This is from a Precision Fuel Testing Systems website at
http://www.ridgenet.net/~hideseng/new_page_1.htmI thought it would be useful for understanding as the usual definition of "gasoline" mentions the dielectric constant......
Q: What is the definition of Dielectric Constant?
A: The dielectric constant (DC) of a substance is a measure of the relative effectiveness of that substance as an electrical insulator. The perfect electrical insulator is a vacuum, which has a DC of 1.00000. By comparison, air has a DC of 1.00059, almost the same as a vacuum, and water has a DC value of 78.2. A dielectric meter measures the relative DC of gasoline by measuring the difference in capacitance of the probe between a standard (usually cyclohexane, with true DC value of 2.025) and the gasoline sample.
Q: Why is measurement of this characteristic an effective test for gasoline?
A: Gasoline as refined is a mixture of pure hydrocarbons. A unique physical property of a pure hydrocarbon fluid is that its DC is virtually the lowest of any liquid. The addition of power enhancing additives to gasoline, such as some oxygen and nitrogen bearing compounds, cause gasoline's DC to rise dramatically. A gasoline dielectric tester thus provides a simple, reliable way of determining whether a competitor's fuel has been adulterated.
Q: Where can I learn more about gasoline?
A: Go to:
www.faqs.org/faqs/autos/gasoline-faq/part1/Q: Is there a list of typical dielectric values for various brands of gasoline?
A: Yes. PFTS maintains an extensive database of racing gasoline dye colors and DC values. Click here to see the Gas DC List.
Q: How does a gasoline dielectric tester work?
A: It measures the difference between the DC of a gasoline sample and that of a reference hydrocarbon (cyclohexane, used to set zero on the meter). The measurement is expressed as a numeric +/- value on the digital display of the meter. This value is then compared to the PFTS Gas DC List and/or the rules of the sanctioning body to determine the legality of the fuel sample. Click here to see the FT-K01 Fuel Tester.
Q: Can you detect the presence of tetraethyl lead (TEL) in gasoline with a dielectric tester.
A: No. There are no field dielectric testers sensitive enough to detect the presence of TEL in unleaded gasoline. TEL typically is blended in a volume of about four grams/gallon or 0.01% by volume in most racing gasoline, and less in aviation gasoline (Av Gas). Even if it could be detected, in that minute volume it would be impossible to differentiate it from any other normal hydrocarbon component.
Q: Can you measure the octane of a gasoline sample with a dielectric tester?
A: No. The octane level of a gasoline sample can only be accurately measured in the laboratory with a special variable compression single cylinder engine designed specifically for that purpose. However, there are several companies using near-IR technology for octane number estimation. These devices look at about 27% of the hydrocarbons, then calculate an octane number based on the HC content and the octane numbers of the pure components that are stored in device memory. Claimed accuracy is equal to an octane engine, but there are serious limitations with this analysis method. Near-IR analyzers are fairly accurate for unleaded gasolines in the 86 to 92 octane range, marginal above that, and definitely will not provide any accuracy for a gasoline that contains TEL. They give an approximate octane number of the gasoline without taking the TEL into account, but do not measure the TEL content, therefore are generally ineffective for leaded gasoline. Click here to go to the Zeltex, Inc. website.
Q: Can a dielectric tester measure the 'quality' of a gasoline? (Is this good gas or bad gas?)
A: No. The best that a gasoline dielectric meter can do is provide a measurement which can be compared to a standard. The PFTS Gasoline DC List is one such standard, and when a specific brand/blend of gasoline is compared to the value published in the PFTS Gasoline DC List, one can determine only that the gas sample is the 'same' or 'different'. The rules of some motorsport associations specify a small range +/- the published value in the Gas DC List to determine legality of a sample, while others specify a maximum dielectric value for all gasoline used in competition , and if a competitor's gasoline exceeds the rule specification, his gas would be considered to be illegal. Dielectric testers can also be useful in determining if there is a difference between gasoline drums, which can be valuable to the competitor in determining if his gasoline has 'aged' (lost some of the more volatile components, or oxidized) or may be defective. This can help avoid poor performance on the track and the possibility of expensive engine damage.
