Re: Idle speed/Circuit Tuning.

["therealdmcvegas" <DMCVegas@xxxx>]

Alrighty then. let's go ahead and answer two seperate posts with one,
since both are so closely related in both content and demeanor.

--- In dmcnews@xxxxxxxxxxxxxxx, "checksix3" <jetjock11@xxxx> wrote:
> Thenn something is wrong with your car and you've compensated for it 
> by using the manual idle.

Wrong! My idle is perfectly fine, save for the stalling without the
Microswitch being properly tripped. A few months back, my car came out
of the shop with a set of fresh injectors, injector seals, and a CO
adjustment. I have NOT opened the idle screws at all. I cannot as ALL
3 HAVE SNAPPED OFF! Don't assume.


> The CIS has nothing to do with this.

Absolutely correct! Why? because we're discussing the Idle Speed
Circuit. Not the Continuous Injection System that controls fuel
delivery, and manages the air/fuel ratio. Save for the Control
Pressure Regulator opening when the ambient air temperature is cold to
simulate a choke condition by enrichening the air/fuel mixture, the
CIS system has absolutely NOTHING to do with Idle Speed Control! Yes,
idle can techicly be affected if the engine is not properly tuned, but
that shouldn't be an issue, as it is expected that proper mantainance
of the motor should always be the #1 priority.


> You clearly have something way out of whack and you're going about 
> fixing it the wrong way. Also, your statments imply you don't have a 
> full grasp of how the CIS system operates.

The only problem that I've had is what I've stated (and I will address
that below). But on the other hand. Duh, gee George. I guess I was a
smart enough ta figure out da difference between da K-Jetronic system,
and da Idle Speed Circuit. I wuz, I wuz! M-O-O-N, That spells CIS! :p

> The Lambda will cause a very 
> minor idle hunt of less than 50 rpms if everything is setup 
> correctly, or none at all if you chose to set it another way.
> All the symptoms you described indicate other problems, your car 
> should do *none* of those things.

Right. But when an engine is out of tune, or has a sudden, massive
power drain, the CIS doesn't always get to respond quickly enough.
Couple this with the extreme severity of how the Idle Speed ECU
correct the engine speed, and engine speed fluctuation becomes
amplified far worse than it would have been, had the motor just have
been using the manual setting as a primary controler of idle speed.


> >By setting the initial Engine Idle Speed manually with the 3 brass
> screws, we create a "pillow" of sorts for the engine speed. The idle
> should stay far more stable.<
> 
> Yes, thats true (see below) but you're not setting it up correctly if 
> you use the brass screw to do that. It will work however but you 
> shouldn't be using the balancing screws at all.

Once again, you're right. You shouldn't have to touch the screws at
all, assuming that the idle speed circuit is flawless. However, it
isn't. It may be closed loop, but it can recieving nonliner input that
will result in radical oscillations. Specificly the the WOT/Choke
condition that causes the severe fluctuation of engine idle speed. The
only positive side of this is you basicly get the physical equivalent
of a "Check Engine" light. Poor engine performance (acelleration/gas
milage), and the LAMBDA lamp are both physical indicators to notify
someone that something is wrong with the motor. In the mean time,
additional wear and tear on the alternator by the regulator forcing
full output at a low speed, and then having to work overtime by
replenishing the deminished charge the battery had to endure. This can
become even worse on cars such as mine where additional loads have
been placed on the electrical system. Increased consumption from
brighter headlights (65 watts each, and I use my high beams
frequently), larger, more power demanding sound system, 3rd brake lamp
that added 4 additional bulbs, various cigarette lighter accessories,
etc... With these acessories in place, the RPM dip becomes greater
when decellerating the motor.


> The CIS valve sets to it's basic position as soon as you turn the 
> ignition on, before you start the engine, as long as the idle switch 
> is made. It only beccomes closed loop after ignition/tach impulses 
> arrive.

And what then is that position? It seems on my car, that without the
Idle Speed Microswitch engaged, it is closed. Which of course would
explain why the DeLorean is the only fuel injected car I've ever come
across that requires you to hold down the acellerator when cranking.
Hmm...


> >>Now, if there is any downside to utilizing the Manual portion of the
> Idle Speed Circuit, then please, let me know. I myself really don't
> see any harm in using it. Only benefit.<<
> 
> No harm but as you say, you shouldn't need to do it. There is no 
> benefit to setting idle speed manually. It has no "improvement" over 
> a properly tuned CIS.

True. But as the old saying goes, "If a frog had wings, he wouldn't
bump his ass a-hoppin'." In other words, it's not nessisary, but it
would greatly help. The system does have a flaw potential. Perfect
example: Your own words.
<SNIP>
> But I'll 
> agree a higher idle is beneficial at times. My ECU has been modified 
> to increase idle rpm to 950 when the headlights, A/C or cooling fans 
> are on.
<SNIP>
If what you said before rings true, then we shouldn't even need to
tamper with the system at all. But since it is flawed by improper
tuning, and unexpected electrical consumption. All items that can
affect the both the idle speed, and with the example of electrical
consumtion, can in addition affect it's reaction time to correct the
issue.

