Research Papers: Internal Combustion Engines

The Effects of Intake Plenum Volume on the Performance of a Small Naturally Aspirated Restricted Engine

[+] Author and Article Information
Leonard J. Hamilton, Jim S. Cowart, Jasen E. Lee, Ryan E. Amorosso

 U.S. Naval Academy, Annapolis, MD 21402

J. Eng. Gas Turbines Power 133(1), 012801 (Sep 24, 2010) (7 pages) doi:10.1115/1.4001071 History: Received September 23, 2009; Revised September 25, 2009; Published September 24, 2010; Online September 24, 2010

Intake tuning is a widely recognized method for optimizing the performance of a naturally aspirated engine for motorsports applications. Wave resonance and Helmholtz theories are useful for predicting the impact of intake runner length on engine performance. However, there is very little information in the literature regarding the effects of intake plenum volume. The goal of this study was to determine the effects of intake plenum volume on steady state and transient engine performance for a restricted naturally aspirated engine for Formula Society of Automotive Engineers (FSAE) vehicle use. Testing was conducted on a four cylinder 600 cc motorcycle engine fitted with a 20 mm restrictor in compliance with FSAE competition rules. Plenum sizes were varied from 2 to 10 times engine displacement (1.2–6.0 l) and engine speeds were varied from 3000 rpm to 12,500 rpm. Performance metrics including volumetric efficiency, torque, and power were recorded at steady state conditions. Experimental results showed that engine performance increased modestly as plenum volume was increased from 2 to 8 times engine displacement (4.8 l). Increasing plenum volume beyond 4.8 l resulted in significant improvement in performance parameters. Overall, peak power was shown to increase from 54 kW to 63 kW over the range of plenums tested. Additionally, transient engine performance was evaluated using extremely fast (60 ms) throttle opening times for the full range of plenum sizes tested. In-cylinder pressure was used to calculate cycle-resolved gross indicated mean effective pressure (IMEPg) development during these transients. Interestingly, the cases with the largest plenum sizes only took 1 to 2 extra cycles (30–60 ms) to achieve maximum IMEPg levels when compared with the smaller volumes. In fact, the differences were so minor that it would be doubtful that a driver would notice the lag. Additional metrics included time for the plenums to fill and an analysis of manifold absolute pressure and peak in-cylinder pressure development during and after the throttle transient. Plenums below 4.8 l completely filled even before the transient was completed.

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Figure 2

Injector calibration at fuel pressure=4.0 bars

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Figure 3

Spark timing curve

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Figure 4

Torque-rpm and plenum volume sweep

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Figure 5

Comparison of torque between smallest and largest plenums tested

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Figure 6

Power-rpm and plenum volume sweep

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Figure 7

Comparison of power output between smallest and largest plenums tested

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Figure 8

Comparison of normalized integrated area under torque and power curves for various plenum sizes

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Figure 9

Plenum volume sweep at 9500 rpm

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Figure 10

Normalized plenum pressure for various plenum volumes during intake valve open event for cylinder No. 1

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Figure 11

The effect of normalized intake pressure on volumetric efficiency at 9500 rpm

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Figure 12

Transient response for 1.2 l plenum

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Figure 13

Effect of plenum volume on the gross indicated mean effective pressure development

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Figure 14

Effect of plenum volume on the peak in-cylinder pressure development

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Figure 15

Cycle-resolved MAP development

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Figure 16

Manifold pressure development during throttle transients

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Figure 17

Time to fill plenum during the 60 ms throttle transient for various plenum volumes



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