’s Turbo Tech103 EXAMPLE:
I have an engine that I would like to use to make 400Hp, I want to choose an air/fuel ratio of 12 and use a BSFC of 0.55. Plugging these numbers into the formula from above:
Wa = 400 * 12 * .55 / 60 = 44.0 lb/min of air.
Thus, a compressor map that has the capability of at least 44 pounds per minute of airflow capacity is a good starting point.

Note that nowhere in this calculation did we enter any engine displacement or RPM numbers. This means that for any engine, in order to make 400 Hp, it needs to flow about 44 lb/min (this assumes that BSFC remains constant across all engine types).

Naturally, a smaller displacement engine will require more boost or higher engine speed to meet this target than a larger engine will. So how much boost pressure would be required?
◊ Calculate required manifold pressure required to meet the horsepower, or flow target:

Where:

• MAPreq = Manifold Absolute Pressure (psia) required to meet the horsepower target
• Wa = Airflowactual(lb/min)
• R = Gas Constant = 639.6
• Tm = Intake Manifold Temperature (degrees F)
• VE = Volumetric Efficiency
• N = Engine speed (RPM)
• Vd = engine displacement (Cubic Inches, convert from liters to CI by multiplying by 61.02, ex. 2.0 liters * 61.02 = 122 CI)

EXAMPLE:
To continue the example above, let’s consider a 2.0 liter engine with the following description:
• Wa = 44 lb/min as previously calculated
• Tm = 130 degrees F
• VE = 92% at peak power
• N = 7200 RPM
• Vd = 2.0 liters * 61.02 = 122 CI

= 41.1 psia (remember, this is absolute pressure. Subtract atmospheric pressure to get gauge pressure (aka boost):
41.1 psia – 14.7 psia (at sea level) = 26.4 psig boost



Later tonight I will discuss how to actually put this information to use by overlaying it onto a compressor map to choose your optimal turbocharger/supercharger, but for now this is a good start to get everyone crunching some numbers!


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Old 09-05-2009, 02:25 PM
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Now that you can read them, time for some practice:

From THIS Thread.

Quote:
Originally Posted by Danny50 on Aug/07/09
GARRETT

Garrett Turbocharger Comparison Sheet found on TurbobyGarrett.com



Garrett GT2560R





Description: Oil and Water Cooled/Ball Bearing Turbo. Lightning spool, however a poor candidate for higher revving engines (See the GT2860RS). Internally gated, rated for 330hp.

Garrett GT2860R




Description: Oil and Water Cooled/Ball Bearing Turbo. T25 Flange, Internally Gated, Rated to 310hp. Comparible to the GT2560R. 5 bolt non-standard T25 flange necessary for downpipe.

Garrett GT2860RS




Description: Oil and Water Cooled/Ball Bearing Turbo. T25 Flange, Internally Gated, Rated to 360hp, though has been proven to be able to sustain 400+hp. Optimum choice for lower displacement, higher revving engines where a fast spool is desired.

Garrett GT2871R




Description: Oil and Water Cooled/Ball Bearing Turbo. T25 Flange, Internally Gated, Bolt on upgrade to GT28R and GT28RS. Rated to 475hp, will yield better top end at the sacrifice of spool time due to the larger exducer diameter of the compressor wheel.

Garrett GT3071R




Description: Rated by Garrett for 300-460hp, largely depending on the Turbine housing selected (which is sold separately). Oil and Water Cooled/Ball Bearing Turbo, T3 Flange, Free float Turbine housing. Differentiated from GT3076R by the smaller exducer diameter of the Compressor Wheel.


Garrett GT3076R




Description: Rated by Garrett for 310-525hp, again largely depending on the Turbine housing selected (which is sold separately), though I personally have made 503hp on the smallest size turbine housing, and plan to make 600hp in the near future. T3 Flange, Oil and Water Cooled/Ball Bearing Turbo, Free float Turbine housing. Differentiated from GT3071R by the larger exducer diameter of the Compressor Wheel and ported shroud on the compressor housing.


