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Discussion Starter · #1 · (Edited)
Background:
So now we've done basic Intake and Exhaust upgrades, but are we taking advantage of it for it's fullest extent? No! Even if we've added next to nothing in power, we can still add a bit more power, and improve throttle response.

The stock ECU's are programmed to run as close to 14.7-1 Fuel Air ratio as possible. This is great for fuel economy and emissions. The drawback is that this ratio is not good for making power, or throttle response. It's too lean. For a N/A engine, we really want October to a 13.5-1 air-fuel ratio.

Theory
We need to add fuel to the mixture.
We've all seen the cheap-o Ebay "gain 22hp engine chips" that sell from between $5-$25.

They work by adding resistance to the I.A.T. Intake Air temperature sensor to make the ECU think the temperature is colder than it really is, in response it will richen the mixture.

The Problem
They don't work on Toyota's as discussed many times before. The ECU isn't fooled for any length of time before it reverts back to normal tuning.

The Solution
The intake air temperature sensor signal isn't the only one that can easily be modified so that the ECU changed the fuel mixture.

Enter the E.C.T. Engine Coolant temperature sensor. By placing a 500 ohm resistor on the ECT sensor wire going to the ECU, we can control what the ECU thinks the coolant temperature is.
By RAISING the resistance on the potentiometer, the ECU thinks the coolant temperature has dropped. In response it not only adds the corresponding amount of fuel, it advances the timing slightly as well!

Instructions
After buying a 500 ohm potentiometer from an electronics store <cough> Radio Shack <cough> electronics store <cough>
Obviously this is a very simple mod, but many will shy away from it because you have to find the wire going from the sensor to the ECU.
Trust me in that if I can wire an 11 wire SMT-6 and tune it with no instructions, or help (and I'm the only one on earth anyone knows of woot!). You guys can cut one wire and solder a dial in.

I suggest looking in whatever manual you have. Toyota, Lexus, Hayes, Chilton. Don't count one book out. They're all equally incorrect on ECU wiring, simply because the wiring can change on what seems like a random basis from one day to another.
Just find the ECT marking on the diagram, and look at which wire it's on.

Tuning
This is how tuning should proceed.
Obviously everyone's potentiometer will adjust at a different rate. Start with the potentiometer turned off 0-resistance. Crank the car. Then turn the knob slowly until your RPM rasises in 100rpm increments.
The greatest performance increase should be with your idle raises somewhere between 950rpm and 1100rpm. Most will probably split the gains between 1000rpm-1050rpm.

Results
This isn't going to give you a huge amount of power. What it will do is advance the timing between .5 and 2 degrees, and add 2-4% extra fuel to the injectors.
It's not much, but we're talking a $2-$3 part and less than 15 min of work.

*note*
The engine reporting a lower than normal temp will not affect the engine's ability to shift the transmission, or rev freely. In the unlikely event you bought the wrong resistance potentiometer and it happens... Turn the dial the other way, or get a 500 ohm potentiometer!




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Other Articles in the Series:
Part I Quicker Transmission Shifting
Part II Adding Airflow
Part III Taking Advantage of Intake/Exhaust Upgrades
Part IV Cheaply Monitoring the ECU & A/F
Part V How to pick up MPG, and sleep with her too!
Part VI Acing Aerodynamics
Part VII Cheap Water Injection
Part VIII Electronic Transmission Controller
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Discussion Starter · #2 · (Edited)
For the guys that know how ECU's work. Don't bring up closed and open loop mode. The mod works in closed loop mode, so don't bring it up and confuse the newbies.

The ECU also never disregards, or has a way to "learn" the mod. Cold sensor = cloder ECU map in closed loop. Cold sensor = different open loop tune.
 

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dont exactly have a manual at hand got any place that might have that i could just look up w/o buying it or might have one for an 88 camry?
 

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the gain you would be getting would be so minimal, its not worth the time.

the only benefit i could see would be timing advancement, but that is really easy to do anyways.

nice writeup though
 

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Toysrme said:
For the guys that know how ECU's work. Don't bring up closed and open loop mode. The mod works in closed loop mode, so don't bring it up and confuse the newbies.

The ECU also never disregards, or has a way to "learn" the mod. Cold sensor = cloder ECU map in closed loop. Cold sensor = different open loop tune.
Well I'm attempting to understand your wording here. "I'm the one who confuses people;)"

By doing this mod you will prevent the ECM from reaching closed loop and send a constant extra flow of fuel into the mix the ecm will not be able to adjust for. The ECM only has a set amount of timing in open loop to prevent engine damage since it does not see all the sensors. This extra fuel could lead to fould plugs and a plugged cat which would negate any benift from this mod.

Of course the same could be said from any engine mod that the ECM cannot compensate for. This is the reason tunnning with the ECM is so critical (prom burning ect..)

If it does show improvemnt that can be backed by track times or on a dyno it would be a great mod for short period period use. I just cant see it.
 

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Discussion Starter · #7 ·
By doing this mod you will prevent the ECM from reaching closed loop and send a constant extra flow of fuel into the mix the ecm will not be able to adjust for.
No, by doing the mod the ECM uses a different closed loop map. That particular map will richen the mixture depending on how "cold" the fluid is.

The ECM only has a set amount of timing in open loop to prevent engine damage
Correct. What you're missing is that the ECM in open loop mode will run the same timing. It is not affected. (timing is closed loop only, and under no more than 2,500rpm. We're also talking less than 2 degrees of timing advance at any setting so stop worrying about that) The engine has knock sensors... There is also a major room for timing advance depending on the RPM range on the earlier v6's. 2vz/3vz.