Q: Can a dielectric tester measure the 'power' in a gasoline?
A: No. There is no correlation between the DC value of a particular gasoline and its specific energy.
Q: Does temperature affect the relative dielectric value of gasoline?
A: Extensive testing by NHRA indicates that the relative DC of gasoline is very sensitive to temperature and some gasolines are also sensitive to exposure (aging) at elevated temperatures for moderate to long periods of time. Accurate relative DC measurements can only be made if the temperature of the test sample is within +/- 5o F of the temperature of the calibration (cyclohexane) sample. Fuel samples above 90o F must be chilled below that temperature to obtain a stable reading.
Q: What other effective tests are there for gasoline?
A: There are several other effective tests to ascertain that the gasoline used by a competitor has not been tainted. Germane Engineering manufactures the Reagent A and D Spot Test chemicals that are effective in identifying several common power additives including propylene oxide, alcohol, masking agents, and paradioxane. Accurate measurement of the density/specific gravity of gasoline is also very effective, although this is most applicable to situations where a racing association has established a 'specified gasoline rule', or at least a short list of 'approved gasolines'. Virtually any chemical when mixed with gasoline will either increase or decrease the density/specific gravity of the sample tested from that of unadulterated gasoline. Precise measurement of the density/specific gravity as allowed by the PFTS Spec. Gasoline Certification Kit will reveal the presence of such additives. When coupled with the use of a good gasoline dielectric meter or the Germane Engineering Spot Tests, the combination of tests will provide an effective cross-verification of purity. Click here to see Gasoline Kits.
Q: Why are two tests better than only one?
A: It is theoretically possible to 'fool' any one of these tests through creative chemistry. It becomes several orders of magnitude more difficult to invent a blend of additives that mirror both the dielectric value, the density/specific gravity, and the dye color of the original gasoline, and still have a gasoline the produces more power than the original unaltered gasoline.
Q: Has the effectiveness of PFTS gasoline certification systems been verified?
A: Yes. One of the major motorsport sanctioning bodies has verified the effectiveness of PFTS fuel certification systems by retaining a mobile test lab utilizing a gas chromatography instrument to analyze fuel samples at their national events. This instrument is so sensitive that it is capable of detecting fuel additives in the low parts per million range. We are pleased to report that our PFTS systems were able to detect every instance of fuel tampering that was detected by the gas chromatography instrument costing more than $20,000.00 and operated by a graduate chemist.
Q: Can PFTS provide assistance in revising racing association gasoline rules?
A: Yes. PFTS can provide sample rule specifications that can be adapted to the specific needs of any racing association.
Q: Is there any one step that a motorsport association can do that will simplify the fuel certification process?
A: Yes, implement a specified gasoline rule. Having to deal with only one brand and blend of gasoline means that fuel inspectors develop an absolute familiarity with the specific characteristics of that fuel, and can use a system such as the FT-K01 Fuel Tester and PFTS Spec. Gasoline Certification Kit to effectively certify the legality of gasoline used in competition.
Q: What is the best way to extract a fuel sample from a race car for the fuel certification process?
A: PFTS recommends that competitors be required to install a valve in a fuel line so that the fuel inspector can be assured that the sample actually comes from the fuel delivery system. An excellent valve, created specifically for this purpose and which allows the fuel inspector to remove a fuel sample without tools or removing a fuel line or carburetor bowl screw, is now available from PFTS. Click here to go to Precision Fuel Sampling Valve page.
Q: Where can I obtain Cyclohexane and Germane Spot Test chemicals?
A: Information on sources for these chemicals is shown on the Supplies page of this website. Click here to go to Supplies page.