This is a project I started for my Spec Racer Ford (SRF).  The SRF is a sanctioned SCCA race car and it is controlled by SCCA Enterprise, meaning that very little on the car can be changed.  This is done to ensure that each car is mechanically the same and that every driver/owner has an equal opportunity to compete in the class with the only difference being the driver's personal ability.  

    The SRF uses a 1.9L SEFI Ford engine with a special head and ECU/ECM (Electronic Control Unit or Electronic Control Module) that was developed by Rousch Racing & Engineering. For a small, but not light-weight car, (1670#) it is amazingly fast and agile on the track and turns lap times very close to the more powerful Corvettes and Porsches.  In the Video section you will find a few on-track videos from my car and one short clip made from the National Runoffs races in 2006 for the SRF Class.

    I am currently using my car for a different purpose that isn't sanctioned by SCCA.  Consequently, I need to conserve and reserve my certified engine and drive train for future use.  As a result, I am removing the sealed components, the 1.9L engine and 5-speed transmission, from the car and replacing them with a new 2.0L engine and 5-speed transmission that I built up.

    I will be using a 1997 2.0L SOHC SPI Ford engine that is readily available and almost a direct drop-in with a similar 5-speed manual transmission. 

    The new Ford engine requires an SPI controller to operate a set of secondary valves in the intake manifold that open at a specified engine RPM.  The original 1.9L engine did not have these valves and the 1.9L ECU does not provide a control for this function.  Since I want to continue using my original 1.9L custom ECU it was necessary to build a controller to operate the SPI motor on these new valves.

    This is what brought about the Picaxe project and as it evolved it also became apparent that several other folks may have a similar need or just want a really good digital tachometer, a shift light and possibly some other RPM-dependent outputs.   Accordingly, I decided to pursue the project in two phases.

    The first design is finished and this has turned into a very robust and accurate tachometer that will work on most engines, not just my SRF, with a shift light and an auxiliary open drain output controlled by RPM that can be used for any other purpose.  The next design of the project, and the one I am most interested in, will incorporate three additional displays for Oil Temperature, Oil Pressure, Coolant Temperature and a visual warning system for an out-of-range condition on any of those displays.  Hopefully, all of this will fit nicely into a re-designed and upgraded modern SRF dash.  Future plans include a built-in GPS timing system with a lap recorder and possibly sequential shift lights.

    This site should provide all of the information needed for anyone wanting to build this custom tachometer.  You are welcome to use and download any of the files and PCB artwork for non-commercial purposes but please remember where they came from and give the proper credits where they are due.  

    So lets get started; sit back and enjoy the site.  You can either fast forward to the section of interest or walk thru the site with the "next" buttons so you don't miss the documentation or the links along the way.  Even the most experienced "coders" will find something of interest in the technical documentation.

Copyright © 2006-8 Rex Lantz. All rights reserved
Revised: March 15, 2008