Like I said...
Don't bring up closed and open loop mode.
The reason is beause we wind up with confusing conversations (what we're doing now) to people that don't know how an ECM works. I also can beat down any arguement on it.


About fuel. It takes it to make power. Re-read the *Background* section to find out why this mod is worth the time . This mod will give the best performance with the ECM "thinking" the temperature is between 150F and 170F.

The amount of fuel this mod can apply is rather astonishing. It can raise the short term fuel trim 6%, and can move the long term fuel trim 2%. That's a lot of fuel for a $2-$3 part. If you dial it in to 1050rpm at idle in Park or Neutral, it will add 4% fuel short term, and will eventually add 1% fuel to the long term fuel trim.
 

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I'll give it a test run and see what happens. But its getting so freaking cold uo here I doubt the ECM will even get out of open loop. :)
 

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Discussion Starter · #9 ·
;)Don't worry when you try it. You have to make the ECM think the coolant is around 120F-130F before it limits the RPM and won't shift down. Don't worry about it.

The idle will be the same in a gear, but in Park or N it will raise the more you increase resistance. (turn the knob) You'll know you've turned it too far (and realise how muhc fuel you can add!) when the engine responce goes from a little better to worse.

I'm doing this because I know a million little tricks that might add a hp or a maybe a few for no-very little cost.
I could easily tell anyone that wanted 200hp out of a 3vz-fe to cut a hole in their airbox and go buy a $300 SMT, richen the fuel until the last two vertical rows (where you need to lean on the top half), build a relay(cause the 6 is finiky with ignition signal changes) and advance the timing from 3 points off idle to 8-12 points in high RPM-WOT TPS/AFM/MAF/MAP setting.

It's easy to make 5-20hp for a few hundred bucks. my thing is that most people on Toyota Nation are not willing to spend $400-$500 on upgrades that won't get them 20hp.

I'm trying to give the tight wads some options!
 

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I wouldn't mind giving this a try. I don't have a manual for me to look up which wire it is. Anyone have info on 94 4cyl camry manual ecu?
 

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alex86 said:
dont exactly have a manual at hand got any place that might have that i could just look up w/o buying it or might have one for an 88 camry?
http://www.autozone.com/servlet/UiBroker?UseCase=RG001&UserAction=beginRepairGuide


Originally posted by superg3
I wouldn't mind giving this a try. I don't have a manual for me to look up which wire it is. Anyone have info on 94 4cyl camry manual ecu?
See link above.


Heres a picture of the ECT (engine coolant temp) sensor on my 3S-FE:

 

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I haven't looked under the hood yet but , how do you wire the pot? It has three prongs right? And how many leads are coming out from the sensor, if there are two, which one do I choose unless there's only one.
 

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userlain said:
the gain you would be getting would be so minimal, its not worth the time.

the only benefit i could see would be timing advancement, but that is really easy to do anyways.

nice writeup though
Noob :disappoin

Advancing your timing requires more fuel, or higher octane. And adding more fuel to the mixture by that amount gives a good boost in power. More than your little intake did.
 

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Discussion Starter · #16 ·
Kind of right. Timing in itself is not a big power adder in any way, shap, or form. Though the stock parameters for all factory engine have a lot of room for advancement at some points; throttle responce is the main gain from increasing timing. Not power. The point of this is not to get a .5* or 1* of timing advance. That's 100% inconciquencial. The point is to get the extra fuel.
 

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sanengo said:
Can someone explain to me what exactly does "advance timing" does? Toysrme, do you have any pictures of this mod?
when each piston reaches a certain point in its travel the ECU tels the sparkplugs to fire -This is timing. If you advance the timing you tell the plug to fire sooner thus getting a better compressed burn on your fuel, and a more complete combution stroke.
 

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superg3 said:
I haven't looked under the hood yet but , how do you wire the pot? It has three prongs right? And how many leads are coming out from the sensor, if there are two, which one do I choose unless there's only one.
The wire you want is the signal wire coming from the ECT to the ECU. If there are 2 wires coming from the ECT, 1 will be ground and that will be easy enough to figure out. What you do is cut the signal wire. Then connect one end of the wire to one of the terminals on the outside of the potentiometer and the other wire to the terminal in the middle of the potentiometer (variable).

The way potentiometers work is, if you measure resistance accross the outter terminals, you will get the value of the potentiometer, in this case 500 ohms. If you measure from say the left terminal to the center, the resistance will vary as you turn the dial. Connecting left terminal and center terminal might make resistance increase as you turn the pot clockwise where connecting right terminal to center would make it decrease in resistance when turning the pot clockwise. Your best bet is to measure it or refer to a diagram that frequently comes with them. So again, you don't do anything with the ground wire from the sensor, you are only adding this variable resistance in series with the signal wire. -JoeB
 

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If i get this straight I attach a 500ohm potentiometer to the ECT wire leading to the ECU. I then start the car, preferably drive for a while until I reach a stable idle, then start turning the potentiometer until my idle RPM increases to ~1100rpms. My car has a very low idle at around 500rpms after I get off the freeway, so do I need a stronger potentiometer?

What if the ambient temperature was below that of the activation point for "closed loop", sorry for bringing it up, will the rpms still increase as I adjust the potentiometer?

EDIT: is there another way to advance a car's timings?
 
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