Ford 302 cubic in., 9.0:1 c.r., GT40 heads, B303 Cam, Edelbrock Performer RPM intake, 650 Holley Carburetor, 1-5/8" Long tube headers.

Test Fuel:

91 Octane (pump gas)

Test Stand:

Stuska Model 800 Engine Dynamometer

Test Assumptions/Parameters:

1. Intercooled: Since it is impractical (would require the use of a wind tunnel to simulate actual airflow around the car and thru the air-to-air intercooler), temperatures and pressures were recorded during an actual 1/4 mile run and reproduced on the dyno using a air-to-water intercooler and restrictors, as needed.

2. Timing: 30 degrees total timing was used for baseline and intercooled supercharged test. A MSD timing retard, set at 1 degree/psi boost, was used for the non-intercooled supercharged test.

Concerns regarding Vortech 3/96 model:

In general, it is surprising that Vortech's entire spreadsheet model (created March 1996) only contains two actual points of "test data" when there was a clear opportunity and obligation to provide actual test data throughout the model (instead of relying on calculations which are in turn based on inaccurate assumptions). The following concerns illustrate that Vortech's "model" is so severely flawed that the model is not only technically incorrect, but also harmful because the model's calculated results are actually contrary to fact, and by a substantial margin.

1. Review of the Vortech 5.0 model has revealed two general observations which question the validity of their entire model:

A. The majority of the data is calculated data, not actual test data as most qualified engineers would use (especially from a company which puts so much weight on it's SAE test cell, standards and procedures). Although the calculations for some of the entries (i.e. horsepower) are required (and their calculations for those points appear to be correct), any credible SAE certified lab would have used as many actual measured data points as possible, in order to ensure accuracy of such a fundamentally and critically important document.

B. Of the two parameters they do claim as test data (pressure drop through the ATI intercooler and P600B compressor efficiency), the pressure drop thru the ATI intercooler is so grossly inaccurate that it completely distorts every conclusion (with cooler) and negates any credibility of the model. Based on the gross deviation from the actual pressure drop readings (refer to exhibits D & G), the only conclusion is the data is completely false or fabricated, and is physically impossible to be scientifically replicated in any resemblance by Vortech Engineering or an independent lab.

ATI's supercharger systems specification describes the compressor discharge pressure and manifold pressures (i.e. 9/12 = 12 psi compressor discharge & 9 psi in the intake manifold, based on a stock motor @ 6,000 rpm; this terminology was dropped in 1995, but does represent the actual boost loss through the intercooler system). Testing of the intercooler by itself (less tubing) shows a maximum drop of 2.9 psi while flowing 1200 SCFM into free air (The pressure drop would be much less flowing this same amount of air under boost conditions because the pressure drop is directly related to the velocity of the air, not the pressure of the air). This is a flow condition that is more than 1-1/2 times greater than produced by a 17 psi ProCharger system on a stock 5.0 engine.

The pressure drop reading across the intercooler is a very simple test to observe and record data. There are many ways to measure this pressure drop, one of most commonly used is a differential pressure gauge. These are readily available locally across the country. They are a single gauge used for indicating pressure differences between to points. Additionally, these numbers have been verified by our Mustang customers over the past 4 years. The market itself would have identified such gross misallegations if indeed Vortech's claims were factual. This has not been the case.

The inaccurate data in line 16 (pressure drop through ATI intercooler) completely falsifies the conclusions (listed below) of the model:

Line 21: Charge density w/ cooler

Line 23 % change in density above ambient (w/ cooler)

Line 31: Est. engine gross hp, w/ cooler

Line 33: Air flow (#/min) w/ cooler

Line 38: Net engine HP, w/ cooler

The second data point, compressor efficiency, is not only understated for the P600B, but the data points are not referenced or substantiated anywhere in any of Vortech's supporting documents. Vortech's compressor map of the P600B stops at 40,000 rpm, while compressor speeds for the ProCharger systems listed are 43,000, 45,900, 49,200, and 53,100 rpm, respectively.

2. The Vortech model claims an intercooler effectivenes of 55% for all ProCharger systems. This value is a completely inaccurate assumption for the following reasons:

a. Actual measured effectiveness of the intercooler system by ATI is between 65 & 80%, dependent on system configuration.

b. This number would not be a constant for all systems. As the charge air increases in flow and temperature (for the different kits), there is not a direct linear increase in cooling airflow across the intercooler. Therefore, a 17 psi kit will have a lower cooler effectiveness value than a 9 psi kit.

c. There is no consideration for cooling air flow across the ATI intercooler. Since this is an air-to-air intercooler, it's effectiveness is solely dependent on cross flow air. In order for an effectiveness value to be stated, their must be a statement regarding the flow, temperature and humidity of the cross flow air in order to simulate real world conditions and to quantify the cooling effectiveness.

3. Vortech's claim of 78% effectiveness for their own intercooler is difficult to believe and highly unlikely in any real world conditions. The intercooler system effectiveness is based not only on their air-to-water intercooler itself, but also on their secondary heat exchanger they use to remove heat from the system water. The system effectiveness is a product of the two heat exchangers, not the highest effectiveness of just the primary heat exchanger (i.e. (70% primary) X (60% secondary) = 42% system effectiveness). This is consistant with the majority of published data concering air-to-water automotive transfer system based intercooler/aftercooler.

4. The estimated blower input data given in rows 35 & 36 are completely contrary to all actual dyno testing perfomed by ATI. As shown in exhibit B, the parasitic load, or input horsepower required to attain a given airflow and boost level, the P600B has a small advantage over the S-Trim at lower flow levels and its advantage continually increases as flow is increased, while maintaining a constant pressure. It is completely without reason why Vortech, who has the ability to perform in-house testing of supercharger parasitic load, did not do so and decided to calculate this data.

5. Compressor discharge pressure: Vortech model assumes compressor discharge pressures based on kit boost level. These numbers should be actual measured test data to be valid. Compressor discharge pressure is dependent on back pressure created by the engine. Variations in exhaust systems, cams, heads etc. will significantly affect the actual boost numbers. However, no statements are made regarding the engine configuration.

6. Finally, there is no mention of engine timing or the octane of fuel used for the test engine model. The assumption is that stock compression ratio is used, therefore, the use of ignition retard or racing fuel must be used for Vortech's non-intercooled applications Timing retard has a significant negative impact on horsepower production (see exhibit E). Vortech customers typically set the timing retard between 1 and 1.5°/psi of boost (on a scale of 0 to 3); ATI conservatively set the ignition retard at 1°/psi in its dyno test, giving Vortech the benefit of the doubt. Vortech's response states that the timing and fuel was "optimized" and "uniform" for both systems, however, optimized for their system requires the use of either ignition retard or racing fuel and optimized for ATI's system requires the use of pump gas and stock timing. Thus, they cannot be both "optimized" and "uniform".

It is not surprising they left out this pertinent information, since they also left out baseline engine performance, compression ratio, type of heads, type of cam, type of intake, type of fuel system and type of exhaust; parameters which any competent engineering company would have included in an engine model.

The aforementioned misassumptions are enough to completely skew the results of the model in Vortech's favor, a conclusion which is completely contrary to fact. The correct results are stated in ATI's dyno test.