The IAT liesss

[Jake_rorx7]

So I've installed my own IAT sensor just before the throttle body. Its a common GM IAT sensor, calibrated by myself. The values correspond to another temperature sensor I have in the mouth of the vehicle for ambient.

The stock sensor lies - by a lot. At cruise, anywhere between 9-12c delta between my new sensor on the elbow, and the stock location, "fast reacting" iat sensor on the manifold underside. Just to be clear, the stock IAT reads well above my sensor.

Now there is a very slight difference in location, about 6 inches or so. But the different values are too high for the location to be the cause of this. I would personally put it down to the stock location being a heat soak prone material (metal), installed in a heat soak prone material (metal manifold), installed in a heat soak prone location (under the manifold). All sensors start out at ambient on engine start, but the stock IAT is diverging within 5 mins.

I see around 3-4c delta between my ambient temp sensor and my new IAT sensor. Until now, I was under the assumption that I have a 17c delta from ambient to intake. I've not done many harder pulls yet because I need to clear out the tank of meh fuel first, but still. Dont trust it! And if you have a custom ecu which uses that sensor data - maybe time to install a new sensor?

 

[RandomVillager]

Do you think the stock one has lost it's accuracy over the years?

I have heard the IAT on the RB series is basically a temp sensor for the cooling system so once that gets hot it takes ages to go down if at all till you let the thing fully cool off.

With a standalone you can put any IAT in the stock location I suppose and set calibrations to use that.

Could be worth maybe if possible using one pre turbo so see the delta better between the two locations. IC will show if it's getting heat soaked or not.

 

[Jake_rorx7]

Do you think the stock one has lost it's accuracy over the years?

I have heard the IAT on the RB series is basically a temp sensor for the cooling system so once that gets hot it takes ages to go down if at all till you let the thing fully cool off.

With a standalone you can put any IAT in the stock location I suppose and set calibrations to use that.

Could be worth maybe if possible using one pre turbo so see the delta better between the two locations. IC will show if it's getting heat soaked or not.

This particular sensor is only a few years old. I think it's just major heat soak.

If I can get my hands on one of those proper temp loggers with an array of tiny sensors I'll stick them all over the intake tract and get a better picture of what's happening and what's not. Pre turbo, post turbo, post IC, and around throttle body.

I think the key takeaway here is.. stock IAT sensor sucks.

 

[RandomVillager]

Yeah the logging would help I'm not sure how you could log that many channels.

What ECU you on? How many inputs does it have?

 

[Temujin]

There’s a few posts about the stock location being subject to heat soak, when I was doing some work I moved it closer to the front of the bay and updated it to a faster reading variant.
Unsure on the difference but I would have thought it won’t make too much of an improvement

 

[Jake_rorx7]

Yeah the logging would help I'm not sure how you could log that many channels.

What ECU you on? How many inputs does it have?

I'm trying to get my hands on a standalone temperature logger, the sort of thing they use in development of intakes and intercoolers and such.

There’s a few posts about the stock location being subject to heat soak, when I was doing some work I moved it closer to the front of the bay and updated it to a faster reading variant.
Unsure on the difference but I would have thought it won’t make too much of an improvement

Seems you were right to do so!

 

[AlexG]

So I've installed my own IAT sensor just before the throttle body. Its a common GM IAT sensor, calibrated by myself. The values correspond to another temperature sensor I have in the mouth of the vehicle for ambient.

The stock sensor lies - by a lot. At cruise, anywhere between 9-12c delta between my new sensor on the elbow, and the stock location, "fast reacting" iat sensor on the manifold underside. Just to be clear, the stock IAT reads well above my sensor.

Now there is a very slight difference in location, about 6 inches or so. But the different values are too high for the location to be the cause of this. I would personally put it down to the stock location being a heat soak prone material (metal), installed in a heat soak prone material (metal manifold), installed in a heat soak prone location (under the manifold). All sensors start out at ambient on engine start, but the stock IAT is diverging within 5 mins.

I see around 3-4c delta between my ambient temp sensor and my new IAT sensor. Until now, I was under the assumption that I have a 17c delta from ambient to intake. I've not done many harder pulls yet because I need to clear out the tank of meh fuel first, but still. Dont trust it! And if you have a custom ecu which uses that sensor data - maybe time to install a new sensor?

