GEMS for 4A-GE

jon hanson redelec at hot.co.za
Mon Nov 25 11:54:59 GMT 1996


At 04:59 25/11/96 EST, you wrote:
>Hi Jon
>
>The GEMS ECU is what is used in Europe for Group A Racing/Rally.
>
>My car is a Corolla GT Coupe (AE86) without any O2 sensor, it use the MAP
sensor
>as  load in the standard ECU and I think the TPS for ACC, but I am not sure.
>

Rene,

I dont know if I can help as you say changing fuel and ignition doesn't help.
However, here's my best shot.         
If the Engine idles and takes throttle when it is still warming up two things
are for sure. firstly the fuelling is enriched and secondly (more than likely)
the ignition is advanced) On the PC side of my system there is a no called
Injection which shows the corrected fuel no (0 - 255) actually going into the
engine and a similar one for the current corrected ign timing.
If I start the engine from cold and watch it warm up while idling the fuel no
slowly decreases (as eng temp and inlet air temp compensation drop due to
the respective increases in temp).
Igntion starts at about 20 degrees (14deg speed + 5deg load related + 2deg 
eng temp related at 18 deg C) 
My reasoning says if your engine runs cold the only diff when warm is 
less fuel and less advance. So by adjusting the two the engine should run.
That as I have learnt is theory and in practice the damm thing doesn't behave
as it should. If you have similar no's monitor them to see if the s/w is giving
you what you asked for. Don't be afraid to goto the current site in the fuel
map and type in a bigger no(in my case +20) and see if engine runs richer
(you can hear it and revs drop slightly) to see if the system is responding
correctly. These things are NOT always bug free.

I have throttle posns 0 to 4 and the posn bewteen columns is divided into
7 finer posns which are used to interpolate between columns (28 posn 
effectively). at small throttle openings the sites are more closely spaced(
(relative to actual physical throttle travel).
the engine idles in col 0. there is a no called Idle Counts(5-15) which governs
when the throttle posn switches to col 1 (some load). I use 10, you just
tickle the throttle and if watching the PC, fuelling jumps immediately to 
throttle posn col 1 ( where the fuelling is increased 10-15%)
This feature is self calibrating but to get it going initially on installation
you have to leave the ign switched on for 30 secs without touching the 
throttle.(a double beep confirms set up). My point is if you dont read
the manual very carefully you miss this point. Now Im sure your system doesn't
work exactly the same way, but maybe buried somewhere in the small print there
may be an answer.
I Dont Know how sophisticated your PC interface is, but generally they let you
check out throttle posn changes with just the ignition on and will
tell you if your sensors are returning reasonable values before starting
while cranking and while actually running.
I'd be very interested to hear if you make any progress.

Reagards Jon Hanson
Johannesburg 
South Africa
















More information about the Diy_efi mailing list