Sorry to ask such a basic question, but does anyone know the thread
 dimensions for the plugs that Mazda uses in the 13b, I'm looking to
 make
 an
 adapter for a Fluke PV350 pressure transducer for a compression
 tester.
 Combined with a peak hold meter it would make a great tool for the
 shop.
 Thanks,
 C. Smith

 Larry sent Craig a modified spark plug that will do the job.

 This little $50 CPU board I am getting from FreeScale would make a
 good
 compression tester. It talks to a PC through a USB cable and it has
 a bunch of analog to digital converters on it. All you need is a
 pressure sensor and a bit of simple asm software to read it
 and send the compression data to the PC over and over again. One
 can get a sample every millisecond while the engine is turning over
 with the starter. (.001 second) I'll know more in a couple
 of days as I will have one up and running.

 It can also study the tuned intake manifold in real time as Matt
 suggested by putting in a couple of tiny pito tubes and pressure
 sensors on either end of the intake runner. Sort of like
 a $10,000 storage oscilloscope only better. Fascinating stuff.

 I am going to get it working on my Linux EeePC 1000 solid state drive
 for a portable data acq system that will work in airplanes. There
 are all sorts of things that can be done with that including cooling
 system pressure measurements. Of course a whole raft of engine
 parameters
 can also be measured and recorded.

 If you want to do an EFI system with one of these boards I recommend
 the $75 one with a lot of I/O. Use two and a relay for redundancy
 like Tracy does.

 A few years or months ago we were thinking of doing the same thing
 with a PicAxe but PicAxe did not quite have their act together.
 FreeScale (Motorola) has spent an order of magnitude more money on the
 software for this board so I expect it will work much better.
 It will be a lot faster. PickAxe was programed in BASIC which is
 very very easy to learn but I already know 68xx asm language :)
 <Free-scale-BR8BITLOWEND.pdf

 Paul Lamar

Paul -

I mentioned an alternative to Motorola microcontrollers (MCUs) over a
year ago.  I know that we could spend eternity debating the merits of
various chips, but I REALLY liked the entry-level development board -
$20 on a usb stick for complete development hardware and software.
You gotta admit, that makes it really easy (and CHEAP) to "stick your
toes in the water".  I have several now, including an RF kit.

The TI chipset was recommended by a friend (who is now on this list)
that used to develop products with the Motorola chips.  The TI MSP430
series is a:
- really low cost (few bucks per chip)
- cheap and easy to test drive ($20 USB-stick-development-kit)
- scalable (up to dozens of I/O pins, ADC, DAC, PWM, watchdog, etc.)
- relatively fast - 16MHz
- 16 bit RISC architecture (it is WAY more elegant than Motorola's)
- ULTRA low power (microamps)

I couldn't resist.  Check it out:
http://www.ti-estore.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=EZ430-F2013

http://en.wikipedia.org/wiki/TI_MSP430

Enjoy.

-Vince Orton


I am not going to learn a new instruction set for the sake of a few bucks.
One computer is more or less the same as any other computer when it comes
to these simple embedded systems. What is far more important is the programming
software and support you get from the vendor. Motorola has been in the biz from
the get-go back in the 1970's. The 6800 was one of the very first chips.
The instruction set for the 68xx chip has changed little in the past 35 years.
There are tons of code and app notes out there on the 68xx.

However you are welcome to do it anyway you wish of course. I am going to explain
and publish everything I do every step of the way. Hopefully someone will learn
enough asm to do it themselves. Once you have the source code and something goes
wrong you have the where-with-all to figure it out and fix it.

Also the early Megasquirt uses the same Motorola part more or less and the asm source
code is published for that as well. If in doubt see how they did it. Here it is
in pdf form. No point in reinventing the wheel.

Paul Lamar