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fooling the ecu into giving more fuel


star_power
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you can now fool the ecu into thinking the car is cold at all times by wireing an 10omh volume switch into the + side of the engine temp sensor. The afore mentioned switch cost 3.99 at raido shack and is ajustable up or down.caution this must be used inconjunction with an A/FR  meter  and  a upgrade fuel pump. I have this device on my car and have more fuel than i kown what to do with.Here is the part info #271-215 mini volume control
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Where you also aware that the engine being cold can change many more variables in the map than you think.

 

For instance, the colder map has retarded ignition. A Colder car with a cold altenator is likely to put out different voltage than a hot car with a hot alternator... What does it do when the car is "cold" and the alternator is hot... it changes the map still.

 

Fuel enrichment by this method will lead you on very short trails of gains, cost in economy, and ruin your paint near your bumper :)

 

Joel

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The alternator is not tied into the engine temp on the Starion system....  However I think there is a bit of extra advance when cold (and no EGR).

 

Yes , fooling the engine temp sensor can add a few extra varaibles.

 

Another way would be to fool the temp sensor in the Mass air flow meter.  If you tell it the air is colder you will get more fuel.

 

You could also try and find a higher pressure point to referance the fuel pressure regulator.  If you had higher pressure than at the throttle body ...  Like before the intercooler you would get a bit more fuel.

 

Be careful though...  Make sure you are going richer and the place you connect to has higher pressure.  If your system is stock and you are not leaning out extra fuel may just get you running slower.

 

Kevin C

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I would like to add that this device can be mounted inside the car and is being used in conjunction with the temp sensor.When the vehicle is cold or hot    i can adjust the fuel up or down. Imust restate that this device is only wired into the positive side of the sensor and dose not replac it  and must be used with the following:A/FR,  EGT, upgrade fuel pump and ignition system.
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  • 9 months later...

AF and an egt, if you got that kinda money to spend on a stock car you should be doing an mpi swap ;)

 

i think it was said that when cold the car has different advance.  i dont think so.  this dist has its mech and vac advance.  the only thing the ignitor can do is retard it in case of a knock detect.  I THINK.

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Putting an end to the fuel cut issue on any 86 and earlier Starion is a must.

(No idea how to fix an 87)

You have to solve this problem before attempting to boost your turbo PSI with a boost controller.

Adding boost also requires you to know if you are leaning out your car. (hence the need for an A/F meter)

No fuel + High PSI = BAD.

Looking at the diagram shown below you need to remember its a top down view of the ECU connector, NOT the plug you pulled out of it.

So when it refers to "Connector A", its not the connector on the harness.

Keep that in mind before you splice into the wrong wire.

 

Installing the Air fuel meter

I used terminals A11 and A4 for the A/F meter.

It works perfectly. Only one light at a time lights up.

Not 2, not 4, just 1.

(you can get power from any 12 volt source, its the sensor ground that is really important. DO NOT use the chassis as a ground)

Fixing the fuel cut problem.

For a "dime store" fuel cut fix (10k adjustable pot) I spliced into A9.

That fixed my 4000+ RPM full boost sputtering problem. The fuel cut must have started to activate at that point.

All I did was cut A9 in half and install a 10K adjustable POT that I bought at Radio Shack.

I connected the wire coming from the sensor to the middle post on the pot, and one of the outer posts I connected to the ECU.

Afterward I mounted it up front on my "control panel" so I could  adjust it if I needed to. (not that I ever would anyway)

 

Side note to that. I used a 10KW Linear Taper Potentiometer not a 10KW Audio Taper Potentiometer.

Today I tried to run with a boost over 13 PSI. It didn't work very well.

It works beautiful at 13 PSI, just no more than maybe 14.

I don't think the linear pot cut the voltage from the boost sensor enough.

I am not sure how an Audio taper one would work.

If anyone knows, email me.

(The pot is an adjustable resistor that lessens the voltage going from the boost sensor to the ECU.

The higher the boost pressure, the higher the voltage.

As soon as the voltage reaches a certain point the ECU shuts you down.)

 

Here is a scan I did of the 1986 intercooled version of the Starion's ECU wiring for your reference.

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nd Tuning the Stock Fuel System

 

 

 

 

Pin      1990-94 Turbo      Wire Color      Mod      Results

4      Oxygen Sensor      wht      Tap into the line with voltmeter      Monitor O2 Readings

8      Intake air temperature sensor      grn-org      Install 10k potentiometer      Add resistance to richen full throttle A/F ratio

16      Barometric pressure sensor      grn-yel      Install 10k potentiometer      Add resistance to lean full throttle A/F ratio

105      Waste gate solenoid valve      org      Tap into line with LED      Monitor when ECU sees excess knock and tries to reduce boost

 

 

Oxygen Sensor monitoring:

You can either use the check connector (click here) or tap into the ecu wire #4. Either way will give you the same results.

