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Boost sensor voltage


danmanTSI
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Idle: 0.2v to 1.2v, and about every two minutes it will jump to 1.5-2.6v as it's checking the altitude. It looks like you have an 84, 84-86 should be the same.

 

I suggest you download the factory service manuals:

http://www.starquest...howtopic=124229

 

And check out these links next time you have a question:

http://www.starquest...howtopic=124270

 

http://www.starquest...showtopic=78870

 

-Robert

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The checking of altitude, is that for the later model black plastic box MAP sensors, that have the solenoid valve mounted close to them?

 

There is mention of altitude verification in the 83 service manual, but the vacuum setup for these models with the metal box type MAP sensor has no provision for connection to anywhere but the inlet manifold, after the throttle plate... Was wondering how these earlier model do altitude testing? Is it just the one reading taken initially before cranking begins for starting?

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The checking of altitude, is that for the later model black plastic box MAP sensors, that have the solenoid valve mounted close to them?

 

There is mention of altitude verification in the 83 service manual, but the vacuum setup for these models with the metal box type MAP sensor has no provision for connection to anywhere but the inlet manifold, after the throttle plate... Was wondering how these earlier model do altitude testing? Is it just the one reading taken initially before cranking begins for starting?

It would fall under Ignition and timing Advance ,

although you might be forgetting the 83 introduction of the Starion in the USA was a 84 model year.

But the vacuum line from the MAP is also below the throttle plate (non intercooled)

 

The ignition system monitors engine vacuum.

Vacuum readings are lower at higher altitudes .

 

The High Alititude Spark Advance Control was introduced in 86 model year.

Mitsubishi offered this to be in compliance with federal emision standards

It is only affective above 3900ft elevation (1188m)

It sends a 5 degree advance signal to the ECU for ignition timing.

 

In earlier models ( Pre 86)

it is still calculated but is routed through the ESC

without the added 5 degree adjustment.

 

The vacuum advance is detected by the ESC Ignitor,

The ISC (idle speed control) gives feedback on throttle pressure,

because it can detect positive accelerator operation.

And would adjust the idle according to the vacuum (atmospheric pressure)

 

The oxygen sensor would give signals to adjust fuel delivery according to it's readings of atmospheric pressures.

Edited by Metric-man
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I'm referring to your 83's here, the first year they came out there. They'll be setup the same as our 82's and 83's I'm assuming. For clarification, any model that had the 'ECI' cap style of fuel rail will be what I'm talking about.

 

The American FSM for 83 models does mention taking a barometric reading to adjust fuel levels for altutide, but it'll have no effect in ignition timing setting whatsoever, as the computer has no bearing on that. It's a seperate system.

 

The MAP sensor is only used by the ignitor to detect overboost conditions, in which case it retards the timing. Same deal on the detonation sensor. These functions are completely independant of the ECU. Apart from these emergency ignition retard functions, the ignitor is actually just an ignition amplifier box, and does no other timing modifications at all, it will just fire a spark when it gets a signal from the reluctor in the distributor, and presumably have some way of controlling dwell to ensure decent spark without burning things out. All the actualy timing of ignition events is done mechanically by the vacuum advance unit and the centripetal weights. AFAIK this is actually the same for all StarQuests, right up to 1989. The one exception is the A184 with the DASH 12v motor, which the ECU does all the ignition timing for, but those cars are crazy, and awesome.

 

The ECU also has no bearing on the idle speed in an 83, this is set mechanically by adjusting the position of the throttle stop. The throttle stop also happens to be the idle position switch which tells the ECU the throttle plate is closed. Idle up for cold starting is taken care of by a wax-stat screw which advances the throttle, also mechanically, whilst the engine coolant is still cold.

 

Basically, what I was asking, was how the 83's (ECI cap models) take a barometric altitude reading. They have no solenoid valve which switches the pressure input signal to the atmosphere like the later models, to take a reading. They are directly connected to the intake manifold, after the throttle plate. This area will almost never see atmospheric pressure while the vehicle is running... Was wondering if it took an initial read on startup, just before the motor started cranking... Or some other way I'm not quite seeing.