Garrett GT3271R




Description: Journal Bearing cousin of the GT30R, Rated to 420hp. Oil Cooled, T3 Flange, Will see a substantial increase in spool time when compared to the GT3071/6R due to the Journal Bearing, though considerably less expensive. Free float Turbine Housing.

Garrett GT3582R




Description: Ball Bearing, Oil and Water cooled, Free float Turbine Housing. Garrett rated at 600hp, though they have been proven to be able to make considerably more power. Will see far more top end than the GT30R family at the expense of spool time.

MITSUBISHI

This is primarily copied from the article:
Turbocharger Compressor Flow Maps for 3000GT and Stealth Owners by Jeff Lucius. All are Air Cooled Journal Bearing Turbos.

TD05H-14G



Description: The coverage of engine demand lines is similar to that of the TD04-15G. There is little advantage to increasing engine redline to 8000 rpm or above with this turbo because there is only marginally more flow at those engine speeds.


TD05H-16G Small



Description: TD05H-16G small wheel. This turbo is a common upgrade for the DSM engine. Demand-line coverage is adequate but shows no advantage over the TD04-15G.


TD05H-16G Large



Description: TD05H-16G large wheel. This is another common upgrade choice for the DSM cars. The larger 16G wheel is also found in the TD06H housing.


TD05HR-16G6



Description: This turbo is used in the Mitsubishi Lancer Evolution IV to VIII. I think this same wheel is used in the Evo III (but cast in mirror image?), which uses a standard TD05H-7cm2 turbine housing. The TD05HR turbine rotates reverse (the "R" in the designation) of the standard TD05H and has a twin-scroll design. The compressor inducer is a little larger (0.01") than the "big" 16G. So is this the "biggest" 16G? Max flow is better than the 16G "large wheel". Efficiency is much better than the 16G "large wheel".


TD05H-18G



Description: This flow map is my speculation based on horizontally squeezing and vertically stretching a MHI 20G map. The 16G-large, 18G, and 20G compressor wheels all share the same 2.680" exducer diameter and differ in trim (and perhaps blade design): 50 trim for the 16G-large, 55 trim for the 18G and 60 trim for the 20G. In wheel "families" like this (same exducer size) higher trim usually means more flow and often lower maximum pressure ratio. Sometimes the higher trim wheel may have a bit less maximum efficiency than the lower trim wheel, such as seen in the Garrett T3 series (compare 50-trim and 60-trim wheels). So to make this map I reduced the 20G flow some and increased the maximum PR some. All "G" maps are somewhat similar in appearance so I think this speculative map may be a reasonable guess as to the MHI 18G performance. Coverage of demand lines is not as good as the 14B and 16G-large, but better than with the 20G. However, efficiency is probably better than either of the other 3 wheels. Note: This is the stock turbo for the GReddy turbo kit.

*UPDATE 9/5* 500hp Turbo Build, for the love of god no 56k please King Motorsports Tuned: 433whp/300wtq @ 17.5psi - 93 503.13whp/372wtq @ 30psi - 110 Octane
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Old 09-05-2009, 03:41 PM
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Heres an LS plotted on a GT2560r (Aka GT28r):

bottom line is 10psi
Second line is 15 psi.


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Old 09-05-2009, 07:34 PM Thread Starter
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Nice!

Now for part 2: Actually putting what we now know to use plotting it on a compressor map to determine the correct compressor.

Quote:
Originally Posted by Garrett TurboTech 103
With Mass Flow and Manifold Pressure, we are nearly ready to plot the data on the compressor map. The next step is to determine how much pressure loss exists between the compressor and the manifold. The best way to do this is to measure the pressure drop with a data acquisition system, but many times that is not practical.

