September 10, 2000

 

Volumetric Efficiency
How does your car stack up?

In our previous article we guided you through the process of calculating the volumetric efficiency of our LS1.  But how does your car stand up against everyone else's?  Through the help of some fellow LS1 enthusiasts we have put together a small database of a wide variety of LS1's.  This list includes the Icon Twin Turbo Stage I, Agostino Racing Engines Stage II heads/cam package, along with several other cars including the LS1 Hot Cam.

Taking a closer look at the findings

We decided to take a closer look at the volumetric efficiency of our engine at different rpm ranges.  We took a log file using Auto Tap and placed the data in a spreadsheet.  From this data we were able to calculate the volumetric efficiency at each data point.  We immediately noticed that the volumetric efficiency varied enough through the rpm's to raise an eyebrow.

The following run was made in second gear.  We have the following performance modifications:  free ram air, K&N air filter (dirty), whisper induction lid, hyper tech power programmer three, and exhaust cut out.

Note:  Both flow rate columns might contain slightly different numbers compared to working it out by hand as shown "Volumetric Efficiency:  Calculating your cars volumetric efficiency".  The spreadsheet carries the calculations out past 9 significant figures.  This is nothing to be alarmed about.

Engine Speed (rpm) MAF Air Flow Rate (lb/min) Intake Air Temp (F) Density Actual Flow Rate (ft3/min) Theoretical Air Flow Rate (ft3/min) V.E. (%)
1236 1.19 72 0.0746 15.952 123.743 13%
1468 1.19 72 0.0746 15.952 146.970 11%
1674 1.18 72 0.0746 15.818 167.594 9%
1865 1.31 72 0.0746 17.560 186.716 9%
2072 2.51 72 0.0746 33.646 207.440 16%
2323 3 72 0.0746 40.214 232.569 17%
2159 4.05 72 0.0746 54.290 216.150 25%
2388 5.58 72 0.0746 74.799 239.076 31%
2298 7.12 72 0.0746 95.442 230.066 41%
2562 8.44 72 0.0746 113.137 256.497 44%
2602 8.37 72 0.0746 112.198 260.501 43%
2784 8.66 72 0.0746 116.086 278.722 42%
2917 9.58 72 0.0746 128.418 292.038 44%
3058 9.8 72 0.0746 131.367 306.154 43%
3198 18.39 72 0.0746 246.515 320.170 77%
3703 19.98 72 0.0746 267.828 370.729 72%
3973 23.88 72 0.0746 320.107 397.760 80%
4248 26.9 72 0.0746 360.590 425.292 85%
4524 28.15 72 0.0746 377.346 452.924 83%
4744 26.68 72 0.0746 357.641 474.949 75%
5022 31.64 72 0.0746 424.129 502.781 84%
5289 32.18 72 0.0746 431.367 529.512 81%
5506 33.37 72 0.0746 447.319 551.237 81%
5791 31.07 72 0.0746 416.488 579.770 72%
5993 34.32 72 0.0746 460.054 599.994 77%
6172 33.53 70 0.0748 448.262 617.914 73%
6300 34.32 70 0.0748 458.824 630.729 73%

You have read that it is generally accepted that most fuel injected cars have a eighty-percent (80%) volumetric efficiency rating.  Look at the table above you can quickly see that our car is only falls in that range between 3900 and 4600 rpms at wide open throttle.  I do not know how websites and magazines come up with that figure of eighty-percent but it seems odd that my car operates that that efficiency less than 13% of the used rpm range at wide open throttle.

Power Adders

A set of ported heads, higher lift cam, turbos, and superchargers all increase the volumetric efficiency of an engine.  Common sense dictates that the more air that that is pushed into the cylinders, the more force that is supplied after ignition because there is a greater supply of oxygen to ignite.

 

 

- Eric Barger

Editor:  Kelly Barger


Works Cited

1.  Deskins, Tom.  Interview.

2.  Vizard, David. How to Build Horsepower. Volume 2.  Page 60.

3.  Green, Don, and Robert H. Perry.  Perry's Chemical Engineers' Handbook.  6th edition.  New York:  McGraw-Hill, 1984.

 

Web Author: Eric Barger  help@installuniversity.com
Copyright 1999 - 2002  Eric Barger.  All rights reserved.
Revised: June 07, 2007.