Re: PI closed loop algorithm for 1227747 ECU?

[Squash <realsquash@yahoo.com>]

This is interesting as this exact thing is happening to me, popping on decel, and the others.  The
idle I can tolerate, the BLM only moves a couple of points if it sits for a while.  It even gives
a pop when the fuel c/o happens above 3000 rpm.

I looked through the anht hac and the "proportional gains" table says it isn't used in anht, and
the only other similar things I find start at 1e6.  Excuse my ignorance, but are these the
equivalent values to the 747 ones you outlined below?

Thanks,
Squash

--- Scott Lundahl <scott@lumenetics.com> wrote:
> I've out of town and away from my e-mail, but I wanted to say thank you for 
> the information.  I've burned an EEPROM as follows:
> 
> Prop tables at $4a8 & $4c7 have been reduced by 2/3 (since the 
> displacement, and hence fueling requirement, of my engine is about 2/3s of 
> the GM unit).  I have suspected the PI overshoot you mentioned for some 
> time (the O2 cross count frequency has been well over 10 Hz).
> 
> Increased $48f int time delay table by 1.5 (since the the distance from the 
> TBI to the O2 sensor in about 50% longer than a stock GM V8 - those 4-2-1 
> headers are quite long)
> 
> Set $2f9 to 1
> 
> Set IAC table at $5c7 up + 1
> 
> Enlean table at $3fa to $80 (go big block)
> 
> So far it seems to run perfectly.  No trace of surging or other 
> badness.  Tailpipe backfire virtually eliminated (pleasant little burble 
> now)!  I haven't put on many miles, so things may converge to other values 
> where things don't work as well as time goes on (this has happened 
> before).  The idle still hunts a bit, so I'll work on that.  But it looks 
> good so far.
> 
> Thanks again,
> 
> Scott
> 
> PS - As for the distributor, I'm working on that too.  It turns out that an 
> early 70's large cap GM HEI unit will fit this engine if you change the 
> drive gear.  I have one with the correct gear.  I've also figured out that 
> the ECU-controlled ignition module from a 90 Corevette will fit in this 
> distributor (with a little re-tapping of mounting holes).  As near as I can 
> tell, this module should talk to the '747 (alternatively I could mount the 
> "correct" module outboard of the distributor but that would look 
> messy).  The ESC and knock sensor modules are a different story.  I know 
> that each set is "tuned" for the engine block application.  The aluminum 
> block on my engine will have totally different characteristics from that of 
> a stock GM unit.  Is it possible to use the ECU controlled spark without a 
> knock sensor (assuming one is careful about advance curves, etc).
> 
> 
> At 11:01 AM 7/4/00 -0400, you wrote:
> 
> >For the cl idle, reduce the prop gain at 0x2f9 to 1. Might also
> >want to go to a larger vac line to the map. A 1/4" line helps
> >when engine is cam'd.
> >
> >If the idle is osc due to iac movement, increase (slightly!), the timer
> >vals at 0x5C7 through 0x5CA.
> >
> >Should have a GM O2 sensor, the response time matches the
> >the PID loop better.
> >
> >Prop gains. May need to be reduced, tables 0x4A8 & 0x4C7. Prop
> >gains are interesting, they always work to bring the O2 val in the
> >opposite direction, it lean, prop adds fuel, if rich, removes fuel.
> >Sometimes it can be too drastic, causing over and under shoot.
> >
> >If backfire is through exhaust, there is a decel enleanment table
> >at 0x3FA, big blocks have some huge numbers there. Don't
> >worry about the int and blm's moving a bit, stock engines are
> >the same way.
> >
> >BobR.
> >
> >Might be worth getting an EST distrib in there. The other
> >half of the drivability is in the SA.
> >
> >Scott Lundahl wrote:
> >
> > > Hello everyone.  I'm new to the list and this is my first post.  I'm doing
> > > an FI addition to a 1980 Triumph TR8.  This is the car with the GM 215 (3.5
> > > liter) cid aluminum block V8 derived Rover engine.  OEM fueling for this
> > > (49 State) car was via twin Zenith carbs in the usual British style.  The
> > > California version had Lucas (really Bosch L Jetronic) port fuel injection.
> > >
> > > On my car, the original Zeniths were later replaced by a good old low tech
> > > Holley 4 barrel and Edelbrock Performer manifold.  I added a tame to medium
> > > cam and headers to perk things up a little.  This setup ran OK, but lacked
> > > many of the usual amenities such as a choke that worked properly, idle
> > > speed control (yes this car has A/C) and so on.  It was also OPEC's 
> > dream car.
> > >
> > > So I decided to add non-eom FI to the car (the eom systems have no
> > > performance potential and are incredibly expensive).  I chose a TBI system
> > > using a 1227747 (C3 series) ECU because it interfaced easily to the current
> > > setup in the car.  The C3s are also easy to manipulate via EPROM (which is
> > > good because I have burned many so far).  This system is driven by the
> > > stock (non-ESC) distributor via a buffer.  A heated O2 sensor is on the
> > > header collector (4-2-1).
> > >
> > > Anyway, I have the system in and dialed in to the point where it will run
> > > with perfection when I set the ECU to run in Open Loop mode.  It will run
> > > well with the fuel map set for slightly lean or slightly rich.  However,
> > > when I set it to run Closed Loop, the system develops a light throttle
> > > cruise surging (very annoying) and backfire on decel (I can almost
> > > eliminated the backfire via the decel params).  It also wants to oscillate
> > > at idle.  The BLMs tend to wander all over the place.
> > >
> > > Since things seem to run OK in Open Loop when fueling is slightly rich or
> > > slightly lean, running at stochiometric does not seem to be the problem
> > > (some engines just don't like to run there).   There must be something
> > > about how C.L. operation is accomplished that is causing an issue (check my
> > > logic here).  Therefore, I suspect that the PI parameters (gain factors,
> > > time delays, etc) may not be correct for this engine (this is somewhat
> > > plausible when you consider that this ECU was originally setup to operate
> > > with an engine 50% larger or more than mine).  Thus it operates at a point
> > > that is close to instability in C.L.  So, I have two questions.
> > >
> > > Does anyone have any suggestions / experience / solutions with a similar
> > > symptoms?
> > >
> > > Does anyone have information on how the PI algorithm operates on this
> > > ECU?  I have seen such details of how the spark control algorithm works.  I
> > > also have the detailed hack of the type $42 (this is an incredible piece of
> > > good work) but the comments in the PI section aren't quite detailed enough
> > > to reverse engineer what's going on.
> > >
> > > Any help/suggestions would be greatly appreciated.
> > >
> > > Thanks,
> > >
> > > Scott
> > >
> > > 
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