Depending upon flow rate, charge air cooler characteristics, piping size, number/quality of the bends, throttle body restriction, etc., the plumbing pressure drop can be estimated. This can be 1 psi or less for a very well designed system. on certain restrictive OEM setups, especially those that have now higher-than-stock airflow levels, the pressure drop can be 4 psi or greater.

For our examples we will assume that there is a 2 psi loss. So to determine the Compressor Discharge Pressure (P2c), 2 psi will be added to the manifold pressure calculated above.




Where:

· P2c = Compressor Discharge Pressure (psia)
· MAP = Manifold Absolute Pressure (psia)
· ΔPloss = Pressure Loss Between the Compressor and the Manifold (psi)

For the 2.0 L engine:

= 43.1 psia

Remember our discussion on inlet depression in the Pressure Ratio discussion earlier, we said that a typical value might be 1 psi, so that is what will be used in this calculation. For this example, assume that we are at sea level, so ambient pressure is 14.7 psia.

We will need to subtract the 1 psi pressure loss from the ambient pressure to determine the Compressor Inlet Pressure (P1).


Where:

· P1c = Compressor Inlet Pressure (psia)
· Pamb = Ambient Air pressure (psia)
· ΔPloss = Pressure Loss due to Air Filter/Piping (psi)

P1c = 14.7 - 1

= 13.7 psia

With this, we can calculate Pressure Ratio () using the equation.



For the 2.0 L engine:


= 3.14


We now have enough information to plot these operating points on the compressor map. First we will try a GT2860RS. This turbo has a 60mm, 60 trim compressor wheel.



Clearly this compressor is too small, as both points are positioned far to the right and beyond the compressor’s choke line.

Another potential candidate might be the GT3076R. This turbo has a 76mm, 56 trim compressor wheel:



This is much better; at least both points are on the map! Let’s look at each point in more detail.

For the 2.0L engine this point is in a very efficient area of the map, but since it is in the center of the map, there would be a concern that at a lower engine speeds that it would be near or over the surge line. This might be ok for a high-rpm-biased powerband that might be used on a racing application, but a street application would be better served by a different compressor.

So now lets look at a GT3071R, which uses a 71mm, 56 trim compressor wheel.



For the 2.0L engine, this is a much more mid-range-oriented compressor. The operating point is shifted a bit towards the choke side of the map and this provides additional surge margin. The lower engine speeds will now pass through the higher efficiency zones and give excellent performance and response.

Now that we have arrived at an acceptable compressor for the 2.0L engine, lets calculate a lower rpm point to put on the map to better get a feel for what the engine operating line will look like.


Now for the fun part...actually seeing where the engine actually operates the compressor.

Quote: Garrett TurboTech 103 We can calculate this using the following formula:


We’ll choose the engine speed at which we would expect to see peak torque, based on experience or an educated guess. In this case we’ll choose 5000rpm.

Where:

· Wa = Airflowactual (lb/min)
· MAP = Manifold Absolute Pressure (psia) =41.1 psia
· R = Gas Constant = 639.6
· Tm = Intake Manifold Temperature (degrees F) =130
· VE = Volumetric Efficiency = 0.98
· N = Engine speed (RPM) = 5000rpm
· Vd = engine displacement (Cubic Inches, convert from liters to CI by multiplying by 61, ex. 2.0 liters * 61 = 122 CI)



= 32.5 lb/min

Plotting this on the GT3071R compressor map gives the following operating points.



This gives a good representation of the operating line at that boost level, which is well suited to this map. At engine speeds lower than 5000rpm the boost pressure will be lower, and the pressure ratio would be lower, to keep the compressor out of surge.
Now, this seems like a lot of work, so to keep things simple, as people plan their builds, please post your plottted compressor maps here for people to view.
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Old 09-06-2009, 06:59 PM
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So I tried the first half using these figures the day this thread was started.