 

Intake Air Temperature Sensor:  

   

Solder up some wire leads to a 10k potentiometer using the last  2 terminals so that when the dial is turned as far as it can go counterclockwise you have 0 ohms resistance. Cut wire 8 and solder the potentiometer in series. It doesn't matter which side of the potentiometer goes to which wire. You should start tuning the car with the knob turned fully counterclockwise (the ecu will see the real air temperature). By turning the knob clockwise the ecu will think that the air is cooler and will add fuel to accommodate the denser air. Do not try and tune without monitoring the O2 sensor with a voltmeter. Tune until you get .88-.92 at wide open throttle. You will only be able to adjust full throttle A/F ratio with this mod. It won't do anything for the lower rpms. Don't adjust this unless you've done some mods to require more fuel. (Mass air flow sensor hacking......etc) If you're running lean without having done mods then check the intake piping between the turbo and mass air flow sensor.

 

Barometric Pressure Sensor:

 

Solder up some wire leads to a 10k potentiometer using the first 2 terminals so that when the dial is turned as far as it can go clockwise  you have 0 ohms resistance.  Cut wire 16 and solder the potentiometer in series. It doesn't matter which side of the potentiometer goes to which wire. You should start tuning the car with the knob turned fully clockwise (the ecu will see the real elevation). By turning the knob counterclockwise the ecu will think that the car is at a higher elevation and will reduce fuel to accommodate less oxygen. Do not try and tune without monitoring the O2 sensor with a voltmeter. Tune until you get .88-.92 at wide open throttle. You will only be able to adjust full throttle A/F ratio with this mod. It won't do anything for the lower rpms. All cars can benefit from this since Mitsubishi programmed the ecu so that it runs rich at full throttle. Don't try and do this unless you understand the fuel system in the car. If you lean it out too much you can cause detonation that can destroy your engine.

 

Waste gate solenoid valve / Knock LED

 

 

Tap off of wire 105 (orange) with either a 12volt internal resistor LED (available at some Radio Shacks) or use a regular LED with a 470 ohm resistor in series (Do not use regular indicator light bulbs). You must have either the boost control solenoid installed even if you're not using it or solder a 40 ohm resistor in it's place. Whatever you do don't just short the 2 wires together or you can damage the ECU. The LED will not work without either the resistor or boost control solenoid installed.

Operation:

When car is turned on the LED will be ignited for 3-5 seconds. It will flash on and off about 10 times then should remain off. This is completely normal and it's the ecu that is playing with the boost control solenoid.

If the ecu detects excess knock and it wasn't able to reduce it by slightly pulling the ignition timing back a few degrees then the LED will start to flash. This is the ECU closing and opening the boost control solenoid to gently reduce the boost level. If knock is still present the LED will remain lit solid and timing will be pulled further back. If you see this happening it is wise to back off the throttle.

If the LED remains lit solid at all times the ECU thinks that you're using cheap gas. The timing has been pulled back and the ecu is trying to limit boost to 8psi by closing the boost control solenoid. The ecu will eventually reset itself but it's much faster just to reset it. You can reset the ecu by pulling the bottom right hand fuse for 10 seconds (after the ecu has clicked off).  If it happens again and you're using premium gas then start looking for problems. Check ignition timing, fuel pressure, a/f mixture, wastegate actuator, knock sensor and vacuum leaks. This is even more important if the boost control solenoid isn't hooked up to the wastegate actuator (you have some other form of boost control) and the ecu no longer controls boost.

 

Good luck with fuel tuning!

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  • 3 weeks later...
Putting an end to the fuel cut issue on any 86 and earlier Starion is a must.

(No idea how to fix an 87)

You have to solve this problem before attempting to boost your turbo PSI with a boost controller....

 

 

Hey this is a cut and paste from my website !!

At least credit me.

: )

 

I changed my 10k pot for my fuel cut to an adjuster for my temp sensor as well.

It allows me to run it richer if I choose but a side effect is that the car idles higher (like its cold)

 

The values you want are not 10k to 0, you really want 3000 to 300.

I've put some resistors on on it and it seems to work good.

I need to make a schematic for it and put it on my site.

 

Right now my low value is 330 ohms. I was thinking of trying to lower it with a file (filing the resistor) to see if a "hot" car will lean it out a little.

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raising the boost cut on an 87 is best done by swapping to later ecu and using a 1gmas....ive never hit any cut, Adi is known for running well over 20 psi on his and never found boost cut either.

 

I have no idea if the 88/89 igniter does any good in this scenario..my 87 has always had an 89 igniter since i bought it

 

ive also heard/read somewhere that putting a switch on the o2 sensor and turning its lead to the ecu "off" will bump your timing a few degrees and add more fuel...

 

Monty

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  • 7 months later...

the only time i found the boost cut on my 84 is when I 'accidentaly' ran the boost unrestricted.  even then the stock gauge was pegged before it cut.  Ive run a little over 10psi on my car and teh stock gauge barely said 7psi.  Now if the fuel cut takes the same map signal as the in dash boost gauge there is your fix.  The map sensor outputs a linear voltage.  you can just take that signal(opamp) and send it to the ecu for whatever the value is for 10psi or 7psi or whatever.  but like i said my fuel didnt cut until i had over 14psi on the stock gauge, no clue what psi really was.  or you can rewire your fuel pump not to run through the ecu.  But you will need to do a few safety precautions.  Shelby told me to use a crash sensor from a ford or similar so if the car is in an accident or flips it cuts the fuel.  fooling the ecu is all the greddy apex stuff does.  ive heard of people wiring pot.s to their coolant temp sensors as well. never tried it though.

 

good luck

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