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I hope you forgive me I was clarifying my post

(editing while your were responding, I forget you're up at this time and burning daylight)

I think you may agree with me or I with you , see if you ask a question I may have to read on some old manual that isn't readily available.

 

So if you have re read my late post and still don't comprehend I'll try my best to try again.

The one thing most don't realize ( I'm sure you probably do) is the ESC on the 83's were metal like the 88/89's except the connector being round they were nearly identical.

 

Anything that compensates for a change in vacuum pressure will do the same for atmosperic.

(Atmosperic pressure into a intake = change in vacuum)

Edited by Metric-man
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Ahhhh, I see what you're saying. The vacuum seen at the map sensor will be lower for a given set of engine conditions just due to the fact that the vehicle is gaining altitude. I didn't think the earlier models used the MAP sensor for much other than running the boost gauge, overboost sensing, and fuel trim under positive pressure... You're saying it uses the map signal to trim the fuel delivery under cruise (vacuum) conditions also?

 

I'm still pretty sure that the ESC box doesn't undertake any timing modifications with respect to MAP pressure, except under an emergency overboost condition.

 

Good discussion man :)

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I don't have access to a 83 service manual,

but if the 83 model used a ISC the ISC would read variances

in the throttle plates position,from significant changes,

in vacuum.

 

The electrical current would change with the position of the throttle when the ECU would test the idle by manipulation of the ISC plunger.

 

The throttle cable is adjusted with slack to allow for free movement of the throttle plate.

What I mean is, it is part of the proceedure of adjusting the ISC.

This contributes to the ISC's fuction as a dashpot by signaling the ECU to cut back fuel on deceleration and,

throttle's position changes from added positive vacuum pressure.

(Too much fuel and in reducing the momentum of,

a rapidly closing throttle plate )

 

The TBI system on our cars is just a glorified feedback carburator.

 

The distributor only uses the ignitor frame and the ignitor itself,is inside the ESC (knock box) otherwise how could it retard timing,when it recived a strong signal,

from the detonation sensor?

 

The vacuum advance on the distributor detects vacuum variations, for example it advances the timing of the distributor when turbocharger pressure is introduced.

 

What really happens at start up on a cold engine ( pre 85.5)

(and the ECU's RAM hasn't been interupted)

The last known successful (boot) operation is used.

So if you transported a Starquest by freight to a significantly

different elevation then it was last driven (operated)

The car might stumble and be rich/lean before warm up.

 

Even pre 87 cars were notorious for their random idle(searching)

That was before Mitsubishi introduced the nose switch at the tip of the ISC to further improve idle quality.

 

 

 

 

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Nah, 83's don't run the same form of ISC as the later models. They have a mechanical system that advances the throttle with a wax-stat device which expands and contracts with the temperature of the water flowing through it. When cold, this device advances the throttle slightly.

 

Check out this: http://prozac.orconhosting.net.nz/eciguide/rebuild.html

 

There are a couple of pictures there of the system used.

 

What I'm saying about the Ignitor/ESC Box/Knock Box is that it has no bearing on the actual mapping of ignition advance/retard in relation to boost/load/rpm/tps or anything else. That is all done mechanically by the vacuum advance/retard unit, and the weights inside the distributor. With the exception of some emergency conditions where it'll pull a bunch of timing out for a pre-determined period to avoid damage to the engine. Apart from that, it's just a pretty basic ignition amplifier with (I'm assuming) some dwell control.

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Did you write that rebuild up on the ECI top throttle body?

That is a nice write up.

 

I see what you are saying about the ESC , all it really does is protect the system, by fuel cut and retard.

there are other piggybacks and or ignition amplifiers that can perform the same tasks .

 

On the part of the later model ISC,

Barometric pressure affects the temperature at which water heats,

so it a way it is adjusted for, by the way the wax valve is heated.

 

If you take the time to consider Mitsubishi and,

their history of manufacturing aeronautical equipment .

They most likely are above average in the learning curve.

Edited by Metric-man
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