HP Target = 400
Engine Size = 2354cc - 143.641 CI
Max RPM = 7600rpm (maybe 7800 or 8k in the future)
Temperature = 61º
Barometric Pressure = 29.94" - 14.97psi

It came out with something like 21psi of boost which I KNOW isn't right just to reach 400hp on a K24a2. I'm currently considering a Rotrex supercharger and they have several sizes to choose from, but I'm not sure and I wan't to do the figures before I do any further research.

C30 100-400hp
C38 300-630hp

All the technical data, compressor maps, etc are in those pdf's. If I need to take the flow charts and make them JPG's and post them I will.

TIA great post!
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Old 09-27-2009, 11:39 PM
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Quote:
Quote: As found on Garrett.com’s Turbo Tech103 Article
--------------------------------------------------------------------------------
2. Plotting Your Data on the Compressor Map
In this section, methods to calculate mass flow rate and boost pressure required to meet a horsepower target are presented. This data will then be used to choose the appropriate compressor and turbocharger. Having a horsepower target in mind is a vital part of the process. In addition to being necessary for calculating mass flow and boost pressure, a horsepower target is required for choosing the right fuel injectors, fuel pump and regulator, and other engine components.
◊ Estimating Required Air Mass Flow and Boost Pressures to reach a Horsepower target.
• Things you need to know:
• Horsepower Target
• Engine displacement
• Maximum RPM
• Ambient conditions (temperature and barometric pressure. Barometric pressure is usually given as inches of mercury and can be converted to psi by dividing by 2)
• Things you need to estimate:
• Engine Volumetric Efficiency. Typical numbers for peak Volumetric Efficiency (VE) range in the 95%-99% for modern 4-valve heads, to 88% - 95% for 2-valve designs. If you have a torque curve for your engine, you can use this to estimate VE at various engine speeds. on a well-tuned engine, the VE will peak at the torque peak, and this number can be used to scale the VE at other engine speeds. A 4-valve engine will typically have higher VE over more of its rev range than a two-valve engine.

• Intake Manifold Temperature. Compressors with higher efficiency give lower manifold temperatures. Manifold temperatures of intercooled setups are typically 100 - 130 degrees F, while non-intercooled values can reach from 175-300 degrees F.

• Brake Specific Fuel Consumption (BSFC). BSFC describes the fuel flow rate required to generate each horsepower. General values of BSFC for turbocharged gasoline engines range from 0.50 to 0.60 and higher. The units of BSFC are lb/(Hp*hr) Lower BSFC means that the engine requires less fuel to generate a given horsepower. Race fuels and aggressive tuning are required to reach the low end of the BSFC range described above.
For the equations below, we will divide BSFC by 60 to convert from hours to minutes.
To plot the compressor operating point, first calculate airflow:
Wa = HP * A/F * BSFC/60
Where:
• Wa = Airflowactual (lb/min)
• HP = Horsepower Target (flywheel)
• A/F= Air/Fuel Ratio
• BSFC/60= Brake Specific Fuel Consumption ÷ 60 (to convert from hours to minutes)
so what should i be using as volumetric efficiency on a gsr engine? 98%? also what are some some people using as the intake manifold temp, BSFC, and A/F?

i just want to make sure im doing things right when i start calculating. cause somehow im getting that a gt2860rs 60mm, 62 trim, 0.6 AR is too small for 300 hp. unless it is?
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Old 10-01-2009, 11:30 AM
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Quote:
Originally Posted by NtegraDryvr on Sep/06/09
So I tried the first half using these figures the day this thread was started.

HP Target = 400
Engine Size = 2354cc - 143.641 CI
Max RPM = 7600rpm (maybe 7800 or 8k in the future)
Temperature = 61º
Barometric Pressure = 29.94" - 14.97psi

It came out with something like 21psi of boost which I KNOW isn't right just to reach 400hp on a K24a2. I'm currently considering a Rotrex supercharger and they have several sizes to choose from, but I'm not sure and I wan't to do the figures before I do any further research.

C30 100-400hp
C38 300-630hp

All the technical data, compressor maps, etc are in those pdf's. If I need to take the flow charts and make them JPG's and post them I will.