You have just contradicted yourself on this statement.

And no, an improperly tuned motor is not acceptable, nor should it be
corrected in any other way than a full 30K service + repair of all
vacuum leaks. But the existing Idle Speed Circuit by itself
exaggerates the symptoms far too much, causing too much wear in the
mean time.


> I see I'm dealing with shadetree mechanics and not engineers.

OMG! You seriously didn't just say that, did you? When you joined the
DML, even the welcome page states that this is a communications
network for everyone reguardless of their background. The only
requirement is for a common interest in the car, the man, and/or the
company. And along the way, discussions like this do arise debating a
topic. And almost always, constructive critisisim occurs, and we all
exchange ideas. However, if you feel that we're "beneath" you somehow,
then why both responding to the conversation if you feel that it's not
going to be productive? This is a discussion board for everyone. It's
not some national car club designed to cater to elitists only.
Everyone here contributes equally into all discussions.


> point I'm making is to stop viewing this as a car part, the CIS is a 
> simple flow control loop.

No one is viewing this as an singular component. The Idle Speed Ciruit
is just that. It is a closed loop system that is comprised of
individual componets, and relies upon input from said components. But
at the same time, other parts can interfere with it.


> If you want a decent idle (assuming the 
> engine is in good health and your CO is set properly) you need to 
> prevent the CIS from controlling *all* the air that enters the 
> engine. CIS conductance is not effected by CPR control pressure and 
> that makes a big difference in mixture management.

The CIS system itself does not manage airflow. It simply measures it
to control the air/fuel ratio, and acheives this task by controling
the amount of fuel that is delivered by the injectors, to match the
volume of air that it has detected entering into the intake manifold.
And yes, the Control Pressure Regulator most definatle affects this
air/fuel mixture. It's purpose is to open the diaphram to lower
pressure in the lower chambers, thus allowing more fuel to be
delivered to the injectors to enrich the air/fule mixture. This occurs
only two times: When the motor is cold, and the bimetal armature
inside bends, and pulls the diaphram open, and durring hard
acelleration, when engine vacuum pulls the same diaphram down. And
even then this enrichment is limited. A heater activates to quickly
warm the bimetal arm, and a Vacuum Delay Valve, which equalizes vacuum
pressure within the upper, and lower chambers surrounding said
diaphram. Both components are designed to close the diaphram as soon
as possible to avoid a prolonged, unessisary enrichment. So in
response to your earlier statement, yeah, I'd say that I have at least
a fair enough grasp of how the K-Jetronic CIS fuel management system
works to know what I'm talking about here.


> By allowing the CIS to control all the air entering after the 
> throttle body you increase it's response (it's proportinal band, for 
> those of you who understand control theory) and this canlead to 
> oscillation. By allowing it to control a window around metered air 
> you decrease it's response to overshoot.

EXACTLY RIGHT! THAT IS PRECISLEY WHAT WE ARE ATTEMPTING TO DO! We are
limiting the control that the Idle Speed Circuit has over idle speed
control! If the speed needs to increase, then the circuit has the full
ability to increase engine speed. HOWEVER. When outside circumstances
interfere with out control theory, we are limiting the negative impact
from the nonlinear feedback. In otherwords, if the Idle Speed Motor
goes WOT (Wide Open Throttle), the idle will be allowed to increase.
BUT, when it Chokes (totally closes off), the manualy set idle speed
will automaticly "catch" the slack, and prevent the motor from
stalling, and dipping into that low RPM range! Oscillation occurs from
data input, NOT from the type of limitation that we are placing on the
proportional band. We're simply setting the lowest RPM level staticly,
rather than giving the Idle Speed circuit full reign to automaticly
set said Idle Speed dynamicly. Since engine tuning plays a big part in
the equasion, along with electrical consumption, the system is not
truly "closed loop". The possibility of nonlinear input conflicting
with out objective Control Theory does indeed exist. Yes, you should
keep the engine tuned, yes, all components which comprise the system
should be in properly working order. I agree totally. But Murphy's Law
can still strike. And when it does, that's what throws the system off
balance. Not an inherent problem.


Why people disconnect 
> the system is beyond me, there are no benefits other than to hide the 
> root cause of problems.

We're not disabling any systems. We're simply adding a secondary one
into the equasion.

Which leads us to Part 2:


--- In dmcnews@xxxxxxxxxxxxxxx, "David Teitelbaum" <jtrealty@xxxx> wrote:
> By allowing air to go through the "brass screws" or the manual idle
> circuit you are reducing the amount of control that the idle motor has
> over the idle speed. It cannot compensate (control) the idle as well.

