Initial VE Table Calculator

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Creating an Initial VE Table for Tuning

This is a tool for establishing a baseline VE table for your tuning efforts with MegaSquirt. It is designed to work in Internet Explorer 6.0, though it may work with other browsers.

Note that an improved VE table generator is built into all recent version of MegaTune, see: www.megamanual.com/mt28.htm#a1tvg

The VE curve is assumed to follow the torque curve (which is not quite right, but close enough for a first approximation). This calculator is based on modeling your engine's wide-open-throttle VE with a quadratic equation of the form

VE = A*rpm² + B*rpm + C
where:

A, B, & C are constants.

These constants are derived from the:

peak torque@rpm,
peak horsepower@rpm,
and the assumption that the peak torque occurs at the VE curve's maximum (i.e. the first derivative with respect to rpm is zero).

An assumption has been made about the VE required to produced 1 lb·ft/ci as well as 1 hp/ci. A further assumption has been made that compressor efficiency=60% for kPa > 100. Finally, a scaling factor has been used to adjust the WOT VE to lower kPa. The factor is derived from examples of working VE tables.

A limit of 5% per rpm bin drop in VE has been applied to prevent the extreme drop-offs that can occur at high rpm & kPa when VE is modeled in this way. As well, all VEs are restricted to be not less than 25% of the highest VE, to prevent unusable idle values.

See the source code for this document for more details on how the calculator works.

This calculator has not been tested on all possible engine combinations and operating parameters.
Use it at your own risk.

1. Input:

Fill in all of the values below (use your best estimate if you don't have measured numbers, but remember your table will only be as good as your estimates, and sometimes quite a bit worse).

Idle RPM is	RPM	300 rpm minimum
Estimated idle vacuum is (the most vacuum you expect from your engine)	"Hg	~24 for stock ~15 for street/strip ~10 for race engine
RPM redline (maximum operating rpm) is	RPM	12,000 rpm maximum
Peak flywheel horsepower is	HP @	RPM
Peak torque is	lb·ft @	RPM
Engine displacement is	liters
Engine maximum boost level (0 for naturally aspirated, max. boost (psi) for turbo/supercharged)	psi	21 psi maximum
Click the "Reset" button to return to default form values.

2. Generate the VE Table in VEX format:

Click on the "Generate VE Table" button:

A 'pop-up' window will open containing the .VEX formatted text (you may have to disable any "pop-up stopping" software). If you get an error alert instead, you will have to correct your input values before continuing.
'Select' entire contents of pop-up window (Click anywhere in the pop-up and press Ctrl-A),
'Copy' entire contents of pop-up window (Ctrl-C),
Open NOTEPAD.exe (under Start/Programs/Accessories/Notepad)
note- WordPad does not work, you need a text editor that preserves the spaces but not the html tags.
'Paste' contents into into Notepad (Ctrl-V),
'Save' as 'YourFile.vex'.

3. Verify and Load to MegaSquirt:

Open MegaTune and 'File/VE Import/YourFile',
Burn the values to the controller when prompted,
Verify that the VE numbers and map/rpm bins are suitable for your engine.
Remember that the table generated is only a starting point for tuning. Using the generated table as a 'final' table under severe operating conditions can destroy your engine. Be sure to follow the tuning guide, and get professional assistance whenever your are not sure.

MegaSquirt^® and MicroSquirt^® controllers are experimental devices intended for educational purposes.
MegaSquirt^® and MicroSquirt^® controllers are not for sale or use on pollution controlled vehicles. Check the laws that apply in your locality to determine if using a MegaSquirt^® or MicroSquirt^® controller is legal for your application.

©2004, 2005 Bruce Bowling and Al Grippo. All rights reserved. MegaSquirt^® and MicroSquirt^® are registered trademarks. This document is solely for the support of MegaSquirt^® boards from Bowling and Grippo.