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JimmyHoffa

open-element IAT sensor for 1JZ/2JZ

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I'm looking for an open-element IAT sensor that will fit in place of the stock JZ IAT sensor. I don't know why the dummies at Toyota used a closed element IAT, but my intake mani heat soaks if I sit and idle and the IAT heat soaks too showing upwards of 70C as my intake air temp when I'm sure it's nowhere near there. Then takes a while of driving for the IATs to come down to a reasonable value. It kinda helps on a boosted car to have fast response on something like IAT since at higher boost levels high intake temps can become a problem pretty quickly.

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Guest gameface

I have the same problem with a gm iat sensor(open element) although probably not the same extent, once I start driving it clears up. This is also with water to air intercooler where even at idle the air should be getting cooled seeing how its constantly circulated with fan running on the heat exchanger. I don't really like the gm iat but haven't experimented with others either. I have doubts about its reaction time.

 

I set MAT correction to start at 55c something like 15% at 70c figured also helps during extended abuse on the engine when iat will really pick up also. Pre det no thx.

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Get bung and weld in charge piping right after intercooler?

 

I've been wondering how the stock ecus work with this for awhile now. I monitor that shit with the emanage and on my non vvti shit temp quickly shoots sky high. With my vvti shit the iAT is in the maf and the temp is pretty consistent with what ambient temp is. I know that after being compressed and ran through heatsoaked piping it isn't the same as the ambient temp and I also know that on the non vvti setup it isn't 200+ degrees either. Since I'll probably be strictly vvti here shortly I've been thinking of using the MaF in blow through fashion since I'm mostly fueling by pressure anyway and this way I'll get a correct-ish reading. Guess I can log timing changes as well.

 

Let us know what you go with.

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I'm likely going to go with a welded bung in the IC piping just before the TB and usd a GM open element sensor from an old 80s/90s Buick, Pontiac or Chevy. Gotta get this sorted before I dyno because I don't trust the stock IAT. On most of my data logs it's reading lower temp under boost doing WOT pulls than at low load cruise on the highway, and that's lower than idle air temps by like 20 degrees. I assume since the sensor is getting less manifold heat soak and actually seeing enough air to effectively read at WOT.

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I got a GM open-element IAT and aluminum bung from DIYAutotune. I'm going to disconnect the stock intake manifold temp sensor (fucking thing doesn't measure actual IATs for shit), and run the GM sensor in my intake piping before the TB.

 

To show how bad it really is, driving around with the ambient temp at -2 degrees C (the car fucking loves this weather) the stock IAT reads around 25-30 degrees C. At idle in the same weather, around 50 degrees C...

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Move to jz/uz tech section? Let us know the difference on the temps. I've been thinking about this myself lately, how my emanage logs would be damn near all the same high ass temp catching heat soak from the engine and how IAT corrections would be fairly inaccurate. Been thinking of doing blow through maf to change this myself.

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Guest FrozenChosin

If the 1J has a CSI [Cold Start Injector] you can pull it and make a plate out of something that's resistant to temp change [like phenolic resin] and mount the sensor in that. Should slow down heat soak. Just another option.

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^ JZs do not have cold-start injectors.

 

The stock sensor is a closed element, so the entire brass cap heats/cools too slowly to give an accurate real-time reading, especially doing pulls when your intake air temp might go from 50F to 150F in a matter of a few seconds. The thermistor in the stock sensor is also not thermally isolated from the mounting plug/body. The GM sensor I got uses an open-element, so the thermistor sits in the middle of a plastic cage, not really hard mounted to anything thermally conductive (other than the wires that run to it), so it will give a lot more accurate reading of real-time intake air temp.

 

Open element

iat.jpg

 

closed element crap

IAT.jpg

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This is for standalones only. With the MS I can use pretty much any IAT sensor, I just have to calibrate based on three known temp vs resistance points (I usually calibrate with an ice bath, boiling water, and room temp, check resistance at those points, plug into TunerStudio, and voila).

 

The stock ECU is expecting to see the numbers that the stock sensor is going to read, even if they're not realistic intake air temp numbers. If anything, doing this with a stock ecu would cause problems and likely not yield any benefits.

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Guest Radial

Hmm...this is not good, as i'm planning on using that stock IAT for my setup. Maybe need to reconsider that.... funny thing this never is almost never mentioned...even at BIG hp projects.

