Hey All,

First let me start out by explaining what the ECT is: The ECT (Engine Coolant Temoerature) Sensor on our engines is a Negative Temperature Coefficient (NTC) Thermistor. What this means is that as the temperature of the ECT Sensor rises, the resistance of it drops.

Here's a chart detailing the characteristics of the ECT Sensor in our engines. This is from a Toyota training document. The ECT Sensor used is the same in all Toyotas.



As you can see by the chart, the Vertical scale on the right shows Resistance and the Horizontal scale shows Temperature. You can see the relationship between the two variables.

Why is this important to know? The ECT tells the ECU what the internal temperature of the engine is, which determines a few things. One thing that it affects is how much fuel is dumped into the cylinders. When an engine is cold, the ECU delivers more fuel and runs more timing advance because cold fuel does not atomize as well as warm fuel.

By modifying the ECT Signal, we can fool the ECU into delivering more fuel into the engine and running a little more timing advance, thereby enhancing power and throttle response. The ECT isn't the ultimate authority when it comes to telling the ECU what to do, but it has a heavily weighted opinion.

The mod involves installing a Potentiometer (Variable Resistor) in series between the ECT and the ECU. By adding resistance to the ECT's circuit, the ECU believes the engine is colder and makes the above mentioned changes almost instantaneously. It's a pretty neat trick.

Since we are using a Potentiometer, we can "Dial In" the appropriate amount of added resistance and we can also turn it off with the quick turn of a knob. Once the Pot is wired into the circuit, the mod is initially adjusted thusly: Start the engine with the Pot "Zeroed Out" or turned fully counter-clockwise. Then once the engine has reached normal operating temperature, slowly turn the pot until the idle RPM's have increased 250-350 RPM's. Take it for a spin to feel the results!

On my truck, I currently have the ECT modded idle set to 1050 RPM's. My normal idle is 700. On my truck, this seems to give the biggest kick and it does not "bog" between shifts. Too much ECT modification can cause bogging between shifts.

By the way, this mod has been around for over 10 years. I didn't originate it. I ran it on my 87 Supra Turbo with great results. I hadn't heard of or seen anyone running it on their 4Runner, so I thought I'd dust it off and install it on my truck. As usual, it worked like a charm. I've been running it for about 6 weeks now. In that time, it has not caused any check engine lights to come on, nor has it appeared to negatively affect fuel economy.

Mark (midiwall) was kind enough to put together a page detailing the installation of the ECT Mod on his 96 4Runner Limited. Mark was/is my Beta Tester for this mod. This article is not meant to be an "End-All, Be-All" how to for this mod, but merely a guide to get you started. We will refine it in the near future. I am posting this because I know some of you are anxious to see what it's all about since I brought this up a few days ago.

Here's a link to the article. I know you will all have questions. So, please feel free to ask away.

I hope you all found this is useful and interesting.
Dr. Z

PS Thanks Mark!

 

Do you think it would be the same colored wire since we have the same year runner? I am questioning whether or not to do this because I sure as hell don't want to clip the wrong wire.:eek:

 

Hi;

You might want to check the web page that I did to show how I did the mod; there's a link to it in Dr. Z's message above. On there, I list 4 ways to trace down the right wire. Dr. Z and I fretted over which wire would be the right one on my truck, but the only way to know for sure was to go investigate on my own.

Being 100% sure will require a VOM (Volt Ohm Meter) but having one around is an excellent diag tool anyway.

 

all this splicing and cutting seems a little extreme for a couple ponies.

 

I can see where it would help us supercharged guys from pinging, but I am still under warrenty (until July) so I wont be doing that mod until after that..

 

So does cutting a 4.5" hole in your airbox... But, I'm glad I did it.

I'm glad I spliced into ONE wire on my ECU also. It's only one wire Ryan, not the whole loom.

All this cutting and splicing he says...


Dr. Z

 

i dunno, the deckplate is worshiped so much, mostly just propaganda to me. gotta look at it in terms of opportunity cost: is the 5 (if that) HP gain from it worth all the extra dirt in your engine?

ECT mod: couldnt messing up one wire ruin the entire unit?

for all these "cheap" mods, gotta make sure the risks out weigh the rewards. i guess its diff for diff people.

dont get me wrong Z, i admire you R&D and your balls to do this stuff. but why not save for the blower and headers?

 

??? As long as you don't pull the air filter out and toss it onto the curb, then the deckplate doesn't introduce any more dirt into the engine. I'll agree though that it does give dirt a larger target to shoot for in getting into the air box.