Like I said before, the goal is indeed to limit the amount of control
that the Idle Speed Circuit has over the engine speed. It will be
allowed to advance the speed all it needs, but will not be allowed to
lower it beyond what we have manually entered in as the lowest speed
possible. It will still be able to control the idle just fine.


> In one sense it is like vacuum leaks.

It is NOT like a vacuum leak in the least bit! A vacuum leak occurs
when air is uncontrolably fed into the engine that occurs after air
metering, and therfore tampers with the air/fuel ratio. Setting the
idle manually uses air drawn from infront of the throttle plates, and
has already been measured by the air flap. It only bypasses the
throttle plates, and NOT the mixture unit. The air/fuel ratio is not
tampered with in the least bit.

> IMHO either stay with the idle
> motor circuit or leave it, I don't see how you can have both.

It's simple. All we're doing here is installing a redundant system to
control the idle speed. It's the exact same senario that we have with
the LAMBDA emissions control system. Just as the Control Pressure
regulator lowers pressure in the lower chambers of the fuel
distributor, so does the LAMBDA system. Except the LAMBDA lowers the
fuel pressure directly at the Primary Pressure Regulator. And instead
of gaining it's data from ambient air temperature, and engine vacuum,
it utilizes coolant temperature, and a physical microswitch mounted
directly on the throttle spool. Both systems attempt to achieve the
same exact goal for engine management. But both use totaly different
control theories and components to achieve said goals.

And that is what we're doing with setting the idle speed manualy. It
is a redundant system in function, *technicly*. And I say *technicly*
because not only will adjusting the idle screws achieve the same
purpose as the Idle Speed Circuit, but setting the default idle speed,
we have also set what the engine is now physicly limited to as the
LOWEST idle speed that it is allowed to achieve. So when the Idle
Speed Circuit malfunctions with an erratic idle due to interference
from non-circuit component input (improperly tuned engine, sudden
power drain, etc...), we can keep the engine from stalling out,
wearing too hard on the alternator. For some reason everytime this
thread has come up in the past, everyone seems to read it and think
that setting the idle manually entails the removal of the stock Idle
Speed Ciruit. No! That's not true. The goal is neither to remove, nor
modify it. We simply want to install a supplimental control system.
Er, rather utilize an existing one.


> The idle system CANNOT compensate for an out of
> tune engine or worn parts.

No, we're not trying to compensate for mistuned, or worn parts. Nor is
anyone blaming the Idle Speed Circuit for any worn/untuned parts that
may exist. We're just trying to alieviate the symptom of the motor
stalling out. Yes, this problem CAN be caused by worn parts/mistuned
engine, but it can also be commonly caused by an excessive power/load
drain. I wouldn't consider excessive power consumption from
aftermarket accessories a malfunction. And in this case, it's not
something that can be easily resolved. We're simply installing a
safety net here to keep the engine from stalling out. And in some
occasional cases that I've read here on the list, and experienced
myself, has been failure of the Idle Speed Circuit. Yes, it's a rare
problem that most DeLorean owners will most likely never experience.
But in my book, an ouce of prevention is worth a TON of cure.

Of course one idea that I've always toyed around with is splicing the
lead wire from the A/C compressor clutch over to the Idle Speed ECU to
trigger a cold engine condition to acellerate the idle speed. But, who
knows how that would turn out. But I too hate unessisary modifications
to stock systems. Hence the alternate of setting the idle to 950±
RPMs. Not just for the increased voltage, but for the flow rate of
coolant, the motor cools allot quicker with the engine RPMs running a
bit faster. I doubt that the increased gas consumption would even be
all thact noticable.


> If you are having a lot of trouble getting the motor to idle down and
> you have to hit the pedal to do it one thing to check is the "quadrant
> link". It is the piece that connects the throttle spool to the
> throttle plates.

Been there, done that. No change. I also got a chance to see this
whole assembly up close and personal not just when troubleshooting my
idle, but when I had to fix my throttle spool. A little know problem
that the DeLorean can encounter, and I happened to on my car (the
bracket that holds the WOT microswitch came loose one one end, flipped
around, and locked my acellerator into place!) caused be to become
quite familiar with this area. The Quadrant Link can be adjusted yes,
but to do it, you MUST addjust both ends! If you rotate just one end,
you'll either lossen the linkage too much, or, you've end up
preloading the throttle plates. I've done it before with no sucess,
but I'll try it again. And yes, I did make sure that everything was
properly lubricated. I learned that lesson too the hard way when I
snapped my pivot bolt in traffic.

So in closing, I hope that this has explained things a bit better as
to what the purpose of setting the idle manually is. And in the
future, if I had only one request, please let it be that my posts are
thoroughly read. Not once did I ever mention disabling/removing the
Idle Speed Circuit, nor did I ever "condem" it for any other parts
failure. Does it cause the problem? No. Does it amplify it? Yes!

-Robert
vin 6585 "X"