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intake air temperature sensor

Old 06-26-19, 06:46 PM
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intake air temperature sensor

i have been using an air temp type K thermocouple for my IAT since 2013 and really like having 4 accurate readings per second. i started looking for solution after noting that my stock sensor read 27 C throughout my entire 2000 to 9000 run on the dyno.

i am just slightly aware that others are using a "fast" thermistor. the 64 $ question is... just how fast is "fast."

an important question because if your sensor lags you are going to think your IAT is just peachy when it might be getting you close to knockville.

i have spent a bunch of time searching including calling my wonderful EGT guys at The Sensor Connection but have come up w nothing as to response data.

consequently, i am going to acquire a "fast" sensor and install it along w my thermocouple in my UIM. we will then do a match race.

BTW, i have no idea as to the outcome, i just want to see them race.

RX7Clubbers, i need your input... what is considered to be the fastest thermosensor to test?

Thanks!

Last edited by Howard Coleman CPR; 06-26-19 at 08:13 PM.
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Old 06-26-19, 09:14 PM
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reaction time of a type-k TC is going to depend on the type of junction at the sensor, are the leads spot welded and exposed or encased as a grounded junction? a type E thermocouple would be better suited for an IAT as it has better accuracy(but only by a little), the benefit of type-K's is that they withstand up to 2200F. the reaction time compared to the stock IAT sensor and other aftermarket options would be interesting data to see though.
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Old 06-26-19, 10:28 PM
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I think a good test would be the triumph sensor that is kind of the standard upgrade to the stock unit. It would be nice to see how good it really is.
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Old 06-27-19, 02:31 AM
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Im pretty confident that there's a thread with all sorts of technical data with the triumph sensor vs stock.
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Old 06-27-19, 04:08 AM
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Originally Posted by Howard Coleman CPR View Post
I...RX7Clubbers, i need your input... what is considered to be the fastest thermosensor to test?

Thanks!
Probably wannaspeed's…..
https://wannaspeed.com/en/home/7-87-...-bosch_pigtail

https://www.rx7club.com/3rd-generati...sensor-882534/

Last edited by Sgtblue; 06-27-19 at 04:10 AM.
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Old 06-28-19, 10:25 AM
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IAT dynamics happen REALLY fast. if there is any lag in your sensor you are in the dark on a very important metric.

here's a recent log proving the point.

boost went from 8.9 psi at 2:59.790 to 19.4 at 3.00.374

just over a half second!

IAT went from 77 F to 126 F according to my thermocouple.

here's 8.9 psi:




here's the log at 3 minutes and .374 seconds:



IAT rose from 77 F to 126 F in less than three quarters of a second. note the bottom section of the log... that's my 100% methanol pressure log. AI pressure rose from 23.2 psi to 121.6 psi. i can't imagine where my IAT would be without it. i do plan to add a bit more meth to drop my IAT below ambient.

thanks to the magic of methanol my IAT trends downward to 117 F at 7722 rpm 24.9 psi boost and approx 585 hp.




my IAT data is generated by a specially engineered "air" thermocouple from The Sensor Connection. the sensor is made by them in the USA and is a product of more than 20 years of engineering to get the right balance between fast and durable. it generates four readings a second and is accurate to around one per cent.

for the record i have no idea as to the speed of other thermister type sensors. looking at the graph in post 5 isn't much help. there are 20 seconds between 140,000 and 160,000 Ms. it appears that the initial rise is about 20% of the 20 seconds so about 4 seconds... the reason we can draw no absolute speed conclusions from the data is that the engine may have taken four seconds to do it's thing. all we can conclude is that it is faster than the glacial speed OE sensor.

i will be adding a thermistor to my UIM shortly and we will have comparison data.

i have a suspicion that if we knew our actual IATs there would be a lot more re-thinking of system design.

SYSTEM DESIGN
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Old 06-28-19, 10:52 AM
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Certainly food for thought. But I feel like I’ve already thought about system design with a better IC, ambient sourcing intake, WI and the relocated fast(er) reacting IAT from wannaspeed for my modest boost and power level.

Last edited by Sgtblue; 06-28-19 at 11:02 AM.
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Old 06-28-19, 11:17 AM
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Howard, just a thought, do you have a temp sensor before the IC?

i wonder if the relative size of the intercooler effects the temperature rise? if someone had a really big intercooler would temp rise be slower?

i suppose i am used to seeing logs from fairly stock cars, and with those the temps come up and kind of stay there, and yours seems like it goes up faster (does it come down fast too?)

i was actually thinking about building a box that could do temp in/temp out of a turbo and pressure in/pressure out, the thinking was to build a compressor map of the turbo on the car.

Last edited by j9fd3s; 06-28-19 at 11:20 AM.
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Old 06-28-19, 07:33 PM
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"do you have a temp sensor before the IC?"

yes. i have had some issues w Exhaust Gas Technologies items, either the amp or sensor so a fair amount of my logs don't have temp out of the turbo before the IC as well as at the UIM stock location...

here is one showing temp out of the turbo before the IC and also temp into the motor.



you will note that temp out of the turbo just trends higher w RPM up to 340 F at 8733 RPM at 13.3 psi. (SX-E 62 .91 off the spring) while IAT at the stock location shows 115 F but since it is horizontal i am pretty sure it is at the bottom of the scale... a precursor of my EGT problems.

i now have my four Sensor Connection thermocouples hooked into a new 4 channel amp. one of the features i like is that it eliminates a set of connectors as the wires just hook into the post.

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