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Tricking sensors... 

 

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 Post subject: Tricking sensors...
Posted: Fri Feb 11, 2005 2:59 pm 
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As per the megasquirt thread, I'm looking at getting one of those but I'm also keen if trying to trick other sensors in the car for the time being.
The jaycar kit fuel adjuster kit apparently doesn't work with the I6s because of MAP sensors rather than MAFs (and analog/digital) which is unfortunate because they sound really cool for the money :x

Anyway, so I assume you can't mess with the output of MAP sensors otherwise ?

I read in an autospeed article that the coolant temperature sensor in many cars is resonsible for making them run richer when cold, and I'd like to try and trick my car into this. When I first start it it goes noticably better - over and above the cold morning air factors. I've got a temp probe in my airbox and while it does heat up in traffic when rolling along it's often not much hotter than when I first start it and yet it's noticably more sluggish.

So... does anyone know if the EECV does rely on the coolant temp sensor to richen the mix ? I'm thinking I could wire a resistor on a switch into teh circuit and when I want it to run richer a flip of the switch would have the computer think it's cold and away we go. Obviously this is no where near as effective as a remap and the various other benefits of chips, piggybacks and ECUs but its a mod that costs $1 in parts so I thought I'd give it a go :)

Any other trickery any one has tried or that in theory should work ?

Thoughts ?

 

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Posted: Fri Feb 11, 2005 3:09 pm 
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All EFI systems use the coolant sensor for warm-up enrichments.

Simply putting a resistor inline and making the ECU think the engine is colder will only trigger the coldstart mode. In this mode, the ECU uses fixed fuel tables which are richer than running fuel tables, accel enrichments are generally a little higher too.
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Posted: Fri Feb 11, 2005 3:10 pm 
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Coolant temp and intake air temp (not sure if the I6 has an IAT?) are used as modifiers to the fuel mapping to richen the mixture.

Have you had your car dynoed? Most falcons see a hp increase from leaning the mixture.

 

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Posted: Fri Feb 11, 2005 3:30 pm 
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It doesn't have an integrated air intake temp sensor, I just put one there that goes to my dash mounted indoor/outdoor thermometre :)

Different fuel tables eh ? Oh well, that's good enough for me!

I'm getting it dyno'd on Monday so I'm probably jumping the gun a little, but if I get time this weekend I'l try and do teh mod before hand so I can compare on the dyno :)

I think it's safe to say mine isn't "most falcons" though and with the stage 4 cam, oversized valves, head porting, high comp ratio etc etc etc I'd be suprised if the stock computer was running things spot on.

 

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Posted: Fri Feb 11, 2005 3:43 pm 
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EB-EL MPEFI definantly have ACT sensor.

The reason your car goes better in the morning is that ur air charge is actually cooler.

The manifolds, tb and intake piping soak up alot of heat.

 

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Posted: Fri Feb 11, 2005 4:28 pm 
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Waggin wrote:
EB-EL MPEFI definantly have ACT sensor.

The reason your car goes better in the morning is that ur air charge is actually cooler.

The manifolds, tb and intake piping soak up alot of heat.


Spot on, I can't remember were EA-ED intake ACT sensor is, but the EF/EL sensor is roughly under the centre of the intake, I haven't looked at one in a while but it is the only sensor on the bottom of the intake with a small plug, so it is easy to find, as I haven't seen any problems with them, so most people don't know the sensor is there.

Heat soak effects LPG (just throwing this in) far worse than petrol and Hyena has noticed the performance gain with a cool intake just with petrol, drive through a deep gully at night and notice the performance increase from cooler dense air, your ECU won't have time to compensate for the changes the ACT has picked up, so you will not be getting extra fuel pumped in and there will still be a performance increase because most factory ECUs have richer fuel tables than required for safety not performance.

 

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Posted: Fri Feb 11, 2005 5:13 pm 
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Hang on, what is it you guys are calling a ACT ?

 

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Posted: Fri Feb 11, 2005 5:26 pm 
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I believe ACT is 6 cylinder speak for the IAT....

 

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Posted: Fri Feb 11, 2005 6:32 pm 
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Hyena wrote:
Hang on, what is it you guys are calling a ACT ?


Dopey me should have just called it a inlet air temperature sensor (IAT)

 

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Posted: Fri Feb 11, 2005 10:26 pm 
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Or Air Charge Temp :P

 

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Posted: Sat Feb 12, 2005 1:28 am 
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It would be a good idea to get a dyno without putting a resistor on the temp sensor because although you have a lot of mods, the I6's still tend to run very rich and get richer with mods. The only benefit you will get if you were leaning out a fair bit at full throttle which usually doesn't occur until 180rwkw+ .

Anyway, with the resistor mod you have to be careful not to drop the voltage too low otherwise you can have lots of running problems. Coolant temp sensor will adjusts fuel mixtures in open loop (WOT or high loads), and reduces timing when temp gets too hot to stop piging. ACT sensor is mainly used for timing advance.
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Posted: Sat Feb 12, 2005 3:13 pm 
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OK, the highly expensive and complicated circuit to hax0r the temp sensor is made and fitted :)
20k pot in line with one wire of the temp sensor and a switch inline with the pot to switch it in and out. Pot on 0 ohms = what ever the car is actually running at, pot at 20k ohms = hard in the cold and one would assume rich with turning of the pot making the temp gauge go up and down. A switch in line with the pot breaks the connection so the output of the sensor isn't seen by the computer = hard in the red, thermos on and one would assume leaning out.

I'm dynoing on monday so I'll try and get a reading on all 3 settings but at the least I'll hopefully sus out the A/F ratios. The car will be pretty hot when it gets after a long drive in traffic so I'm not expecting an optimal reading, but I should still be able to make some sort of comparison.

I havent touched the air temp sensor...

 

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Posted: Sat Feb 12, 2005 3:34 pm 
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Let us know the dyno result but I am nearly sure you won't see any improvement, IMO it the AF ratios need to go leaner not richer.
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Posted: Sat Feb 12, 2005 4:52 pm 
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Hyena, tricking teh air temp sensor won't do anything.

IAT is sued to calculate air density. If you trick teh ECU to thinking teh air is more dense than it is, the exhaust will be rich and teh EGO will pull the AFR back to 14.7:1. All you'll do is make your car run worse.

Only way to get around that is to disable that is to send a 0.5V signal to the ECU telling it that the engine is running @ 14.7:1.
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Posted: Sat Feb 12, 2005 5:10 pm 
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unclewoja wrote:
Hyena, tricking teh air temp sensor won't do anything.

IAT is sued to calculate air density. If you trick teh ECU to thinking teh air is more dense than it is, the exhaust will be rich and teh EGO will pull the AFR back to 14.7:1. All you'll do is make your car run worse.

Only way to get around that is to disable that is to send a 0.5V signal to the ECU telling it that the engine is running @ 14.7:1.


The IAT is used as a guide to air density for load calculation and modifying the signal will throw out load but that is already occuring because of the cam. IAT is also used to trigger more timing advance when air intake is cooler (ie denser), this is how you may benefit from changing the output. When it comes down to it though, the potential for damage and engine running problems far outweigh the possible small benefits of modifying sensor readings IMO.
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