As a validation Consultant who does temperature logging of big Pharma kit, I applaud your approach to this. Nicely done sir!

I have one of these TC0521 Datalogger that I bought for a similar set of experiments.

I plan on doing what you are doing and also have a TC pre and post intercooler to see what the delta is there.

You can make up your own length of thermocouple from mini plugs and Type T or Type K wire or just buy stainless ones from Aliexpress for not much cash K Type Thermocouple Sensor 1/8 NPT or just have the wire TC's which react quickly Type K TC. You can dot these wherever you want and if you want to surface mount just use Kapton tape

Can't comment on the reaction rate of the stainless probe TC's but the brief play I've had with them they seem to show changes within a second, which is more than enough for me to monitor the air temp trend and snapshot.

Good luck with it.

AL.

 

[Jake_rorx7]

As a validation Consultant who does temperature logging of big Pharma kit, I applaud your approach to this. Nicely done sir!

View attachment 44616

Thanks for the love, and pointers!

I think after the probes are set up, verify my current readings, wideband installed, I can measure the effect of running an intercooler sprayer, then water and then water/meth injection on the aem kit I have ready. Might be difficult to get a probe in the manifold, but I'm thinking of feeding it down a vac line port, assuming I can get a good enough seal to not pop out under boost.

 

[AlexG]

Yeah, sealing with a TC placed down a vac line on a spigot would be critical. You can use a blob of silicon seal to fill in any gaps caused by the TC wire and them use a good tight clamp on the outside of the hose. Let that go off and then try it. It's a fine balance to not crush the TC as well, just tight enough to seal, not full-etard tight

One word of warning is to make sure that the TC wire isn't long enought to get dragged into the butterfly valve or anything downstream (and upstream incase of flow reversal) of the insertion point. I warned someone about this when he was working on an autoclave, but he knew better. His TC's got chewed up by the main chamber discharge valve and that added 2 days to a 3 hour job

If you are choosing a port see if there's on that is on a metal spigot rather than a plastic spigot. Clamping on a plastic spigot is fraught with danger of damaging the tube under the clamping force. The intake manifold take off for the boost gauge might be a good point.

You can also get these if you need to get a probe in an intake pipe

https://www.viperperformance.co.uk/product/70mm-air-sensor-silicone-coupler-hose

 

[AlexG]

Picture better than words

 

[Jake_rorx7]

"No thermocouple in the spinny zone"

 

[AlexG]

"No thermocouple in the spinny zone"

Exactamundo

 

[AlexG]

"No thermocouple in the spinny zone"

This has got to be the first time my chosen profession has actually been useful in the real world lol

 

[Jake_rorx7]

This has got to be the first time my chosen profession has actually been useful in the real world lol

I'm going to find your expertise extremely useful my friend because almost everything I do to modify this car is to do with temperature control. I have a massive list of modifications pending that are purely "keep the hot in the hot and the cold in the cold", which could ideally do with validation using temperature probes.

When I come to measuring engine bay/tunnel/exhaust/cabin heat measurements I will consult you once again. Hopefully the temperature logger we have at my workplace can go up that high, into the few hundred to a thousand celcius.

 

[AlexG]

I'm going to find your expertise extremely useful my friend because almost everything I do to modify this car is to do with temperature control. I have a massive list of modifications pending that are purely "keep the hot in the hot and the cold in the cold", which could ideally do with validation using temperature probes.

When I come to measuring engine bay/tunnel/exhaust/cabin heat measurements I will consult you once again. Hopefully the temperature logger we have at my workplace can go up that high, into the few hundred to a thousand celcius.

Sounds awesome. Happy to help where I can. Just shout

 

[SullyKP]

I think the stock location of the IAT is pretty good from a tuning point of view, notwithstanding the heat-soak issues.

Wondering if you could isolate the sensor body from the UIM with a nylon adaptor and sensor with a smaller thread. Maybe some shielding too...

And/or relocate the sensor position to the top of the UIM.

I have WI in the elbow just before the TBs so cant really move the IAT sensor downstream.