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I know a few guys who have told me not to worry about the IAT signal being representative of reality and to just use it as a reference. Eg if it usually sits at 50 deg. C in the summer and it hits 75 or 80 to start worrying about pre-ignition, but I would rather spend 30 bucks on a sensor that will read accurately without much lag and allow me to run IAT based fueling and ignition correction so I can just keep mashing the pedal and not have to worry too much about shitting out my pistons.

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Guest FrozenChosin

Interesting; I gotcha.

Does the GM sensor use the same signal [as temp goes up resistance goes down]?

 

How's it working? Do you still have heat soak with it?

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I'm running a map ecu2 and instead of the me2 IAT sensor and intake air temp compensation I run a early 90's Corolla IAT on the stock vvt-i ecu and disable the me2 intake air temp compensation . This setup works well as it reads the same resistance as the stock IAT in the maf and it plugs into a rubber grommet in the intake pipe before the turbo .

$(KGrHqZ,!nUE63Tf7ptUBO-5l+0yMQ~~60_12.JPG

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I'm 95% sure the scaling of the thermistor range is different, so it's not going to be interchangeable, nor would you want to try it with a stock ecu.

 

I won't actually have any results until spring. My car is away for the winter since it's snowing and the roads are covered with salt. I'm sure that it will work as planned, or at least 95% better with this IAT before the TB than the stock sensor in the intake mani.

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Guest Radial

I'm running a map ecu2 and instead of the me2 IAT sensor and intake air temp compensation I run a early 90's Corolla IAT on the stock vvt-i ecu and disable the me2 intake air temp compensation . This setup works well as it reads the same resistance as the stock IAT in the maf and it plugs into a rubber grommet in the intake pipe before the turbo .

$(KGrHqZ,!nUE63Tf7ptUBO-5l+0yMQ~~60_12.JPG

 

Maybe i'm just being stupid resonating about this, and I very might be terribly wrong. but isn't half the point of an IAT is to compensate for hot air entering the Intake manifold.?

So by measuring the intake temp on the turbo, you are missing the heat buildup in the compressor in different attitudes and temps, and the cooling/heating in the IC in different speeds.....in other words, your temp measurements would be kinda useless in front of the turbo?

 

I know MAF's work that way, but they compensate for that by measuring the actual volume of air entering the turbo too.. that makes it more accurate as long as the system behind is within standards.

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A lot of MAFs have the IAT built in. This does completely disregard the fact that your actual IATs might go up or down depending on boost and how much cooling your IC does. The ideal place for the IAT is in the intake manifold or just before the TB. You want the temperature of the air that is entering the ports as close as is reasonably possible to the ports without the sensor heat-soaking or causing restriction/turbulence to the air flow.

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No vvt-i jz-gte's came with IAT sensors in the manifold like non vvt-i jz-gte's did so I used this sensor to satisfy the IAT signal requirements of the stock ecu . I have used this sensor for about six months now with no trouble codes and no tuning issues . I use Toyota Techstream to monitor obd data and this IAT sensor's siginal is dead nuts the same as the IAT in the stock maf . When I first installed the ME2 I used the resistor it came with to clamp the stock IAT signal , welded a bung just before the throttle and installed the ME2 IAT . It ran fine but it heat soaked and had a fit on hot and cold starts due to bad fuel trims it built because of the differential between coolant temp and intake air temp . I than moved the ME2 IAT to the intake pipe and it cut the trouble almost in half . I had a Corolla IAT around the shop so for shits and giggles I tried it and it has bean 100% like stock . I now have it running with no maf , the Corolla IAT in the four inch intake pipe before the turbo with the ME2 IAT compensation disabled , no trouble codes and good fuel trims .

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I'm guessing 92ish? I'd like to try this on the emanage.

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Yea 92ish. Turbo mr2s have that same iat sensor on the engine lid. Car uses it to turn on the intercooler fans. I also used it when I wired the stock 3s harness to run the newer gen ecu that uses map and iat.

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Disco mr2 is same as Gte gen 1 that screws into the intake? Or as the corolla style that's plastic and is designed for the intake tract? Gameface I believe just wired in a gm unit and said fuckit.

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Usd mr2 was always maf so it only had the plastic one as a thermostat for the intercooler fan. The maf had the iat for the ecu built in. The 3rd gen and on 3sgte used the 2, the screw on one on the manifold and the plastic one on the intake. Dont know why Both. But they both use the same resistance across different ttemps.

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