Well, if you ended up accidently shorting an input to the ECU against a live 12v... You certainly need to be careful when messing with anything having to do with the ECU, but practical sense will keep you from seeing sparks and smoke trails.


As you say, diff for diff. But, I think the grand total for what I've spent on the ECT, Deckplate, and ISR mod is under $20. The bang-for-the-buck quotient is pretty high.

 

Try hooking your gadget upto the IAT...

Gadget

www.GadgetOnline.com

 

The maker of the pot isn't important, just the resistance (preferably 500 ohms) and the taper (linear).

The pot you see in the pic is mine, and I did get it from a local "real" electronics store. I tend to shop there versus 'Shack because of the greater selection of physical formats for things like this (along with a stock of other things like PICs, chips, sockets...). The pots that are locally stocked at 'Shack tend to be huge. For my mounting location, I needed something fairly compact.

I think Dr. Z mounted his in the glove compartment which is a location that you can use just about any size you can think of.


Dr. Z has tried this as well, but I don't think he noticed an appreciable difference when compared to the ECT. He's on day-long fact-finding mission right now, but I'm sure he'll pop in here when he gets back.

 

Ahh, okay...

Active Electronics (where I shop here) is a chain, but I think that each store is indivdually owned and can pull their stock from wherever based on an allowance.

With me being in Seattle, pulling from B.C. may make sense.

I think that Allied and Fry's are in Texas, but it sounds like you know of a shop around.

Good luck!

 

If you don't mind mailorder, try digikey (www.digikey.com) - they have just about everything, including a metric ton of pots, resistors, and other goodies.

Cool mod BTW, I'm feeling the urge to go mod something this week so I'll see what I have lying around and go from there. What would be just ducky, would be to take the resistance output of the ECT sensor and use it to automatically taper the pot accordingly as temps rose, for a fully automated solution - then you just need an on/off switch. This'd require some more fancy circuitry, but given that we're talking about low power it should be fairly easy to pull off. Mental note to think about this, or if someone else wants to design a circuit, have at it.

My plans for this rig include a "control panel" of sorts, with gauges Toyota should have included, and controls for various gadgetry like this. Should be interesting when i get it done. (I'm also debating going with a full digital dash, but we'll see...)

 

Wouldn't doing this mod on an automatic car cause some problems? At least for the second gen. I know that my transmission will not shift into OD until the engine has reached operating temperature. If the computer thinks that the engine is running below operating temperature, would the transmission not shift into OD? Just a thought.

 

Hey Gadget,

I do have a pot on my IAT. A 10K Ohm pot to be exact. With it I can bring the "Apparent" Intake Air Temperature down to about 5 Degrees Farenheit. But, it seems to do nothing for performance. According to Jay, the IAT on Toyota engines does not have anything to do with Injector Pulse timing. Seat of the pants impressions seem to bear this out, as well as readings from my BR-2.

Thanks for the input though.

Dr. Z

 

Good point. There's no way to be sure about that unless someone tries it. However, I can say this: The "Apparent" temperature when I have the ECT mod set to where it performs best is 160 Degress F.

I have never owned an automatic vehicle. But, does the truck have to be TOTALLY warmed up before it will shift into OD? Or will it if the truck is very nearly warmed up?

Answer please if you can. Thanks.

Dr. Z

 

Yes, on your truck the wire should be the same color as mine. The color on Mark's truck is not the same as on mine. I will post the pin location on the ECU and color tomorrow. I have been meaning to get around to doing that since I never documented it initially. I knew I'd be back in there at some point before ever posting about this. But the point was raised a little before I was ready.

I meant to answer you sooner, sorry about that.

Dr. Z

 

Dr. Z,

Yes my truck has to be totally warmed up. All the way to the point where the thermostat will open up. When the engine is cold it will not shift into overdrive until it has reached operating temperature and not a hair colder. Even if the engine is warm and not at operating temperature it will not shift into overdrive. This is on a 2nd gen though. I don't know about the 3rd gen.

 

Hmmm. I bet there's a way around that.

I'll see if I can figure that out.

Dr. Z

 

My '96 is an automatic (with the 3.4L 6 banger).

I haven't seen any issues with it getting into OD using this mod. I'm currently running the mod at Idle = 1050 (temp = 151). I've got some highway driving to do tonight and will play with it then to see if I can stop it from flipping up to OD.

 

The location of the ECT Wire on the ECU harness on my 2000 4Runner V6 5 Spd is on the "B" connector, middle row, third from the left as you look at the connector when it is plugged into the ECU. The wire color is GREEN. There is no stripe on this wire. It is simply green.

Hope this helps.
Dr. Z