For your information, changes were last made on: 22 July 2005 04:34 -0400
The Lotus Esprit 4 cylinder uses a GM (also Vauxhall, Opel or even Holden depending what country you live in) Delco ECU which controls all things to do with the engine, A/C and Fans.
My ECU is labelled up as follows:
| No: |
86CAKDM643193757 |
| Service ID: |
01228708 |
| EPROM ID: |
16252789 |
| Prog ID: |
0x74, (116d) |
P.S. If you own a V8 Esprit, scroll to the bottom of this page!
Exploring The ECU Tables
Well, I took the decision in January 2000 that I would remove the MemCal from my Esprit and disassemble the code in it. After many, many hours I'm approximately 90% finished. You wouldn't believe how complicated an Engine Management System has to be just to emulate a Carburettor.
Within the GT3 MemCal there are 5571 lines of calibration data and 12684 lines of assembler code. Because the code is executed sequentially, there are many different cryptic status bits within the code to create, in effect, a state machine. The execution path of the code depends entirely on these bits.
Another point: the GM ECUs are programmed procedurally. However, this is not the best way to code a CPU with limited calculation power. For example, in one of the I/O sections, there is a block routine that sets-up the I/O device, hangs around for approximately 32 cycles and then reads the device. If I only had an 8-bit CPU, I'd go and do something else with these rather than hang around wasting them.
TunerCat have a wonderful tool to allow you to explore your ECU and, more importantly, alter the various tables and mappings within it, i.e. boost. However, you need to have a definition file for your particular ECU to allow you to do this. Over the past couple of weeks I've been building such a file, which is now finished. I'm charging £500.00 (GBP) for this to compensate for the considerable time that it has taken me to produce it.
Anyhow, enjoy what I've got so far and keep checking for updates!
Andy's ECU Tables **UPDATED 29th August 2000 **
Communicating With the ECU (FreeScan)
It's really difficult making a project accessible to as many enthusiasts as possible. I'm sure everybody who visits this page would like to give the software a try-out. However, with most things in life, there is a certain amount of work that needs to be done to achieve your goals.
Writing the software is no easy task. It takes many hours and drinks to turn an experimental, personal tool into something that a wider audience can use and appreciate. Also, I know that many features will be requested and have to be evaluated before they can be coded. The evaluation also includes whether I can find the time to do it.
OK, now that I've got that off my chest, here's what you've got to do! Click on the links to get to the place you're after:
RS232 connector summary page.
Sample Esprit Log Files from FreeScan
A few people have asked me to provide example logs from FreeScan, well here they are! Note that these were done with a beta version of FreeScan; they've an incorrect Baro reading.
ecu/logs/coldstart150_1.zip
Demonstrating a full warm-up from cold to operating temperature.
ecu/logs/Warmstart150_1.zip
After waiting for around 30 minutes from the first cold start, my Esprit is warm started and then took on a drive.
ecu/logs/0to60_150.zip
Couldn't resist this! After performing the above runs, I do a 0 to 60mph run in the Esprit. You'll notice that it's done is around 5 seconds, all this with a gentle take-off (around 3000rpm) and no overboost.
Tuning
Other 
ECU sites
I had a trawl around the net and came up with some interesting links. These people have GM ECU equipped cars and have written their own tools. This is where I'm getting the majority of my information from. From these sites, you will also come across many companies who sell commercial PC-based systems.
Note: *** None of these tools will work with an Esprit nor Elan! ***
- Dave's PCCommECU
He has written a utility for a 1995 Camaro with auto-transmission. I gained my initial knowledge from here when he used to publish the source-code for his ALDL program. - Andrew Mattei
Provides some interface drawings and other information on the ALDL format. - Peter Gargano
Details of hardware interfacing to the ALDL port. Some links as well. The first site I've seen that's got circuit diagrams in colour! - CarBytes
A fully-configurable, ALDL reader program by Paul Blackmore. - Project Electronic Diagnosis
This is a great site.... it's in Russian! Some of the links are understandable though. - Carsten "Russ" Meyer
Some information here on his Camaro Z28 respectively 1227730 ECM. - ECMGuy
Great info, also has info on OBD-II.
It is with sadness that Ward Spoonemore passed away on 4th June 2000 after a long illness. Ward was known as ECMGUY and was respected by a lot of people. - TunerCat
Tuner Cat has generated a series of software tools to help you explore your GM ECM or PCM. This is what I am using to tweak the Lotus ECU. - http://www.cruzers.com/~ludis/
Ludis Langens' home page. Ludis has lots of information if GM ECUs, including circuit diagrams which he has created himself. - TTS Power Systems
Gary Harris has written Windows software for OBD1 GM ECU's. He makes the software available for free download to encourage its adoption. It will freely playback any recordings, but has the "free" recording capability limited to 5 runs for evaluation purposes. - Syclone and Typhoon
Various utilities. - http://www.3wad.net/efi/prod/ew.htm
EPROM Wizard is a commercial, customisable piece of software for ECU tuning. - http://www.thrasher-ep.com/Chips_htm/cal_hints.htm
This is well worth a look. Thrasher Engineered Performance's "Calibration Secrets and Tuning Hints". - http://www.winaldl.webhop.net/
160 baud stuff. - http://www.seanster.com/scantool/
This was the first page I ever accessed concerning ECU stuff. The original link went dead but now I've found another one.
Bits and Pieces
OBD-II Esprit V8 Information
For later V8 models, these use an OBD-II interface.
There is a discussion list of OBD-II interfacing on the E-Groups list. It's mainly for Audi/VW interfacing.
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Elan M100 Information