Toyota iat sensor calibration

[Wolf_Tm250]

Hi,
I'm using suggested calibration for Toyota IAT sensor ( bosch 2500 Ohms ), but as far as I understand, looking at my log files, it seems to me that is not working properly, as I'm getting only 1 deg. C of range in spite of various engine working conditions:



What do you think?

Thank you.

[Holmz]

Hi,
I'm using suggested calibration for Toyota IAT sensor...

What do you think?

Is it the intake before the sc or after.
If it is before then it is believable, and then maybe you need a sensor after the compressor.

[Wolf_Tm250]

Hi,
no, the sensor is in the intake plenum, so it's after the turbo/intercooler... that's why i thought it to give a strange output...
But even stranger is that i checked my engine temp sensors at cold engine and i got 21 deg C from ALL of them!
I mean engine temp, oil temp, egt 1, egt2, external temp and even the intake air temp... so it really seems to work well at cold....
Thanks

[Scott@FP]

Where in the plenum is it located? Does it get a good flow of air?

Is it a fully encapsulated sensor element or exposed thermistor in a cage?

If it is fully encapsulated type that might be the issue.

[Wolf_Tm250]

Where in the plenum is it located? Does it get a good flow of air?

Is it a fully encapsulated sensor element or exposed thermistor in a cage?

If it is fully encapsulated type that might be the issue.

Hi Scott,
here are pics of it... and yes, it is fully encapsulated in a plastic material...







Thanks a lot for the help

[Blu302]

I just had a run in with a similar setup on my V8 where i mounted one in the manifold. The tuner said that factory sensors are compensated in the computer(+20deg or more) due to them being heavily affected by the manifold heat soak directly into the sensor body. He suggested to either make a thermal barrier between the sensor and manifold (nylon bush etc) or mount it so that air flow will have the most impact on the sensor and try to calibrate/compensate for heat soak. I opted for the heat spacer.

[Wolf_Tm250]

I just had a run in with a similar setup on my V8 where i mounted one in the manifold. The tuner said that factory sensors are compensated in the computer(+20deg or more) due to them being heavily affected by the manifold heat soak directly into the sensor body. He suggested to either make a thermal barrier between the sensor and manifold (nylon bush etc) or mount it so that air flow will have the most impact on the sensor and try to calibrate/compensate for heat soak. I opted for the heat spacer.

Ok, thanks...
Anyway I think mine is not affected by manifold heat soak, as the temps I got were only around 33 deg C., and while using the car is almost dangerous to touch with hand the manifold...

So you just made a nylor washer to solve it?

[Blu302]

I happen to have 50mm dia nylon rod at work where I drilled then tapped the inside to fit the sensor. I then threaded the outside to suit the LARGE hole i tapped in the manifold creating a space between the sensor and manifold. Can give drawings if you want.

[Wolf_Tm250]

I happen to have 50mm dia nylon rod at work where I drilled then tapped the inside to fit the sensor. I then threaded the outside to suit the LARGE hole i tapped in the manifold creating a space between the sensor and manifold. Can give drawings if you want.

Hi blu, thanks, but no need for any drawing... I understood what you mean...
I think I'm going to buy a smaller diameter temp sensor from Motec (12mm) so I can make I similar spacer to the oem housing (16mm), so I even avoid the sensor to be behind the air flow.

[Scott@FP]

I think your response time issue is more due to the encapsulated sensor element, these are typically designed for use near the MAF area or inlet ducting and measure more on the ambient temp side of things, and don't require response speed.

After experimenting with small very fast response thermocouples in various locations on the intake tract (turbo engine with cast manifold) the 'heat soak' as described is REAL air temp. If you have two temp sensors, one in the upper IC pipe pre throttle body, and one as close to the intake valve as possible, when the engine bay is fully heat soaked and you are at low mass flow rates (idle, cruise) there is a HUGE temp delta as the air passing thru the manifold/head picks up heat. Once you go WOT and the mass flow rate increases, the downstream temp sensor shows temps getting cooler and cooler as the increased mass flow cools off the intake tract until both sensors are near equal.

What's my point? Well, since we are making compensations based on air temp, shouldn't we be trying to compensate for actual temp the engine is seeing? IAT locations prior to the head cause quite a bit of variance in required compensation based on other conditions because it is not measuring inlet temp accurately, IAT comps need to be fudged quite a bit, and they still aren't right. By using a small low mass (fast response) thermistor located as close to the valve as possible (without getting fuel spray) you can use a simple 2D IAT fuel comp that stays close to correct under all conditions. A 2.3mm glass bead thermistor potted in a 1/16" pipe thread nipple is unobstructive and can be located damn near anywhere.