Injector firing points
Nicholas Parker
NRPARKER at XTRA.CO.NZ
Wed Aug 11 02:58:05 GMT 1999
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Hi,
I've sort of jumped the gun here.
I have already written the guts of an open loop sequential fuel =
injection and ignition unit in assembler for an 80c552 (8051 variant), =
uses map , rpm , coolant temp so far. I've only tested it with a scope =
on a bench
(along with pulse inputs and a MAP sensor..)
Now I have an Infineon (Siemens) developement kit for the 167 mpu (16 =
bit, all features and instructions you can possibly imagine + a big =
errata sheet ahem....) and I'm starting to code an ecu in C because, =
shit its easy to do floating point maths! and plus the 167 is so fast =
you can write in C and not be hugely clever (Microsofts motto ?) like =
when you're using an 8051 based slug..not that you need it. My =
application is sequention injection in a 4 cyl, my question is; When do =
injectors fire ? What I think I know:
The injector in question should fire after the appropriate inlet =
valve(s) are open, and subtract from this position, the time required =
for the injector to open etc..problem is I have heard that injectors =
stay on from 6- 8 ms.
How can this be ? At 7500rpm, you've got only 4ms / 180degs of crank =
rotation ? 8ms sounds too much,
even when I imagine the momentum of the intake air stopping 'itself' it =
coming out the intake valve when the piston is beginning to compress the =
mixture...?
Anyone know a very ugly approx for injector pulse width, based on =
cylinder size, inj flow rate, and manifold pressure...If I wasn't lazy =
I'd make and rig up a 'logger' to my car....
Also do most factory cars (say 4 cyl for this question) have a =
distribtor sensor that gives a pulse for each cyclinder when its say 50 =
degs before tdc , so that only a delay 0- 50 degs (for example) is =
required to generate all possible igntion firing points ? (This is what =
I implemented in my 80c552 system). I have got such a
distributor off of a friend, but unfortunately, no info as to its angle =
relative to cam/crank.
Thanks,
Nick Parker.
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<DIV><FONT size=3D2>Hi,</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=3D2>I've sort of jumped the gun here.</FONT></DIV>
<DIV><FONT size=3D2>I have already written the guts of an open loop =
sequential=20
fuel injection and ignition unit in assembler for an 80c552 =
(8051=20
variant), uses map , rpm , coolant temp so =
far. </FONT><FONT=20
size=3D2>I've only tested it with a scope on a bench</FONT></DIV>
<DIV><FONT size=3D2>(along with pulse inputs and a MAP =
sensor..)</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>Now I have an Infineon (Siemens) developement kit =
for the 167=20
mpu (16 bit, all features and instructions you can possibly imagine + a =
big=20
errata sheet ahem....) and I'm starting to code an ecu </FONT><FONT =
size=3D2>in C=20
because, shit its easy to do floating point maths! and plus the 167 is =
so fast=20
you can write in C and not be hugely clever (Microsofts motto ?) like =
when=20
you're using an 8051 based slug..not that you need it. =
</FONT><FONT=20
size=3D2><FONT size=3D2>My application is sequention injection in a 4=20
cyl</FONT></FONT><FONT size=3D2>, my question is; When do =
injectors fire=20
? What I think I know:</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=3D2>The injector in question =
should fire after the=20
appropriate inlet valve(s) are open, and subtract from this position, =
the time=20
</FONT><FONT size=3D2>required for the injector to open etc..problem is =
I have=20
heard that injectors stay on from 6- 8 ms.</FONT></DIV>
<DIV><FONT size=3D2>How can this be ? At 7500rpm, you've got only =
4ms /=20
180degs of crank rotation ? 8ms sounds too much,</FONT></DIV>
<DIV><FONT size=3D2>even when I imagine the momentum of the intake air =
stopping=20
'itself' it coming out the intake valve when the piston is beginning to =
compress=20
the mixture...?</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=3D2>Anyone know a very ugly approx for injector pulse =
width, based=20
on cylinder size, inj flow rate, and manifold pressure...If I wasn't =
lazy I'd=20
make and rig up a 'logger' to my car....</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=3D2>Also do most factory cars (say 4 cyl for this =
question) have a=20
distribtor sensor that gives a pulse for each cyclinder when its say 50 =
degs=20
before tdc , so that only a delay 0- 50 degs (for example) is =
required to=20
generate all possible igntion firing points ? (This is what I =
implemented=20
in my 80c552 system). I have got such a</FONT></DIV>
<DIV><FONT size=3D2>distributor off of a friend, but unfortunately, no =
info as to=20
its angle relative to cam/crank.</FONT></DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV><FONT size=3D2>Thanks,</FONT></DIV>
<DIV><FONT size=3D2>Nick Parker.</FONT></DIV></BODY></HTML>
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