TIA great post!
There is no way that the temp inside the engine bay is going to be 60 degrees while the car is running. Also, where did you get your numbers for barometric pressure? Keep in mind that it is based on elevation, so different parts of the country are going to have different values. Easiest way to figure it out is to check your local weather. There should be an average for you area.

If your going to build a setup, then why not build it to accomodate the type of driving that your going to be doing 80% of the time? Horse power is expensive. If your unsure about your goal, just come up with a budget for how much you want to spend.
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Old 10-01-2009, 11:41 AM
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BSFC is going to be different depending on who you talk to. For instance Garrett recommends using a value of .55 while some injector companies use .60. But to be honest it is really not going to make that big of a difference in the end.

In most cases the A/F ratio is usually 12, I mean you could shoot for 11.5 if you want to be anal. But keep in mind that this is just a prediction. It is not the definite end all result.
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Old 10-01-2009, 05:44 PM
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I don't understand why the VE changed from 92% to 98% with the shift from the 7200 RPMs to 5000 RPMs. Can someone please explain?

Quote:
Originally Posted by sgtmillhouse648 on Sep/04/09
• VE = 92% at peak power
• N = 7200 RPM
• Vd = 2.0 liters * 61.02 = 122 CI








Quote: sgtmillhouse648 on Sep/05/09 · VE = Volumetric Efficiency = 0.98
· N = Engine speed (RPM) = 5000rpm
· Vd = engine displacement (Cubic Inches, convert from liters to CI by multiplying by 61, ex. 2.0 liters * 61 = 122 CI)


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Old 10-01-2009, 06:32 PM
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max volumetric efficiency occurs at max torque. that is why they plug in the 98% at 5000 where they expect max torque to occur.
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Old 10-04-2009, 11:47 AM
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Yep, think about it like a mountain and peak volumetric efficiency (where peak torque occurs in the rpms) is at the top. When you start out at the bottom you have to work your way up to it and once you pass it, you start working your way down the other side.
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Old 10-04-2009, 07:11 PM
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Quote:
Originally Posted by MrMoe on Oct/01/09
Quote: NtegraDryvr on Sep/06/09So I tried the first half using these figures the day this thread was started.
HP Target = 400
Engine Size = 2354cc - 143.641 CI
Max RPM = 7600rpm (maybe 7800 or 8k in the future)
Temperature = 61º
Barometric Pressure = 29.94" - 14.97psi

It came out with something like 21psi of boost which I KNOW isn't right just to reach 400hp on a K24a2. I'm currently considering a Rotrex supercharger and they have several sizes to choose from, but I'm not sure and I wan't to do the figures before I do any further research.

C30 100-400hp
C38 300-630hp

All the technical data, compressor maps, etc are in those pdf's. If I need to take the flow charts and make them JPG's and post them I will.

TIA great post!


There is no way that the temp inside the engine bay is going to be 60 degrees while the car is running. Also, where did you get your numbers for barometric pressure? Keep in mind that it is based on elevation, so different parts of the country are going to have different values. Easiest way to figure it out is to check your local weather. There should be an average for you area.
Your right the engine bay is way hotter so I figure with a CAI taking in ambient temps. The average temperature for my location is 61º in a year. Also I know that the pressure is right I looked that up several times.
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Old 10-04-2009, 07:15 PM Thread Starter
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one very important thing I would like to point out is that although the air taken in at the filter may be ambient, that does not necessarily mean that your IAT's are that temperature. As the air travels through the intake system (tube/turbo/SC/intercooler/intake manifold) it does indeed pick up quite a bit of heat. This is one reason why the thermal barrier intake manifold gaskets are so successful.
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Old 10-04-2009, 07:20 PM
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Good point I'm not sure what to put in then really. I will be running water/meth and thats a whole other issue to calculate for I'm sure. Right now on my JRSC my IAT's AFTER blower I've seen reach as high as 188ºF.
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