Test report for the Tuneable Accumulator

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Milo Flowers
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1 Tuesday, February 15, 2005 Test report for the Tuneable Accumulator Summary The purpose of the test was to achieve 2 objectives: a. To endurance cycle the accumulator to determine the seal integrity (leakage) in dynamic & static over-pressure and b. To measure dynamic performance after the endurance portion of the test was finished. Author and data collector: Michael Swann. Assistant: Doug Petterson. Start/finish date: Feb. 9 th - Feb. 11 th, 2005 Equipment list, See system diagram for further clarification gallon dune -buggy gas tank. 2. Bosch EFI fuel pump, Porsche turbo 930 application. 3. Aeromotive EFI fuel regulator. 4. SAIS, Inc psig pressure transducer. 5. Edelbrock Qwikdata Basic data acquisition unit. S.N Ball valve for bypass percentage control. 7. NOS Cheater solenoid, # Nitrous fuel simulation Jet #60 (about equal to a 400 hp shot at 45psig) vdc drycell battery. 10. B&K signal generator. 11. Battery charger (not shown). 12. Laptop PC gallons of paint thinner.

4 To get an understanding of the nature of the test, refer to diagram #1, graph data. Note: the Qwikdata has graphical display curve averaging and has errors in the graphical data shown. In order to zoom in on the data for further review, you can download the actual data and setup files from the download section of the website. The Qwikdata application can be downloaded at Diagram #1, Graph Data is a Qwikdata data set sampling at 50 sample per sec. per channel. The purple trace is the voltage to the solenoid and the green trace is the fuel pressure. Point markers are as follows: a. Solenoid closed, no voltage. b. Onset of accumulator displacement, accumulator is increasing volume. c. Solenoid opens, voltage present. d. Onset of flow to nitrous flow control jet. e. Onset of accumulator displacement, accumulator is decreasing volume. f. Accumulator is fully discharged. g. Fuel pressure returns to baseline pressure. Part A. Endurance Test: The endurance test was performed to determine if the accumulator was going to leak internally. The accumulator was designed to have low internal friction and we wanted to make sure the piston seal was going to perform properly. Due to the nature of an accumulator, there is low differential pressure across the seal and sealing occurs primarily due to o-ring compression and surface finish. Referring to diagram #1 graph data: the duty cycle was set up to achieve maximum accumulator internal displacement. This proved to be about 6 seconds per cycle. The test was allowed to run for 3 days continuously, amounting to 43,200 cycles. After the test, the accumulator was disassembled and the fluid volume that had made it across the o-ring seal in to the pre-charge chamber measured 4 cu-cm. Part B. Dynamic test: This test has 4 parts: a. 6 second duty cycle test with the accumulator removed. b. 6 second duty cycle test with the accumulator present. c. 20 Hz duty cycle test with the accumulator removed. d. 20 Hz duty cycle test with the accumulator present.

5 The 6 second cycle tests are intended to show the before & after pressure characteristics of the system and response time characteristics of the system. The 20 Hz before & after tests are to intended to show the pressure control characteristics of the system simulating EFI injector firing and/or a progressive timer nitrous function. NOTE: After the endurance testing, the Qwikdata s internal power supply failed, hence we were unable to take the dynamic test data we wished to take. Analyzing the data from the initial endurance test, the following information is presented: Note: the Qwikdata has graphical display curve averaging and has errors in the graphical data shown. In order to zoom in on the data for further review, you can download the actual data and setup files from the download section of the website. The Qwikdata application can be downloaded at a. Point B, this is where the piston starts moving; 38psig, 3 psig above the pre-charge pressure. b. Point C to Point D, is the flow latency from when the voltage is applied to the solenoid coil to when the fuel actually starts flowing though the solenoid. This is measured at 20 msec. c. Point D, This is where the accumulator started discharging, at 35psig. d. Point D to Point E, is the response time of the accumulator. This is measured at less 20 msec. e. Point E to Point F, is the discharge time of the accumulator. This measure amount of time is 1.74 seconds while flowing into a #60 fuel jet (400hp shot). f. Point F to Point G is after the accumulator is discharged and the fuel pressure returns to baseline pressure. This occurs in 40 msec.

6 CONCLUSIONS All in all, the test went quite well. We were disappointed that the Qwikdata failed, not allowing us to take the final dynamic data. We felt that there were benefits to be measured by the wearing in of the o-ring after the endurance test in terms of reduced running friction. Furthermore, the dynamic data that we do have is skewed due to the fact that the sample rate is only 50 samples per second per channel. We intended to perform the dynamic testing with the sample rate increased to 250 samples per second per channel. We intend to finish the dynamic portion of the test and report this test at a later date. We are making the following conclusions for now: 1. The accumulator will give desirable fuel pressure control on an EFI and/or nitrous enhanced system. 2. The accumulator piston seal is adequate and should give long life. 3. The accumulator should perform as predicted in the tunability tables show elsewhere in the documents pertaining to the accumulator. 4. There is an o-ring breakaway friction associated with getting the piston to move. 5. There is a good possibility of diminished accumulator performance in low-pressure applications of less than 7 psig fuel pressure. 6. As a final test, we static pressure tested the accumulator assembly to 300psig, then dropped it on concrete from waist level. It is safe to say that the burst pressure is higher than 300psig. Disclaimer Racing is a dangerous sport. If you engage in racing or any activity described in this document, you are acknowledging and assuming responsibility for all risks incurred. The accumulator is not EPA certified and are not to be used on any emission controlled, street driven vehicle. The information herein is for reference only and is not an authoritative document. We are not liable for misuse, accidents, loss of property, personal injury or death.

7 SYSTEM PICTURE

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